Arturo Merino, Torsten Mütze, and Namrata Apply Gliders for Hamiltonicty!

Happy Passover to all our readers

On the way from Cambridge to Tel Aviv I had a splendid three hour visit to London (from Kings Cross to UCL and back), where I met my graduate student Gabriel Gendler and Freddie Illingworth from UCL. (Like Tim Gowers and Imre Leader but a few decades later, Freddie and Gabriel first met at an IMO.)  Gabriel and Freddie told me about several striking things including the remarkable “glider” proof for showing that Kneser graphs, Schrijver graphs, and stable Kneser graphs are Hamiltonian.  (These proofs settled old standing conjectures.) To quote Merino, Mütze, and Namrata:

“Our main technical innovation is to study cycles in Kneser graphs by a kinetic system of multiple gliders that move at different speeds and that interact over time, reminiscent of the gliders in Conway’s Game of Life.”

Here are relevant links: 

  1. Arturo Merino, Torsten Mütze, and Namrata:  Kneser graphs are Hamiltonian.
  2.  Torsten Mütze and Namrata, Hamiltonicity of Schrijver graphs and stable Kneser graphs.
  3. (A forthcoming survey article in the Notices of the AMS) Torsten Mütze, On Hamilton cycles in graphs defined by intersecting set systems.
  4.  Torsten Mütze, Gliders in Kneser graphs, Internet site.
  5.  (While looking at 4. I discovered this very cool site) COS++: The combinatorial object server.

     

 

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Updates from Cambridge

I am writing from Cambridge, UK, where I participated in an impressive conference celebrating Tim Gowers’s 60 birthday and I am about to take part in a satellite workshop of Theoretical computer science. Coming here was the first time I travelled since the start of the war on October 7, and earlier today (April 14, around 02:00) we witnessed a major dangerous escalation of the war with a direct Iranian drone and missile attack on Israel.

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(The sky in Israel during the attack  source: Haaretz.)

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The group photo of the conference. (Tim Gowers is second on the right on the first row.)

Let me tell you a little about the conference. This was an opportunity to meet old friends, to have very interesting conversations with some new friends, and to witness many young stars. I suppose that most talks will soon be available on you Tube, but in the meantime Ryan O’Donnell’s lecture (that was given by Zoom) on random reversable circuits is already on the air in Ryan’s great  You-tube channel. Incidentally, I spent much effort on studying random quantum circuits that Ryan mentioned in his talk and my previous post Random Circuit Sampling: Fourier Expansion and Statistics was devoted to their study using analysis of Boolean functions, which is also a common interest of both Ryan and me.

Avi Wigderson was scheduled to talk on Wednesday and a few hours before his talk we heard the news that Avi wis the recepient of this year’s Turing award! Congratulations, Avi!  This is also great news for the theoretical computer science community and for Israeli mathematical community. Avi and his work are frequently mentioned on my blog. This is also a good opportunity to congratulate Michel Talagrand who was awarded the 2024 Abel Prize, and Vitali Milman, Yanki Ritov, and Hagai Bergman who were awarded the Israel Prize this year.

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The counterexample to the Daisy Conjecture

The first talk was by Imre Leader and he showed the disproof by David Ellis, Maria-Romina Ivan, Imre Leader of the Daisy conjecture. (Here is the link to the paper.) A daisy is an r-uniform hypergraph with six edges. All these edges contain a common set of (r-2) vertices  and in addition each edge contains a pair of vertices from four additional vertices. (You can think about the daisy as (r-2)-fold cone over K_4.

The question was about the maximum number of edges of an r-uniform hypergraph that does not contain a Daisy. The conjecture was that the density of such a hypergraph must tend to zero as r tends to infinity.  The crucial ingredient in the example is the following construction: Take n=2^r-1 and consider the vertices as the nonzero points in V=F_2^n and the edges as bases in V. Consider r-2 linearly independent vectors and suppose that they span the vector space W. Let a,b,c,d by four additional vectors in V^* and let \bar a, \bar b, \bar c, \bar d be their images in the 2-dimensional quotient V/W.

If (v_1,v_2,\dots, v_{r-2} a,b), (v_1,v_2,\dots, v_{r-2} a,c), (v_1,v_2,\dots, v_{r-2} a,d), (v_1,v_2,\dots, v_{r-2} b,c), (v_1,v_2,\dots, v_{r-2} b,d), and (v_1,v_2,\dots, v_{r-2} c,d) form bases in V then (\bar a, \bar b), ~(\bar a, \bar c), (\bar a, \bar d), (\bar b, \bar c), (\bar d, \bar d), and (\bar c, \bar d) are all bases in the two-dimensional vector space V/W and this is impossible.

Polymath project?

We also talked a little about possibilities for a new polymath project. Suggestions are welcome. Stay tuned.

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Random Circuit Sampling: Fourier Expansion and Statistics

Update: In the comment section,  Kodlu asked me about my overall review of the Google 2019 supremacy claim and my response is here.

Update 2 (04/04/34): See the end of the post for quantum computers news from Microsoft and Quantinuum:

Our new paper

Yosi Rinott, Tomer Shoham and I wrote a new paper on our statistical study of the data from the 2019 Google quantum supremacy experiment.

Random Circuit Sampling: Fourier Expansion and Statistics, by Gil Kalai, Yosef Rinott, and Tomer Shoham

This version is still a draft and any corrections, comments, related thoughts, and discussion are most welcome. In my view the results are quite interesting; we develop statistical tools and study data from experiments and simulations. As before, we try to discuss as much as possible the findings and possible interpretations with the authors of the Google paper other papers that we study. 

Summary: We use Fourier-Walsh analysis for statistical analysis of samples coming from noisy quantum circuits. For this purpose we develop some models and statistical tools such as a Fourier-based refinement of the linear cross entropy estimator. We also develop computational methods that allow us to compute more efficiently some estimators introduced in our statistical science paper. We applied these tools to the samples from the 2019 quantum supremacy experiment, and also to simulations of noisy circuits via Google’s “Weber QVM simulator” and IBM’s  “Fake Guadalupe simulator”, and we ran a few 5-qubit experiments of our own on IBM’s  quantum computers.

We compared the behavior between samples of the 2019 experiment and samples from Google’s simulator.  Recently, we ran our analysis tools on samples coming from the Harvard-MIT-QuEra 2024 paper on neutral atom logical circuits.

What we do in the paper and some of our findings

A) We define and study a 2-parameter noise model that seems appropriate for NISQ experiments. Our model is more general than Google’s noise model and it captures the effect of readout errors and (to some extent) of gate errors. We refer to one of the estimated parameters as the “effective readout error”: It accounts for the average readout error and additional similar mathematical effect that comes from gate errors.

B) We refine the XEB type fidelity estimators to an estimator \Lambda_k that estimates the degree-k Fourier-Walsh component of the (normalized) XEB.

C) We use the fast Fourier-Walsh algorithm to efficiently compute estimators (mainly those related to readout errors) from our statistical science paper.

D) We analyze data using our Fourier methods (and tools from our stat, sci. paper) that comes from:

  • The Google 2019 quantum supremacy paper
  • Noisy simulations using both Google’s and IBM’s simulators
  • Five-qubit circuits that we ran on IBM computers “Jakarta” and “Nairobi”.
  • (Very new) Data from 12-qubit logical circuits from the 2024 paper by Bluvstein et al.

E) One of our findings is that the effect of gate errors towards larger effective readout errors is witnessed in data coming from Google’s simulator (and other simulators) but not in the samples of the Google quantum supremacy experiment.

F) (preliminary) The Fourier behavior of the samples for 12-qubit logical circuits (via the [8,3,2]-color code) from the 2024 paper by Bluvstein et al. is highly stable unlike the behavior for samples coming from other sources. (We discussed this paper in this earlier post.)

Once we get more data about the Harvard/MIT/QuEra neutral atoms logical circuits experiment from the researchers we will apply our programs to the data (and perhaps develop new tools to study it).

Let me mention Ohad Lev who was a member of our team and did a great job in running simulations and real quantum circuits.

Some tables and Figures

In the following tables the two parameters (s,q) that give the best fit with our model were computed for the 12-14 experimental circuits both for the experimental data and for the Google simulator. We refer to the estimated value of q as the “effective readout error” and it captures both the readout errors and a similar (usually smaller) mathematical effect of the gate errors.

1214GED

1214GS

Here are some nice Figures. In the top figures we see the contribution of degree-k Fourier-Walsh coefficients to the (normalized) XEB-estimators for the Google experimental data (10 different circuits). In the bottom figure we see the contribution of degree-k Fourier-Walsh coefficients to the (normalized) XEB-estimators for the data coming from the Harvard/MIT/QuEra experiment  (16 samples based on different error-detection based post-selection of the same circuit). I had a statistics teacher in the 70s who would refer to histograms like the bottom one as “smooth as a baby’s bottom”.

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Relations to my earlier research directions

Here are five issues that I studied over the years, and I am quite happy to see that the new paper has some connections to all five. (The main connection is with the third item which is emphasized.)

1) Fourier analysis of Boolean functions, the noise operator, and the notions of noise sensitivity and noise stability.

2) Applying Fourier analysis to the study of noisy intermediate scale (NISQ) quantum computers.  (In my work, this was connected to quantum computers skepticism.) This reflects my work on quantum computing from 2013.

3) Studying statistical aspects of samples coming from NISQ computers and especially data coming from the  Google 2019 “quantum supremacy” experiment. Much of this study is around the XEB estimator for fidelity. This reflects my work with Yosi Rinott and Tomer Shoham since December 2019 or so.

4) Scrutinizing the Google 2019 “quantum supremacy” experiment:  raising concerns about the quality and the reliability of the data and of the experiment. This reflects another aspect of my work with Yosi Rinott and Tomer Shoham.

5) Studying correlation between errors as a potential obstacle for quantum computation. This reflects my work on quantum computing between 2005-2013.

I find the third item more pleasant than the fourth item. Raising concerns about a scientific paper by colleagues is a delicate matter and it gives me personally a feeling of being some sort of a detective. (I had some experience in that in the late 90s.) Of course, the primary responsibility of scrutinizing scientific claims lies at the hands of the researchers themselves.

