Conformal Densities on Limit Sets

NOTE: THIS TALK WAS CANCELLED.

Speaker: Chaitanya Tappu

Date: 1st May 2018

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

We will quickly recap the last talk (hyperbolic space, discrete group of hyperbolic motions, limit sets). We will show the construction of measures on the boundary which possess nice ergodicity properties with respect to the action of the group on the boundary. Specifically, if the group is non-elementary or has bounded fundamental domain, then the action is ergodic on the conical limit set.

Prerequisites:

I will assume familiarity with linear algebra and metric space topology. Attendance in the previous talk on 17 April would help.

 

Area: Hyperbolic geometry, Ergodic theory

References: 

1. Nicholls, P.J. (1989). The Ergodic Theory of Discrete Groups, volume 143 of the London Mathematical Society Lecture Note Series. Cambridge University Press.

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What are modular forms?

Speaker: Pramath Anamby

Date: 24th April 2018

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

Modular forms are interesting number theoretic objects and are used widely to study arithmetic functions. In this talk I will briefly introduce modular forms, mainly through examples.

Prerequisites:

Basics of number theory, linear algebra and complex analysis.

 

Area: Number Theory

Discrete Groups and Limit Sets

Speaker: Chaitanya Tappu

Date: 17th April 2018 (Tuesday)

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

We will define the n-dimensional hyperbolic space. An object of study in hyperbolic geometry is the group of isometries, i.e. distance preserving transformations of the hyperbolic space, and its action on the hyperbolic space. These correspond to Mobius transformations, and their action extends onto the boundary of the hyperbolic space. The action of discrete subgroups of this group has orbits that accumulate on the limit set, which lies on the boundary. We will show the construction of measures on the limit set which possess nice ergodicity properties with respect to this action.

Prerequisites:  Familiarity with linear algebra and metric space topology will be assumed.

 

Area: Hyperbolic Geometry, Ergodic Theory

References: 

1. Nicholls, P.J. (1989). The Ergodic Theory of Discrete Groups, vol. 143 of London Mathematical Society Lecture Note Series, Cambridge University Press

Two Summation Formulas for Arithmetical Functions and a Few Applications

Speaker: Ritwik Pal

Date: 10th April 2018 (Tuesday)

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

Various summation formulas are very important tools in analytic number theory. We here wish to discuss two elementary (they don’t need complex analysis) summation formulas, namely, Abel’s summation formula and Dirichlet’s hyperbola method. We will also show some applications of them to estimate sums. I hope that the talk will be accessible to students who have had a course in real analysis in one variable.

Prerequisites:  Basic real analysis

 

Area: Number Theory

Basics of discrete time Markov chains with finite state space

Speaker: Subhajit Ghosh

Date: 3rd April 2018 (Tuesday)

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

In this talk, I shall discuss discrete time Markov chains with finite state space briefly. Mainly, I’ll prove a version of the Perron-Frobenius theorem, which ensures the existence and uniqueness of the stationary distribution for irreducible chains; moreover, if the chain is aperiodic, then the distribution after the nth transition will converge to the stationary distribution.

Prerequisites: Basic Probability and Linear Algebra

 

Area: Probability

Alternating Sign Matrices (ASMs)

Speaker: Nimisha Pahuja

Date: 27th March 2018 (Tuesday)

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

ASMs are a class of square matrices in combinatorics. The formula enumerating all nxn ASMs was conjectured in 1983 and it took nearly two decades to find a bijective proof for the identity. In this talk, I will briefly go over the proof and will discuss a few of the many objects like plane partitions, fully packed loops etc. which are in bijection with ASMs. Further, I will give some of their applications.

Prerequisites: Basic Linear Algebra and elementary ideas about bijections and recursions.

Area: Combinatorics

Identities vs. Bijections

Speaker: Abhay Jindal

Date: 20th March 2018 (Tuesday)

Time: 09:15 pm-10:15 pm

Venue: Lecture Hall I, Department of Mathematics

Abstract:

This talk is based on the chaper “Identities vs. Bijection” from the celebrated book “Proofs from the Book”.

As is well known that infinite products are replete with unexpected identities, in many cases the coefficients of the monomials can be given a combinatorial meaning. And, in this talk, we would discover many such fascinating interpretations.

Area: Combinatorial Identities in Number Theory

References:

1. Proofs from THE BOOK, by Martin Aigner and Gunter M. Ziegler.