Colm Mulcahy (born September 1958) is an Irish mathematician, academic, columnist, book author, public outreach speaker, and amateur magician, long on the faculty of Spelman College. In addition to algebra, number theory, and geometry, his interests include mathemagical card magic and the culture of mathematics–particularly the contributions of Irish mathematicians and also the works of iconic mathematics writer Martin Gardner. He has blogged for the Mathematical Association of America, The Huffington Post, Scientific American, and (aperiodically) for The Aperiodical; his puzzles have been featured in The New York Times. Mulcahy serves on the Advisory Council of the Museum of Mathematics in New York City. He is currently Vice-President of Gathering 4 Gardner, Inc.
Education and career
Mulcahy got his BSc and MSc in mathematical science at University College Dublin in 1978 and 1979, and a PhD from Cornell University in 1985 where his advisor was Alex F. T. W. Rosenberg. Since 1988 he has been teaching at Spelman College, in Atlanta, Georgia where he is currently professor. He served as chair of the department of mathematics at Spelman from 2003 to 2006 and recently created the Archive of Spelman Mathematicians. In 1997 he received the MAA's Allendoerfer Award for excellence in expository writing for a paper on the basics of wavelet image compression. In 2014 he was one of the organizers of Mathematics Awareness Month. An article he co-authored, on the centennial of Martin Gardner, was featured in the book, The Best Writing on Mathematics 2015.
Mulcahy is recognised as an authority on the mathematical principles and effects underlying cards tricks. From 2004 to 2014 he authored Card Colm, a column about mathematics and magic–especially card magic–for the Mathematical Association of America. Much of this work is collected in his book Mathematical Card Magic: Fifty-Two New Effects  He has appeared in Brady Haran's Numberphile web series.
Legacy of Martin Gardner
Mulcahy was a friend of longtime Scientific American columnist Martin Gardner during the last decade of Gardner's life. In 2016 Mulcahy became the Vice-President of Gathering for Gardner, an organisation formed to honour the wide ranging contributions made by the celebrated mathematician, skeptic, magician, philosopher, and writer. Usually shortened to G4G, it first met in 1993 and since 1996 meets every two years. In 2013 he created the official Martin Gardner site, and in 2013–2014 he chaired the Martin Gardner Centennial Committee. Mulcahy has been particularly active in promoting an associated series of meetings known as Celebration of Mind, also inspired by the works of Gardner. These days there are over 100 of these latter events every year, all around the world.
Irish mathematicians and mathematics
Mulcahy frequently writes about the culture and history of mathematics in Ireland. He is active in both Maths Week Ireland, the world's largest mathematics outreach program, and the Irish Mathematical Society. He is the creator and curator of the Annals of Irish Mathematics and Mathematicians, which chronicles four centuries of mathematical activity in Ireland. This is now sponsored by Maths Week Ireland, which produced the first Irish Mathematics Calendar in 2016.
- Mathematics Awareness Month 2014: Mathematics, Magic, and Mystery Committee Members
- The Aperiodical
- Celebrations of Mind Honor Math’s Best Friend, Martin Gardner by Colm Mulcahy, Scientific American, 29 October 2013
- 11 Stories By Colm Mulcahy In Scientific American
- Museum of Mathematics: Advisory Council
- Gathering 4 Gardner: Board of Directors
- Carl B. Allendoerfer award: Plotting and Scheming with Wavelets by Colm Mulcahy
- Spelman College January 2016
- The Best Writing on Mathematics 2015 Edited by Mircea Pitici, Princeton University Press, 2015, ISBN 0691169659
- Coauthors of Paul Erdos, see Neil Calkin Gallia Est Omnis Divisa in Partes Quattuor by Neil Calkin and Colm Mulcahy, in The mathematics of various entertaining subjects: research in recreational math, edited by Jennifer Elaine Beineke and Jason Rosenhouse, Princeton University Press,  ISBN 0691164037
- Celebration of Mind with Colm Mulcahy
- MAA Columns: Card Colm by Colm Mulcahy Mathematical Association of America
- Mathematical Card Magic: Fifty-Two New Effects A K Peters/CRC Press (2013) ISBN 1466509767
- Little Fibs – Numberphile 'Mathemagician' Colm Mulcahy, 2 June 2016
- Tom Rodgers, Organizer of Gathering for Gardner and Celebration of Mind, Dies at 67
- official Martin Gardner site
- Who wants to host a Celebration of Mind? There’s still time by Colm Mulcahy, 19 October 2012
- Food for Thought: Savory Treats for the Mind From the Julia Child of Mathematics and Rationality by Colm Mulcahy, HuffPost, 10 December 2012
- Mathematical (and Poetic) Offerings From the Land of Saints and Scholars by Colm Mulcahy, HuffPost, 23 May 2015
- Ahlstrom, Dick (11 October 2015). "More than 250,000 people to take part in Maths Week". The Irish Times. Retrieved 25 January 2018.
- Mathematics Ireland Newsletter March 2016
- Annals of Irish Mathematics & Mathematicians: Origin