This letter denotes ordinal numbers that are the fixed point of the exponential map. The Galois group of a field extension is linked to the properties of elliptic curves in a conjecture denoted by this (-5[1])letter that was proved by Ken Ribet. Transitions (15[1])denoted by this letter can be used to simplify the state diagram of a nondeterministic (-5[1])finite automaton. For any positive number denoted by this letter, there exists a positive (*) delta (10[2])that a function (-5[1])is arbitrarily closed to L in a definition of the limit. The identity (10[1])element of the concatenation operation is denoted by this letter. A quantity denoted (10[1])that characterizes the shapes of conic sections is called eccentricity. For 10 points, identify this Greek letter that denotes the empty strings, which can also denote an arbitrarily (10[1])small number. ■END■