The Fourier connection (items 1 and 2)

The Fourier connection is quite close to my heart. It is related to old papers of mine from the late 1980s and 1990s. The 1999 Benjamini-Kalai-Schramm paper on noise stability and noise sensitivity, the 1988 Kahn-Kalai-Linial paper on influences and quite a few other papers. The Fourier connection is also related to  more recent papers about quantum computing starting with a 2014 paper with Guy Kindler. The Fourier connection in the quantum context is related to works of people on our mailing list regarding the Google experiment:  a 2017 paper by Boixo, Smelyanskiy, and Neven; a 2018 paper by Gao and Duan;   a 2021 paper by Gao, Kalinowski, Chou, Lukin, Barak, and Choi; and  a  2023 paper by  Aharonov, Gao,  Landau, Liu, and Vazirani. Let me mention that similar Fourier-type decomposition in the context of statistics were studied by  Yosi Rinott  in the early 1980s. Also, Ashley Montanaro, and Tobias J. Osborne (and perhaps others) extended ABS (analysis of Boolean function) to the quantum setting in a 2008 paper.

Some technical details

A) Fourier analysis of Boolean functions and the noise operator.

Recall that every real function f defined on 0-1 vectors x of length n, the Fourier–Walsh expansion of f

\displaystyle f(x)=\sum \{\widehat f(S)W_S(x):S \subset [n]\},

is a representation of f as a linear combination of the Fourier–Walsh functions W_S(x), where S goes over all subsets of [n].  The coefficients \widehat f(S) are referred to as the Fourier-Walsh coefficients of f, and if k=|S| then \widehat f(S) is referred to as a degree-k Fourier–Walsh coefficient.

A basic insight in the analysis of Boolean functions is the relevance of the noise operator T_{\rho}, where \rho is a real number, 0 \le \rho\le 1, defined as follows.

\displaystyle T_{\rho}(f) = \sum \{\rho^{|S|} \widehat f(S)W_S(x):S \subset [n]\}.

Readout errors, namely, reading with probability $q$ a qubit as “0″ when it is in fact “1″ and vice versa, directly correspond to the noise operator T_{(1-2q)}.

B)  Our basic 2-parameter noise model

When the probability distribution described by a random circuit C on n qubits is given by the function {\cal P}_C(x), our basic two-parameter noise model is

\displaystyle s T_{(1-2q)} ({\cal P}_C(x)) + \frac{1-s}{2^n}.

One ingredient of our analysis is finding the best fit to this model.

Here are three noise models:

1) GNM – The Google noise model from the Google 2019 quantum supremacy paper. For this model q=0 and s=\phi where \phi is the fidelity. This noise model assumes that every gate or readout error leads to a random uniform bitstring.

2) RNM – The (symmetric) readout noise model that we considered in our Statistical Science paper. For this model  q is the average rate of readout errors (q=0.038 in the case of Google’s 2019 quantum supremacy experiment) and s=\phi_g is the probability of the event of “no gate errors”. (By the statistical assumptions of the Google paper \displaystyle \phi_g= \phi \frac {1}{ (1-0.038)^n}, where \phi is the fidelity.)  For RNM we still assume that every gate error leads to a random uniform bitstring.

(Note that both the Google noise model where every error takes you to a random bitstring and our symmetric readout model where every gate error takes you to a random bitstring leads to correlated errors that are quite “unfriendly” to error correction schemes.)

3) WNM – the noise model described by Google’s Weber-QVM simulator which is Google’s most accurate publicly available full noise model for the Sycamore quantum computer. We cannot analyze analytically the effective readout error for WNM  but simulations show that it leads to an effective readout error which is substantially larger than the “physical” readout errors.

C) Fourier refinement of the (normalized) XEB fidelity estimators

We  define a refinement \Lambda_k of the (normalized) XEB fidelity estimator that gives the degree k-contribution to the estimated fidelity. Roughly speaking we write the probability distribution described by the circuit as a sum of terms that corresponds to the degree k Fourier-Walsh component.

\displaystyle {\cal P}_C(x)=P_0(x)+P_1(x)+\cdots P_k(x)+ \cdots +P_n(x).

The estimator \Lambda_k is based on the inner product between the empirical distribution and P_k. (Look at the paper for the full definition.)

D)  Comparing the Google 2019 experimental data to simulations

We used  maximum likelihood estimator (MLE) for the pair (s,q) of our main noise model. For the samples of the Google 2019 samples the estimated value of q that we refer to as the effective readout error was quite close to the physical readout error 0.038 (in fact, a little smaller). For simulators with 12 and 14 qubits coming from Google’s “Weber QVM” simulator, the effective readout error was substantially larger than 0.038.

One of our findings is (roughly) that the behavior of Fourier-Walsh coefficients for the data from the 2019 supremacy experiment agrees with a model of noise where every gate-error sends you to random uniform bitstrings (RNM), and does not agree with the behavior of WNM based on the Google’s simulator  where gate errors have similar (but smaller) additional effect on the Fourier-Walsh coefficients to that of readout errors.  An additional effect of gate errors of the kind observed in simulations is seen for the IBM simulators “Fake Guadalope” and our 5-qubit quantum computer experiments on the IBM quantum computers. The behavior of the simulators appears to be consistent with the results of the papers of Gao et al. and Aharonov et al.

E) The interpretation of the findings:  Do they raise additional concerns (or support earlier concerns) about the Google 2019 experiment?

The finding regarding noise modeling of the Sycamore quantum computer may be a genuine interesting finding about NISQ devices, or specific finding about the Sycamore  quantum computer, and it may be an artifact of some methodological problem with the 2019 experiment of the kind suggested by our previous papers.

As I said, at this stage, we try to discuss as much as possible the findings and possible interpretations with the authors of the original papers, especially with the Google team (mainly with Sergio Boixo and John Martinis), with whom (and a few others) we had a useful email discussion from late 2019 to May 2023.  I look forward to further discussion in the context of our new paper.

We also had useful correspondence with Seth Merkel who was an author of the IBM 6-qubit experiment and with Dolev Bluvstein from the very recent Harvard/MIT/QuEra logical circuit experiment (and the first author of that paper).

Comparing Google and IBM

This is sort of an interesting side issue. As far as we can see, the difference between Google’s empirical assertions from 2019 for random circuits with 12–53 qubits and the current situation with random circuit sampling on IBM quantum computers is quite substantial. While IBM offered online quantum computers in the range between 7 and 133 qubits, we are not aware of random circuit experiments on those IBM computers with more than seven qubits. We ran some experiments with 5 qubits (on 7-qubit quantum computers “Jakarta” and “Nairobi”) and there is a 2021 paper by Kim et al. describing an experiment with 6 qubits.  Seth Merkel  helped us setting our 5-qubit experiment and ran by himself a  seven-qubit experiment on an IBM QC. We are not aware of IBM random circuit sampling experiments with more qubits, and we do not know if running on the actual IBM Guadalupe quantum computer (or some other IBM quantum computer) 12-qubit circuits similar to those we simulated on the “Fake Guadalupe” simulator can lead to samples of fair quality or even to quality similar to the simulations. We note that recently, IBM changed their policy making it harder for researchers (and students) to experiment on their quantum computers.

The situation is not clear to me: on the one hand it looks that IBM is more advanced than other companies. For example, IBM is the only company having a high quality fabrication facility for quantum computers and people I talked to think that this makes a notable difference for higher quality quantum computers. On the other hand, it seems to me that IBM did not (and perhaps cannot) present  a 12-qubit random circuit with a good quality.

If any reader has some more information on running random circuits on IBM quantum computers (or other quantum computers) we will be happy to learn about them.

Coefficient of variation

Here is one more technical detail regarding the Google experimental data and Google’s simulations. Recall that the coefficient of variation (CV) is the standard deviation divided by the average. It is a standardized measure of dispersion of a probability distribution. Another interesting finding from our paper is that the CV  of the estimated parameters s,q for the Google experimental data is smaller than that of the Google Weber QVM simulator. Indeed, if we compare the coefficient of variation over different circuits for the estimated values of s,q between the models RNM and WNM we can expect larger values for WNM because of the dependence on the individual circuits. But, on the other hand, the Google experimental data differs substantially from both GNM and RNM and the coefficient of variation for measurements from experimental data tends, in general, to be larger compared to simulations.

We wrote three earlier papers. Here are links to all four:

  1. Y. Rinott, T. Shoham, and G. Kalai, Statistical Aspects of the Quantum Supremacy Demonstration, Statistical Science  (2022)
  2. G. Kalai, Y. Rinott and T. Shoham, Google’s 2019 “Quantum Supremacy” Claims: Data, Documentation, & Discussion  (see this post).
  3. G. Kalai, Y. Rinott and T. Shoham, Questions and Concerns About Google’s Quantum Supremacy Claim (see this post).
  4. G. Kalai, Y. Rinott and T. Shoham, Random circuit sampling: Fourier expansion and statistics. (this post)

Microsoft and Quantinuum logical qubits (update)

Microsoft and Quantinuum announced logical qubits that are 800 times better than the corresponding physical qubits! For the paper see here; for the announcements see here and here; for an enthusiastic yet cautious blog post over Shtetl optimized see here; for a praising yet more cautious comment by Craig Gidney see here, for a reply by Krysta Svore from Microsoft see here.

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Plans and Updates: Complementary Pictures

Jerusalem October 4, 2023

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The picture on the right is from ~ 60 years ago.

Tel Aviv, five sunsets and a horse

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Updates and Plans IV

red-flowers

A carpet of flowers in Shokeda, near Gaza, a few years ago.

This is the fourth post of this type (I (2008); II(2011); III(2015).) I started planning this post in 2019 but as it turned out, earlier drafts have quickly became obsolete and the process of writing this post did not converge.

Updates

Current academic life around here

In an earlier post I wrote about the hectic academic scene around here last spring. These were post-corona times, we had many visitors, workshops, conferences, and other activities. Since October 7, things are different also on the academic side of my life: only few visitors have come to Israel and I find myself talking much more than before with Israeli colleagues about a variety of academic matters and I also try to make progress on some old projects. A special personal goal is to transfer people who are mentioned on my homepage as “frequent collaborators” to the status of “coauthors”.

