7,405 research outputs found
N-flation: Non-Gaussianity in the horizon-crossing approximation
We analyze the cosmic non-gaussianity produced in inflation models with multiple uncoupled fields with monomial potentials, such as Nflation. Using the horizon-crossing approximation to compute the non-gaussianity, we show that when each field has the same form of potential, the prediction is independent the number of fields, their initial conditions, and the spectrum of masses/couplings. It depends only on the number of e-foldings after the horizon crossing of observable perturbations. We also provide a further generalization to the case where the fields can have monomial potentials with different powers. Unless the horizon-crossing approximation is substantially violated, the predicted non-gaussianity is too small to ever be observed
Nflation: observable predictions from the random matrix mass spectrum
We carry out numerical investigations of the perturbations in Nflation models
where the mass spectrum is generated by random matrix theory. The
tensor-to-scalar ratio and non-gaussianity are already known to take the
single-field values, and so the density perturbation spectral index is the main
parameter of interest. We study several types of random field initial
conditions, and compute the spectral index as a function of mass spectrum
parameters. Comparison with microwave anisotropy data from the Wilkinson
Microwave Anisotropy Probe shows that the model is currently viable in the
majority of its parameter space.Comment: 5 pages RevTeX with 4 figures. Minor corrections to match version to
appear in Physical Review
Isospin Mixing and Model Dependence
We show that recent calculations of \Delta I=3/2 effects in nonleptonic
hyperon decay induced by m_d-m_u\neq 0 are subject to significant model
dependence.Comment: 8 page standard Latex fil
Dynamics of assisted quintessence
We explore the dynamics of assisted quintessence, where more than one scalar field is present with the same potential. For potentials with tracking solutions, the fields naturally approach the same values—in the context of inflation this leads to the assisted inflation phenomenon where several fields can cooperate to drive a period of inflation though none is able to individually. For exponential potentials, we study the fixed points and their stability confirming results already in the literature, and then carry out a numerical analysis to show how assisted quintessence is realized. For inverse power-law potentials, we find by contrast that there is no assisted behavior—indeed those are the unique (monotonic) potentials where several fields together behave just as a single field in the same potential. More generally, we provide an algorithm for generating a single-field potential giving equivalent dynamics to multifield assisted quintessence
Holographic entanglement entropy of a dimensional -wave superconductor
We examine the behavior of entanglement entropy of a subsystem in a fully
backreacted holographic model of a dimensional wave superconductor
across the phase transition. For a given temperature, the system goes to a
superconducting phase beyond a critical value of the charge density. The
entanglement entropy, considered as a function of the charge density at a given
temperature, has a cusp at the critical point. In addition, we find that there
are three different behaviors in the condensed phase, depending on the
subsystem size. For a subsystem size smaller than a critical size ,
entanglement entropy continues to increase as a function of the charge density
as we cross the phase transition. When lies between and another
critical size the entanglement entropy displays a non-monotonic
behavior, while for it decreases monotonically. At large charge
densities entanglement entropy appears to saturate. The non-monotonic behavior
leads to a novel phase diagram for this system.Comment: 16 pages, 17 figures, v2: references added, section 3.1 added, JHEP
styl
Mass Spectrum Dependence of Higgs-mediated mu-e Transition in the MSSM
In this paper, we study non-decoupling - transition effects by
Higgs-mediated contribution in the MSSM, when some SUSY mass parameters are
much greater than TeV. In order to treat CP-odd Higgs mass as a
free parameter, we consider the non-universal Higgs mass model (NUHM), and
assume the only left- or right-handed sleptons had flavor-mixing mass terms. If
both Higgs-mediated and ordinary SUSY contribution are significant, the ratio
of branching ratios \BR(\meg) / \BR(\maleal) becomes sensitive to SUSY mass
parameters. We investigated these mass-sensitive regions and the behavior of
the ratio \BR(\meg) / \BR(\maleal) in some mass spectrum of the NUHM, and
found that this ratio drastically depends on the mass spectrum structure and
chirality of flavor violation. Log factor from two split mass scale influences
the way of interference between gaugino- and Higgs-mediated contributions
significantly.Comment: 19 pages, 8 figures, it will appear in PR
Nflation: multi-field inflationary dynamics and perturbations
We carry out numerical investigations of the dynamics and perturbations in
the Nflation model of Dimopoulos et al. (2005). This model features large
numbers of scalar fields with different masses, which can cooperate to drive
inflation according to the assisted inflation mechanism. We extend previous
work to include random initial conditions for the scalar fields, and explore
the predictions for density perturbations and the tensor-to-scalar ratio. The
tensor-to-scalar ratio depends only on the number of e-foldings and is
independent of the number of fields, their masses, and their initial
conditions. It therefore always has the same value as for a single massive
field. By contrast, the scalar spectral index has significant dependence on
model parameters. While normally multi-field inflation models make predictions
for observable quantities which depend also on the unknown field initial
conditions, we find evidence of a `thermodynamic' regime whereby the predicted
spectral index becomes independent of initial conditions if there are enough
fields. Only in parts of parameter space where the mass spectrum of the fields
is extremely densely packed is the model capable of satisfying the tight
observational constraints from WMAP3 observations.Comment: 6 pages RevTeX4, 4 figures included. Updated to match PRD accepted
version. Analysis and conclusions unchanged. New references, especially
astro-ph/0510441 which was first to give the general r=8/N resul
CP violating dimuon charge asymmetry in general left-right models
The recently measured charge asymmetry of like-sign dimuon events by the D0
collaboration at Tevatron shows the 3.9 \sigma\ deviation from the standard
model prediction. In order to solve this mismatch, we investigate the
right-handed current contributions to and
mixings which are the major source of the like-sign dimuon events in production in general left-right models without imposing manifest or
pseudo-manifest left-right symmetry. We find the allowed region of new physics
parameters satisfying the current experimental data.Comment: 9 pages, 4 figure
Chromosomal diversification and karyotype evolution of diploids in the cytologically diverse genus Prospero (Hyacinthaceae)
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited
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