Welcome to the Home Page of William Sit
Professor Emeritus
Department of Mathematics
The City College of The City University of New York
160 Convent Avenue, New York, NY 10031
Office: R6/291D (North Academic Center)
Office Tel: 212-650-5179
Office Fax: 212-862-0004
Email: wsit@ccny.cuny.edu

Home Page: wsit.ccny.cuny.edu  Last Updated on: January 31, 2016

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My research interests are differential algebra, computer algebra, and their intersection. One area of differential algebra studies the solution space of systems of partial differential polynomial equations and develops algorithms to simplify such systems when possible. My earlier papers were related to differential Galois theory, differential algebraic groups, and dimension theory. Later papers were more algorithmically oriented. I have published algorithms on parametric linear systems, on quasi-algebraic sets, on finding first integrals of autonomous systems and (with Leon Pritchard) on simplifying over-determined non-linear systems of ordinary differential equations. Recently my research (jointly with Li Guo and others) is related to the classification of linear operators on associative algebras, a problem first posed by Gian-Carlo Rota in the 1970s. Other symbolic computation projects involved Mathematica Notebooks for differential equations, Rota-Baxter type algebras and differential type algebras, and for recreation, crossnumber puzzles. For details, please click here.

The algorithms on parametric linear equations, first integrals, and initial value problems for non-linear ordinary differential equations are implemented in Axiom. The algorithms to enumerate Rota-Baxter words and searching for linear operators on associative algebras are implemented in Mathematica. I have also implemented a package DiffEqn consisting of tutorial notebooks for differential equations in Mathematica for student use.

I have organized and co-organized many international conferences and workshops, and served on their program committees. I have also co-edited several proceedings and special issues in leading journals on symbolic computations. For details, please click here.

Currently, I co-organize the Kolchin Seminar in Differential Algebra with Richard Churchill (Hunter College and Graduate Center, CUNY), Alice Medvedev (CCNY), and Alexey Ovchinnikov (Queens College and Graduate Center, CUNY), and Ronnie Nagloo (Graduate Center CUNY, visiting), and recently served on the Program Committee for DART VI, held from August 10--14, 2015 in Beijing.


I have retired from teaching since September, 2006 and have no official departmental or college responsibilities. Before retirement, I actively participated in committee work both departmentally, and college-wide. I was a member of the Executive Committee for the Strategic Plan, 2002--3. I worked on the College-wide Resource Subcommittee of the Faculty Senate, and served as a representative of the Faculty Senate on the Tech Fee Committee. I was the chair for the Applied Mathematics Program Committee of the Mathematics Department, the faculty supervisor for the Advanced Computation (Artino) Lab, and course supervisor for Math 391 (Differential Equations).