paper

Degeneration of Groups of Type E7 and Minimal Coupling in Supergravity

arXiv:1202.1290 · doi:10.1007/JHEP06(2012)074

Abstract

We study properties of D = 4, N >1 extended supergravities (and related compactifications of superstring theory) and their consistent truncation to the phenomenologically interesting models of N = 1 supergravity. This involves a detailed classification of the "degenerations" of the duality groups of type E7, when the corresponding quartic invariant polynomial built from the symplectic irreducible representation of G4 "degenerates" into a perfect square. With regard to cosmological applications, we conclude that the consistent truncation to N = 1 from higher-dimensional or higher-N theory gives a zero measure minimal coupling of vectors. A non-minimal coupling involving vectors coupled to scalars and axions is generic. These features of supergravity, following from the electric-magnetic duality, may be useful in other applications, like stabilization of moduli, and in studies of non-perturbative black-hole solutions of supergravity/string theory.

1+40 pages, 5 Tables; v2 : 1+41 pages, Sec. 3 extended, Sec. 3.1 replaced, Sec. 4.3 removed, one Ref. added, other minor changes

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