This is a page of the online seminar on algorithmic aspects of information theory,
a follow up of Dagstuhl Seminar 22301.
If you want to add your address to the mailing list or if you want to suggest a talk please contact
us.

12 October 2022
Laszlo Csirmaz (Central European University, Budapest).
Around entropy inequalities.
Abstract:
This will be an introductory talk on linear inequalities for Shannon's entropy:
what the problem is, what the methods are, what is known and what is not known.

26 October 2022
Andrei Romashchenko (CNRS LIRMM, Montpellier).
Basic proof techniques for entropic inequalities.
Abstract:
We will consider again several classical theorems mentioned in the survey by
Laszlo Csirmaz
(the first lecture) and discuss the proof techniques behind these results.

9 November 2022
Andrei Romashchenko (CNRS LIRMM, Montpellier).
The ZhangYeung inequality: an attempt to explain.
Abstract:
We will discuss a magical proof of the first example of a nonShannon type inequality
(ZhangYeung'1998) and try to explain how this and similar arguments could be invented without magic.

23 November 2022
Laszlo Csirmaz (Central European University, Budapest). The entropy region is not polyhedra.
Abstract:
We present the two ingredients of the proof: a set of
entropy inequalities and a collection of sample distributions,
and how these yield the famous result of Fero Matus.
If time permits, we sketch the proof of the used inequalities, and
indicate the shortcomings of other applications of the same idea.

7 December 2022
Alexander Shen (CNRS LIRMM, Montpellier). Information inequalities: combinatorial interpretation.
Abstract:
Information inequalities like H(A,B) ≤ H(A)+H(B) or H(A)+H(A,B,C) ≤ H(A,B)+H(A,C) have natural interpretation. It is enough to check them for "uniform" random variables that can be constructed starting from a group and its subgroups (Chan,Yeung). On the other hand, they can be translated to Kolmogorov complexity language. Combining these tools, one can get a combinatorial characterization of the class of information inequalities.

04 January 2023 Frederique Elise Oggier (Nanyang Technological University, Singapore).
An overview of Ingleton's inequality from a group theory point of view.
Abstract:
We will review several works that use group theory to approach Ingleton's inequality and entropic vectors.

18 January 2023 LI Cheuk Ting (Chinese University of Hong Kong).
Existential Information Inequalities, NonShannon Inequalities, and Automated Theorem Proving.
Abstract:
Existential information inequality is a generalization of linear information inequalities, where random variables can not only be universally quantified, but also existentially quantified. We study the structure of existential information inequalities, and describe algorithms for automated verification of existential information inequalities, which are also useful for proving (nonexistential) nonShannon inequalities. We also describe how a wide range of results in network information theory (e.g. 32 out of 56 theorems in Chapters 114 of Network Information Theory by El Gamal and Kim) can be proved automatically using the proposed algorithms. The algorithms are implemented in the PSITIP framework (
github.com/cheuktingli/psitip).

01 February 2023 Alexander Kozachinskiy (Catholic University of Chile).
On the recent progress on Frankl's conjecture.
Abstract:
Frankl's conjecture states that for any nonempty family of nonempty finite sets which is closed under finite union there exists an element belonging to at least 1/2 of the sets from the family. I will present a
recent result of Gilmer that this conjecture holds for some positive constant.

15 February 2023 Andrei Romashchenko.
Quasiuniform distributions and the method of random covers.
Abstract:
We will talk about variations of the classical method of typical sequence and its applications useful in studying information inequalities. In particular, we will discuss the AhlswedeKörner lemma in the form that can be used to prove nonShannon type inequalities for entropy.

