Faculty Name

Colm Mulcahy, Ph.D.


Professor Emeritus






Ph.D., M.A.,  Cornell University
M.Sc., B.Sc.,  University College Dublin, Ireland


Colm Mulcahy is professor of mathematics at Spelman College, in Atlanta, where he has taught since 1988. He trained in algebra, and has also written papers on CAGC and wavelets. Since 2000, he has been at the forefront of publishing original "mathemagical" principles and effects, particularly in his long-running bi-monthly Card Colm for the Mathematical Association of America (MAA).

His 380-page book of largely original creations, Mathematical Card Magic: Fifty-Two New Effects (AK Peters/CRC Press) was published in Aug 2013.

He tweets at @CardColm and blogs at the Huffington Post and at Scientific American, as well as the Aperiodical. Some of his puzzles have appeared online at the New York Times.

He's particularly active in Gathering for Gardner and the associated Celebration of Mind initiative. He was fortunate to know Gardner for the last ten years of his life, and he chairs the Martin Gardner Centennial Committee. He was also part of the team heading up Mathematics Awareness Month 2014.

A recent project of his has been the creation and curation of the free online Archive of Irish Mathematics and Mathematicians.

In 1997, Mulcahy received the MAA's Allendoerfer Award for excellence in expository writing, for an article on image compression using wavelets from Mathematics Magazine (Dec 1996). His interests are broad, and include algebra, number and geometry.

Mulcahy earned a B.Sc. and M.Sc. in mathematical science from University College Dublin, in his native Ireland, and a Ph.D. from Cornell University for research in the abstract algebraic theory of quadratic forms, under Alex F.T.W. Rosenberg.

Courses Taught

107 Contemporary Mathematics
193 Honors Quantitative Reasoning
252 Calculus II
322 Geometry
361 Theory of Numbers

Research Interests

Number Theory
Image Compression
Mathematical Magic


Mathematical Card Magic: Fifty-Two New Effects, AK Peters/CRC, August 2013

Book Chapters
(with Neil Calkin, to appear) “Gallia est omnis divisa in partes quattuor (Mathematics Inspired by Dealing Cards into a Pile),” in The Earnest Contemplation of Trivial Pursuits: Progress in Recreational Mathematics, edited by Jennifer Beinecke & Jason Rosenhouse, Princeton University Press, August 2015

“Mathemagical Miracles,” in Expeditions in Mathematics–The Second Book of BAMA Talks, 25–30, edited by Tatiana Shubin et al, Mathematical Association of America, March 2011

“His Genetic Evolution — One to Eight Inclusive (The g4g8 Bracelet),” a chapter in G4G8 Gathering for Gardner Exchange Book, edited by Scott Hudson, Jan 2011

“Mathematical Idol,” in Mathematical Wizardry for a Gardner, 155–164, edited by Ed. Pegg Jr, Alan H. Schoen & Tom Rodgers, AK Peters, April 2009

“Horses In the Stream and Other Short Stories,” (as Earnest Hammingway) in Homage to a Pied Puzzler, 233–247, edited by Ed. Pegg Jr, Alan H. Schoen & Tom Rodgers, AK Peters, February 2009

“Low-Down Triple Dealing,” in A Lifetime of Puzzles, 29–34, edited by Eric Demaine, Martin Demaine & Tom Rodgers, AK Peters, November 2008