Burt A. Ovrut

Supersymmetric calculation of mixed Kähler-gauge and mixed Kähler-Lorentz anomalies

We present a manifestly supersymmetric procedure for calculating the contributions from matter loops to the mixed Kahler-gauge and to the mixed Kahler-Lorentz anomalies in N = 1, D = 4 supergravity-matter systems. We show how this procedure leads to the well-known result for the mixed Kahler-gauge anomaly. For general supergravity-matter systems the mixed Kahler-Lorentz anomaly is found to contain a term proportional to R2 with a background field dependent coefficient as well as terms proportional to (Cmnpq)2 and to the Gauss-Bonnet topological density. We briefly comment on the relationship between the mixed Kahler-Lorentz anomaly and the moduli dependent threshold corrections to gravitational couplings in ZN orbifolds.

Effective d = 2 supersymmetric lagrangians from d = 1 supermatrix models

We discuss d = 1, N = 2 supersymmetric matrix models and exhibit the associated d = 2 collective field theory in the limit of dense eigenvalues. From this theory we construct, by the addition of several new fields, a d = 2 supersymmetric effective field theory, which reduces to the collective field theory when the new fields are replaced with their vacuum expectation values. This effective theory is Poincare invariant and contains perturbative and non-perturbative information about the associated superstrings. We exhibit instanton solutions corresponding to the motion of single eigenvalues and discuss their possible role in supersymmetry breaking.

Large scale structure from biased non-equilibrium phase transitions - percolation theory picture

Abstract We give an analytical description of the spatial distribution of domain walls produced during a biased nonequilibrium phase transition in the vacuum state of a light scalar field. We discuss in detail the spectrum of the associated cosmological energy density perturbations. It is shown that the contribution coming from domain walls can enhance the standard cold dark matter spectrum in such a way as to account for the whole range of IRAS data and for the COBE measurement of the microwave background anisotropy. We also demonstrate that in case of a biased phase transition which allows a percolative description, the number of large size domain walls is strongly suppressed. This offers a way of avoiding excessive microwave background distortions due to the gravitational field of domain walls present after decoupling.

Natural supergravity inflation

Abstract We show that a single uncharged chiral superfield, canonically coupled to N = 1 supergravity with vanishing superpotential, naturally drives inflation in the early universe for a class of simple Kahler potentials. Inflation occurs due to the one-loop generation of a Kahler anomaly proportional to R 2 . The coefficient of this R 2 term is of the correct magnitude to describe all aspects of an inflationary cosmology, including sufficient amplitude perturbations and reheating. Higher order terms proportional to R n for n ⩾3 are naturally suppressed relative to the R 2 term and, hence, do not destabilize the theory.

Chern-Simons induced massive gauge fields in four dimensions

Abstract A phenomenon, reminiscent of topological mass generation in (2+1)-dimensions, is extracted out of the theory of new minimal supergravity coupled to a linear multiplet with superfield Chern-Simons terms in four dimensions. A physical, massive abelian gauge field, originally not in the theory, is induced by the addition of a specific Chern-Simons term to the lagrangian.

Domain wall formation in the post-inflationary universe

We consider the evolution of the probability distribution P(χ, χ, t), associated with an inhomogenous light scalar field χ in the Robertson-Walker Universe, where the inhomogeneties are produced by quantum fluctuations during an earlier inflationary epoch. For a specific choice of scalar potential which occurs in models of so-called late-time phase transitions in which domain walls are produced, P is shown to evolve from a gaussian to a non-gaussian distribution. The structure of the latter justifies the recent use of three-dimensional percolation theory to describe the initial distribution of domain walls in these models.We consider the evolution of the probability distribution P(χ, ¯ χ, t), associated with an inhomogeneous light scalar field χ in the Robertson-Walker Universe, where the inhomogeneities are produced by quantum fluctuations during an earlier inflationary epoch. For a specific choice of scalar potential which occurs in models of so called late-time phase transitions in which domain walls are produced, P is shown to evolve from a Gaussian to a non-Gaussian distribution. The structure of the latter justifies