1 March 2023
Milan Studený (Institute of Information Theory and Automation, Prague).
On conditional Ingleton inequalities.
Abstract:
Linear information inequalities valid for entropy functions induced by discrete random
variables play an important role in the task to characterize discrete conditional independence
structures. Specifically, the socalled conditional Ingleton inequalities in the case of 4 random variables are in the center of interest: these are valid under conditional independence assumptions on the inducing random variables. The four inequalities of this form were earlier revealed: by Yeung and Zhang (
1997), by Matúš (
1999) and by Kaced and Romashchenko (
2013). In our recent paper (
2021) the fifth inequality of this type was found. These five information inequalities can be used to characterize all conditional independence structures induced by four discrete random variables. One of open problems in that 2021 paper was whether the list of conditional Ingleton inequalities over 4 random variables is complete: the analysis can be completed by a recent finding of Boege (
2022) answering that question.

15 March 2023 Vlad Demartsev (Max Planck Institute of Animal Behavior).
Economy of vocal repertoires: Zipf's laws in animal communication.
Abstract:
Zipf's Law of Brevity (negative correlation of words' length with the frequency of their use) was found across multiple lexicons and text corpora and often claimed to be one of unifying features of human language. This intriguing linguistic regularity could be explained by the Principle of Least Effort — a compromise between the need for transferring information in a detailed and comprehensive manner and the pressure for minimising the effort (cost) associated with producing signals.
If Zipf's principles are indeed fundamental for communication we should be able to find them in animal systems. Animal communication systems are likely to be are constrained by the same fundamental tradeoff between minimizing signalling costs while maintaining informational integrity. However, the pressure towards optimization of signalling is not the only force shaping animal vocal repertoires. Factors like, sexual selection, social organization and habitat features can generate evolutionary forces which might push vocal repertoires further away from Zipfian optimization.

22 March 2023
Oriol Farràs (Universitat Rovira i Virgili).
Introduction to Secret Sharing Schemes: Constructions.
Abstract:
A secret sharing scheme is a method by which a dealer distributes shares to parties such that only authorized subsets of parties can reconstruct the secret. The family of these authorized subsets is called the access structure of the scheme. This introductory talk is focused on the problem of finding efficient secret sharing schemes for general access structures. We will see some general constructions as well as their limitations. We will review connections between the problem of finding efficient schemes and other problems, such as finding small monotone formulas and monotone span programs for monotone Boolean functions, and problems of matroid theory and entropy optimization.

29 March 2023 Carles Padro (Universitat Politècnica de Catalunya).
Lower Bounds in Secret Sharing from Information Theory.
Abstract:
Information theory has been used for decades in the search for lower bounds in secret sharing. The main achievements and limitations of that technique are discussed in this survey talk. Among the former, Csirmaz's general lower bound, which is still the best of the known ones, and the findings of exact optimal information ratios for several families of access structures. For the latter, some intuition on the limits of the method and a comparison with the existing lower bounds for linear secret sharing schemes.

12 April 2023
Tianren Liu (Peking University).
From Private Information Retrieval to Secret Sharing.
Abstract:
We will revisit the first general secret sharing scheme with 2^cn complexity, where c is strictly smaller than 1. Until quite recently, its best known complexity is about 2^n. Our work established a connection between secret sharing and private information retrieval. The talk is based on joint works with Vinod Vaikuntanathan and Hoeteck Wee.

26 April 2023
Hung Q. Ngo (relationalAI).
An Information Theoretic Approach to Estimating Query Size Bounds.
Abstract:
Cardinality estimation is one of the most important problems in database management. One
aspect of cardinality estimation is to derive a good upper bound on the output size of a query,
given a statistical profile of the inputs. In recent years, a promising informationtheoretic
approach was devised to address this problem, leading to robust cardinality estimators which
are used in practice.
The information theoretic approach led to many interesting open questions surrounding
optimizing a linear function on the almostentropic or polymatroidal cones. This talk
introduces the problem, the approach, summarizes some known results, and lists open
questions.