Jerusalem and Tel Aviv,  HUJI  and RUNI

Five years ago we sold our apartment in Jerusalem and bought and renovated an apartment in Tel Aviv in a neighborhood called “Kohav hatzafon” (The star of the north). Our apartment is very close to the Yarkon river and quite close to the beach. It is also rather close to where our three children and three grandchildren live.

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The view from my home

As of October 2018 I am a Professor Emeritus at the Hebrew University of Jerusalem and I am a (half-time) Professor of Computer Science at the Reichman University (RUNI), formally known as the Herzelia Interdisciplinary Center (IDC).  Essentially I split my activity between HUJI and RUNI. The Hebrew University and the area of mathematics are still homes for me, and I enjoy also my new hat as an RUNI-IDC faculty member in the very lovely Effi Arazi Computer Science school at Reichman University.

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A beautiful group photo, the Efi Arazi School of Computer Science

This is not the first time I am a member of a computer science department. In 1990/1991 I visited the (CS) theory  group at IBM, Almaden.  I had the repeated thought that if only I could learn C++ and master it I will be able to make important contributions in practical aspects of computation!  Logically, I was correct, since I did not learn C++.  (Since then I reach a stage that I can slightly modify programs written by others in C++ and Python.) Next, I was affiliated for 5 years with the CS department at Yale (like Laci Lovasz and Ravi Kannan) before moving to Mathematics at Yale.

NYC visit fall 2022.

This was the first time since 1991 that we spent a prolonged period together abroad. Spending a semester at NYC was a long-time dream for Mazi and me and we had a great time. We are deeply thankful to the one and only Oded Regev who wonderfully hosted me at the Courant Institute. We also used this opportunity to make short visits to Chicago, Washington DC, Princeton,  Rutgers, and Warren NJ.

A project with Dor, Noam and Tammy

Dor Minzer was visiting me during fall 2023 and Dor, Noam Lifshitz, Tamar Ziegler and me had a very nice project leading to the paper  A dense model theorem for the Boolean slice. (And we have another project in progress.)

In our paper “we show that for every k \in \mathbb N, the normalized indicator function of the middle slice of the Boolean hypercube $latex {0,1}^{2n}$  is close in Gowers norm to the normalized indicator function of the union of all slices with weight $latex t=n(mod2^{k1})$. Using our techniques we also give a more general `low degree test’ and a biased rank theorem for the slice.” (A quote from the abstract.) As we recently learned, the case of linearity testing was proved independently by our friends Irit Dinur and Avishay Tal.

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The following picture shows an analogy between integers and the Boolean cube, between primes and the middle slice of the Boolean cube, and between the papers I mentioned and two famous papers of  early 2000.

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A project with Micha, Moshe and Moria

Moria Sigron, Moshe White, Micha A. Perles and I are involved in a project of studying fine notions of order types (see this post and this lecture). Our purpose is to define and study a finer notion of order type for configurations of n points in $ latex \mathbb R^d$. This project is strongly motivated and influenced by the paper of Perles and Sigron “Strong general position” and by Barany’s recent paper on Tverberg’s theorem. Our fine order type relates to Tverberg’s theorem and strong general position, much in the same way that the (regular) order type relates to Radon’s theorem and general position.

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An Interview with Toufik Mansour

Toufik Mansour interviewed me for the interview section of the journal “Enumerative Combinatorics and Applications” that Toufik founded..

Toufik: You have been managing a wonderful blog, “Combinatorics and more”, since 2008 and publish very interesting notes there. What was your motivation for it?

Me: Thank you! I think a main motivation was that I like to write about works of other people. I was also encouraged by several people that are mentioned in the “about” page, and wanted to experience collective mathematical discussions.

In a sense it is Aesop’s litigious cat fable in reverse. In Aesop’s story, a monkey helps two cats divide a piece of cheese by repeatedly eating from the larger piece. In my case, I think that I need to balance my blog and to do justice to areas/problems/people I have not mentioned yet, and the more I write the more I feel that work is still required to make the blog’s coverage (within subareas of combinatorics that I have some familiarity with) sufficiently complete, just, and balanced.

A potential new direction

Click here

Non-academic life around here

After January 2023 and before the war I tried to get involved in detailed dialogues with people with different views and especially with people who hold opposite views to mine about the political situation and the controversial judicial reforms. I have a personal preference for technical discussions over exchange of ribbing but it is not easy to find partners for calm detailed discussions.

Israel Journal of Mathematics: Nati’s birthday volume

Volume 256 of the Israel Journal of Mathematics is dedicated to Nati Linial on the occasion of his 70th birthday. Great papers, great personal dedications, and its all open access (Issue 1, Issue2). Rom Pinchasi’s paper deals with the odd area of the unit discs: Consider a configuration \cal F of  odd number of unit discs in the plane. The odd area OA({\cal F}) of the configuration is the area of all the points that are covered by an odd number of discs. The odd area conjecture asserts that

\displaystyle OA({\cal F}) \ge \pi.

Some mathematical news

Traditionally, I start with some mathematical news. Indeed I  had quite a list, but as this post did not progress, over the years,  all the items found their way to regular posts in my blog and sometimes in other blogs. New items arrived and here is a large yet incomplete list.

1) The Daisy conjecture was refuted: David Ellis, Maria-Romina Ivan, and Imre Leader, disproved the Daisy conjecture.

2) Toward the dying percolation conjecture: Gady Kozma and Shahaf Nitzan showed a derivation of the dying percolation conjecture from a proposed conjecture about percolation for general graphs.

3) First passage percolation: Barbara Dembin, Dor Elboim, and Ron Peled settled a problem raised by Itai Benjamini, Oded Schramm and me about first passage percolation. The paper is On the influence of edges in first-passage percolation on Z^d, and the planar case was proved in an earlier paper of Barbara, Dor, and Ron.

4) Around the Borsuk problem: Gyivan Lopez-Campos, Deborah Oliveros, Jorge L. Ramírez Alfonsín wrote about Borsuk’s problem in space and Reuleaux polyhedra. (On the arXiv there are quite a few interesting papers on Releaux polyhedra, Ball polyhedra and Meissner polyhedra.) Andrei M. Raigorodskii and Arsenii Sagdeev wrote a note on Borsuk’s problem in Minkowski spaces.

5) Around the flag conjecture and 3^d conjecture: Dmitry Faifman, Constantin Vernicos, and Cormac Walsh proposed an interesting conjecture that interpolates between Mahler’s conjecture and my flag conjecture. There are several interesting papers about the 3^d conjecture by Gregory R. Chambers and Elia Portnoy and by Raman Sanyal and Martin Winter. (We discussed the 3^d problem, the flag conjecture and the related Mahler conjecture in this post.) 

6) Around Helly’s theorem: Nati Linial told me about Nóra Frankl, Attila Jung, and István Tomon’s paper about a quantitative fractional Helly theorem;  Minki Kim and  Alan Lew gave Extensions of the Colorful Helly Theorem for d-collapsible and d-Leray complexes, which contain also an interesting Tverberg-type theorem. Natan Rubin made a dramatic progress on point selections and halving hyperplanes.

7) Around the Kelly-Meka breakthrough. We wrote about the Kelly-Meka bounds for Roth’s theorem in this post. Zander Kelley, Shachar Lovett, and Raghu Meka, applied some techniques from that paper for showing Explicit separations between randomized and deterministic Number-on-Forehead communication, and together with Amir Abboud and Nick Fischer, for New Graph Decompositions and Combinatorial Boolean Matrix Multiplication Algorithms. I heard a lecture of Shachar Lovett about these breakthroughs and some further hopes. Yuval Filmus, Hamed Hatami, Kaave Hosseini, and Esty Kelman gave A generalization of the Kelley–Meka theorem to binary systems of linear forms, and Thomas F. Bloom, and Olof Sisask gave An improvement to the Kelley-Meka bounds on three-term arithmetic progressions.

8) Spectral graph theory. Matthew Kwan and Yuval Wigderson proved that  The inertia bound is far from tight (and I heard Yuval giving a beautiful lecture about it.)

9) Hypercontractivity and groups. Equiped with a whole array of global hypercontractivity inequalities (see this post and this one) problems in group theory and their representations are becoming targets.  Here are four papers in this direction:  David Ellis, Guy Kindler, Noam Lifshitz, Dor Minzer,  Product Mixing in Compact Lie Groups; Nathan Keller, Noam Lifshitz, Ohad Sheinfeld, Improved covering results for conjugacy classes of symmetric groups via hypercontractivity; Peter Keevash, Noam Lifshitz, Sharp hypercontractivity for symmetric groups and its applications; Noam Lifshitz, Avichai Marmor Bounds for Characters of the Symmetric Group: A Hypercontractive Approach.

10) Hodge theory and combinatorics.  Semyon Alesker told me about the paper of Andreas Bernig, Jan Kotrbatý, and Thomas Wannerer, Hard Lefschetz theorem and Hodge-Riemann relations for convex valuations.   There are many interesting other developments on Hodge theory and combinatorics for metric, arithmetic, and combinatorial study of polytopes and convex sets.

11) AP with restricted difference and the theory of computing.  Amey Bhangale, Subhash Khot, and  Dor Minzer are involved in a long term project primarily addressing important problems in theoretic computer science with important applications to additive combinatorics. Here is one of their papers in the additive combinatorics direction: Effective Bounds for Restricted 3-Arithmetic Progressions in \mathbb F^n_p.

The theme of bounds for Roth-type questions for  the existence of restricted AP is quite important in additive combinatorics: A recent paper is Roth’s theorem with shifted square common difference by Sarah Peluse, Ashwin Sah, Mehtaab Sawhney. 

12) Thresholds. Following the Park-Pham proof of the expectation threshold conjecture (that I and Jeff Kahn reluctantly made), and the earlier Frankston-Kahn-Narayanan-Park proof of a weaker fractional version, there were quite a few subsequent papers in various directions and I will mention only few of them. Short proofs were offered by P. Tran, V. Vu and by Bryan Park and Jan Vondrák and  (for more general product measures). Elchanan Mossel, Jonathan Niles-Weed, Nike Sun, and Ilias Zadik’s paper  On the Second Kahn–Kalai Conjecture proves a weaker version of a second conjecture from our paper for graphs. (Both the main conjecture and the second conjecture looked at the time “too good to be true.” We had, however, stronger confidence in a third conjecture that would derive the second conjecture from the first. This third conjecture turned out to be false 🙂 .)

