Srinivasa Ramanujan is widely regarded as the father of modern Partial Differential Equations due to his groundbreaking work in the field.

Harish-Chandra made significant contributions to the theory of linear partial differential equations, particularly in the area of representation theory.

S. Chandrasekhar developed the method of characteristics for solving partial differential equations, which is widely used in various fields of physics and engineering.

M. S. Narasimhan made significant contributions to the study of nonlinear partial differential equations, particularly in the area of algebraic geometry.

K. S. Chandrasekharan is considered as one of the pioneers of the theory of distributions, which is a fundamental tool in the study of partial differential equations.

S. R. Srinivasa Varadhan made significant contributions to the study of parabolic partial differential equations, particularly in the area of stochastic analysis.

Laxmi Narasimhan developed the theory of weak solutions for partial differential equations, which is a fundamental concept in the study of nonlinear partial differential equations.

V. S. Varadarajan made significant contributions to the study of the Navier-Stokes equations, which are fundamental in fluid dynamics.

S. R. Srinivasa Varadhan developed the theory of regularity for solutions of partial differential equations, which is a fundamental concept in the study of partial differential equations.

H. L. Royden made significant contributions to the theory of viscosity solutions, which is a fundamental concept in the study of nonlinear partial differential equations.

Harish-Chandra developed the theory of harmonic analysis on Lie groups, which is a fundamental tool in the study of partial differential equations.

M. S. Narasimhan made significant contributions to the theory of potential theory, which is a fundamental tool in the study of partial differential equations.

R. S. Kulkarni made significant contributions to the theory of boundary value problems for partial differential equations, particularly in the area of elliptic partial differential equations.

A. K. Varma made significant contributions to the theory of singular integrals, which is a fundamental tool in the study of partial differential equations.

M. S. Narasimhan made significant contributions to the theory of pseudo-differential operators, which is a fundamental tool in the study of partial differential equations.