We are organizing a weekly seminar, Meet-in-the-Middle, from 18th August 2021. This seminar is held on each Wednesday from 16:00. The aim of this seminar is to create the diversification of the knowledge and to share and explore new research ideas in Computer Science and Mathematics among the researchers and the students. Each week, a designated speaker from IAI (Faculties and Students) or from other institutes will be delivering the talk. A prior notice about the topic is intimated a week before the talk.

Co-ordinator: Dr. Avijit Dutta (avijit.dutta@tcgcrest.org).

Online Meeting Link:

Meeting ID: 823 6262 7024
Passcode: 502333


Upcoming Talk (on 29/03/2023)

  • Speaker: Dr. Prahllad Deb
  • Affiliation: Postdoctoral Fellow at Ben-Gurion University of the Negev, Israel
  • Title: Towards a noncommutative theory of Cowen-Douglas class of noncommuting operators
  • Abstract: The classical Cowen-Douglas class of (commuting tuples of) operators possessing an open set of (joint) eigenvalues of finite constant multiplicity was introduced by Cowen and Douglas generalizing the backward shifts. Their unitary equivalence classes are determined by equivalence classes of certain hermitian holomorphic vector bundles associated to them on this set, and as emphasized in the work of Curto and Salinas, they are modelled by the adjoints of the multiplication operators by the independent variable(s) on a reproducing kernel Hilbert space. Our goal is to develop a free noncommutative analogue of the Cowen-Douglas theory aiming to understand the notion of noncommutative vector bundles. We define the noncommutative Cowen–Douglas class using matrix joint eigenvalues as envisioned by Taylor and use the Taylor-Taylor series of free noncommutative function theory to show that the joint eigenspaces together constitute — in a natural sense — a noncommutative hermitian holomorphic vector bundle. If time permits, we also discuss noncommutative reproducing kernel Hilbert space models and the noncommutative Gleason problems.


All Previous Talks

  • Speaker: Sagnik Nandy
    Affiliation: University of Pennsylvania
    Date: 11/01/2023
    Title: Orchestrated AMP: A novel way of Data Integration
    Abstract: In modern-day data science, we are faced with the dilemma of integrating data carrying information about the same latent parameters but coming from multiple sources. In this talk, we shall see how a novel technique called the Orchestrated Approximate Message Passing introduced by Ma and Nandy (2021) can be leveraged to perform such data integration optimally. We shall consider two different settings. In the first setting, we shall consider the task of recovering a latent community assignment of $n$ vertices from $m$ different interaction networks between them with different connectivity patterns and a set of correlated Gaussian feature vectors for each of the vertex. We shall see how our Orchestrated Approximate Message Passing algorithm can be used to perform this task of recovering the communities, optimally. Next, we shall explore a linear regression problem where the feature vectors are indexed by an undirected network. The smoothness of the regression parameters is characterized by the connectivity pattern of the observed network. Such data is common in several biological applications (Li and Li (2010)). The traditional approach to combine the linear model with such network side information is to use penalized least squares with a penalty on the Laplacian of the observed network (Li and Li (2010), Tran et. al. (2022)). However, such methods are extremely slow in high dimensions and not provably optimal. We apply the Orchestrated Approximate Message Passing algorithm to this problem and the resulting solution is shown to vastly outperform the traditional penalized estimators in terms of the reconstruction error. Our method is also extremely fast compared to the existing methods and provably Bayes optimal in the proportional asymptotic regime when $n/p \rightarrow c \in (0,1)$. This talk is based on two joint projects with Zongming Ma and Subhabrata Sen.

  • Speaker: Debsoumya Chakraborti
    Affiliation: Post Doctoral Fellow at Institute for Basic Sciences (IBS), South Korea
    Title: Colorful combinatorics
    Abstract: There have been extensive studies on the following question: given $k$ graphs $G_1,\dots, G_k$ over a common vertex set of size $n$, what conditions on $G_i$ ensure a \textit{rainbow} copy of $H$, i.e., a copy of $H$ with at most one edge from each $G_i$? In the first half of this talk, we will survey some results on this topic. Joos and Kim showed that for $k=n$, the condition that each $G_i$ has minimum degree at least $n/2$ confirms a rainbow Hamiltonian cycle. This generalizes the classical Dirac’s theorem. In the second half, we will discuss our recent rainbow generalizations of some results on embedding oriented Hamiltonian cycles in tournaments.

