717 research outputs found
Solution Of Wheeler-De Witt Equation, Potential Well And Tunnel Effect
This paper uses the relation of the cosmic scale factor and scalar field to
solve Wheeler-DeWitt equation, gives the tunnel effect of the cosmic scale
factor a and quantum potential well of scalar field, and makes it fit with the
physics of cosmic quantum birth. By solving Wheeler-DeWitt equation we achieve
a general probability distribution of the cosmic birth, and give the analysis
of cosmic quantum birth.Comment: 12 page
On the Erasure and Regeneration of the Primordial Baryon Asymmetry by Sphalerons
We show that a cosmological baryon asymmetry generated at the GUT scale,
which would be destroyed at lower temperatures by sphalerons and possible new
B- or L-violating effects, can naturally be preserved by an asymmetry in the
number of right-handed electrons. This results in a significant softening of
previously derived baryogenesis-based constraints on the strength of exotic B-
or L-violating interactions.Comment: 10 pp. LaTex (2 figures, included) UMN-TH-1201/9
Large-scale cosmic flows and moving dark energy
Large-scale matter bulk flows with respect to the cosmic microwave background
have very recently been detected on scales 100 Mpc/h and 300 Mpc/h by using two
different techniques showing an excellent agreement in the motion direction.
However, the unexpectedly large measured amplitudes are difficult to understand
within the context of standard LCDM cosmology. In this work we show that the
existence of such a flow could be signaling the presence of moving dark energy
at the time when photons decoupled from matter. We also comment on the relation
between the direction of the CMB dipole and the preferred axis observed in the
quadrupole in this scenario.Comment: 11 pages, 2 figures. New comments and references included. Final
version to appear in JCA
Entropy of the Universe
After a discussion on several limiting cases where General Relativity turns
into less sophisticated theories, we find that in the correct thermodynamical
and cosmological weak field limit of Einstein's field equations the entropy of
the Universe is R^(3/2) -- dependent, where R stands for the radius of the
causally related Universe. Thus, entropy grows in the Universe, contrary to
Standard Cosmology prediction.Comment: To be published by International Journal of Theoretical Physic
Protogalactic Extension of the Parker Bound
We extend the Parker bound on the galactic flux of magnetic
monopoles. By requiring that a small initial seed field must survive the
collapse of the protogalaxy, before any regenerative dynamo effects become
significant, we develop a stronger bound. The survival and continued growth of
an initial galactic seed field G demand that . For a given
monopole mass, this bound is four and a half orders of magnitude more stringent
than the previous `extended Parker bound', but is more speculative as it
depends on assumptions about the behavior of magnetic fields during
protogalactic collapse. For monopoles which do not overclose the Universe
(), the maximum flux allowed is now cm^{-2}
s^{-1} sr^{-1}, a factor of 150 lower than the maximum flux allowed by the
extended Parker bound.Comment: 9 pages, 1 eps figur
Measuring dark energy spatial inhomogeneity with supernova data
The gravitational lensing distortion of distant sources by the large-scale
distribution of matter in the Universe has been extensively studied. In
contrast, very little is known about the effects due to the large-scale
distribution of dark energy. We discuss the use of Type Ia supernovae as probes
of the spatial inhomogeneity and anisotropy of dark energy. We show that a
shallow, almost all-sky survey can limit rms dark energy fluctuations at the
horizon scale down to a fractional energy density of ~10^-4Comment: 4 pages; PRL submitte
Modular Cosmology, Thermal Inflation, Baryogenesis and Predictions for Particle Accelerators
Modular cosmology is plagued by overproduction of unwanted relics, gravitinos
and especially moduli, at relatively low energy scales. Thermal inflation
provides a compelling solution to this moduli problem, but invalidates most
baryogenesis scenarios. We propose a simple model in which the MSSM plus
neutrino mass term is supplemented by a minimal flaton sector to
drive the thermal inflation, and make two crucial assumptions: the flaton
vacuum expectation value generates the -term of the MSSM and . The second assumption is particularly interesting in that it
violates a well known constraint, implying that there exists a nearby deep
non-MSSM vacuum, and provides a clear signature of our model which can be
tested at future particle accelerators. We show that our model leads to thermal
inflation followed by Affleck-Dine leptogenensis along the flat
direction. A key feature of our leptogenesis scenario is that the flat
direction is also induced to temporarily acquire a large value, playing a
crucial role in the leptogenesis, as well as dynamically shielding the field
configuration from the deep non-MSSM minimum, ensuring that the fields relax
into our MSSM vacuum.Comment: v3; 19 pages, 3 figures; added a reference for section
Photon Spectrum Produced by the Late Decay of a Cosmic Neutrino Background
We obtain the photon spectrum induced by a cosmic background of unstable
neutrinos. We study the spectrum in a variety of cosmological scenarios and
also we allow for the neutrinos having a momentum distribution (only a critical
matter dominated universe and neutrinos at rest have been considered until
now). Our results can be helpful when extracting bounds on neutrino electric
and magnetic moments from cosmic photon background observations.Comment: RevTex, 14 pages, 3 figures; minor changes, references added. To
appear in Phys. Rev.
Dark Energy and Extending the Geodesic Equations of Motion: Connecting the Galactic and Cosmological Length Scales
Recently, an extension of the geodesic equations of motion using the Dark
Energy length scale was proposed. Here, we apply this extension to the
analyzing the motion of test particles at the galactic scale and longer. A
cosmological check of the extension is made using the observed rotational
velocity curves and core sizes of 1393 spiral galaxies. We derive the density
profile of a model galaxy using this extension, and with it, we calculate
to be ; this is within experimental error of the
WMAP value of . We then calculate to be
kpc, which is in reasonable agreement with observations.Comment: 25 pages. Accepted for publication in General Relativity and
Gravitation. Paper contains the published version of the second half of
arXiv:0711.3124v2 with corrections include
Conditions for Successful Extended Inflation
We investigate, in a model-independent way, the conditions required to obtain
a satisfactory model of extended inflation in which inflation is brought to an
end by a first-order phase transition. The constraints are that the correct
present strength of the gravitational coupling is obtained, that the present
theory of gravity is satisfactorily close to general relativity, that the
perturbation spectra from inflation are compatible with large scale structure
observations and that the bubble spectrum produced at the phase transition
doesn't conflict with the observed level of microwave background anisotropies.
We demonstrate that these constraints can be summarized in terms of the
behaviour in the conformally related Einstein frame, and can be compactly
illustrated graphically. We confirm the failure of existing models including
the original extended inflation model, and construct models, albeit rather
contrived ones, which satisfy all existing constraints.Comment: 8 pages RevTeX file with one figure incorporated (uses RevTeX and
epsf). Also available by e-mailing ARL, or by WWW at
http://star-www.maps.susx.ac.uk/papers/infcos_papers.html; Revised to include
extra references, results unchanged, to appear Phys Rev
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