Schur Multiplier and Representation Theory (2025)

Convener(s)

 
Name:  Prof. Manoj Kumar Dr. Sunil Kumar Prajapati                    
Mailing Address: HRI Prayagraj IIT Bhubaneswar
Email: myadav at hri.res.in  skprajapati at iitbbs.ac.in

Abstract: It is well established that cohomology theory and representation theory of groups  have profound connections. Such connections also exist for category theory, Lie algebras and more.  In the proposed AIS, we have a plan to train students with basic cohomology and representation theory of groups so that they can explore these connections in group theory settings. Starting with the basics of the second cohomology group of a finite group; the restriction, inflation, and transgression homomorphisms will be studied, and the Hochschild-Serre exact sequence for cohomology of groups will be established. We then specialise to the  Schur multiplier M(G) of a finite group G, which is defined to be the second cohomology group of G with coefficients in C^{*}, the group of non-zero complex numbers. The Schur multiplier plays an important role in the theory of extensions of groups and the study of Projective representations of finite groups. Schur Multiplier is also used as a powerful tool in other areas such as algebraic number theory, block theory of group algebras, and classification of finite simple groups etc. On the other hand, representation theory, as is well known, is one of the very fundamental objects in mathematics.  Having its origins in algebra and number theory,  representation theory of groups has applications in diverse areas such as physics, statistics, and engineering, to name a few. This workshop will focus on the second cohomology of groups,  Schur multiplier, and (projective) representation theory of finite groups. Assuming that participants are familiar with groups, rings, and modules, in the first week, we will develop the basic character theory of representations in characteristic zero along with the concept of cohomology of finite groups. In the second week, we will discuss the projective representations of finite groups and the Schur Multiplier of finite groups in detail.  Representations of GL_2(F_q) will be discussed in adequate detail.

Dates: 

Thursday, December 4, 2025 - 09:00 to Tuesday, December 16, 2025 - 21:00

Venue: 

Venue Address: 

 

Harish-Chandra Research Institute, Prayagraj

 

 

Venue State: 

Venue City: 

PIN: 

211019

Syllabus: 

Detailed syllabus

Speaker

No. of Lectures (90 min.)

Detailed Syllabus

Sunil K Prajapati (IIT Bhubaneswar)

2

Group Representation (GR): Group representations and characters, Maschke’s Theorem and Complete Reducibility, Orthogonality Relations

Amit Kulshrestha (IISER Mohali)

2

Irreducibility Criteria (IC): Frobenius reciprocity theorem, conjugate representation, Mackey Irreducibility criteria, Wigner-Mackey Method of Little Group

Shripad Garge (IIT Bombay)

6

Group Cohomology (GC): Cohomology Groups, Second cohomology group, and central extensions, The homomorphism restriction, inflation and transgression, Hochschild-Serre exact sequence

Sumana Hatui (NISER Bhubaneswar)

4

Projective Representation (PR): Projective representation, twisted group algebra, representation groups (existence and characterization)

Pradeep Rai (Mahindra University, Hyderabad)

6

Schur Multiplier (SM): Basic results, Schur Multiplier of abelian groups, Schur’s formula, covering groups, exponent and central quotient, some results on p-groups

Anupam Kumar Singh (IISER Pune)

4

General linear group over F_q (GLG): Representations of GL_2(F_q)

References:

  1. M. Isaacs, Character Theory of Finite Groups
  2.  C. W. Curtis, Pioneers of Representation Theory
  3. J. Alperin and R. Bell, Groups and Representations
  4. G. Karpilovsky, Projective Representations of Finite Groups
  5. G. Karpilovsky, The Schur Multiplier
  6. J.-P. Serre, Linear Representations of Finite Groups
  7. W. Fulton and J. Harris, Representation Theory
  8. D.J. Benson, Representations and Cohomology, Volumes I and II

Tutor's Name with affiliation:

  1. Ram Karan Choudhary, IIT Bhubaneswar
  2. Saikat Panja, ISI Bangalore
  3. Vipul Kakkar, Central University of Rajasthan, Ajmer
  4. Harish Krishnani, IISER Mohali 

 

Time Table: 

 

 

Day

Date (Dec 2025)

Lecture 1

(9:30-11)

Tea (11:05-11:25)

Lecture 2 (11:30-1:00)

Lunch (1:05-2:25)

Tutorial Session (TS) (2:30-3:30)

Tea (3:35-3:55)

Tutorial Session (TS) (4:00-5:00)

Snacks (5:05-5:30)

Thur

04

SKP

 

SG

 

TS- GC

 

TS- GC

 

Fri

05

SKP

SG

TS- GR

TS- GR

Sat

06

AK

SG

TS- GC

TS- GC

Sun

07

AK

SG

TS- IC

TS- IC

Mon

08

SH

SG

TS- GC

TS- GC

Tues

09

SH

SG

TS- PR

TS- PR

WEDNESDAY-OFF

Thur

11

PKR

 

SH

 

TS- PR

 

TS- PR

 

Fri

12

PKR

SH

TS- SM

TS- SM

Sat

13

PKR

AKS

TS- PR

TS- GLG

Sun

14

PKR

AKS

TS- SM

TS- SM

Mon

15

PKR

AKS

TS- GLG

TS- GLG

Tues

16

PKR

AKS

TS- SM

TS- SM

 

Full forms for the abbreviations of speakers:

     SKP: Sunil Kumar Prajapati (IIT Bhubaneswar)

    AK: Amit Kulshrestha(IISER Mohali)

    SG: Shripad Garge (IIT Bombay)

    SH: Sumna Hatui (NISER Bhubaneswar)

    PKR: Pradeep Kumar Rai (Mahindra University)

    AKS: Anupam Kumar Singh (IISER Pune)

Full forms for the abbreviations related to the Tutorial session and Tutors' Name:

  1. TS- GR and TS- IC:Tutorial session on Group Representation (GR) and Irreducibility Criteria (IC)- Ram Karan Choudhary (IIT Bhubaneswar)

  2. TS- GC and TS- GLG: Tutorial session on Group Cohomology (GC) and General linear group over F_q (GLG)- Saikat Panja (ISI Bangalore)

  3. TS- PR: Tutorial session on Projective Representation (PR)- Harish Krishnani (IISER Mohali)

  4. TS- SM: Tutorial session on Schur Multiplier (SM)- Vipul Kakkar (Central University of Rajasthan, Ajmer)

Selected Applicants: 

 

 

 

 

How to Reach: 

TBA

School Short Name: 

smrt

Last Date Application: 

Monday, March 31, 2025

School Type: 

AIS

Separate faculty form: 

0