3,342 research outputs found
`Thermodynamics' of Minimal Surfaces and Entropic Origin of Gravity
Deformations of minimal surfaces lying in constant time slices in static
space-times are studied. An exact and universal formula for a change of the
area of a minimal surface under shifts of nearby point-like particles is found.
It allows one to introduce a local temperature on the surface and represent
variations of its area in a thermodynamical form by assuming that the entropy
in the Planck units equals the quarter of the area. These results provide a
strong support to a recent hypothesis that gravity has an entropic origin, the
minimal surfaces being a sort of holographic screens. The gravitational entropy
also acquires a definite physical meaning related to quantum entanglement of
fundamental degrees of freedom across the screen.Comment: 12 pages, 1 figur
Gravitational waves from first order phase transitions during inflation
We study the production, spectrum and detectability of gravitational waves in
models of the early Universe where first order phase transitions occur during
inflation. We consider all relevant sources. The self-consistency of the
scenario strongly affects the features of the waves. The spectrum appears to be
mainly sourced by collisions of bubble of the new phases, while plasma dynamics
(turbulence) and the primordial gauge fields connected to the physics of the
transitions are generally subdominant. The amplitude and frequency dependence
of the spectrum for modes that exit the horizon during inflation are different
from those of the waves produced by quantum vacuum oscillations of the metric
or by first order phase transitions not occurring during inflation. A moderate
number of slow (but still successful) phase transitions can leave detectable
marks in the CMBR, but the signal weakens rapidly for faster transitions. When
the number of phase transitions is instead large, the primordial gravitational
waves can be observed both in the CMBR or with LISA (marginally) and especially
DECIGO. We also discuss the nucleosynthesis bound and the constraints it places
on the parameters of the models.Comment: minor changes in the text and the references to match the published
versio
Single Field Baryogenesis
We propose a new variant of the Affleck-Dine baryogenesis mechanism in which
a rolling scalar field couples directly to left- and right-handed neutrinos,
generating a Dirac mass term through neutrino Yukawa interactions. In this
setup, there are no explicitly CP violating couplings in the Lagrangian. The
rolling scalar field is also taken to be uncharged under the quantum
numbers. During the phase of rolling, scalar field decays generate a
non-vanishing number density of left-handed neutrinos, which then induce a net
baryon number density via electroweak sphaleron transitions.Comment: 4 pages, LaTe
Friedmann Equations from Entropic Force
In this note by use of the holographic principle together with the
equipartition law of energy and the Unruh temperature, we derive the Friedmann
equations of a Friedmann-Robertson-Walker universe.Comment: latex, 8 pages, v2: minor modifications and to appear in PRD (Rapid
Communication
CPT violation and B-meson oscillations
Recent evidence for anomalous CP violation in B-meson oscillations can be
interpreted as resulting from CPT violation. This yields the first sensitivity
to CPT violation in the B_s^0 system, with the relevant coefficient for CPT
violation constrained at the level of parts in 10^{12}.Comment: 4 pages two-column REVTeX; Rapid Communications, Physical Review D,
in pres
Information-preserving black holes still do not preserve baryon number and other effective global quantum numbers
It has been claimed recently that the black hole information-loss paradox has
been resolved: the evolution of quantum states in the presence of a black hole
is unitary and information preserving. We point out that, contrary to some
claims in literature, information-preserving black holes still violate baryon
number and any other quantum number which follows from an effective (and thus
approximate) or anomalous symmetry.Comment: Honorable Mention on Gravity Essay Competition 2005; Published in the
special Essay issue of Int.J.Mod.Phy
Baryon and lepton numbers in two scenarios of leptogenesis
Baryon and lepton numbers of the Universe in leptogenesis with Dirac neutrino
and leptogenesis with Majorana neutrino scenarios are considered. It is shown
that despite quite different features of Dirac and Majorana fermions both
scenarios yield the same relation among the initial lepton and the final baryon
asymmetries. Moreover right-handed neutrinos in the leptogenesis with Dirac
neutrino scenario have very little impact on the effective number of
relativistic degrees of freedom, constrained by BBN. Thus the two scenarios are
similar from the cosmological point of view. It is also pointed out that in
thermal equilibrium the 3B+L sum is zero for left-handed fermions.Comment: 9 pages, 4 figure
Leptonic CP violation studies at MiniBooNE in the (3+2) sterile neutrino oscillation hypothesis
We investigate the extent to which leptonic CP-violation in (3+2) sterile
neutrino models leads to different oscillation probabilities for
and oscillations at
MiniBooNE. We are using a combined analysis of short-baseline (SBL) oscillation
results, including the LSND and null SBL results, to which we impose additional
constraints from atmospheric oscillation data. We obtain the favored regions in
MiniBooNE oscillation probability space for both (3+2) CP-conserving and (3+2)
CP-violating models. We further investigate the allowed CP-violation phase
values and the MiniBooNE reach for such a CP violation measurement. The
analysis shows that the oscillation probabilities in MiniBooNE neutrino and
antineutrino running modes can differ significantly, with the latter possibly
being as much as three times larger than the first. In addition, we also show
that all possible values of the single CP-violation phase measurable at short
baselines in (3+2) models are allowed within 99% CL by existing data.Comment: Fixed a typo following PRD Erratum. 8 pages, 5 figure
Baryogenesis by B - L generation due to superheavy particle decay
We have shown that the generation due to the decay of the thermally
produced superheavy fields can explain the Baryon assymmetry in the universe if
the superheavy fields are heavier than GeV. Note that although the
superheavy fields have non-vanishing charges under the standard model gauge
interactions, the thermally prduced baryon asymmetry is sizable. The
violating effective operators induced by integrating the superheavy fields have
dimension 7, while the operator in the famous leptogenesis has dimension 5.
Therefore, the constraints from the nucleon stability can be easily satisfied.Comment: 12 pages, 4 figures, 3 table
Synchrotron Radiation and Quantum Gravity
Photons may evade a synchrotron radiation constraint on quantum gravity by
violating the equivalence principle.Comment: 4 pages. Comment on Jacobson et al astro-ph/0212190. Presentation
revised for brief communication to Nature with extended bibliograph
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