Superfluid transition temperature in a Fermi gas with repulsion allowing for higher orders of perturbation theory

Higher-order perturbation-theory corrections to the superfluid transition t emperature in a weakly nonideal Fermi gas with repulsion are determined. Th is involves calculating the contribution of third- and fourth-order diagram s in terms of the gas parameter ap(F) to the effective interaction which de termines the superfluid transition temperature and also allowing for effect s associated with retardation and renormalization of the polar part of the Green's function. The expressions obtained provide evidence in support of a ttraction in the effective interaction in the second, third, and fourth ord ers of perturbation theory. It is shown that the critical temperature is ma inly determined by second- and third-order terms of perturbation theory. Ca lculations are made of the superfluid transition temperature for a gas comp rising neutral Fermi particles in a magnetic field. The limits of validity of the theory are analyzed and the possibility of applying the results to d ilute solutions of He-3 in He-4 and neutral-particle Fermi gases in magneti c traps is discussed. (C) 2000 MAIK "Nauka/Interperiodica".