Ashwin Sah, Mehtaab Sawhney, and Michael Simkin found the Threshold for Steiner triple systems. Michael gave a talk at HUJI about this paper and explained to me also how the expectation threshold theorem can lead to exact results even in cases where the gap between the expectation threshold and the threshold is smaller than \log n.  Let me mention three more papers: Huy Tuan Pham, Ashwin Sah, Mehtaab Sawhney, and Michael Simkin wrote A Toolkit for Robust Thresholds; Searching for (sharp) thresholds in random structures: where are we now? by Will Perkins, and Threshold phenomena for random discrete structures  by Jinyoung Park.

In a different direction Eyal Lubetzky and Yuval Peled estimated The threshold for stacked triangulations. This paper is related to the Linial-Meshulam model for random simplicial complexes, to bootstrap percolation, and to algebraic shifting.

13) Achieving Shannon capacity.  A proof that Reed-Muller codes achieve Shannon capacity on symmetric channels, by Emmanuel Abbe and Colin Sandon. In my previous “update and plans” I wrote about  remarkable proofs (using sharp threshold results) that Reed-Muller Codes Achieve Capacity on Erasure Channels. The new paper by Emmanuel and Colin shows that this is also the case for symmetric channels. The proof uses a terrific combination of combinatorial and analytical tools and novel ideas that are of much interest on their own.

14) Envy free partitions. Amos Fiat and Michal Feldman told me about a great problem, but, on second thought, it fits very nicely with the “test your intuition” corner.

15) Reconstructing shellable spheres from their puzzles. Blind and Mani proved that simple polytopes are determined by their graphs. I gave a simple proof that applies (in the dual form) to a  subclass of shellable spheres. (see this post). It is an open conjecture that simplicial spheres are determined by their “puzzle” (namely the incidence graph of facets and subfacets). The case of shellable spheres has now been proved by Yirong Yang in the paper Reconstructing a Shellable Sphere from its Facet-Ridge Graph.

16) Around the (generalized) Hardy-Littlewood conjecture and inverse Gowers theorem. A great mathematical achievement of the last decades was the proof by Ben Green, Terry Tao and Tamar Ziegler of the (generalized) Hardy-Littlewood conjecture on the asymptotic number of solutions to equations over the primes when the number of variables is larger than the number of equations by two or more. (Arithmetic progressions of length k is an important special case.) This theorem required a proof of the inverse theorem for Gowers norms. In recent years better and better quantitative versions of the inverse Gowers theorem were found by Manners, and recently James Leng, Ashwin Sah, and Mehtaab Sawhney gave  almost polynomial bounds in Quasipolynomial bounds on the inverse theorem for the Gowers $latex U^{s+1}[N]$-norm. This paper is related to another paper by the same authors with improved bounds for Szemeredi’s theorem, and to an earlier paper by Leng Efficient Equidistribution of Nilsequences.

Regarding additive combinatorics let me also mention three survey articles about the utility of looking at toy versions over finite fields of problems in additive combinatorics. In some cases you can transfer the methods from the finite field case to the integer case. For some methods this is not known. It is a lovely question if there are ways to transfer results from the finite field case to the case of integers. The survey article are by Ben Green from 2005, by Julia Wolf from 2015  and by Sarah Peluse from 2023.

17) Ramanujan graphs. Ryan O’Donnell and coauthors wrote several exciting papers about Ramanujan graphs. Explicit near-fully X-Ramanujan graphs by  Ryan O’Donnell and Xinyu Wu; Explicit near-Ramanujan graphs of every degree, by Sidhanth Mohanty, Ryan O’Donnell, Pedro Paredes; and Ramanujan Graphs, by  Sidhanth Mohanty and Ryan O’Donnell.

Plans

Traditionally I write here about my plans for the blog. I plan to tell you more over my blog about my own mathematical projects and papers and perhaps also about half-baked ideas.  I plan to write, at last,  something  about cryptography, to explain Micha Sageev’s construction (as promised here), and to revisit a decade old MO question (related to a lot of interesting things).

My own research directions

Let me briefly share with you what I think about mathematically. One topic in my research is about  analysis of Boolean (and other) functions, discrete Fourier analysis, sensitivity and stability of noise, and related matters. This study has applications within combinatorics and mathematics and also to theoretical computer science, social choice theory and to quantum computing which, in the last two decades, has become a central area of my interest. Another topic that I study is geometric, topological and algebraic combinatorics. I study especially convex polytopes and related cellular objects and Helly-type theorems. This topic is related to linear programming and other areas of theoretical computer science. Pursing mathematical fantasies of various kind (what Miklos Simonovits called “Sunday’s afternoon mathematics”) is also a favorite activity of mine, which is one reason I liked polymath projects while they lasted.

Programming

One of my personal plans is to learn (again, I learned FORTRAN in my teens) to program, and to actually program from time to time. Some of my mathematical friends who are fluent at programming like Sergiu Hart, Dan Romik,  (and, of course, Doron Zielberger) do use programming in their research. (In the case of Doron, perhaps Shalosh B. Ekhad uses Doron for her research.) Another of my mathematical heroes, Boris Tsirelson,  told me once that he liked programming a lot and it was never a clear call for him if he likes proving theorems and developing mathematical theories more than writing codes. I know that ChatGPT and alike can now program for me, and I think that this will make re-learning programming and actually using programming for research easier.

A planned Kazhdan’s seminar on hypercontractivity.

In 2003/2004 David Kazhdan and I ran a seminar on polytopes, toric varieties, and related combinatorics and algebra, and it was centered around a theorem of Kalle Karu. My plan was to have such a seminar every decade and the next one (with Leonid Polterovich, Dorit Aharonov, and Guy Kindler) was in 2019 about computation, quantumness, symplectic geometry, and information. (Life events caused it to be delayed by a few years.) I also participated also in Karim Adiprasito’s Kazhdan seminar on “positivity in combinatorics and beyond” where he presented his proof of the g-conjecture. We now have a plan to run a Kazhdan seminar in 2025/2026 on hypercontractivity together with Noam Lifshitz and Guy Kindler and perhaps others.

Posted in Combinatorics, Computer Science and Optimization, Geometry, People, personal, Updates | Tagged , | 1 Comment

Three Remarkable Quantum Events at the Simons Institute for the Theory of Computing in Berkeley

2020-2025d

In the picture (compare it to this picture in this  post) you can see David DiVincenzo’s famous 7-steps road map (from 2000) to quantum computers, with one additional step “quantum supremacy on NISQ computers” that has proposed around 2010. Step 4 of logical memory with a substantial longer lifetime than physical qubits has not yet been achieved (Craig Gidney expects it in five years); However, Dolev Bluvstein et al.’s paper makes a bold move toward higher steps in DiVincenzo’s plan and toward some kind of quantum fault tolerance even before reaching very stable logical qubits.

I would like to report on three remarkable quantum computing events at the Berkeley Simons Institute. Two events are future events. In a few hours, Oded Regev will talk about his new (now famous, see here and here ) quantum algorithm for factoring. On Monday March 25 there will be a workshop in honor of Michael Ben-Or. Update: Here is the link to Oded Regev videptaped lecture; Here is the link (livestreaming and recording) to the lectures of the Michael Ben-Or workshop. Here is my toast to Michael.

simons

The event that already took place is a lecture by Dolev Bluvstein. The lecture described a remarkable recent work that draws much attention in the quantum computing community and gives hope for further experimental breakthroughs. In fact, Michael Ben-Or told me about the lecture, and I also read about the paper in Scott’s blog. Scott did a good job of mentioning various concerns and limitations of the work and at the same time expressed (in his characteristic style) hope that this progress will eventually make it harder to justify quantum computer skepticism; be that as it may be, let me take off my skeptical hat for this post and tell you what I learned from Dolev. A few days after the lecture Dolev and I had a zoom discussion where Dolev clarified some matters for me and told me a lot of interesting things.

The neutral atom approach dates back to early proposals and experiments in optical lattices, and in particular the theoretical work of Rydberg blockade led by Misha Lukin, Peter Zoller, and Ignacio Cirac. It is different from ion-trapped quantum computing and from superconducting quantum computing; (Among these two it is perhaps closer to ion-trapped QC).

Dolev explained how prior to the very recent paper described in the talk there were earlier breakthrough papers. Over the years these ideas were explored, among others,  by Antoine Browaeys, Mark Saffman, and Harvard / MIT team, led by Lukin, Vladan Vuletic and Markus Greiner. Several years ago, analog processing with neutral atom arrays began to show great promise. For example, a 2017 U.S.-Russia Harvard based 51 qubit experiment by Bernien et al. (At the time, I reported about this paper in this post.) Increasing the fidelity of 2-gates from 80% or so to 97.5+%and very recently 99.5%and building useful programmable devices brought neutral atoms (at least on some fronts) to the big-league of quantum computing methods.

Dolev started his lecture with the following statement:

Fighting decoherence is the central challenge in large scale quantum computation. Quantum error correction is the only known realistic route to suppress gate errors to the required levels for useful algorithms  {\bf (10^{-3}\to 10^{-10})}.

Here is what was achieved in the very recent paper (as far as I understand)

  1. They created a large variety of quantum error-correcting codes including surface code, color code, and certain high-dimensional codes.
  2. To check that the state they created is indeed what they aimed for, they measured the state against a large number of product states.
  3. Using these coded qubits, they created a variety of logical states such as GHZ state (with 4 logical qubits)  and IQP state.
  4. For this purpose  they developed a method  of parallel control: applying simultaneously 1-qubit logical state or 2-qubit logical state for all the corresponding physical qubits.
  5. Once a logical state was created they measured it and (repeating the process) obtained a large sample of bitstrings corresponding to the measurements of physical qubits.
  6. At this point the following steps used (classical) computation on the samples. Each “physical” sample represents a “logical sample”.
  7.  Removing bitstrings that had “many” errors leads to higher quality (yet smaller) samples for the logical state. (for the IQP circuits they do “error detection” or postselection as the codes are distance 2, but for the other circuits they do error correction without relying on postselection).
  8. (Normalized) XEB (linear cross-entropy) is used as a measure of quality. For noiseless IQP states XEB=2.

