Triskaidekaphobia is a fear of the number 13. It is usually considered to be a superstition. A specific fear of Friday the 13th is called paraskavedekatriaphobia or friggatriskaidekaphobia.
Let's hope these fears do not manifest in Elista today. I'm sure we all are looking forward to some great chess. It is my hope that Kramnik wins, if for no other reason than to put the unification debate to rest.