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Monday, 30 June 2025
Time Speaker Title Resources
09:45 to 10:00 Prof. Rajesh Gopakumar (ICTS-TIFR, Bengaluru, India) Welcome remarks
10:00 to 11:15 Ram Murty (Queen's University, Kingston, Canada) Ramanujan, Modular Forms and Beyond

This is an informal survey of the theories of modular forms, quasi-modular forms, and mock modular forms. These topics owe much to Srinivasa Ramanujan whose mystic vision of mathematics shaped 20th century number theory and now continues to shape the 21st century going beyond number theory and into combinatorics, representation theory and even mathematical physics!

11:45 to 13:00 Nick Andersen (Brigham Young University, Provo, USA) Introduction to harmonic Maass forms

We discuss the definitions and basic properties of harmonic Maass forms having arbitrary weight, level, and multiplier system. These properties include: (1) the Fourier expansion, (2) decomposition into holomorphic & non-holomorphic parts, (3) the Maass raising and lowering operators, and the xi operator, and (4) mock modular forms and shadows.

14:30 to 15:30 Michael Griffin (Vanderbilt University, USA) Maas operators in integral weight

We discuss the Maass operators in integer weight. We consider Bol's identity, along with its image and relation to the xi operator, as well as the Petersson inner product and the Bruinier-Funke pairing.

15:35 to 16:25 Ranveer Kumar Singh (Rutgers University, New Jersey, USA) Generalization of Monster denominator identity to higher level using harmonic Maass forms

The Monster denominator identity is an infinite product representation of j(z)-j(\tau), where j is the Klein’s j-function invariant under the action of SL(2,Z). I will describe a generalization of the Monster denominator formula to higher level using harmonic Maass forms.

17:00 to 18:00 Ken Ono (University of Virginia, Charlottesville, USA) Eichler-Selberg Relations for Traces of Singular Moduli

The Eichler–Selberg trace formula expresses the trace of Hecke operators on spaces of cusp forms as weighted sums of Hurwitz–Kronecker class numbers. We extend this formula to a natural class of relations for traces of singular moduli, where one views class numbers as traces of the constant function \( j_0(\tau) = 1 \). More generally, we consider the singular moduli for the Hecke system of modular functions. For each \( \nu \geq 0 \) and \( m \geq 1 \), we obtain an Eichler–Selberg relation. For \( \nu = 0 \) and \( m \in \{1, 2\} \), these relations are Kaneko’s celebrated singular moduli formulas for the coefficients of \( j(\tau) \). For each \( \nu \geq 1 \) and \( m \geq 1 \), we obtain a new Eichler–Selberg trace formula for the Hecke action on the space of weight \( 2\nu + 2 \) cusp forms, where the traces of \( j_m(\tau) \) singular moduli replace Hurwitz–Kronecker class numbers.

Tuesday, 01 July 2025
Time Speaker Title Resources
09:30 to 10:45 Michael Griffin (Vanderbilt University, USA) Examples of harmonic Maass forms of integral weight

We give explicit examples of harmonic Maass forms of integral weight, including non-holomorphic Eisenstein series and Weierstraass-mock modular forms. We also discuss Borcherds' obstruction theorem (a consequence of Serre-duality).

11:15 to 12:30 Nick Andersen (Brigham Young University, Provo, USA) Examples of harmonic Maass forms of half-integral weight

We give motivating examples of harmonic Maass forms of half-integral weight, including Poincare series and Zagier's Eisenstein series. We also discuss the sesquiharmonic lift of Zagier's Eisenstein series by Duke, Imamoglu, and Toth.

14:30 to 15:30 Koustav Banerjee (University of Cologne, Köln, Germany) Mock modular forms and partition statistics: a Fine set up

In this talk, I will present in brief the (pair of) Rogers–Ramanujan identities from MacMahon’s perspective and then following Fine’s framework, will discuss on certain partition statistics which are related to mock theta functions. This is an ongoing joint work with Kathrin Bringmann.

16:00 to 17:00 Atul Dixit (IIT Gandhinagar, India) Combinatorics of certain third order mock theta functions and their generalizations

Mock theta functions lie at the interface of harmonic Maass forms and combinatorics. While the former deals with their analytic behavior, the latter aims at viewing them as generating functions of interesting restricted partition functions.

In 2015, George Andrews, Ae Ja Yee and I found out that Ramanujan's third mock theta functions $\omega(q)$ and $\nu(q)$ have nice partition-theoretic interpretations. Along with Daniel Schultz, we subsequently studied overpartitions related to $\omega(q)$. A year later, Andrews and Yee established beautiful results involving bivariate generalizations of these third order mock theta functions, thereby extending their earlier results with the speaker. Generalizing the Andrews-Yee identities for Choi's trivariate generalizations of these mock theta functions remained a mystery and was partially solved by Bruce Berndt, Rajat Gupta and I.