Dolev responded to a question asked in his lecture that I also repeated whether their “transversal gates” globally acting on several pairs of physical qubits would not yield correlated errors: No, Dolev explained, globally acting on many physical qubits (to apply a logical 1-gate) or on many pairs of physical qubits (which form a logical 2-gate) does not lead to correlated errors. The laser just indicates on which qubits (or pairs) we need to apply a gate but the action of the gates themselves are statistically independent.

Besides that, Dolev briefly told me about various interesting things. He explained the Yale group approach to error correction and hailed them for making many of the innovations for superconducting quantum computing that we see today, he mentioned ion-trapped quantum computers and the different approaches of  Ion-Q and Quantinuum, he mentioned some other quantum error correcting experiments, including the recent Google experiment, and various other things.

Another thing that I learned is that (as I suspected) Dolev is an Israeli name and indeed Dolev (joined by his family) moved from Israel to California at the age of four.

Here are links to some relevant papers:

a) This is the paper Dolev talked about

Bluvstein, D., Evered, S.J., Geim, A.A. et al. Logical quantum processor based on reconfigurable atom arrays. Nature 626, 58–65 (2024).

b) Here are two papers (that appeared back to back) one from the Lukin Group and one from the Saffman group on recent successful neural atoms quantum computers.

Bluvstein, D., Levine, H., Semeghini, G. et al. A quantum processor based on coherent transport of entangled atom arraysNature 604, 451–456 (2022).

Graham, T.M., Song, Y., Scott, J. et al. Multi-qubit entanglement and algorithms on a neutral-atom quantum computer. Nature 604, 457–462 (2022).

Dolev mentioned some earlier breakthroughs for 2-gate fidelities for neutral atom qubits and especially the work of Harry Levine.

A few additional comments, some with a bit of skeptical flavor:

  1. In my view the community of quantum computing should carefully scrutinize experimental claims and especially claims of substantial progress. Of course, the primary responsibility of scrutinizing scientific claims lies at the hands of the researchers themselves, and it is also the responsibility of the researchers to document the experiment and to give the community access to the raw data.
  2. Over SO Craig Gidney made the following thoughtful comment (December 8th, 2023 at 12:58 pm) regarding how close we are to logical qubits of a substantially higher quality than physical qubits:

    “With respect to the question of “who showed/will-show the first logical>physical advantage”… I’ve surveyed the QEC experiment papers over the past two decades. Something that caught me off guard was how every single one of them, even the old NMR ones, managed to find some way to claim logical > physical. Doing single rounds instead of multiple rounds, doing rep codes instead of quantum codes, using detection instead of correction, postselecting out effects like leakage… there’s lots of ways to scale the difficulty to your current experimental capabilities.IMO, if you focus on the benchmarks that actually matter, then 5 years ago the field was obviously physical>logical. Currently the field is arguably physical ~= logical. And within 5 years I expect the field to be obviously logical>physical across multiple architectures.”

  3. My “argument against quantum computers” asserts that logical qubits and gates of a substantially higher quality than (current) physical qubits and gates are inherently infeasible.
  4. We had an earlier post over here about an interesting (theoretical) paper by Gao et al. from the Lukin group. 
  5. There were several interesting questions and comments during Dolev’s lecture and later during the panel discussion with a lot of prominent quantum computer researchers present in the audience. The entire event was terrific.

Update (29/3): A Quanta Magazine article by Philip Ball.  It mentions another pioneering paper by Ivan Deutsch. For a more complete picture of the history, see Ivan Deutsch’s comment that mentions the 1999 paper by Gavin K. Brennen, Carlton M. Caves, Poul S. Jessen, and Ivan H. Deutsch, and the follow up 2000 paper by D. Jaksch, J. I. Cirac, P. Zoller, S. L. Rolston, R. Côté, and M. D. Lukin.

Posted in Computer Science and Optimization, Physics, Quantum | Tagged , , | 4 Comments

Yair Shenfeld and Ramon van Handel Settled (for polytopes) the Equality Cases For The Alexandrov-Fenchel Inequalities

Two weeks ago, I participated (remotely) in the discrete geometry Oberwolfach meeting, and Ramon van Handel gave a beautiful lecture about the equality cases of Alexandrov-Fenchel inequalities which is among the most famous problems in convex geometry.

afi9

In the top left, Ramon explains the AF-inequality and its equality cases for three dimensions. The extremal bodies, also depicted in the top right, remind me of “stacked polytopes.” On the bottom right, you can see the AF-inequality, with the definition of mixed volumes above it. In the bottom left, there’s a discussion on equality cases and why they are challenging.

Following Ramon’s lecture, Igor Pak gave a presentation demonstrating that detecting cases of equality for the Alexandrov-Fenchel inequality is computationally hard. (If it is in the polynomial hierarchy then the hierarchy collapses.) Igor’s blog post (reblogged here) eloquently delves into this issue.

Here is some background. Given convex bodies K_1,K_2,\dots,K_n in \mathbb R^n, the volume of the Minkowski sum t_1K_1+t_2K_2+\cdots +t_nK_n  where t_1,t_2,\dots,t_n\ge 0  is a polynomial in t_1,t_2,\dots, t_n. The mixed volume V(K_1,K_2,\dots,K_n) is defined as the coefficient of the mixed term of this polynomial. 

The Alexanderov-Fenchel inequality asserts that

\displaystyle V(K_1,K_2,\dots,K_n)^2 \ge V(K_1,K_1,K_3,\dots,K_n)V(K_2,K_2,K_3,\dots ,K_n)

And some overview: There exist intricate connections between three areas of convexity. The first concerns metric theory, particularly the study of valuations and the “Brunn-Minkowski” theory. The second involves arithmetic theory, specifically the “Eberhard theory” of counting integer points in dilations of integral polytopes. The third revolves around the combinatorial theory of faces, particularly the study of f-vectors. All these areas are related to algebraic geometry and commutative algebra, particularly to “Hodge theory.”

Here are links to the relevant papers:

Yair Shenfeld and Ramon van Handel, The Extremals of the Alexandrov-Fenchel Inequality for Convex Polytopes.

Abstract: The Alexandrov-Fenchel inequality, a far-reaching generalization of the classical isoperimetric inequality to arbitrary mixed volumes, lies at the heart of convex geometry. The characterization of its extremal bodies is a long-standing open problem that dates back to Alexandrov’s original 1937 paper. The known extremals already form a very rich family, and even the fundamental conjectures on their general structure, due to Schneider, are incomplete. In this paper, we completely settle the extremals of the Alexandrov-Fenchel inequality for convex polytopes. In particular, we show that the extremals arise from the combination of three distinct mechanisms: translation, support, and dimensionality. The characterization of these mechanisms requires the development of a diverse range of techniques that shed new light on the geometry of mixed volumes of nonsmooth convex bodies. Our main result extends further beyond polytopes in a number of ways, including to the setting of quermassintegrals of arbitrary convex bodies. As an application of our main result, we settle a question of Stanley on the extremal behavior of certain log-concave sequences that arise in the combinatorics of partially ordered sets.

Comments: I recall Rolf Schneider presenting (at Oberwolfach in the 1980s) his extensive class of examples for equality cases in A-F inequalities and formulating various conjectures about them. I also remember the relations discovered by Bernard Teissier and Askold Khovanskii between A-F inequalities and algebraic geometry. This connection is discussed in the last section of the paper.

Yair Shenfeld and Ramon van Handel, The Extremals of Minkowski’s Quadratic Inequality

Abstract: In a seminal paper “Volumen und Oberfläche” (1903), Minkowski introduced the basic notion of mixed volumes and the corresponding inequalities that lie at the heart of convex geometry. The fundamental importance of characterizing the extremals of these inequalities was already emphasized by Minkowski himself, but has to date only been resolved in special cases. In this paper, we completely settle the extremals of Minkowski’s quadratic inequality, confirming a conjecture of R. Schneider. Our proof is based on the representation of mixed volumes of arbitrary convex bodies as Dirichlet forms associated to certain highly degenerate elliptic operators. A key ingredient of the proof is a quantitative rigidity property associated to these operators.

Comment: For this special case of the A-F inequality Shenfeld and van Handel gave a complete characterization of the extremal cases. A special case of this special case asserts that 

S^2(K) \ge W(K)V(K) 

where V(K),S(K),W(K) are the volume, surface area, and mean width of K, respectively. 

Swee Hong Chan and Igor Pak, Equality cases of the Alexandrov–Fenchel inequality are not in the polynomial hierarchy

Abstract: Describing the equality conditions of the Alexandrov–Fenchel inequality has been a major open problem for decades. We prove that in the case of convex polytopes, this description is not in the polynomial hierarchy unless the polynomial hierarchy collapses to a finite level. This is the first hardness result for the problem, and is a complexity counterpart of the recent result by Shenfeld and van Handel (arXiv:archive/201104059), which gave a geometric characterization of the equality conditions. The proof involves Stanley’s order polytopes and employs poset theoretic technology.

Igor Pak’s blog post elaborate on this paper.

Three more (among quite a few)  relevant papers: 

Yair Shenfeld and Ramon van Handel, Mixed volumes and the Bochner method; D. Cordero-Erausquin, B. Klartag, Q. Merigot, F. Santambrogio, One more proof of the Alexandrov-Fenchel inequality ; Ramon van Handel,  Shephard’s inequalities, Hodge-Riemann relations, and a conjecture of Fedotov.

Posted in Combinatorics, Convexity, Geometry | Tagged , , , , | 2 Comments

On the Limit of the Linear Programming Bound for Codes and Packing

Samorodnitsky

Alex Samorodnitsky

The most powerful general method for proving upper bounds for the size of error correcting codes and of spherical codes (and sphere packing) is the linear programming method that goes back to Philippe Delsarte. There are very interesting results and questions about the power of this method and in this post I would like to present a few of them, especially results from 2001 and 2004 papers by Alex Samorodnitsky, a 2001 paper by Alexander Barg and David Jaffe, and a 2009 paper by Alex and Michael Navon. Finally I will very briefly mention three recent papers on the limitations of the linear programming method for sphere packings (for dimension \le 32) by  Cohn and Triantafillou, Li, and de Courcy-Ireland,  Dostert, and  Viazovska. I will also mention some other related papers. Two recent posts over here on sphere packing are this post and this post.

