158 research outputs found
Baryogenesis in the Two-Higgs Doublet Model
We consider the generation of the baryon asymmetry in the two-Higgs doublet
model. Investigating the thermal potential in the presence of CP violation, as
relevant for baryogenesis, we find a strong first-order phase transition if the
extra Higgs states are heavier than about 300 GeV. The mass of the lightest
Higgs can be as large as about 200 GeV. We compute the bubble wall properties,
including the profile of the relative complex phase between the two Higgs vevs.
The baryon asymmetry is generated by top transport, which we treat in the WKB
approximation. We find a baryon asymmetry consistent with observations. The
neutron electric dipole moment is predicted to be larger than about 10^{-27}ecm
and can reach the current experimental bound. Low values of tan\beta are
favored.Comment: 25 pages, 7 figure
Generalized Second Law of Thermodynamics on the Event Horizon for Interacting Dark Energy
Here we are trying to find the conditions for the validity of the generalized
second law of thermodynamics (GSLT) assuming the first law of thermodynamics on
the event horizon in both cases when the FRW universe is filled with
interacting two fluid system- one in the form of cold dark matter and the other
is either holographic dark energy or new age graphic dark energy. Using the
recent observational data we have found that GSLT holds both in quintessence
era as well as in phantom era for new age graphic model while for holographic
dark energy GSLT is valid only in phantom era.Comment: 8 pages, 2 figure
B-Pol: Detecting Primordial Gravitational Waves Generated During Inflation
B-Pol is a medium-class space mission aimed at detecting the primordial
gravitational waves generated during inflation through high accuracy
measurements of the Cosmic Microwave Background (CMB) polarization. We discuss
the scientific background, feasibility of the experiment, and implementation
developed in response to the ESA Cosmic Vision 2015-2025 Call for Proposals.Comment: Experimental Astronomy - The original publication is available at
http://www.springerlink.co
The Future Evolution of White Dwarf Stars Through Baryon Decay and Time Varying Gravitational Constant
Motivated by the possibility that the fundamental ``constants'' of nature
could vary with time, this paper considers the long term evolution of white
dwarf stars under the combined action of proton decay and variations in the
gravitational constant. White dwarfs are thus used as a theoretical laboratory
to study the effects of possible time variations, especially their implications
for the future history of the universe. More specifically, we consider the
gravitational constant to vary according to the parametric relation , where the time scale is the same order as
the proton lifetime. We then study the long term fate and evolution of white
dwarf stars. This treatment begins when proton decay dominates the stellar
luminosity, and ends when the star becomes optically thin to its internal
radiation.Comment: 12 pages, 10 figures, accepted to Astrophysics and Space Scienc
Baryogenesis, Electric Dipole Moments and Dark Matter in the MSSM
We study the implications for electroweak baryogenesis (EWB) within the
minimal supersymmetric Standard Model (MSSM) of present and future searches for
the permanent electric dipole moment (EDM) of the electron, for neutralino dark
matter, and for supersymmetric particles at high energy colliders. We show that
there exist regions of the MSSM parameter space that are consistent with both
present two-loop EDM limits and the relic density and that allow for successful
EWB through resonant chargino and neutralino processes at the electroweak phase
transition. We also show that under certain conditions the lightest neutralino
may be simultaneously responsible for both the baryon asymmetry and relic
density. We give present constraints on chargino/neutralino-induced EWB implied
by the flux of energetic neutrinos from the Sun, the prospective constraints
from future neutrino telescopes and ton-sized direct detection experiments, and
the possible signatures at the Large Hadron Collider and International Linear
Collider.Comment: 32 pages, 10 figures; version to appear on JHE
Cosmological Perturbations From Inhomogeneous Reheating, Freeze-Out, and Mass Domination
We generalize a recently proposed mechanism for the origin of primordial
metric perturbations in inflationary models. Quantum fluctuations of light
scalar fields during inflation give rise to super-horizon fluctuations of
masses and reaction rates of various particles. Reheating, freeze-out, and
matter-domination processes become inhomogeneous and generate super-horizon
metric perturbations. We also calculate the degree of non-Gaussianity
for this new model of cosmological perturbations. The precise value of
depends on the specific models, but few is a natural lower bound
for our mechanisms. This is much larger than the currently assumed theoretical
value , and is thought to be observable. In a
particularly attractive model of inhomogeneous mass-domination, the
non-Gaussianity of perturbations generated by our mechanism is simply
, irrespective of the detailed structure of the underlying field
theory.Comment: 13 page
Minimal Noncanonical Cosmologies
We demonstrate how much it is possible to deviate from the standard
cosmological paradigm of inflation-assisted LambdaCDM, keeping within current
observational constraints, and without adding to or modifying any theoretical
assumptions. We show that within a minimal framework there are many new
possibilities, some of them wildly different from the standard picture. We
present three illustrative examples of new models, described phenomenologically
by a noncanonical scalar field coupled to radiation and matter. These models
have interesting implications for inflation, quintessence, reheating,
electroweak baryogenesis, and the relic densities of WIMPs and other exotics.Comment: 20 pages, 5 figures, 3 table
Cosmological model with interactions in the dark sector
A cosmological model is proposed for the current Universe consisted of
non-interacting baryonic matter and interacting dark components. The dark
energy and dark matter are coupled through their effective barotropic indexes,
which are considered as functions of the ratio between their energy densities.
It is investigated two cases where the ratio is asymptotically stable and their
parameters are adjusted by considering best fits to Hubble function data. It is
shown that the deceleration parameter, the densities parameters, and the
luminosity distance have the correct behavior which is expected for a viable
present scenario of the Universe.Comment: 6 pages, 8 figure
Genus Topology of the Cosmic Microwave Background from WMAP
We have independently measured the genus topology of the temperature
fluctuations in the cosmic microwave background seen by the Wilkinson Microwave
Anisotropy Probe (WMAP). A genus analysis of the WMAP data indicates
consistency with Gaussian random-phase initial conditions, as predicted by
standard inflation.Comment: PDF: http://www.astro.virginia.edu/~wnc5c/WMAPtopology.pd
Second-order corrections to noncommutative spacetime inflation
We investigate how the uncertainty of noncommutative spacetime affects on
inflation. For this purpose, the noncommutative parameter is taken to
be a zeroth order slow-roll parameter. We calculate the noncommutative power
spectrum up to second order using the slow-roll expansion. We find corrections
arisen from a change of the pivot scale and the presence of a variable
noncommutative parameter, when comparing with the commutative power spectrum.
The power-law inflation is chosen to obtain explicit forms for the power
spectrum, spectral index, and running spectral index. In cases of the power
spectrum and spectral index, the noncommutative effect of higher-order
corrections compensates for a loss of higher-order corrections in the
commutative case. However, for the running spectral index, all higher-order
corrections to the commutative case always provide negative spectral indexes,
which could explain the recent WMAP data.Comment: 15 pages, no figure, version published in PR
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