Nature of the glassy phase of RNA secondary structure

We characterize the low-temperature phase of a simple model for RNA secondary structures by determining the typical energy scale E (l) of excitations involving l bases. At low enough temperatures, including T = 0, we find a scaling law E (l) similar to l(theta) with a small exponent. Above a critical temperature, there is a different phase characterized by a relatively at free-energy landscape resembling that of a homopolymer with a scaling exponent theta = 1. These results strengthen the evidence in favour of the existence of a glass phase at low temperatures.