Recall that the rate R(C) of a binary code C of length n is defined as \displaystyle \frac {\log |C|}{n}. Let us start with the following central questions:

Question 1: For a real number \alpha, 0 < \alpha < 1/2, what is (asymptotically) the maximum rate f(\alpha) of a binary error-correcting binary code of length n and minimum distance $d=\alpha n$?

Question 2: For a real number \theta < \pi/2 and a spherical d-dimensional code C with minimal distance \theta. What is the maximum value of \displaystyle \frac {\log |C|}{d} as d goes to infinity?

The best known bound upper bound for Question 1 is the McEliece, Rodemich, Rumsey
and Welch (MRRW) bound; The best known upper bound for Question 2 is the Kobatyanski-Levenshtein (KL) bound.

Of course, questions 1 and 2 are important asymptotic special cases of even more general questions regarding upper bounds for the sizes of binary and spherical codes.

We will mainly discuss in this post the following two problems.

Question 3: For a real number \alpha, 0 < \alpha < 1/2, what is (asymptotically) the best upper bound B(\alpha) for  f(\alpha) that follows from Delsarte’s linear program.

Question 4: For a real number \theta <\pi/2, what is (asymptotically) the best upper bound B(\theta) for  f(\theta) that follows from Delsarte’s linear program.

We start with the following paper:

On the optimum of Delsarte’s linear program, A. Samorodnitsky, Journal of Combinatorial Theory, Ser. A, 96, 2, 2001

Abstract: We are interested in the maximal size A(n, d) of a binary error-correcting code of length n and distance d, or, alternatively, in the best packing of balls of radius (d-1)/2 in the n-dimensional Hamming space. The best known lower bound on A(n, d) is due to Gilbert and Varshamov, and is obtained by a covering argument. The best known upper bound is due to McEliece, Rodemich, Rumsey and Welch, and is obtained using Delsarte’s linear programming approach. It is not known, whether this is the best possible bound one can obtain from Delsarte’s linear program. We show that the optimal upper bound obtainable from Delsarte’s linear program will strictly exceed the Gilbert-Varshamov lower bound. In fact, it will be at least as big as the average of the Gilbert-Varshamov bound and the McEliece, Rodemich, Rumsey and Welch upper bound. Similar results hold for constant weight binary codes. The average of the Gilbert-Varshamov bound and the McEliece, Rodemich, Rumsey and Welch upper bound might be the true value of Delsarte’s bound. We provide some evidence for this conjecture

For 0 \le \alpha \le 1 let H(\alpha) denote the entropy function.   

Samorodnitsky Theorem (2001):  B(\delta) \ge (H(1/2 - \sqrt{\delta(1-\delta)}) + (1-H(\delta))/2.

I remember that I was (around 1998) completely fascinated by Alex’s result. This was still in the BB era (before blog) so I did not write about it. As we will see, Alex himself improved the result and thus refuted the conjecture at the end of the abstract. Motivated by Alex’s paper, Alexander Barg and David Jaffe conducted numerical experiments for n=1000. In their paper  Numerical results on the asymptotic rate of binary codes, they wrote: “the most important conclusion is that Delsarte’s linear programming method is unlikely to yield major improvements of the known general upper bounds on the size of codes,” leading to the following conjectures:

Conjecture 6 (supported by numerical computation by Barg and Jaffe): Asymptotically, the MRRW bounds  are the best that can be derived from Delsarte’s linear programming.

Conjecture 7 (by analogy): For spherical codes, asymptotically, the KL bounds are the best that can be derived from the linear programming method.

I find Conjectures 6 and 7 very fascinating and yet perhaps not hopeless.

We note that MRRW themselves (naturally) conjectured that Delsarte’s LP can lead to better bounds than their bounds.

In 2004 Alex proved an analogous result for his result about binary codes to the case of spherical codes. (The paper also studies spherical designs.) The best known upper bounds by Grigory Kabatiansky and Vladimir Levenshtein are based on Delsarte’s LP. The best known lower bounds are achieved by greedy spherical codes (or random spherical codes) and only slight improvements for them are known. (See this post; these small improvements have no bearing on the rate.) 

On linear programming bounds for spherical codes and designs, A. Samorodnitsky, Discrete and Computational Geometry, 31, 3, 2004.

Abstract: We investigate universal bounds on spherical codes and spherical designs that could be obtained using Delsarte’s linear programming methods. We give a lower estimate for the LP upper bound on codes, and an upper estimate for the LP lower bound on designs. Specifically, when the distance of the code is fixed and the dimension goes to infinity, the LP upper bound on codes is at least as large as the average of the best known upper and lower bounds. When the dimension n of the design is fixed, and the strength k goes to infinity, the LP bound on designs turns out, in conjunction with known lower bounds, to be proportional to k^{n-1}

The next paper I want to discuss is Linear programming bounds for codes via a covering argument, M. Navon, A. Samorodnitsky, Discrete and Computational Geometry, 41, 2, 2009.

This paper contains results in various directions, but related to the topic of our post it improves Alex 2001 bound about the limitation of Delsarte’s LP:

Navon and Samorodnitsky Theorem (2009):

B(\delta) \ge 1/2 H(1 - 2\sqrt{\delta(1-\delta)}).

This gives better bounds for large values of \delta and is the current world record for B(\delta).

Let me mention three recent papers about the limitations of  Cohn-Elkies’ linear program for sphere packing. The first is: Henry Cohn, Nicholas Triantafillou, Dual linear programming bounds for sphere packing via modular forms, the second is by Rupert Li, Dual Linear Programming Bounds for Sphere Packing via Discrete Reductions, and the third is by  Matthew de Courcy-Ireland, Maria Dostert, and Maryna Viazovska, Six-dimensional sphere packing and linear programming.

Some comments:

1) MRRW1 and MRRW2. MRRW beautifully derived their bound (H(1/2 - \sqrt{\delta(1-\delta)}) (referred to as MRRW1) from the LP programs, went on to apply Delsarte’s linear program  for constant weight codes and obtained similar upper bounds for them. Then they used these bounds to improve MRRW1 to stronger bounds (referred to as MRRW2) for some values of \delta. As it recently turned out  MRRW2 could also be derived directly from Delsarte’s LP for the Hamming cube.

2) The Fourier connections. There is a nice way to get the Delsarte’s linear programming by Fourier analysis of Boolean functions. This is explained in a 1995 paper by Nati Linial and me On the distance distribution of binary codes.

3) Various proofs for MRRW1.  Although the original proof of MRRW1 (and MRRW2) are not very complicated new proofs shed light on the theorem. Let me mention a few papers: Friedman and Tillich’s ingenious paper, Generalized Alon–Boppana theorems and error-correcting codes; The paper by Navon and Samorodnitsky mentioned above; A recent paper by Samorodnitsky, One more proof of the first linear programming bound for binary codes and two conjectures; A recent paper by Linial and Elyassaf Loyfer, An Elementary Proof of the First LP Bound on the Rate of Binary Codes.

4) What will it take to improve MRRW or KL? This is, of course, a holy grail in the area, and a central problem in mathematics. Over the years there were several interesting proposals on how to improve Delsarte’s LP and improve the MRRW and KL bounds. So far, there have been no improvements of the bounds themselves. This is a topic for a whole new post.

5) Can hypercontractivity help? A suggestion from my old paper with Nati was to add to Delsarte’s LP  hypercontractive inequalities. It will be nice to pursue this direction. Alex’s conjectures in the paper mentioned in comment 3 are related. Alex told me that hypercontractive inequalities (and discrete isoperimetric inequalities) are also useful for understanding the limitations of Delsarte’s LP.

Two additional pictures

fbds

From a Facebook discussion about the breakthrough of Marcelo Campos, Matthew Jenssen, Marcus Michelen, and Julian Sahasrabudhe. 

hcnt

Links to various relevant papers. (Please comment on additional relevant papers especially on the central question of the limitations of Delsarte’s LP.)

  1. R McEliece, E Rodemich, H Rumsey, L Welch New upper bounds on the rate of a code via the Delsarte-MacWilliams inequalities,  IEEE Transactions on Information Theory 23 (1977)
  2. G.A. Kabatyanskii and V. I. Levenshtein, Bounds for  packings on a sphere and in space, Probl. Inform.Transm.,14 (1978).
  3. Philippe Delsarteand and Vladimir I. Levenshtein,  Association Schemes and Coding Theor, IEEE Transactions on Information Theory. 44 (1998)
  4. Gil Kalai and Nati Linial, On the distance distribution of binary codes., IEEE Trans. Inf. Th., 41(1995).
  5. A. Samorodnitsky, On the optimum of Delsarte’s linear program, Journal of Combinatorial Theory, Ser. A, 96, 2, 2001
  6. Linear codes and character sums, N. Linial and A. Samorodnitsky, Combinatorica 22 (2002), no. 4, 497–522.
  7. Alexander Barg and David Jaffe, Numerical results on the asymptotic rate of binary codes,
  8. Alexei Ashikhmin, Alexander Barg, and Simon Litsyn, Estimates_of_the_distance_distribution_of_codes_and_designs, IEEE Transactions on Information Theory, 47 (2001).
  9.  Joel Friedman and Jean-Pierre Tillich, Generalized Alon–Boppana theorems and error-correcting codes, SIAM J. Discret. Math. 19(2005), 700-718. 
  10. A. Schrijver. New code upper bounds from the Terwilliger algebra and semidefinite
    programming. IEEE Transactions on Information Theory, 51 (2005) 2859–2866.
  11. M. Navon, A. Samorodnitsky,  Linear programming bounds for codes via a covering argumentDiscrete and Computational Geometry, 41 (2009).
  12. Alex Samorodnitsky,  A modified logarithmic Sobolev inequality for the Hamming cube and some applications,  arXiv:0807.1679.

