MathOverflow will be down for maintenance for approximately 3 hours, starting Monday evening (06/24/2013) at approximately 9:00 PM Eastern time (UTC-4).
show/hide this revision's text 2 edited tags
show/hide this revision's text 1

Does the exponential function have a square root?

(asked by Nathaniel Hellerstein on the Q&A board at JMM)

Is there a "half-exponential" function h(x) such that h(h(x))=ex? Is it unique? Is it analytic?

Related question: Is there an invertible smooth function E such that E(x+1)=eE(x)? Is it unique? If so, then we can take h(x)=E(E-1(x)+1/2).

[Ed: please retag appropriately]