10 May 2023
Raymond W. Yeung (The Chinese University of Hong Kong).
Entropy Inequalities: My Personal Journey.
Abstract:
Shannon's information measures, namely entropy, mutual information, and their conditional versions, where each of them can be expressed as a linear combination of unconditional joint entropies. These measures are central in information theory, and constraints on these measures, in particular in the form of inequalities, are of fundamental interest. It is wellknown that all Shannon's information measures are nonnegative, forming a set of inequalities on entropy. However, whether these are all the constraints on entropy was unknown, and the problem had been rather evasive until the introduction of the entropy function region in the late 1990s.
This talk consists of two part. The first part is about how I became interested in this subject in the late 1980s. It began with my PhD thesis in which I needed to use inequalities on Shannon's information measures (viz. information inequalities, or equivalently entropy inequalities) to prove converse coding theorems. During that time I was also intrigued by the underlying settheoretic structure of Shannon's information measures, namely their representation by diagrams that resemble the Venn diagram. In 1991 I introduced the IMeasure to formally establish the onetoone correspondence between set theory and Shannon's information measures. In the mid1990s, I introduced the entropy function region Γ* that provides a geometrical interpretation of entropy inequalities. Shortly after, Zhen Zhang and I discovered socalled nonShannontype inequalities which are beyond the nonnegativity of Shannon's information measures. Since then this subject has been under active research
A byproduct of the entropy function region and the associated geometrical interpretation is the machineproving of entropy inequalities. In the second part of this talk, I will discuss the research along this line, including some recent results.

24 May 2023
Mahmoud Abo Khamis (relationalAI).
The Polymatroid Bound: Extensions and Applications in Database Query Evaluation (part 1).
Abstract:
Information theory has been used to compute upper bounds on the output sizes of database queries as well as to devise matching algorithms that can answer these queries within these bounds. The polymatroid bound generalizes many of these bounds and has a matching query evaluation algorithm, called PANDA [Abo Khamis et al, PODS’17].
In this talk, we present extensions of the polymatroid bound that utilize the query structure to derive new constraints on entropies. We state open problems regarding the relationship between these extensions and the original bound. On the algorithmic side, we present the PANDA algorithm in detail and discuss its shortcomings and related open problems.

7 June 2023
Mahmoud Abo Khamis (relationalAI).
The Polymatroid Bound: Extensions and Applications in Database Query Evaluation (part 2).
Abstract:
This is the second part of the talk, the first part of which took place on May 24.
I continue our discussion of informationtheoretic upper bounds on the output sizes of database queries. I will recap the polymatroid bound and present a corresponding query evaluation algorithm, called PANDA, whose runtime matches the polymatroid bound
[Abo Khamis et al, PODS’17].
I will also discuss this algorithm's shortcomings and related open problems.
Acquaintance with the first part of the talk is very desirable, although formally it is not required.
Bibliography:
Mahmoud Abo Khamis, Hung Q. Ngo, Dan Suciu.
What do Shannontype Inequalities, Submodular Width, and Disjunctive Datalog have to do with one another?
arXiv:1612.02503.
(Also in Proceedings of the 36th ACM SIGMODSIGACTSIGAI Symposium on Principles of Database Systems, 2017.)

21 June 2023
Alexander V. Smal
(Technion, Israel; PDMI, Russia).
Information theoretic approach to Boolean formula complexity.
Abstract:
We will discuss the informationtheoretic approach to proving lower
bounds on the formula complexity of Boolean functions. In the late
80s, Karchmer and Wigderson discovered that Boolean formulas could be
characterized using the language of communication complexity. This
observation allowed us to apply communication complexity methods to
prove lower and upper bounds on the Boolean formula complexity.
In particular, we can use informationtheoretic methods from
communication complexity to prove formula complexity lower bounds.
This talk is a brief introduction to these techniques, as well as to some
applications.