  13. Henry Cohn, Nicholas Triantafillou, Dual linear programming bounds for sphere packing via modular forms
  14. On the weight distribution of random binary linear codes, Nati Linial and Jonathan Mosheiff, Random Strutures and Algorithms, 56(1): 5-36 (2020).
  15. Leonardo N. Coregliano, Fernando G. Jeronimo, Chris Jones, A Complete Linear Programming Hierarchy for Linear Codes, arXiv:2112.09221
  16. Rupert Li, Dual Linear Programming Bounds for Sphere Packing via Discrete Reductions,  arXiv 2206.09876
  17. Alex Samorodnitsky, Hypercontractive Inequalities for the Second Norm of Highly Concentrated Functions, and Mrs. Gerber’s-Type Inequalities for the Second Rényi Entropy,
  18. Matthew de Courcy-Ireland, Maria Dostert, and Maryna Viazovska, Six-dimensional sphere packing and linear programming.
  19. Alex Samorodnitsky, One more proof of the first linear programming bound for binary codes and two conjectures, Israel Journal of Mathematics
  20. Nati Linial and Elyassaf Loyfer, New LP-based upper bounds in the rate-vs.-distance problem for linear codes, arXiv 2206.09211.
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  22. Steven Dougherty, Jon-Lark Kim, and Patrick Sole, Open_Problems_in_Coding_Theory, 2015.
Posted in Combinatorics, Convexity, Geometry | Tagged , , , | 2 Comments

TYI 54: A Variant of Elchanan Mossel’s Amazing Dice Paradox

The following question was inspired by recent comments to the post on Elchanan Mossel’s amazing Dice Paradox.

A fair dice is a dice that when thrown you get each of the six possibilities with probability 1/6. A random dice is such that you get the outcome ‘k‘ with probability p_k where (p_1,p_2, \dots ,p_6) is a vector chosen uniformly at random from the 5-dimensional simplex.

Test your intuition:

You throw a random dice until you get 6. What is the expected number of throws (including the throw giving 6) conditioned on the event that all throws gave even numbers?

rd
Addition: Test your intuition also on the following simpler question. We have a coin that gives head with probability p and tail with probability 1-p, and p is itself chosen (once and for all) uniformly at random in [0,1]. What is the expected number of coin tosses until we get head.

Addition:  Note that there are two different ways to understand the question itself. One way is to regard the conditioning as applying both to the dice throwing and to the random choice of the probabilities (p_1,p_2,\dots ,p_6). A second way is to consider the parameters (p_1,p_2,\dots,p_6) as being determined at random uniformly; and then taking the average over (p_1,p_2,\dots,p_6) for the expected number of throws conditioned on the event that all throws gave even numbers.

Posted in Probability, Test your intuition | Tagged , | 14 Comments

Riddles (Stumpers), Psychology, and AI.

Two months ago I presented five riddles and here, in this post, you will find a few more. (These types of riddles are called by Maya Bar-Hillel “stumpers”.) This time, we will have a discussion about how riddles are related to psychology and how this relation might be connected to (or even explored by) AI. Let’s start with three new riddles.

Three new riddles

Cecil is a criminal lawyer. Many years ago, he spent a couple of days in hospital. When he was discharged, he was in perfect health. Indeed, there was nothing at all wrong with him. Nonetheless, he was incapable of leaving his hospital bed on his own and had to be carried off of it. Please explain.

Explain how it is possible for Christmas and New Year’s to fall in the same year.

A ping pong ball was hit. It flew in the air, stopped, reversed direction, and returned to where it originated. The ball was not attached to anything, nor bounced off anything. Explain in a few words how that is possible.

GPT3 and ChatGPT are facing the ping-pong riddle

pingpong2

Note that the first two sentences by GPT3 are a fine solution to the riddle. But the third sentences spoils it: a) The reversal had already occured at the apex. b) hitting the ground violate the stipulation that the ball did not bounce off anything.

pingpong4

Here, ChatGPT (Dec. 2023) clearly failed. This specific answer is not similar to any human response we have collected.

Riddles and Psychology

There is a long tradition of using riddles to study human thinking and problem solving. The riddles Maya calls “stumpers” are closely related to riddles called “one-step insight problems” by Aisling Murray and Ruth Byrne.

When a listener hears a stumper she forms a (typically visual) mental representation of the narrative, from which it is not possible to see the solution. However, there exist other representations, consistent with the narrative, in which the solution is immediate. 

This post is based on conversations with Maya as well as on three papers:

Maya Bar-Hillel, Tom Noah and Shane Frederick, Learning psychology from riddles: The case of stumpers, Judgment & Decision Making, 13 (2018), 112-122. (We may also refer to the authors by the acronym BNF or by their first names Maya, Tom, and Shane.)

Maya Bar-Hillel, Tom Noah and Shane Frederick, Solving stumpers, CRT and CRAT: Are the abilities related? Judgment & Decision Making , 14 (2019) , 620 – 623.

Maya Bar Hillel,  An annotated compendium of stumpers, Thinking and Reasoning, 27 (2021),  536–566.

Outline 

Following Bar-Hillel (2021), I will start with the work of Eleanor Rosch to explain people’s reliance on default mental representations that hinder them in solving certain stumpers;  I will then mention the work of Paul Grice to explain why people fail to solve other stumpers that actually require default mental representations to solve the stumpers.  Maya calls these two categories “Roschian stumpers” and “Gricean stumpers,” respectively. Next, I will tell you about my attempt with Maya to solve stumpers using AI generative programs, and we will see a lot of entertaining examples along the way. Specifically, we gathered some data on how AI tries to solve these riddles or to represent relevant fragments thereof. In this context, we pondered questions such as: Can an understanding of human psychology be gleaned from experimenting with AI? Alternatively, do AI systems exhibit distinctive “psychological” characteristics of their own?

Maya and I had several fruitful discussions with Daphna Shahaf from The Hebrew University and I had interesting conversations with Ohad Fried and Arik Shamir from Reichman University. By the way, Maya’s father, Yehoshua Bar-Hillel, Arik’s father (and my dear friend) Eli Shamir, and my “academic father” (and also dear friend) Micha A. Perles, wrote together a famous paper about automata On formal properties of simple phrase structure grammars. Z. Phonetik, Sprachwissen. Kommun., 14(1961), 143–172.

GPT3 faces the Christmas-New Year’s riddle

Christmas1

Here GPT3 had difficulties

Eleanor Rosch and Roschian stumpers

Let’s go over some of the riddles from the previous post. Identifying the default mental representation evoked by a riddle is related to Rosch’s work. To put it briefly, Rosch argues that people’s representations of natural language categories are based on the category prototypes rather than on formal definitions. At the end of the post, you will find some more details on Rosch’s theory.

Successful Roschian stumpers are those whose default representation is so prevalent and durable, that most respondents remain locked into it, and fail to solve the stumper, and here are three examples.

Two men play five checkers games. Each wins an even number of games, with no ties. How is this possible?

The overwhelming visual representation is that of two players playing with each other.  The visual image of two players playing checkers against each other is more economical than the image of two players playing checkers against two other players. This is an example of a general principle of “cognitive economy, ” namely preferring the representation requiring  least cognitive effort.

Individual bus rides cost one dollar each. A card good for five rides costs five dollars. A first-time passenger boards the bus alone and hands the driver five dollars, without saying a word. Yet the driver immediately realizes, for sure,that the passenger wants the card, rather than a single ride and change. How is that possible?

BNF hypothesized that “it is mentally easier to conjure a representation of a single item than of multiple items. Thus, a five dollar bill is easier to ‘see’ than five singles”.

In our market, a small potato bag costs 5 taka, a medium potato bag costs 7 taka, and a large potato bag costs 9 taka. However, a single potato costs 15 taka. Please explain.

The default representation of a potato bag is that of a bag filled with potatoes rather than an empty bag, and the explanation is that  although the purpose of containers (bottles, boxes, jugs, bags) is to contain, BNF hypothesized that they (bottle, box, jug) would be represented as empty unless referencing specific contents (e.g., wine bottle, cereal box, milk jug).

Paul Grice and Gricean Stumpers

Gricean stumpers rely on destroying the default representation. Respondents are steered away to an alternative representation by the certain words in the narrative, whereas the solution actually lies in the default.

For example, consider the following riddle:

A big brown cow is lying down in the middle of a country road. The streetlights are not on, the moon and stars are not out, and the skies are heavily clouded. A truck is driving towards the cow at full speed, its headlights off. Yet the driver sees the cow from afar easily and stops in time. How is that possible?

The default visual representation of any generic scene, in particular, for a “a big brown cow is lying down in the middle of a country road,” is that it happens in daylight. However, adding that the streetlights are not on, etc. modifies the default representation. The reason yields another important insight into psychology that was studied by Paul Grice. As BNF explain: “One of Grice’s (1975) conversational maxims is “Do not make your contribution more informative than is required” (p. 45). Hence, when the narrative bothers to mention the absence of light sources, darkness is evoked (since those light sources are otherwise irrelevant). 

At the end of the post, you will find some more details on  Grice’s paper “Logic and Conversation.”

Enters AI generative programs

Together with Maya, we asked ourselves some questions about AI generative programs and gathered some data on the results of letting AI current at the time try to solve these riddles or to represent relevant fragments of the riddles. Since we did not know much about AI it was a good opportunity to learn about them. Maya was especially interested in visual representations and therefore was especially interested in Dall-E 2 experiments. Most of our experiments with AI took place in the summer and fall of 2022. We used Dalle E 2, GPT3, and chatGPT.  (These AI programs were rapidly advancing, and GPT4 had not yet been released.) 

My main conclusion from many experiments was that, overall, AI responses showed that computers conjure the same default representations that cause humans to be stumped by riddles. That is, the AI followed the default mental representations that BNF identified, and the AI responses also (sometimes, explicitly) followed Grice’s rules. Maya’s interpretation was different. She thought that the data is a big mess: sometimes the AI were stumped in the same way as humans, and sometimes not. Moreover, Maya’s impression was that often the AI were not advanced enough even to tell.

I sort of like Maya’s interpretation because I find self-critical, cautious, and non-self-promoting interpretations endearing; I even tend to agree with her that some of the data is a big mess. However, I also think that nontheless the data clearly showed that AI manifest similar “behavior” to humans.

There were several points Maya and I agreed upon. We both agree that some inherent weaknesses of (otherwise highly impressive) AI affect the ability to draw conclusions in our case. (I even thought that the AI responses could sometimes be seen as an exaggerated form or even a caricature of human responses.) We also agree that it is difficult to conduct a quantitative analysis similar to the analysis of experiments with many individuals. Maya also mentioned that her impression from a recent conference was that many researchers are trying to conduct research with AI using their favorite tasks.

