Soma Purkait

Mathematics Institute
University of Warwick
Coventry
CV4 7AL
United Kingdom

E-mail: Soma.Purkait@warwick.ac.uk

  Soma Purkait

I am currently a Research Fellow at Mathematics Institute, University of Warwick. I completed my PhD under the supervision of Professor Samir Siksek. My research interests broadly lie in number theory and I have been working on modular forms of half-integral weight. Here is a link to my thesis.

Previously, I did M.Math. degree at Indian Statistical Institute, Bangalore and worked under the supervision of Professor B.Sury.

 

Research Abstract

Let k be an odd integer and N be a positive integer divisibe by 4. Let χ be a Dirichlet character modulo N. Shimura decomposes the space of half-integral cusp forms of weight k/2, level N and character χ as a direct sum of subspace generated by single-variable theta-series and direct sum of subspaces of forms that are ''Shimura-equivalent'' to φ; here φ runs through the newforms of weight k-1, level dividing N/2 and character, square of χ. In my thesis I gave an explicit algorithm for computing this decomposition.
Once we have the decomposition, we can explore Waldspurger's theorem expressing the critical values of the L-functions of twists of an elliptic curve in terms of the coefficients of modular forms of half-integral weight. Following Tunnell, this often allows us to give a criterion for the n-th twist of an elliptic curve to have positive rank in terms of the number of representations of certain integers by certain ternary quadratic forms.
The Waldspurger's theorem comes with a hypothesis that the newforms of integral weight must have either level divisible by 16 or their corresponding local automorphic representation at the prime 2 must not be supercuspidal. I am currently interested in extending Waldspurger kind of result in general case by allowing supercuspidal representations at the prime 2 with small conductors. The other things I am interested in are questions regarding algebraicity of Fourier coefficients of half integral weight modular forms and distribution of the Fourier coefficients of half integral weight Hecke eigenforms.

 

Publications

  1. (Joint with N. Kumar) A note on the Fourier coefficients of half-integral weight modular forms. To appear in Archiv der Mathematik . on arXiv
  2. Hecke operators in half-integral weight. To appear in Journal de Théorie des Nombres de Bordeaux. on arXiv
  3. Explicit application of Waldspurger's theorem, LMS Journal of Computation and Mathematics, Vol. 16 (2013), 216-245.
  4. On Shimura's decomposition, International Journal of Number Theory, Vol. 9, no. 06, (2013), 1431-1445.
  5. (Joint with B. Sury) Some vanishing sums involving binomial coeffcients in the denominator, Albanian Journal of Mathematics,Vol. 2 (2008), 27-32.
 

Some MAGMA Codes

  1. For computing Shimura's decomposition (shimuraspacewtk.m)
  2. For computing the Shimura equivalent space of an elliptic curve that comes from theta series of ternary quadratic forms; it includes implementation of Dickson's algorithm (quadratic.m)
 

Teaching

I was a lecturer for MA3H1 Topics in Number Theory. Here is my lecture note.
Previously, I was teaching assistant for Topics in Number Theory during Autumn 2011 and for Analysis II during Spring 2011.
I have been supervisor of undergraduate first and second year Mathematics students since October 2008 to April 2012.  

Recent Visits, Conferences and Invited Talks

October 14-18, 2013: Women in Numbers workshop, CIRM Luminy.
September 16-20, 2013: Minicourses on Algebraic and Explicit Methods in Arithmetic, Laboratoire de Mathematiques de Besancon.
March 20-22, 2013: Attending Explicit Methods for Modular Forms, University of Warwick.
March 17-19, 2013: Attending Automorphic Forms and L-Functions, University of Darmstadt.
March 7, 2013: Invited speaker at OberSeminar, MPIM Bonn.
February 25-March 02, 2013: Visiting University of Luxembourg.
December 12, 2012: Invited speaker at Algebra and Number Theory Seminar, University of Luxembourg.
January 22, 2013: Invited speaker at Number Theory Seminar, University of Cologne.
January 01-March 31,2013: Visiting MPIM, Bonn, Germany.
December 12, 2012: Invited speaker at Number Theory Seminar, Tel Aviv University.
December 08-22, 2012: Visiting Technion - Israel Institute of Technology, Israel.
November 15 2012: Invited speaker at Oxford Number Theory Seminar.
October 01-03,2012: Attending Arithmetic of L-functions, University of Bristol.
September 24-28,2012: Attending Selmer Groups, Descent and the Distribution of Ranks, University of Warwick.
September 12, 2012: Speaking at Number Theory Seminar in Kyushu University, Japan.
August 06-10, 2012: Attending Building Bridges: 1st EU-US conference on Automorphic Forms and related topics in RWTH, Aachen.
June 17-22, 2012: Attending CNTA XII in Lethbridge.
June 10-17, 2012: Attending BIRS summer school on Contemporary methods for solving Diophantine equations.
April 2, 2012: Invited speaker at ISI Colloquium in Indian Statistical Institute, Bangalore.
February 22, 2012: Invited speaker at Bristol Heilbronn Seminar.
November 18, 2011: Giving a talk at London Mathematical Society GSM 2011.
August 29-September 8, 2011: Attending Summer School and Conference on "Computations with Modular Forms 2011" in Heidelberg.
July 12-14, 2011: Invited speaker at Foundation of Computational Mathematics 2011 in Budapest.
May 4-6, 2011: Attending the BSD conference in Cambridge.
April 18-21, 2011: Attending British Mathematical Colloquium 2011 in University of Leicester.
April 14-16, 2011: Giving a talk at Young Researchers in Mathematics 2011 in Warwick.

 

Photos

I love photography. Here is a small selection.

Curriculum Vitae

Here is my CV.