  • Speaker: Prof. Mridul Nandi
    Affiliation: Professor, ISI Kolkata
    Date: 09/11/2022 
    Title: A Brief Overview of Streaming Algorithm
    Relevant Links: [Video]

  • Speaker: Dr. Payel Sadhukhan
    Affiliation: Post Doctoral Fellow, IAI, TCG CREST
    Date: 02/11/2022 
    Title: Random Walk-steered Majority Undersampling

    Abstract: This paper proposes Random Walk-steered Majority Undersampling (RWMaU), an undersampling approach to address the class imbalance problem for binary classifiers. RWMaU is focused to find the majority points which lie at the overlapped region of the minority and the majority classes. Such points meddle with the learning and detection of the minority points. RWMaU uses random walks to mark the majority points satisfying the above characteristic in a non-parametric fashion. For each majority point, a proximity score is calculated on the basis of — their visit frequencies and the order of visits of the majority points in the random walks. This score is used to perceive the closeness of the majority class points to the minority class. The majority points lying close to the minority class are subsequently undersampled. Empirical evaluations on 21 datasets using 3 classifiers demonstrate substantial improvement in the performance of RWMaU over existing methods for addressing class imbalance and show that it is an efficient and effective way to address class imbalance in binary classification problems.

  • Speaker: Dr. Arun Maiti
    Affiliation: Post Doctoral Fellow, IIT Bombay
    Date: 12/10/2022
    Title: Cohomology of unordered flag manifolds
    Abstract: The (complex and real) complete flag manifolds are important objects in algebraic topology and geometry. The cohomology of these spaces is well known. Viewing complete flags as ordered bases, we obtain unordered complete flag manifolds by forgetting the ordering of the bases. Motivated by questions arising in algebraic topology and Banach geometry, we (jointly with Lorenzo Guerra) study the cohomology of the later spaces. In this talk, I will present a method for computing the mod-2 cohomology and obtain a complete description of the cohomology of these spaces in lower orders. A few of the important applications of our work will also be discussed.

  • Speaker: Dr. Navnath Daundkar 
    Affiliation: Post Doctoral Fellow, IIT Bombay
    Date: 28/09/2022
    Title: Moduli spaces of polygonal linkages via cellular surgery
    Abstract: The planar polygon space (or the moduli space of a polygonal linkage) with generic side lengths is a smooth, closed manifold. It is known that these spaces contain the real points of the moduli space of genus-zero curves as a dense subset; hence are a compactification. Kapranov showed that the real points of the Deligne-Mumford-Knudson compactification can be obtained from the projective Coxeter complex of type A by blowing up along the minimal building set. In this talk, we show that the planar polygon spaces can also be obtained from the projective Coxeter complex of type A, but, by performing iterative cellular surgery along a subcollection of the minimal building set. Interestingly, this sub-collection is encoded by a combinatorial data associated with the length vector called its genetic code. This is a joint work with Priyavrat Deshpande.

  • Speaker: Dr. Mrinal Nandi 
    Affiliation: Assistant Professor, Department of Statistics, West Bengal State University
    Date: 21/09/2022
    Title: Some Applications of Algebra and the concept of Symmetry
    Relevant Links: [Boardwork] [Video]

  • Speaker: Dr. Avisek Gupta
    Affiliation: Post Doctoral Fellow, IAI – TCG CREST
    Date: 10/08/2022
    Title: Machine Learning under Weak Supervision: Reducing the cost of labelling data
    Relevant Links: [Slides] [Video]

  • Speaker: Dr. Rahul Gangopadhyay
    Affiliation: Post Doctoral Fellow, EIMI and SPbU, Saint Petersburg.
    Date: 27/07/2022
    Title: Crossings in Geometric Hypergraphs
    Relevant Links: [Slides]  [Video]

  • Speaker: Dr. Aranya Lahiri
    Affiliation: SEW Visiting Assistant Professor at UC San Diego
    Date: 06/07/2022
    Title: Irreducibility of rigid analytic vectors in p-adic principal series representations.
    Abstract: For the $L$-rational points $G:=\mathbb{G}(L)$ of a p-adic reductive group, let  $Ind^G_B(\chi)$  be the continuous p-adic principal series representations. Here $L$ is a finite extension of $\mathbb{Q}_p$,  $B$ is the borel subgroup corresponding to a maximal torus $T$ and $\chi$ is a character of $T$. We will consider the globally analytic vectors of the pro-p Iwahori group  $I$ in the principal series representations.  This is done by endowing the pro-p Iwahori with a $p$-valuation and subsequently giving it structure of a rigid analytic group. We will talk about topological irreducibility of these globally analytic vectors under certain assumptions on $\chi$. This is a generalization of works of Clozel ($GL_2$ case) and Ray in the case of $G:= GL_n(L)$ . This is joint work with Claus Sorensen.

  • Speaker: Dr. Benjamin Wesolowski
    Affiliation: CNRS researcher (Chargé de Recherche), Institut de Mathématiques de Bordeaux (IMB), France
    Date: 22/06/2022
    Title: Hard Problems for Isogeny-based Cryptography
    Abstract: Isogeny-based cryptography is one of the few branches of public-key cryptography that promises to resist quantum attacks. The security of these cryptosystems relates to the (presumed) hardness of a variety of computational problems: finding paths in large “isogeny graphs”, computing endomorphisms of elliptic curves, or inverting group actions. We present these problems, and analyse how they relate to each other: which are equivalent, easier, or harder, and how they relate to cryptosystems.