Selected AI Experiments

1. Falling from a 60-foot tall ladder

Pedro was washing windows outside a tall office building when he fell off his 60-foot ladder onto the ground below. Incredibly, he did not injure himself in any way. He was not wearing any safety equipment, and nothing broke his fall. Explain in a few words how he was not injured.

(Test your intuition: is this a Roschian stumper or a Gricean stumper)

GPT-3’s response (Sept. 2022) to the full riddle

Pedro was not injured because he landed in a pile of feathers. The feathers cushioned his fall and prevented him from being injured.

We let Dalle-E2 make a drawing prompted by “Nancy fell from a 60-feet ladder by Goya”

60feet

All AI programs that we tried (just as humans) located Pedro high up on his ladder.

And here is ChatGPT (Jan. 2023)

60feetchatgpt

Although the chatGPT’s response looks a little funny, in a sense, it represents quite a good reaction to the prompt. The prompt (as commonly understood by humans and apparently also as “understood” by chatGPT) describes an unlikely scenario that chatGPT politely disbelieved. (Using the word “incredibly” in the riddle supports this interpretation.)

2. Sharing a pizza

(GPT) Six Italians are sharing a Pizza. The older Italian is the father of the younger Italians. Try to Guess the names of the Italians.

  1. Paolo
  2. Gino
  3. Franco
  4. Angelo
  5. Marco

For each one, say if it is a man or a woman.

  1. Men [sic.]
  2. Men
  3. Men
  4. Men
  5. Men

Why did you choose them all to be men?

There is no specific reason, it is just a guess.

Remark: we noticed is that AI programs tend to regard all members of a group of people to be of the same gender. Therefore if one member is marked as a man or as a women AI will tend to mark all of them as such. This seems to express some form of “cognitive economy”; we do not know if this is similar to human behavior.

Prompt: Three Italians are sharing a pizza. The older Italian is the mother of the younger Italians

Here is what Dalle-E2 produced to this prompt

pizza3W

3.  Facing opposite directions 

Two old friends are standing together on a hilltop, in complete silence. Nora is facing north, and Sara is facing south. Suddenly Nora asks: “Why are you smiling, Sara?” Explain briefly how Nora saw Sara’s smile.

Here is a screenshot of the first hits in Google Images for “two people face opposite directions.”

opposite

In most images the people do not see each other. 

norasara

4. Playing Checkers

Two men play five checker games. Each wins an even number of games, with no ties. How is this possible?

checkers

5. Eggs for breakfast

Farmer Joe eats two fresh eggs from his own farm for breakfast every day. Yet there are no chickens on his farm. 

We told chatGPT the story about farmer Joe and asked it to elaborate. This was the response:

Farmer Joe was a hardworking man who lived on a sprawling farm in the countryside. Every day, he would wake up early and work tirelessly to tend to his crops and animals. He was always up before the sun, and one of the first things he did each morning was to prepare himself a delicious breakfast.

For breakfast, Farmer Joe would always eat two fresh eggs from his own farm. They were his favorite food, and he looked forward to them every day. Despite the fact that there were no chickens on his farm, the eggs were always there for him in the morning, as if by magic.

At first, Farmer Joe thought nothing of this strange occurrence. He simply assumed that one of his neighbors had given him the eggs as a gift. However, as the weeks went by and the eggs continued to mysteriously appear on his kitchen counter each morning, he began to wonder how it was possible. He asked around and no one in the area had any chickens.

One day, Farmer Joe decided to investigate. He scoured the entire farm, searching for any signs of chickens or eggs, but he found nothing. He even checked with his neighbors, but they had no explanation either.

In the end, Farmer Joe was left with a mystery that he could not solve. How could he be eating two fresh eggs every day if there were no chickens on his farm? The eggs seemed to be appearing out of thin air, and no one could explain how it was possible.

Despite the mystery, Farmer Joe continued to eat his beloved eggs every morning, grateful for their delicious taste and the memories they brought

Prompt: But now write a new version where there is no mystery left. The eggs are not from anybody else but from the farm and at the same time there are no chickens in the farm.

Farmer Joe runs a successful and innovative farm that specializes in producing high-quality eggs. Despite not having any chickens on the property, he has found a way to produce fresh eggs for his daily breakfast using advanced methods of egg cultivation.

Every morning, Farmer Joe enjoys a hearty breakfast consisting of two perfectly cooked, fresh eggs from his farm. He takes great pride in the quality of his eggs and the methods used to produce them.

At first, it may seem like a mystery as to how Farmer Joe is able to have eggs for breakfast every day without any chickens on the farm. However, with the advancements in agriculture and food production, there are now methods of cultivating eggs without the need for traditional egg-laying hens. This technology allows for the production of fresh eggs in a controlled environment, ensuring that they are of the highest quality.

So, there is no mystery left, just a dedicated farmer who is taking advantage of the latest in egg production technology to provide himself with delicious, fresh eggs every day.

Prompt: Now tell a similar story, also with no mystery being left that occurred in 1927.

In 1927, Farmer Joe lived on a large farm in the countryside. Despite not having any chickens on the property, he was still able to enjoy fresh eggs for breakfast every day. This was because he had taken a unique approach to raising his own poultry.

Instead of having chickens, Farmer Joe had decided to raise a breed of domesticated ducks that laid high-quality, nutritious eggs. These ducks

were well-cared for and lived in spacious coops that provided them with plenty of room to roam and plenty of fresh water to swim in.

Every day, Farmer Joe would collect a basket of fresh eggs from the coops and bring them into the kitchen to cook for his breakfast. He took great pride in the taste and quality of the eggs, and would often invite friends and neighbors over to sample them for themselves.

Despite the unusual approach to raising poultry, Farmer Joe’s farm was thriving and his eggs were in high demand. He became known as the “Duck Egg Farmer” and was celebrated for his innovative and sustainable farming practices.

By embracing an alternative method of raising poultry, Farmer Joe was able to provide himself and others with a delicious and healthy source of protein, all while avoiding the traditional challenges and expenses associated with raising chickens

Conclusion (for now)

Try for yourself!

More on Grice’s paper “Logic and Conversation” 

 “Logic and Conversation” is a seminal paper in the field of philosophy of language and pragmatics by H. P. Grice, originally published in 1975. The paper is part of a broader exploration of how speakers convey meaning and communicate in natural language, going beyond the literal meaning of words and sentences. Grice introduces the concept of implicature, which is a way of understanding what is communicated beyond the explicit content of an utterance and the logical inferences therefrom.
 
In the paper, Grice discusses the Cooperative Principle, which is the assumption that speakers and listeners cooperate to communicate effectively. He identifies four maxims of conversation that underlie this principle: the Maxim of Quality, Quantity, Relation, and Manner. Grice argues that these maxims guide conversation by informing speakers and listeners about how to convey and interpret meaning. These maxims afford implicatures, which are the additional implied meanings in a conversation.
 
Grice’s paper emphasizes the importance of conversational implicature in understanding how people communicate and infer meaning in everyday language use. He also distinguishes between implicatures that arise from the maxims and implicatures that are calculable and derived through reasoning. This distinction has been influential in the study of pragmatics and has had a lasting impact on linguistic and philosophical discussions of language and communication.
 
Overall, “Logic and Conversation” by H. P. Grice is a foundational work that has significantly contributed to the development of the theory of implicature and the understanding of how language is used in real-world conversations. It has had a profound influence on the study of pragmatics and continues to be a central reference in the field of linguistics and philosophy.

(Source: ChatGPT with two little corrections by Maya.) 

P. Grice,   Logic and Conversation. In Syntax and Semantics, 3(1975), 41- 58. 

More on Elinor Rosch

Eleanor Rosch, a prominent cognitive psychologist, is best known for her groundbreaking work in the field of categorization and prototype theory. Rosch developed the prototype theory of categorization, challenging traditional views of categorization as being based on defining features. Rosch proposed that people organize objects and concepts into categories based on prototypes – typical or representative examples that embody the most salient features of a category.

Her influential research, particularly the seminal paper “Natural Categories,” published in 1973, demonstrated that people tend to categorize objects based on family resemblances rather than strict definitions. Rosch’s work has had a profound impact on cognitive science, linguistics, and philosophy, influencing how researchers and scholars understand the cognitive processes underlying human conceptualization and categorization. Additionally, her contributions have influenced fields such as artificial intelligence and have paved the way for a more nuanced understanding of how individuals structure their mental representations of the world.

And here we discuss Ludwig Wittgenstein’s influence on Rosch:

Eleanor Rosch’s work, particularly her development of prototype theory and her contributions to the study of categorization, has been influenced by the ideas of Ludwig Wittgenstein, a philosopher known for his work in the philosophy of language and the philosophy of mind. Wittgenstein’s later philosophy, especially as expressed in his posthumously published work “Philosophical Investigations,” had a significant impact on Rosch’s thinking.

Wittgenstein’s ideas challenged traditional views of language and meaning, emphasizing the importance of language use in specific contexts rather than relying solely on fixed definitions. His concept of “family resemblances,” where members of a category share overlapping features rather than possessing a set of defining characteristics, has been particularly influential. Rosch applied and extended these notions to the realm of cognitive psychology, proposing that people categorize objects based on prototypes or typical examples that capture the family resemblance of a category. This departure from a strict, rule-based definition of categories marked a shift in how researchers understand human cognition and categorization, with Wittgenstein’s ideas serving as a philosophical foundation for Rosch’s empirical work.

(Sources: ChatGPT)

E. Rosch, Natural Categories, Cognitive psychology, 4 (1973), 328-350.

E. Rosch,  Principles of categorisation. In E. Rosch & B. B. Floyd (Eds.),Cognition and categorisation, pp. 27–48. Lawrence Erlbaum Associates, 1978.

Finally, here is Cecil the criminal lawyer at the age of two (Dalle-E2)

DALL·E 2023-02-07 20.51.25 - Cecil is a criminal lawyer. Show a picture of Cecil at age of two.

And as a bonus, Dalle-E2’s view of Karl Marx at the age of two

DALL·E 2023-12-27 22.34.56 - Show a picture of Karl Marx at the age of two.

Posted in AI, Computer Science and Optimization, Philosophy, Psychology | Tagged , , , | 9 Comments