The classical nucleation rate in two dimensions
  In many systems in condensed matter physics and quantum field theory, first order phase transitions are initiated by the nucleation of bubbles of the stable phase. In homogeneous nucleation theory the nucleation rate $\Gamma$ can be written in the form of the Arrhenius law: $\Gamma=\mathcal{A} e^{-\mathcal{H}_{c}}$. Here $\mathcal{H}_{c}$ is the energy of the critical bubble, and the prefactor $\mathcal{A}$ can be expressed in terms of the determinant of the operator of fluctuations near the critical bubble state. In general it is not possible to find explicit expressions for $\mathcal{A}$ and $\mathcal{H}_{c}$. If the difference $\eta$ between the energies of the stable and metastable vacua is small, the constant $\mathcal{A}$ can be determined within the leading approximation in $\eta$, which is an extension of the ``thin wall approximation''. We have done this calculation for the case of a model with a real-valued order parameter in two dimensions. 
Gernot M\"unster (1) and Sergei B. Rutkevich (2) ((1) University of   Muenster, (2) Institute of Physics of Solids & Semicon...