## Saturday, March 11, 2023

### Bruce Berndt (UIUC) - Thurs Mar 16 - 6:00 PM (Note Special Time)

Dear all,

We are happy to announce our next talk is by Professor Bruce Berndt, the world's biggest authority on Ramanujan's mathematics and related areas.

Please note the special time. It is two hours later than usual. Please circulate this announcement in your department.

Please see a further announcement below.

Talk Announcement:

Title: Finite Trigonometric Sums: Evaluations, Estimates, Reciprocity Theorems

Speaker: Bruce Berndt (University of Illinois at Urbana Champaign)
When: Mar 16, 2022, 6:00 PM- 7:00 PM IST (7:30 AM - 8:30 AM (CDT))

Abstract
First, motivated by a theorem in Ramanujan's lost notebook, Martino Fassina, Sun Kim, Alexandru Zaharescu, and the speaker developed representations for finite sums of products of trig functions for which we provided theorems and several conjectures.

Second, a paper of Richard McIntosh served as motivation.  First, he made a very interesting conjecture, which was recently proved by Likun Xie, Zaharescu, and the speaker.  Second, he examined a particular trigonometric sum, which inspired Sun Kim, Zaharescu, and the speaker to evaluate in closed form several classes of trigonometric sums, and find reciprocity theorems for others.

New conference announcement
A new conference on algebraic combinatorics has been announced by Arvind Ayyer. It is called
Meru Annual Combinatorics Conference
Dates: 29th to 31st May, 2023

## Sunday, February 26, 2023

### B. Ramakrishnan, ISI, Tezpur - Thursday, Mar 2, 2023 - 4:00 PM

The next talk is by B. Ramakrishnan (popularly known as Ramki), formerly of HRI, Allahabad, and now in ISI, Tezpur.

Talk Announcement:

Title: An extension of Ramanujan-Serre derivative map and some applications.

Speaker: B. Ramakrishnan (Indian Statistical Institute North-East Center, Tezpur)
When: Mar 2, 2022, 4:00 PM- 5:00 PM IST

Abstract

In this talk, we present a simple extension of the Ramanujan-Serre derivative map and
describe how it can be used to derive a general method for explicit evaluation of convolution sums  of the divisor functions. We provide explicit examples for four types of convolution sums.

This is a joint work with Brundaban Sahu and Anup Kumar Singh.

## Saturday, February 11, 2023

### Galina Filipuk, University of Warsaw - Thursday, Feb 16, 2023 - 4:00 PM

We are back to our usual time with a talk by Galina Filipuk all the way from Warsaw, Poland. Please note that we will be open to changing the time, since speakers from the US find this time to be very inconvenient, and we surely would like speakers from the US. The discussions in the previous talk went quite late into the night (for New Zealand) and we thank Shaun Cooper for a very nice talk.

Talk Announcement:

Title: (Quasi)-Painleve equations and Painleve equivalence problem

Speaker: Galina Filipuk (University of Warsaw, Poland)
When: Feb 16, 2022, 4:00 PM- 5:00 PM IST (11:30 CET in Warsaw)

Abstract

Painleve equations are second order nonlinear differential equations solutions of which have no movable critical points (algebraic singularities). They appear in many applications (e.g., in the theory of orthogonal polynomials) but in disguise. How to find a transformation to the canonical form? This is known as the Painleve equivalence problem.
The so-called geometric approach may help in many cases.

In this talk I shall present some recent results on the geometric approach for the Painleve and quasi-Painleve equations.

## Saturday, January 28, 2023

### Ramanujan Special: Shaun Cooper (Massey University) - Thursday, Feb 2, 2023 - 2:30 PM

Happy new year.

The first talk of the year (on Feb 2, 2023) is a "Ramanujan Special". This year's speaker is Shaun Cooper. Please note that the talk will be earlier than usual.

The last year was quite exciting for our group with many talks as well as a mini course. We hope this year is equally exciting. Please consider the seminar to present your latest preprint.

Talk Announcement: Ramanujan Special

Title: Apéry-like sequences defined by four-term recurrence relations: theorems and conjectures

Speaker: Shaun Cooper (Massey University, Auckland, New Zealand)

When: Feb 2, 2022, 2:30 PM- 3:30 PM IST (Note special time) (IST= GMT - 5:30)

Where: Zoom. Write to sfandnt@gmail.com for a link.

