743 research outputs found
Ultra High Energy Cosmic Rays and Inflation Relics
There are two processes of matter creation after inflation that may be
relevant to the resolution of the puzzle of cosmic rays observed with energies
beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable
particles, and 2) non-thermal phase transitions leading to formation of
topological defects. We review both possibilities.Comment: Submitted to Physics Report
Evolution of the Order Parameter after Bubble Collisions
If a first-order phase transition is terminated by collisions of new-phase
bubbles, there will exist a period of nonequilibrium between the time bubbles
collide and the time thermal equilibrium is established. We study the behavior
of the order parameter during this phase. We find that large nonthermal
fluctuations at this stage tend to restore symmetry, i.e., the order parameter
is smaller than its eventual thermal equilibrium value. We comment on possible
consequences for electroweak baryogenesis.Comment: 11 page LaTeX file with two figures, fig1.ps and fig2.p
Metric perturbations at reheating: the use of spherical symmetry
We consider decay of the inflaton with a quartic potential coupled to other
fields, including gravity, but restricted to spherical symmetry. We describe
analytically an early, quasilinear regime, during which inflaton fluctuations
and the metric functions are driven by nonlinear effects of the decay products.
We present a detailed study of the leading nonlinear effects in this regime.
Results of the quasilinear approximation, in its domain of applicability, are
found to be consistent with those of fully nonlinear lattice studies. We
discuss how these results may be promoted to the full three dimensions.Comment: 18 pages, revtex, 2 figure
A remark on sphaleron erasure of baryon asymmetry
We complete an existing result for how the baryon asymmetry left over after a
period of full thermal equilibrium depends on different lepton asymmetries.Comment: 5 pages; small clarifications and a reference added; to appear in PR
Reheating in the Presence of Inhomogeneous Noise
Explosive particle production due to parametric resonance is a crucial
feature of reheating in an inflationary cosmology. Coherent oscillations of the
inflaton field lead to a periodically varying mass in the evolution equation of
matter and gravitational fluctuations and often induce a parametric resonance
instability. In a previous paper (hep-ph/9709273) it was shown that homogeneous
(i.e. space independent) noise leads to an increase of the generalized Floquet
exponent for all modes, at least if the noise is temporally uncorrelated. Here
we extend the results to the physically more realistic case of spatially
inhomogeneous noise. We demonstrate - modulo some mathematical fine points
which are addressed in a companion paper - that the Floquet exponent is a non-
decreasing function of the amplitude of the noise. We provide numerical
evidence for an even stronger statement, namely that in the presence of
inhomogeneous noise, the Floquet exponent of each mode is larger than the
maximal Floquet exponent of the system in the absence of noise.Comment: 21 pages, 4 figure
Brane-worlds and theta-vacua
Reductions from odd to even dimensionalities ( or ), for
which the effective low-energy theory contains chiral fermions, present us with
a mismatch between ultraviolet and infrared anomalies. This applies to both
local (gauge) and global currents; here we consider the latter case. We show
that the mismatch can be explained by taking into account a change in the
spectral asymmetry of the massive modes--an odd-dimensional analog of the
phenomenon described by the Atiyah-Patodi-Singer theorem in even
dimensionalities. The result has phenomenological implications: we present a
scenario in which a QCD-like -angle relaxes to zero on a certain
(possibly, cosmological) timescale, despite the absence of any light axion-like
particle.Comment: 44 pages, 4 figure
Recommendations on reforming the current legislation on the import and export of research materials
The article provides the analysis of the current state in importing and exporting of materials for research and development activity, its problems and prospects of further development. The authors note the imperfection of the legislation in this area and offer a wide range of recommendations for qualitative improvement of the situation. The relevance of the research topic is determined by the fact that in the 21st century the role and place of Russian Federation in the world economy would largely depend on the level of its scientific and technological development, the ability to create and effectively replicate its own achievements and make extensive use of imported high-end technologies, the degree of its presence on the world market of high and new technologies.peer-reviewe
First-order nonthermal phase transition after preheating
During preheating after inflation, parametric resonance rapidly generates
very large fluctuations of scalar fields. In models where the inflaton field
oscillates in a double-well potential and interacts with another scalar
field , fluctuations of X can keep the \phi to -\phi symmetry temporarily
restored. If the coupling of \phi to X is much stronger than the inflaton
self-coupling, the subsequent symmetry breaking is a first-order phase
transition. We demonstrate the existence of this nonthermal phase transition
with lattice simulations of the full nonlinear dynamics of the interacting
fields. In particular, we observe nucleation of an expanding bubble.Comment: RevTeX, 4 page
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