  • Speaker: Dr. Tanmay Basu
    Affiliation: Assistant Professor, IISER Bhopal
    Date: 15/06/2022
    Topic: Role of NLP for Information Extraction from Unstructured Biomedical Text
    Abstract: Natural Language Processing (NLP) is the process of using computer algorithms to identify, analyze and derive key elements in unstructured text in a smart and effective way. With the widespread use of online social media and electronic health records (EHRs), unstructured text is a veritable gold mine, and NLP is the best way to extract value from these resources. Some recent research works and scopes of further works regarding the potential of NLP for information extraction from the unstructured biomedical text will be discussed.

  • Speaker: Daniel Vallieres
    Affiliation: Assistant Professor, California State University Chico
    Date: 01/06/2022
    Title: Iwasawa theory and graph theory
    Abstract: In the 1950s, Iwasawa proved his celebrated theorem on the growth of the p-part of the class number in Zp-extensions of number fields, and this discovery sparked the study of various arithmetic objects such as class groups and selmer groups in infinite towers of number fields.  Recently, similar phenomena have emerged in the context of graph theory where infinite towers of number fields are replaced with infinite towers of graphs.  In this talk, I will explain the basic objects of study in this area and depending on the time I will present some results obtained in this direction in collaboration with either Kevin McGown, or Antonio Lei, or still Sage DuBose.

    Relevant Links: [Video]

  • Speaker: Dr. Luca De Feo
    Affiliation: Research Staff Member, IBM Research Europe
    Date: 25/05/2022
    Title: Isogeny graphs for cryptography
    Relevant Links: [Abstract][Slides][Video]
  • Speaker: Prof. Steven Galbraith
    Affiliation: Head, Mathematics Department, Cyber Security Foundry, University of Auckland
    Date: 18/05/2022
    Title:  Isogeny based cryptography and zero-knowledge proofs of isogeny
    Relevant Links: [Abstract] [Video]

  • Speaker: Mr. Cédric Dion 
    Affiliation: Ph.D. student at Université Laval
    Date: 11/05/2022
    Title: Arithmetic statistics for 2-bridge links
    Relevant Links: [Abstract] [Video]

  • Speaker: Dr. Debanjana Kundu
    Affiliation: PIMS Postdoctoral Fellow at UBC, Vancouver
    Date: 04/05/2022
    Title: Introduction to the theory of elliptic curves and Iwasawa theory
    Relevant Links: [Abstract] [Board-Work] [Video]

  • Speaker: Dr Angsuman Das
    Affiliation: Assistant Professor, Presidency University, Kolkata
    Date: 27/04/2022
    Title: Groups and Graphs
    Relevant Link: [Abstract] [Slides] [Video]

  • Speaker: Dr. Apratim Chakraborty
    Affiliation: Post Doctoral Fellow, IAI TCG CREST
    Date: 06/04/2022
    Title: Elsers conjecture and the topology of U-nucleus complex
    Links: [Abstract] [Slides] [Boardwork] [Video]

  • Speaker: Prof. Prasant Mohapatra
    Affiliation: Professor, Vice Chancellor for Research at University of California, Davis (UC Davis)
    Date: 04/04/2022
    Title: Vulnerabilities in Federated Learning Networks
    Links: [Abstract] [Slides] [Video]

  • Speaker: Prof. Avishek Adhikari
    Affiliation: Professor, Head of Mathematics Department, Presidency University
    Date: 17/03/2022
    Title: Practical Attacks on a Class of Secret Image Sharing Schemes: Few Open Issues
    Links: [Abstract] [Slides] [Board-work] [Video]

  • Speaker: Dr. Angshul Majumdar
    Affiliation: Associate Professor, IIIT Delhi
    Date: 16/03/2022
    Title: Deep Learning based Clustering
    Links: [Abstract] [Slides] [Video]

  • Speaker: Dr. Debolina Ghatak
    Affiliation: Post-Doctoral Fellow at IAI, TCG CREST
    Date: 09/03/2022
    Title: Inference from Private Microdata 
    Links: [Abstract] [Slides] [Video]

  • Speaker: Mr. Arka Banerjee
    Affiliation: Final year Ph.D. student at the University of Wisconsin-Milwaukee 
    Date: 02/03/2022
    Title: Obstruction to coarse embedding
    Links: [Abstract] [Board-Work] [Video]

  • Speaker: Dr. Avik Chakraborti
    Affiliation: Lecturer in Computer Science (E&R), University of Exeter.
    Date: 23/02/2022
    Title: A Brief Introduction to White-box Cryptography
    Links: [Abstract] [Slides] [Video]