Abstract

The Apéry numbers are famous for having been introduced and used by R. Apéry to prove that~$\zeta(3)$ is irrational. They may be defined by the recurrence relation
$$(n+1)^3A(n+1)=(2n+1)(17n^2+17n+5)A(n)-n^3A(n-1),$$
with the single initial condition $A(0)=1$ being enough to start the recurrence. The Apéry numbers are all integers, a fact not obvious from the recurrence relation, and they satisfy interesting congruence properties. The generating function
$$y=\sum_{n=0}^\infty A(n)w^n$$
has a splendid parameterisation given by
$$y = \prod_{j=1}^\infty \frac{(1-q^{2j})^7(1-q^{3j})^7}{(1-q^{j})^5(1-q^{6j})^5} \quad \mbox{and} \quad w=q\,\prod_{j=1}^\infty \frac{(1-q^{j})^{12}(1-q^{6j})^{12}}{(1-q^{2j})^{12}(1-q^{3j})^{12}}.$$
In this talk I will briefly survey other sequences defined by three-term recurrence relations that have properties similar to those satisfied by the Apéry numbers described above. I will also introduce some sequences defined by four-term recurrence relations and describe some of their properties.

Several conjectures will be presented.

Here are the slides of the talk.

## Saturday, November 12, 2022

### Nishu Kumari (IISc, Bangalore) - Thursday Nov 17, 2022 - 4:00 PM to 5:00 PM

Dear all,

The next talk is by Nishu Kumari, a graduate student in IISc, Bangalore. The announcement is below.

Talk Announcement

Title: Factorization of Classical Characters twisted by Roots of Unity

Speaker: Nishu Kumari (IISc, Bangalore)

When: Thursday, November 17, 2022 - 4:00 PM - 5:00 PM (IST)

Abstract:

Schur polynomials are the characters of irreducible representations of classical groups of type A parametrized by partitions. For a fixed integer $t \geq 2$ and a primitive $t$'th root of unity \omega, Schur polynomials evaluated at elements $\omega^{k} x_i$ for $0 \leq k \leq t-1$ and $1 \leq i \leq n$, were considered by D. J. Littlewood (AMS press, 1950) and independently by D. Prasad (Israel J. Math., 2016). They characterized partitions for which the specialized Schur polynomials are nonzero and showed that if the Schur polynomial is nonzero, it factorizes into characters of smaller classical groups of type A.

In this talk, I will present a generalization of the factorization result to the characters of classical groups of type B, C and D. We give a uniform approach for all cases. The proof uses Cauchy-type determinant formulas for these characters and involves a careful study of the beta sets of partitions. This is joint work with A. Ayyer and is available here. (Preprint: https://arxiv.org/abs/2109.11310)

## Tuesday, November 1, 2022

### Nicholas Smoot (RISC, Johannes Kepler University, Linz, Austria) - Thursday Nov 3, 2022 - 4:00 PM to 5:00 PM

The talk this week is by Nicholas Smoot from the Research Institute of Symbolic Computation (RISC) at Johannes Kepler University (JKU), Linz, Austria. The announcement is below.

Talk Announcement:

Title:  Partitions, Kernels, and Localization

Speaker: Nicholas A. Smoot (RISC at JKU, Austria)

When: Thursday, November 3, 2022 - 4:00 PM - 5:00 PM (IST)

Where: Zoom. Please write to the organisers if you require the link (sfandnt@gmail.com)

Abstract:

Since Ramanujan's groundbreaking work, a large variety of infinite congruence families for partition functions modulo prime powers have been discovered. These families vary enormously with respect to the difficulty of proving them. We will discuss the application of the localization method to proving congruence families by walking through the proof of one recently discovered congruence family for the counting function for 5-elongated plane partitions. In particular, we will discuss a critical aspect of such proofs, in which the associated generating functions of a given congruence family are members of the kernel of a certain linear mapping to a vector space over a finite field. We believe that this approach holds the key to properly classifying congruence families.

## Sunday, October 16, 2022

### Sunil L. Naik (IMSc, Chennai) - Thursday, October 20, 2022 - 4:00 PM - 5:00 PM (IST)

Our next speaker is Sunil Naik, a grad student in IMSc, Chennai.

Talk Announcement:

Title:  Prime factors of non-zero Hecke eigen values

Speaker: Sunil L. Naik (IMSc, Chennai)

When: Thursday, October 20, 2022 - 4:00 PM - 5:00 PM (IST)

Abstract:

The non-vanishing as well as primitivity of the values of the Fourier
coefficients of non-CM Hecke eigen forms, in particular the Ramanujan
$\tau$ function is a deep and mysterious theme in Number theory.
In this talk, we will report on our recent work on the number of
distinct prime factors of the values of the Fourier coefficients of
non-CM Hecke eigen forms, in particular the Ramanujan $\tau$ function.

