  Formation of RNA secondary structures is an example of the sequence-structure
problem omnipresent in biopolymers. A theoretical question of recent interest
is whether a random RNA sequence undergoes a finite temperature glass
transition. We answer this question affirmatively by first establishing the
perturbative stability of the high temperature phase via a two replica
calculation. Subsequently, we show that this phase cannot persist down to zero
temperature by considering energetic contributions due to rare regions of
complementary subsequences.
