Restoration of dynamically broken chiral symmetry by a toroidal space-time.

Abstract

The phase structure of the Nambu--Jona-Lasinio model with [ital N]-component fermions is investigated, in a toroidal ([ital S][sup 1][times][ital S][sup 1][times][ital R][sup 2]) space-time, in the leading order of the 1/[ital N] expansion. Examining the effective potential for composite fields, we find that the dynamically broken chiral symmetry may be restored below certain critical lengths of the toroidal dimension [ital l][sub 1],[ital l][sub 2]. We then derive critical-line equations in terms of the parameters of the model and the sizes of the toroidal dimension.