13,462 research outputs found
Reheating After Quintessential Inflation and Gravitational Waves
We investigate the dependence of the gravitational wave spectrum from
quintessential inflation on the reheating process. We consider two extreme
reheating processes. One is the gravitational reheating by particle creation in
the expanding universe in which the beginning of the radiation dominated epoch
is delayed due to the presence of the epoch of domination of the kinetic energy
of the inflaton (kination). The other is the instant preheating considered by
Felder et al. in which the Universe becomes radiation dominated soon after the
end of inflation. We find that the spectrum of the gravitational waves at MHz is quite sensitive to the reheating process. This result is not
limited to quintessential inflation but applicable to various inflation models.
Conversely, the detection or non-detection of primordial gravitational waves at
100 MHz would provide useful information regarding the reheating process
in inflation.Comment: 15 pages, 5 figures, to be published in CQ
Quintessential Affleck-Dine baryogenesis with non-minimal couplings
We present a novel Affleck-Dine scenario for the generation of the observed
baryon asymmetry of the Universe based on the non-trivial interplay between
quintessential inflationary models containing a kinetic dominated
post-inflationary era and a non-minimally coupled field with a weakly
broken symmetry. The non-minimal coupling to gravity renders heavy the
Affleck-Dine field during inflation and avoids the generation of isocurvature
fluctuations. During the subsequent kinetic era the Ricci scalar changes sign
and the effective mass term of the Affleck-Dine field becomes tachyonic. This
allows the field to dynamically acquire a large expectation value. The symmetry
of the Affleck-Dine potential is automatically restored at the onset of
radiation domination, when the Ricci scalar approximately equals zero. This
inverse phase transition results in the coherent oscillation of the scalar
field around the origin of its effective potential. The rotation of the
displaced Affleck-Dine field in the complex plane generates a non-zero
asymmetry which can be eventually converted into a baryon asymmetry via the
usual transfer mechanisms.Comment: 9 pages, 1 figure, minor corrections and clarifications added.
Matches the published versio
Semiparametric posterior limits
We review the Bayesian theory of semiparametric inference following Bickel
and Kleijn (2012) and Kleijn and Knapik (2013). After an overview of efficiency
in parametric and semiparametric estimation problems, we consider the
Bernstein-von Mises theorem (see, e.g., Le Cam and Yang (1990)) and generalize
it to (LAN) regular and (LAE) irregular semiparametric estimation problems. We
formulate a version of the semiparametric Bernstein-von Mises theorem that does
not depend on least-favourable submodels, thus bypassing the most restrictive
condition in the presentation of Bickel and Kleijn (2012). The results are
applied to the (regular) estimation of the linear coefficient in partial linear
regression (with a Gaussian nuisance prior) and of the kernel bandwidth in a
model of normal location mixtures (with a Dirichlet nuisance prior), as well as
the (irregular) estimation of the boundary of the support of a monotone family
of densities (with a Gaussian nuisance prior).Comment: 47 pp., 1 figure, submitted for publication. arXiv admin note:
substantial text overlap with arXiv:1007.017
Perfect Simulation of Queues
In this paper we describe a perfect simulation algorithm for the stable
queue. Sigman (2011: Exact Simulation of the Stationary Distribution of
the FIFO M/G/c Queue. Journal of Applied Probability, 48A, 209--213) showed how
to build a dominated CFTP algorithm for perfect simulation of the super-stable
queue operating under First Come First Served discipline, with
dominating process provided by the corresponding queue (using Wolff's
sample path monotonicity, which applies when service durations are coupled in
order of initiation of service), and exploiting the fact that the workload
process for the queue remains the same under different queueing
disciplines, in particular under the Processor Sharing discipline, for which a
dynamic reversibility property holds. We generalize Sigman's construction to
the stable case by comparing the queue to a copy run under Random
Assignment. This allows us to produce a naive perfect simulation algorithm
based on running the dominating process back to the time it first empties. We
also construct a more efficient algorithm that uses sandwiching by lower and
upper processes constructed as coupled queues started respectively from
the empty state and the state of the queue under Random Assignment. A
careful analysis shows that appropriate ordering relationships can still be
maintained, so long as service durations continue to be coupled in order of
initiation of service. We summarize statistical checks of simulation output,
and demonstrate that the mean run-time is finite so long as the second moment
of the service duration distribution is finite.Comment: 28 pages, 5 figure
Lectures on Cosmic Inflation and its Potential Stringy Realizations
These notes present a brief introduction to Hot Big Bang cosmology and Cosmic
Inflation, together with a selection of some recent attempts to embed inflation
into string theory. They provide a partial description of lectures presented in
courses at Dubrovnik in August 2006, at CERN in January 2007 and at Cargese in
August 2007. They are aimed at graduate students with a working knowledge of
quantum field theory, but who are unfamiliar with the details of cosmology or
of string theory.Comment: 68 pages, lectures given at Dubrovnik, Aug 2006; CERN, January 2007;
and Cargese, Aug 200
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