## Saturday, September 17, 2022

### Kaneenika Sinha (IISER, Pune) - Mini Course - Thursday, Sept 22 and Oct 6 - 4-5:00 PM (IST)

We are happy that Kaneenika Sinha (IISER, Pune) has consented to give a mini-course on Central limit theorems in number theory. The course will comprise two lectures. The announcement is below. Graduate students who are interested in number theory are especially welcome to hear Professor Sinha.

Mini-course announcement

Title:  Central Limit theorems in Number Theory

Speaker: Kaneenika Sinha (IISER, Pune)

Abstract:
The goal of these lectures is to review a theme that binds the study of different types of arithmetic functions, namely central limit theorems.  After reviewing the "prototype" theorem in this theme, namely the classical Erdos-Kac theorem about the prime-omega function, we will survey different types of central limit theorems in the context of zeroes of zeta functions, eigenvalues of Hecke operators acting on spaces of cusp forms and eigenvalues of regular graphs.

Talk 1:  Thursday, September 22, 2022 - 4:00 PM - 5:00 PM (IST)

Talk 2:  Thursday, October 6, 2022 - 4:00 PM - 5:00 PM (IST)

Talk 1

Talk 2

## Friday, September 2, 2022

### Ole Warnaar (Queensland, Australia) - Thursday, September 8, 2022 - 4:00 PM-5 PM (IST)

After a refreshing break in a summer with many opportunities to meet in person, we are back with a talk by Professor Ole Warnaar of the University of Queensland, Australia.

Talk Announcement:

Title:  Cylindric partitions and Rogers--Ramanujan identities

Speaker: S. Ole Warnaar (University of Queensland, Australia)

When: Thursday, September 8, 2022 - 4:00 PM - 5:00 PM (IST)

Abstract:

Cylindric partitions, first introduced by Gessel and
Krattenthaler in 1997, are an affine (or toroidal) analogue of
ordinary plane partitions. Perhaps somewhat surprisingly, cylindric
partitions have a close connection to Rogers--Ramanujan-type $q$-series
identities. In this talk I will try to explain this connection, and report
on some new Rogers--Ramanujan identities for the affine Lie algebra
$\mathrm{A}_2^{(1)}$ that follow naturally from this connection.

## Friday, June 24, 2022

### Neelam Kandhil (IMSc, Chennai) - Thursday, June 30, 2022 - 4:00 PM - 5:00 PM (IST)

We are delighted to welcome Neelam Kandhil  (soon to become Dr. Neelam Kandhil) of IMSc, Chennai for our next talk.  The talk announcement is below.

Talk Announcement:

Title:  On an extension of a question of Baker

SpeakerNeelam Kandhil (IMSc, Chennai)

When: Thursday, June 30, 2022 - 4:00 PM - 5:00 PM (IST)

Abstract:

It is an open question of Baker whether the numbers $L(1, \chi)$ for non-trivial Dirichlet characters $\chi$ with period $q$ are linearly independent over $\mathbb{Q}$. The best known result is due to Baker, Birch and Wirsing which affirms this when $q$ is co-prime to $\varphi(q)$.  In this talk, we will discuss an extension of this result to any arbitrary family of moduli. The interplay between the resulting ambient number fields brings in new technical issues and complications hitherto absent in the context of a fixed modulus. In the process, we also extend a result of Okada about linear independence of the cotangent values over $\mathbb{Q}$ as well as a result of Murty-Murty about ${\overline{\mathbb{Q}}}$ linear independence of such $L(1, \chi)$ values.

If time permits, we will also discuss the interrelation between the non-vanishing of Dedekind zeta values and its derivatives.

## Monday, May 30, 2022

### Arindam Roy (UNC, Charlotte) - Thursday, June 2, 2022 - 3:55 PM

Our next speaker is Arindam Roy of the University of North Carolina at Charlotte. The talk announcement is below.

Talk Announcement:

Title: On the Hyperbolicity of Jensen Polynomials for Power Partitions.

Speaker: Arindam Roy (UNC, Charlotte)

When: Thursday, June 2, 2022 - 4:00 PM - 5:00 PM (IST)

Where: Zoom

Abstract:

Polya established that the Riemann Hypothesis is equivalent to the hyperbolicity of Jensen polynomials for the Riemann zeta function. This led to the study of Jensen polynomials for large classes of functions. Recently, Jensen polynomials for various partition functions and more generally, the Jensen polynomials for weakly holomorphic forms are considered. Their hyperbolicity was established under various conditions. In this talk we will consider the Jensen polynomials for power partitions and discuss the hyperbolicity of these Jensen polynomials

## Wednesday, May 18, 2022

### Amita Malik (Max Plank Institute, Bonn) - Thursday, May 19, 2022 - 4:00 PM - 5:00 PM (IST)

Our next speaker is Amita Malik of the Max Plank Institute. The talk announcement is below.

