Superconformal symmetry, supergravity and cosmology

We introduce the general N = 1 gauge theory superconformally coupled to supergravity. The theory has local SU(2, 2\1) symmetry and no dimensional parameters. The superconformal origin of the Fayet-Iliopoulos (FI) terms is clarified. The phase of this theory with spontaneously broken conformal symmetry gives various formulations of N = 1 supergravity interacting with matter, depending on the choice of the R-symmetry fixing. We have found that the locally superconformal theory is useful for describing the physics of the early universe with a conformally flat FRW metric. Few applications of superconformal theory to cosmology include the study of (a) particle production after inflation, particularly the nonconformal helicity-/-1.2 sates of gravitino, (b) the super-Higgs effect in cosmology and the derivation of the equations for the gravitino interacting with any number of chiral and Vector multiplets in the gravitational background with varying scalar fields, (c) the weak-coupling limit of supergravity Mp --> infinity and gravitino-goldstino equivalence. This explains why gravitino production in the early universe is not suppressed in the limit of weak gravitational coupling. We discuss the possible existence of an unbroken phase of the superconformal theories, interpreted as a strong-coupling limit of supergravity Mp --> 0.