Dear all,
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Abstract:
Organizers: Gaurav Bhatnagar (Ashoka University) , Atul Dixit (IIT, Gandhinagar) and Krishnan Rajkumar (JNU). Contact: sfandnt@gmail.com
Dear all,
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Abstract:
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:
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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.
Our next speaker is Sunil Naik, a grad student in IMSc, Chennai.
Talk Announcement:
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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.
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
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Talk 1
Talk Announcement:
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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.
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:
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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.
Our next speaker is Arindam Roy of the University of North Carolina at Charlotte. The talk announcement is below.
Talk Announcement:
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Abstract:
Our next speaker is Amita Malik of the Max Plank Institute. The talk announcement is below.
Talk Announcement:
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Abstract:
Our next speaker is Murali Srinivasan of IIT Bombay (at Mumbai). The talk announcement is below.
Talk Announcement:
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Abstract:
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.
Dear all,
Our next speaker is Soumyarup Banerjee of IIT, Gandhinagar. The talk announcement is below.
Talk Announcement:
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Abstract:
Our next speaker of Wenguang Zhai of the China Institute of Mining and Technology, Beijing, who will speak on recent work with Xiadong Cao (Beijing Institute of Petro-Chemical Technology, Beijing) and Yoshio Tanigawa (Nagoya, Japan).
Talk Announcement:
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Abstract:
The next talk is by Krishnan Rajkumar. This talk will be recorded but not available online immediately.
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Abstract:
Gaurav Bhatnagar (Ashoka), Atul Dixit (IIT, Gandhinagar) and Krishnan Rajkumar (JNU)
Dear all,
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Abstract: In a series of works, Zhi-Guo Liu extended some of the central summation and transformation formulas of basic hypergeometric series. In particular, Liu extended Rogers' non-terminating very-well-poised $_{6}\phi_{5}$ summation formula, Watson's transformation
formula, and gave an alternate approach to the orthogonality of the Askey-Wilson polynomials. These results are helpful in number-theoretic contexts too. All this work relies on three expansion formulas of Liu.
This talk will present several infinite families of extensions of Liu's fundamental formulas to multiple basic hypergeometric series over root systems. We will also discuss results that extend Wang and Ma's generalizations of Liu's work which they obtained using $q$-Lagrange inversion. Subsequently, we will look at an application based on the expansions of infinite products. These extensions have been obtained using the $A_n$ and $C_n$ Bailey transformation and other summation theorems due to Gustafson, Milne, Milne and Lilly, and others, from $A_n$, $C_n$ and $D_n$ basic hypergeometric series theory. We will observe how this approach brings Liu's expansion formulas within the Bailey transform methodology.
This talk is based on joint work with Gaurav Bhatnagar. (https://arxiv.org/abs/2109.02827)
Gaurav Bhatnagar (Ashoka), Atul Dixit (IIT, Gandhinagar) and Krishnan Rajkumar (JNU)
sfandnt@gmail.com
Dear all,
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Abstract:
A matrix $M$ of real numbers is called totally positive
if every minor of $M$ is nonnegative. Gantmakher and Krein showed
in 1937 that a Hankel matrix $H = (a_{i+j})_{i,j \ge 0}$
of real numbers is totally positive if and only if the underlying
sequence $(a_n)_{n \ge 0}$ is a Stieltjes moment sequence.
Moreover, this holds if and only if the ordinary generating function
$\sum_{n=0}^\infty a_n t^n$ can be expanded as a Stieltjes-type
continued fraction with nonnegative coefficients:
$$
\sum_{n=0}^{\infty} a_n t^n
\;=\;
\cfrac{\alpha_0}{1 - \cfrac{\alpha_1 t}{1 - \cfrac{\alpha_2 t}{1 - \cfrac{\alpha_3 t}{1- \cdots}}}}
$$
(in the sense of formal power series) with all $\alpha_i \ge 0$.
So totally positive Hankel matrices are closely connected with
the Stieltjes moment problem and with continued fractions.
Here I will introduce a generalization: a matrix $M$ of polynomials
(in some set of indeterminates) will be called
coefficientwise totally positive if every minor of $M$
is a polynomial with nonnegative coefficients. And a sequence
$(a_n)_{n \ge 0}$ of polynomials will be called
coefficientwise Hankel-totally positive if the Hankel matrix
$H = (a_{i+j})_{i,j \ge 0}$ associated to $(a_n)$ is coefficientwise
totally positive. It turns out that many sequences of polynomials
arising naturally in enumerative combinatorics are (empirically)
coefficientwise Hankel-totally positive. In some cases this can
be proven using continued fractions, by either combinatorial or
algebraic methods; I will sketch how this is done. In many other
cases it remains an open problem.
One of the more recent advances in this research is perhaps of
independent interest to special-functions workers:
we have found branched continued fractions for ratios of contiguous
hypergeometric series ${}_r \! F_s$ for arbitrary $r$ and $s$,
which generalize Gauss' continued fraction for ratios of contiguous
${}_2 \! F_1$. For the cases $s=0$ we can use these to prove
coefficientwise Hankel-total positivity.
Reference: Mathias P\'etr\'eolle, Alan D.~Sokal and Bao-Xuan Zhu,
arXiv:1807.03271