  • Speaker: Dr. Ruhul Amin
    Affiliation: Assistant Professor, Computer and Information Sciences Department, Fordham University 
    Date: 16/02/2022
    Title: Homology Based Sequence Annotation Algorithms
    Links: [Abstract] [Slides] [Video]


  • Speaker: Bibhas Chandra Das
    Affiliation: Research Scholar, IAI – TCG CREST
    Date: 09/02/2021
    Title: Dynamic Symmetric Searchable Encryption for Conjunctive Queries
    Links: [Abstract] [Slides] [Video]

  • Speaker: Dr. Dipayan Das
    Affiliation: Post Doctoral Fellow, CISPA-Helmholtz Center for Information Security
    Date: 29th December 2021
    Title: Digital Signatures from ID scheme: Lattice Challenges & Open Problems
    Links: [Abstract] [Slide] [Video]

  • Speaker: Dr. Satrajit Ghosh
    Affiliation: Assistant Professor, IIT Kharagpur
    Date: 22nd December 2021
    Title: In search for sub-linear PSI protocols
    Links: [Abstract] [Board-Work] [Video]

  • Speaker: Mr. Anirban Sanyal
    Affiliation: Department of Economics, UCSC
    Date: 17th December 2021
    Title: Forecasting with Real Time Information
    Links: [Slides]

  • Speaker: Dr. Kuldeep Saha
    Affiliation: Post Doctoral Fellow, IAI TCG CREST, Kolkata
    Date: 08th December 2021
    Title: Persistent Homolgy and Data Analysis
    Abstract:  In recent times, various tools from algebraic topology are  being heavily applied to tackle problems in data analysis. Persistent homology, for the past two decades, has been one of the main tools. We shall  talk about the basics of persistent homology and some of its applications.
    Links: [Slides] [Video]

  • Speaker: Prof. Mridul Nandi
    Affiliation: Professor, Indian Statistical Institute, Kolkata
    Date: 01st December 2021
    Title: Some Indifferentiable Attacks on Cryptographic Designs
    Links: [Abstract] [Board-work] [Video]


  • Speaker: Dr. Kaushik Chakraborty
    Affiliation: Senior Research Associate, University of Edinburgh, UK
    Date: 24th November 2021
    Title: How to Secure your Cryptosystem with Key-Recycling even if P=NP
    Links: [Slides] [Video]

  • Speaker: Dr. Payel Sadhukhan
    Affiliation: Post Doctoral Fellow, IAI, TCG CREST
    Date: 17th November 2021
    Title of the talk: Open set classification – when you predict more than what you learn
    Links: [Slides] [Video]

  • Speaker: Prof. Samiran Chattopadhyay
    Affiliation: Professor, IAI, TCG CREST
    Date: 10th November 2021
    Title of the talk: A Learning Experience in Performance Improvement of High Throughput Wireless Access Networks
    Links: [Slides] [Video]

  • Speaker: Mr. Arijit Shaw
    Affiliation: Junior Research Fellow, IAI, TCG CREST
    Date: 22nd October 2021
    Title of the talk: CrystallBall: Gazing in the Black Box of SAT Solving
    Links: [Slides] [Video] [Abstract]

  • Speaker: Prof. Rana Barua
    Affiliation: Visiting Scientist, IAI, TCG CREST
    Date: 22nd September 2021
    Title of the talk: On the equation $RX^2+SY^2\equiv 1\bmod N$ and its application to Cryptography
    Abstract: We shall look at attempts at solving the congruence and how it has been used in constructing certain cryptographic primitives.

  • Speaker: Prof. Utpal Chattopadhyay
    Affiliation: Professor at Indian Statistical Institute, Bangalore
    Date: 15th September 2021
    Title of the talk: Quantum Mechanics- Looking back after 100 years
    Links: [Abstract] [Video]

  • Speaker: Dr. Prasenjit Majumder
    Affiliation: Professor at DAIICT, Gandhinagar and Visiting Scientist at IAI, TCG-CREST.
    Date: 8th September 2021
    Title of the talk: Natural Language Processing: Miles to go
    Links: [Abstract] [Slides] [Video]
  • Speaker: Dr. Avijit Dutta
    Affiliation: Post-doctoral Scholar at IAI, TCG-CREST
    Date: 25th August, 2021
    Title of the talk: A Brief Introduction to Zero-Knowlege Proofs
    Links: [Slides] [Video]

  • Speaker: Prof. Bimal Kumar Roy (Inauguration talk)
    Affiliation: Professor at ISI, Honorary Chairman at IAI, TCG-CREST
    Date: 18th August 2021.
    Title of the talk: Some Interesting Ongoing Research Problems in Cryptology, Artificial Intelligence and Machine Learning, and Mathematics.