The first part of this talk will be a survey on these works. In the second part, we will announce new results in an ongoing related work with Kathrin Bringmann and Koustav Banerjee.

Wednesday, 02 July 2025
Time Speaker Title Resources
09:30 to 10:45 Michael Griffin (Vanderbilt University, USA) Hecke theory of harmonic Maass forms

We review the basic properties of hecke operators, Atkin-Lehner involutions and trace operators, and show how these operators act on harmonic Maass forms. We also discuss certain p-adic results that follow from this theory.

11:15 to 12:30 Nick Andersen (Brigham Young University, Provo, USA) Introduction to mock theta functions

We give a brief introduction to the history of mock theta functions, beginning in 1920 with Ramanujan's last letter to Hardy, and ending just before Zwegers' thesis in 2002

14:30 to 15:30 Balesh Kumar (IIT Ropar, India) Traces of cycle integral attached to harmonic weak Maass forms

We discuss the traces of cycle integral attached to harmonic Maass forms of negative weights. Also we discuss some applications of it, classifying weakly holomorphic modular forms which lie in the space of harmonic weak cusp forms in terms of vanishing of certain `modified' traces.

16:00 to 17:00 Vaibhav Kalia (IIT Ropar, India) Traces of Poincaré series at square discriminants and Fourier coefficients of mock modular forms

In this talk, we discuss the Fourier coefficients of a family of mock modular forms that extends Borcherds' basis of weakly holomorphic modular forms. We define modified traces of cycle integrals of Poincaré series and sesqui-harmonic Maass forms at square discriminants, which provide an explicit interpretation of these coefficients. We also explore the relationship between these modified traces and the regularized inner products of (weakly) holomorphic modular forms. This is joint work with Balesh Kumar.

Thursday, 03 July 2025
Time Speaker Title Resources
09:30 to 10:30 Michael Griffin (Vanderbilt University, USA) Indefinite theta functions

We review the theory of ordinary theta functions, followed by a brief introduction to Zweger's theory of indefinite theta functions.

11:00 to 12:00 Nick Andersen (Brigham Young University, Provo, USA) Mock theta functions in the context of harmonic Maass forms

As a continuation of our previous lecture, we study the mock theta functions in the context of harmonic Maass forms, beginning with Zwegers' thesis in 2002. We discuss (1) universal mock theta functions, (2) a proof of the mock theta conjectures, and (3) exact formulas for coefficients of mock theta functions, beginning with Dragonette and Andrews.

14:30 to 15:30 Rajat Gupta (University of Maine, Orono, Maine, USA) Summation Formulas: From Classical Foundations to Harmonic Maass Forms

In the first part of this talk, I will provide a brief introduction to classical summation formulas and their significance in number theory. We will review the foundational contributions of Bochner, Koshliakov, and the seminal work of Chandrasekharan and Narasimhan on summation formulas for a broad class of arithmetical functions.

In the second part, I will present recent developments involving new summation formulas in the theory of harmonic Maass forms. As an application of our summation formula, I will discuss the asymptotic behavior of the Riesz means of the Hurwitz class numbers.\\

This talk is based on recent joint work with Olivia Beckwith, Nikolaos Diamantis, Larry Rolen, and Kalani Thalagoda.

16:00 to 17:00 Aradhita Chattopadhyaya (CMI, Siruseri, India) Mock modular forms in Vafa Witten theory

Computation of rank N semi-stable sheaves on complex projective plane leads to Appell Lerch sums which in turn are generating functions of instantons in field theories namely Vafa Witten theory. The mock modular properties of these Appell Lerch sums can be understood from Vigneras' theorem. We study the properties of these higher depth mock modular forms and their explicit construction when the gauge group is SU(N). In our ongoing work we also show that the holomorphic anomaly associated with these partition functions correspond to gauge groups of lower ranks.

Friday, 04 July 2025
Time Speaker Title Resources
09:30 to 10:45 Micheal Griffin (Vanderbilt University, USA) Theta lifts and holomorphic projection

We briefly cover two selected topics: 1) The principle of holomorphic projection, and 2) theta lifts.

11:15 to 12:30 Nick Andersen (Brigham Young University, Provo, USA) Cycle integrals of the j-function by Duke, Imamoglu, and Toth

We present the work of Duke, Imamoglu and Toth on cycle integrals of the j-function and mock modular forms.

14:30 to 15:30 Ram Murty (Queen's University, Kingston, Canada) The Partition Function Revisited

The asymptotic behavior of the partition function was first determined by Hardy and Ramanujan in 1918 using their famous circle method. Since then, many new ways of deriving their asymptotic formula have been discovered. I will discuss these and report on my recent work with Karin Ikeda.

16:00 to 17:00 Ashoke Sen (ICTS-TIFR, Bengaluru, India) Why Are Siegel Modular Forms Relevant for Black Hole Physics?

I shall review why Siegel modular forms are relevant for the study of black holes in string theory