Winding number transition at finite temperature: the Mottola-Wipf model with and without the Skyrme term Original Research Article

The winding number transition in the Mottola-Wipf model with and without Skyrme term is examined. For the model with Skyrme term the number of discrete modes of the fluctuation operator around the sphaleron is shown to be dependent on the value of λm2. Following Gorokhov and Blatter we derive a sufficient condition for the sharp first-order transition, which indicates that first-order transition occurs when 0 < λm2 < 0.0399 and 2.148 < λm2. In the intermediate region of λm2 the winding number transition is conjectured to be smooth second order. For the model without Skyrme term the winding number transition is always first order regardless of the value of parameter.