A systematic study of the influence of exchange terms in the longitudinal and
transverse nuclear response to quasi-elastic (e,e') reactions is presented. The
study is performed within the framework of the extended random phase
approximation (ERPA), which in conjuction with a projection method permits a
separation of various contributions tied to different physical processes. The
calculations are performed in nuclear matter up to second order in the residual
interaction for which we take a (pi+rho)-model with the addition of the
Landau-Migdal g'-parameter. Exchange terms are found to be important only for
the RPA-type contributions around the quasielastic peak.Comment: 29 pages, 6 figs (3 in postscript, 3 faxed on request), epsf.st