Talk Announcement:

Title: Partitions into primes in arithmetic progressions

Speaker: Amita Malik (Max Plank Institute, Bonn)

When: Thursday, May 19, 2022 - 4:00 PM - 5:00 PM (IST)

Abstract:

In this talk, we discuss the asymptotic behavior of the number of partitions into primes in arithmetic progressions. While the study for ordinary partitions goes back to Hardy and Ramanujan, partitions into primes were recently re-visited by Vaughan. Our error term is sharp and improves on previous known estimates in the special case of primes as parts of the partition. As an application, monotonicity of this partition function is established explicitly via an asymptotic formula.

## Saturday, April 30, 2022

### Murali K Srinivasan (IIT Bombay) - Thursday, May 5, 2022

Our next speaker is Murali Srinivasan of IIT Bombay (at Mumbai). The talk announcement is below.

Talk Announcement:

Title: A q-analog of the adjacency matrix of the n-cube.

Speaker: Murali K Srinivasan (IIT Bombay)

When: Thursday, May 5, 2022 - 4:00 PM - 5:00 PM (IST)

Where: Zoom

Abstract:

Random walk on the $n$-cube gives rise to two matrices, the adjacency matrix and the Kac matrix, that have an elegant spectral theory with many applications.

We define a random walk on subspaces that yields q-analogs of the adjacency and Kac matrices with an equally elegant spectral theory (though more difficult to prove). We give an application to tree counting.

This is joint work with Subhajit Ghosh.

## Monday, April 18, 2022

### Gaurav Bhatnagar - Talk 2 on Thursday, April 21, 2022

On the coming Thursday, Atul Dixit (IIT, Gandhinagar) and Gaurav Bhatnagar (Ashoka University) will present the talks they presented at the recently concluded JMM meeting held online. Each talk will be approximately 20 minutes followed by 10 minutes for questions. The titles and abstracts are below.

Here is the announcement for the second talk of the day.

Title: An easy proof of  Ramanujan's famous mod $5$ congruences

Speaker: Gaurav Bhatnagar (Ashoka University)

When: Thursday, April 21, 2022 - 4:30 PM - 5:00 PM

Where: Zoom

Abstract

We give an elementary proof of Ramanujan's famous congruences $p(5n+4) \equiv 0 \mod 5$ and $\tau(5n+5)\equiv 0 \mod 5$. The proof requires no more than Euler's techniques and a result of Jacobi. The proof extends to embed the congruences into 4 infinite families of congruences for rational powers of the eta function.

This is joint work with Hartosh Singh Bal.

The video below is the same as the one in Atul's talk. It just begins in the middle.

### Atul Dixit (IIT Gandhinagar) - Talk 1 on Thursday April 21, 4:00 PM - 4:30 PM

Dear all,

On the coming Thursday, Atul Dixit (IIT, Gandhinagar) and Gaurav Bhatnagar (Ashoka University) will present the talks they presented at the recently concluded JMM meeting held online. Each talk will be approximately 20 minutes followed by 10 minutes for questions. The titles and abstracts are below.

We should say that during the summer, the talks in the seminar may be less as we are finally able to catch up with colleagues in person.

Here is the announcement for Atul's talk.

Title:  Combinatorial identities associated with a bivariate generating function for overpartition pairs

Speaker: Atul Dixit (IIT, Gandhinagar)

When: Thursday, April 21, 2022 - 4:00 PM - 4:30 PM

Where: Zoom

Abstract

We obtain a three-parameter $q$-series identity that generalizes two results of Chan and Mao. By specializing our identity, we derive new results of combinatorial significance in connection with $N(r, s, m, n)$, a function counting certain overpartition pairs recently introduced by Bringmann, Lovejoy and Osburn. For example, one of our identities gives a closed-form evaluation of a double series in terms of Chebyshev polynomials of the second kind, thereby resulting in an analogue of Euler's pentagonal number theorem. Another of our results expresses a multi-sum involving $N(r, s, m, n)$ in terms of just the partition function $p(n)$. Using a result of Shimura we also relate a certain double series with a weight 7/2 theta series. This is joint work with Ankush Goswami.