Evaporation of a two-dimensional charged black hole

We construct a dilatonic two-dimensional model of a charged black hole. The classical solution is a static charged black hole, characterized by two parameters m and q representing the black hole’s mass and charge. Then we study the semiclassical effects, and calculate the evaporation rate of both m and q, as a function of these two quantities. Analyzing this dynamical system, we find two qualitatively different regimes, depending on the electromagnetic coupling constant g_A. If the latter is greater than a certain critical value, the charge-to-mass ratio decays to zero upon evaporation. On the other hand, for g_A smaller than the critical value, the charge-to-mass ratio approaches a non-zero constant that depends on g_A but not on the initial values of m and q.