Magnus Carlsen is that rare chess grandmaster who is both the No. 1 player in the world and, according to the U.K. edition of Cosmopolitan magazine, one of the 100 sexiest men of 2013. ("Check this hottie out!") The boyishly handsome Carlsen, with his dimpled grin and surfer's hair, has done some modeling and wears snazzy blazers to advertise his sponsors during matches. The 22-year-old Carlsen is a celebrity fixture, too, having defeated Stephen Colbert in rock-paper-scissors and, of course, met Jay-Z.

His global...