269 research outputs found
Supernovae as a probe of particle physics and cosmology
It has very recently been demonstrated by Csaki, Kaloper and Terning (CKT)
that the faintness of supernovae at high redshift can be accommodated by mixing
of a light axion with the photon in the presence of an intergalactic magnetic
field, as opposed to the usual explanation of an accelerating universe by a
dark energy component. In this paper we analyze further aspects of the CKT
mechanism and its generalizations. The CKT mechanism also passes various
cosmological constraints from the fluctuations of the CMB and the formation of
structure at large scales, without requiring an accelerating phase in the
expansion of the Universe. We investigate the statistical significance of
current supernova data for pinning down the different components of the
cosmological energy-momentum tensor and for probing physics beyond the standard
models.Comment: 17 pages, LaTeX, 4 figures; v2: typos corrected, minor changes,
references added; v3: updated figures, details regarding fits include
Higgs Boson studies at future particle colliders
This document aims to provide an assessment of the potential of future colliding beam facilities to perform Higgs boson studies. The analysis builds on the submissions made by the proponents of future colliders to the European Strategy Update process, and takes as its point of departure the results expected at the completion of the HL-LHC program. This report presents quantitative results on many aspects of Higgs physics for future collider projects of sufficient maturity using uniform methodologies
BPS pp-wave brane cosmological solutions in string theory
We construct time dependent BPS pp-wave brane solutions in the context of
M-theory and type II supergravity. It is found that N-brane solutions we
considered satisfy the crossing rule as S-brane solutions but 1/8 supersymmetry
remains. By applying them to the cosmological setting, inflationary solutions
are obtained. During this inflation, the size of the extradimensions becomes
smaller than our four-dimensional spacetime dynamically. We also discuss the
mechanism for terminating this inflation and recovering the hot big-bang
universe.Comment: 10 page
Noncommutative Quantum Cosmology
We propose a model for noncommutative quantum cosmology by means of a
deformation of minisuperspace. For the Kantowski-Sachs metric we are able to
find the exact wave function. We construct wave packets and show that new
quantum states that ``compete'' to be the most probable state appear, in clear
contrast with the commutative case. A tunneling process could be possible among
these states.Comment: 5 pages, 5 figures, revtex4 file, major style changes, to be
published in PR
Echoes of the fifth dimension?
In this article we examine the question of whether the highest energy cosmic
ray primaries could be ultra relativistic magnetic monopoles. The analysis is
performed within the framework of large compact dimensions and TeV scale
quantum gravity. Our study indicates that while this hypothesis must be
regarded as highly speculative it cannot be ruled out with present data.Comment: Revised version accepted for publication in Physical Review D. The
bibliography has been considerably reduced for the journal version due to
limited spac
On Time-dependent Backgrounds in Supergravity and String Theory
Time-dependent solutions of supergravity and string theory are studied. The
examples are obtained from de Sitter deformation of gauge/gravity dualities,
analytical continuation of static solutions, and ``exactly solvable''
worldsheet models. Among other things, it is shown that turning on a Hubble
parameter in the background of a confining gauge theory in four dimensions can
restore chiral symmetry. Some of the solutions obtained from analytical
continuation have the interpretation of a universe with a bounce separating a
big bang from a big crunch singularity. In the worldsheet context, it is argued
why string propagation close to a Milne-type cosmological singularity might be
physically non-singular.Comment: 38 pages, 1 figure, v2: refs adde
On Bouncing Brane-Worlds, S-branes and Branonium Cosmology
We present several higher-dimensional spacetimes for which observers living
on 3-branes experience an induced metric which bounces. The classes of examples
include boundary branes on generalised S-brane backgrounds and probe branes in
D-brane/anti D-brane systems. The bounces we consider normally would be
expected to require an energy density which violates the weak energy condition,
and for our co-dimension one examples this is attributable to bulk curvature
terms in the effective Friedmann equation. We examine the features of the
acceleration which provides the bounce, including in some cases the existence
of positive acceleration without event horizons, and we give a geometrical
interpretation for it. We discuss the stability of the solutions from the point
of view of both the brane and the bulk. Some of our examples appear to be
stable from the bulk point of view, suggesting the possible existence of stable
bouncing cosmologies within the brane-world framework.Comment: 35 pages, 7 figures, JHEP style. Title changed and references adde
The Universal One-Loop Effective Action
We present the universal one-loop effective action for all operators of
dimension up to six obtained by integrating out massive, non-degenerate
multiplets. Our general expression may be applied to loops of heavy fermions or
bosons, and has been checked against partial results available in the
literature. The broad applicability of this approach simplifies one-loop
matching from an ultraviolet model to a lower-energy effective field theory
(EFT), a procedure which is now reduced to the evaluation of a combination of
matrices in our universal expression, without any loop integrals to evaluate.
We illustrate the relationship of our results to the Standard Model (SM) EFT,
using as an example the supersymmetric stop and sbottom squark Lagrangian and
extracting from our universal expression the Wilson coefficients of
dimension-six operators composed of SM fields.Comment: 30 pages, v2 contains additional comments and corrects typos, version
accepted for publication in JHE
Physics at the e+ e- Linear Collider
A comprehensive review of physics at an e+e- Linear Collider in the energy
range of sqrt{s}=92 GeV--3 TeV is presented in view of recent and expected LHC
results, experiments from low energy as well as astroparticle physics.The
report focuses in particular on Higgs boson, Top quark and electroweak
precision physics, but also discusses several models of beyond the Standard
Model physics such as Supersymmetry, little Higgs models and extra gauge
bosons. The connection to cosmology has been analyzed as well.Comment: 179 pages, plots and references updated, version to be published at
EPJ
Bouncing Braneworlds Go Crunch!
Recently, interesting braneworld cosmologies in the Randall-Sundrum scenario
have been constructed using a bulk spacetime which corresponds to a charged AdS
black hole. In particular, these solutions appear to `bounce', making a smooth
transition from a contracting to an expanding phase. By considering the
spacetime geometry more carefully, we demonstrate that generically in these
solutions the brane will encounter a singularity in the transition region.Comment: 17 pages, 4 figures, ref adde
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