Fabio Zwirner | PubMed Health

PubMed2005

de Sitter vacua via consistent terms.

We introduce a new mechanism for producing locally stable de Sitter or Minkowski vacua, with spontaneously broken N = 1 supersymmetry and no massless scalars, applicable to superstring and M-theory compactifications with fluxes. We illustrate the mechanism with a simple N = 1 supergravity model that provides parametric control on the sign and the size of the vacuum energy. The crucial ingredient is a gauged U(1) that involves both an axionic shift and an R symmetry, and severely constrains the F- and D-term contributions to the potential.

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PubMed2002

Generalized symmetry breaking on orbifolds.

We reconsider the phenomenon of mass generation via coordinate-dependent compactifications of higher-dimensional theories on orbifolds. For definiteness, we study a generic five-dimensional theory compactified on S(1)/Z(2). We show that the presence of fixed points, where the fields or their derivatives may be discontinuous, permits new realizations of the Scherk-Schwarz mechanism where, for example, the mass terms are localized at the orbifold fixed points. Our technique can be used to describe the explicit breaking of global flavor symmetries and supersymmetries by brane-localized mass terms. It can also be applied to the spontaneous breaking of local symmetries, such as gauge symmetries or supergravities.

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