Richard Hammack

Professor Department of Mathematics and Applied Mathematics
(804) 828-6237


Ph.D. in Mathematics, University of North Carolina at Chapel Hill, 1996

MS in Computer Science, Virginia Commonwealth University, 1988

B.F.A. in Painting, Rhode Island School of Design, 1983


Graph theory and combinatorics, especially product graphs and cycle structures; also the interconnections between mathematics and the visual arts


Handbook of product graphs, Second edition, by R.Hammack, W. Imrich, and S. Klav┼żar,   CRC Press, Boca Raton, FL, 2011.

A prime factor theorem for bipartite graphs, European Journal of Combinatorics, in press.

Zero divisors among digraphs (with Heather Smith), Graphs and Combinatorics30(1), 171–181, 2014.

Cancellation of digraphs over the direct product, European Journal of Combinatorics, 34: 846–858, 2013.

On uniqueness of prime bipartite factors of graphs, Discrete Mathematics313: 1018–1027, 2013.

Cancellation of direct products of digraphs (with Katherine Toman), Discussiones Mathematicae Graph Theory, 30(4): 575–590, 2010.

Direct product factorization of bipartite graphs with bipartition-reversing involutions (with Ghidewon Abay-Asmerom, Craig Larson and Dewey Taylor), SIAM Journal on Discrete Mathematics23(4): 2042–2052, 2010.

On Cartesian skeletons of graphs (with Wilfried Imrich), Ars Mathematica Contemporanea2(2): 191–205, 2009.

Proof of a conjecture concerning the direct product of bipartite graphs, European Journal of Combinatorics (Special Issue on 44: 265–272, 2009.

On direct product cancellation of graphs, Discrete Mathematics309: 2538–2543, 2009.


American Mathematical Society
Mathematical Association of America