An application of semi-free gas and collective coordinates models on fermion systems

Victor A. Alessandrini, Daniel R. Bes, B. Machet

K. B. Efetov, C. Pépin, Hannes Meier

We present an exact mapping of models of interacting fermions onto boson models. The bosons correspond to collective excitations in the initial fermionic models. This bosonization is applicable in any dimension and for any interaction between fermions. Introducing superfields, we derive a field theory that may serve as a new way of analytical study. We show schematically how the mapping can be used for Monte Carlo calculations and argue that it should be free from the sign problem.

P. Buck, Hans Feldmeier

Mitsuto Fukuma, Satoshi Takada

Quantum statistical mechanics of soliton systems is developed in the path integral formalizm by making use of the non-canonical collective coordinate method. The free energy is calculated in the ideal-gas approximation up to the order of two-loop. Explicit calculations are given for the sine-Gordon model. The classical limit of the present quantum calculation agrees with the exact result of the low-temperature expansion of the transfer-integral method. Numerical calculation reveals the quantum effect on the specific heat.

Leon N. Cooper

Shuji Takagi

A relation between collective motion and particle excitation in many fermion system is investigated. A method to construct collective coordinates is presented. Preliminary application to nuclear structure is done. Relations to other theory of collective motion are briefly discussed.