September 13, 2023 (17h CET):
Laszlo Csirmaz (Alfréd Rényi Institute of Mathematics, Budapest and UTIA, Prague).
The power of nonShannon inequalities: a short proof of the GácsKörner theorem.
Abstract:
We present a short proof of a celebrated result of Gács and Körner
giving sufficient and necessary condition on the joint distribution of
two discrete random variables X and Y for the case when their
mutual information matches the extractable (in the limit) common
information. Our proof is based on the observation that the mere
existence of certain random variables jointly distributed with
X and Y can impose restrictions on all random variables jointly
distributed with X and Y.

September 27, 2023: Andrei Romashchenko (CNRS LIRMM, Montpellier). On the common information and the AhlswedeKörner lemma in oneshot settings.
Abstract:
The GácsKörner common information, Wyner's common information, and other related information quantities apply by design to long series of independent identically distributed random variables. We will talk about a possible adaptation of these quantities to the oneshot setting, when the random objects cannot be represented as series of i.i.d. variables, and the usual technics of typical sequences do not apply. We will discuss the connection of informationtheoretic profiles with combinatorial and spectral properties of graphs.

October 11, 2023: LI Cheuk Ting (Chinese University of Hong Kong). Functional Representation Lemma and Minimum Entropy Coupling.
Abstract:
The functional representation lemma states that for two jointlydistributed random variables X, Y, it is possible to express Y as a function of X and another random variable Z that is independent of X. There are two interesting extreme points. If we minimize H(YZ), the minimum can be bounded by the "strong functional representation lemma", and has implications in lossy compression and channel simulation. If we instead minimize H(Z), this is equivalent to the minimum entropy coupling problem, which concerns finding the coupling of several given distributions that gives the smallest joint entropy. In this talk, we will discuss several recent developments regarding these problems

October 25, 2023:
Alexander Shen (CNRS LIRMM, Montpellier).
Information theoretic proofs (a survey).
Abstract:
Some theorems that have nothing to do with information theory can
be proven using an informationtheoretic argument
(entropy, or Kolmogorov complexity, or counting via compression).
For example, why are there infinitely many prime numbers?
If there were only M prime numbers, then
each integer could be encoded by the list of M exponents in its prime decomposition,
so we could specify each nbit number by only M×O(log n) bits,
a contradiction.
We will discuss several examples of proofs of that type,
including other bounds for the distribution of prime numbers, but not only them.

November 8, 2023: Batya Kenig (Technion). Approximate Implication for Probabilistic Graphical Models.
Abstract:
The graphical structure of Probabilistic Graphical Models (PGMs) represents the conditional
independence (CI) relations that hold in the modeled distribution.
The premise of all current systemsofinference for deriving conditional independence relations in PGMs, is that the set of CIs used for the construction of the PGM hold exactly.
In practice, algorithms for extracting the structure of PGMs from data discover approximate
CIs that do not hold exactly in the distribution.
In this work, we ask how the error in this set propagates to the inferred CIs read
off the graphical structure. More precisely, what guarantee can we provide on the inferred CI
when the set of CIs that entailed it hold only approximately?
In this talk, I will describe new positive and negative results concerning this problem.

November 22, 2023: Mokshay Madiman (University of Delaware). Analogies between entropy, volume, and cardinality inequalities for projections.
Abstract:
It is well known that entropy inequalities are a quick way of obtaining volume inequalities for projections of sets in a Euclidean space (or cardinality inequalities for projections of subsets of the integer lattice): for example, the LoomisWhitney inequality follows easily from the classical Han’s inequality. There is also a well known connection with integral inequalities. We will review more such analogies, as well as their limitations. For example, we will observe that volume of projections to coordinate subspaces is not submodular (though entropy is), and discuss general dualities between entropy and integral inequalities. These will give at least one set of reasonable answers to questions raised by Alexander Shen in the AAIT Seminar on 7 December 2022
(
video). We will also discuss some particularly useful classes of Shannontype inequalities that may be new to the AAIT audience: these also have applications to volume or cardinality. Most of this talk will be tutorial: it will be based on the work of many people in the geometry, combinatorics, probability, and information theory communities, rather than just the work of the speaker.