Longevity of supersymmetric flat directions

We examine the fate of supersymmetric flat directions. We argue that the non-perturbative decay of the flat direction via preheating is an unlikely event. In order to address this issue, first we identify the physical degrees of freedom and their masses in presence of a large flat direction VEV (Vacuum Expectation Value). We explicitly show that the (complex) flat direction and its fermionic partner are the only light {\it physical} fields in the spectrum. If the flat direction VEV is much larger than the weak scale, and it has a rotational motion, there will be no resonant particle production at all. The case of multiple flat directions is more involved. We illustrate that in many cases of physical interest, the situation becomes effectively the same as that of a single flat direction, or collection of independent single directions. In such cases preheating is not relevant. In an absence of a fast non-perturbative decay, the flat direction survives long enough to affect thermalization in supersymmetric models as described in hep-ph/0505050 and hep-ph/0512227. It can also ``terminate'' an early stage of non-perturbative inflaton decay as discussed in hep-ph/0603244.Comment: 9 revtex pages, v3: expanded discussion on two flat directions, minor modifications, conclusions unchange

Perturbation amplitude in isocurvature inflation scenarios

We make a detailed calculation of the amplitude of isocurvature perturbations arising from inflationary models in which the cold dark matter is represented by a scalar field which acquires perturbations during inflation. We use this to compute the normalization to large-angle microwave background anisotropies. Unlike the case of adiabatic perturbations, the normalization to COBE fixes the spectral index of the perturbations; if adiabatic perturbations are negligible then $n_{iso} \simeq 0.4$. Such blue spectra are also favoured by other observational data. Although the pure isocurvature models are unlikely to adequately fit the entire observational data set, these results also have implications for models with mixed adiabatic and isocurvature perturbations.Comment: 7 pages RevTeX file with one figur

Theory of triangular lattice quasi-one-dimensional charge-transfer solids

Recent investigations of the magnetic properties and the discovery of superconductivity in quasi-one-dimensional triangular lattice organic charge-transfer solids have indicated the severe limitations of the effective 1/2-filled band Hubbard model for these and related systems. Our computational studies of these materials within a 1/4-filled band Hubbard model in which the organic monomer molecules, and not their dimers, constitute the sites of the Hamiltonian are able to reproduce the experimental results. We ascribe the spin gap transition in kappa-(BEDT-TTF)_2B(CN)_4 to the formation of a two-dimensional paired-electron crystal and make the testable prediction that the spin gap will be accompanied by charge-ordering and period doubling in two directions. We find enhancement of the long-range component of superconducting pairing correlations by the Hubbard repulsive interaction for band parameters corresponding to kappa-(BEDT-TTF)_2CF_3SO_3. The overall results strongly support a valence bond theory of superconductivity we have proposed recently.Comment: 8 pages, 7 figure

On input/output maps for nonlinear systems via continuity in a locally convex topology

In this paper we show that the output of a nonlinear system with inputs in () whose state satisfies a nonlinear differential equation with standard smoothness conditions can be written as the composition of a nonlinear map with a linear Hilbert-Schmidt operator acting on the input. The result also extends to abstract semi-linear infinite dimensional systems. The approach is via the study of the continuity of the solution in a locally convex topology generated by seminorms of Hilbert-Schmidt operators in Hilbert space. The result reveals an entirely new structure related to nonlinear systems which can lead to useful approximation results