Richard Hammack

Richard Hammack, Ph.D.


(804) 828-6237

Grace E. Harris Hall, 1015 Floyd Ave., room 4166


  • 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

Research Interests

  • Graph theory and combinatorics, especially product graphs and cycle structures
  • Interconnections between mathematics and the visual arts

Select Publications

  • Handbook of product graphs, Second edition, by R. Hammack, W. Imrich, and S. Klavžar, 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 Combinatorics, 30(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 Mathematics, 313: 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 Mathematics, 23(4): 2042–2052, 2010.
  • On Cartesian skeletons of graphs (with Wilfried Imrich), Ars Mathematica Contemporanea, 2(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 Mathematics, 309: 2538–2543, 2009.


  • American Mathematical Society
  • Mathematical Association of America