46,789 research outputs found
String Theory and Cosmology
We discuss the main cosmological implications of considering string-loop
effects and a potential for the dilaton in the lowest order string effective
action. Our framework is based on the effective model arising from regarding
homogeneous and isotropic dilaton, metric and Yang-Mills field configurations.
The issues of inflation, entropy crisis and the Polonyi problem as well as the
problem of the cosmological constant are discussed.Comment: 7 pages, plain Tex, no figure
Infinity in string cosmology: A review through open problems
We review recent developments in the field of string cosmology with
particular emphasis on open problems having to do mainly with geometric
asymptotics and singularities. We discuss outstanding issues in a variety of
currently popular themes, such as tree-level string cosmology asymptotics,
higher-order string correction effects, M-theory cosmology, braneworlds, and
finally ambient cosmology.Comment: 37 pages, to appear in the IJMPD, v2: matches published versio
String theory and primordial cosmology
String cosmology aims at providing a reliable description of the very early
Universe in the regime where standard-model physics is no longer appropriate,
and where we can safely apply the basic ingredients of superstring models such
as dilatonic and axionic forces, duality symmetries, winding modes, limiting
sizes and curvatures, higher-dimensional interactions among elementary extended
object. The sought target is that of resolving (or at least alleviating) the
big problems of standard and inflationary cosmology like the spacetime
singularity, the physics of the trans-Planckian regime, the initial condition
for inflation, and so on.Comment: 17 pages, 5 figures, published in "Springer Handbook of Spacetime",
ed. by A. Ashtekar and V. Petkov (Springer-Verlag, Berlin Heidelberg, 2014,
Chapter 3
Towards an Observational Appraisal of String Cosmology
We review the current observational status of string cosmology when
confronted with experimental datasets. We begin by defining common
observational parameters and discuss how they are determined for a given model.
Then we review the observable footprints of several string theoretic models,
discussing the significance of various potential signals. Throughout we comment
on present and future prospects of finding evidence for string theory in
cosmology, and on significant issues for the future.Comment: Review accepted for publication in the CQG focus issue on string
cosmology. Minor clarifications and references adde
Soft gluon resummation for squark and gluino pair-production at hadron colliders
We report on the study of soft gluon effects in the production of squarks and
gluinos at hadron colliders. Close to production threshold, the emission of
soft gluon results in the appearence of large logarithmic corrections in the
theoretical expressions. In order to resum these corrections at
next-to-leading-logarithmic accuracy appropriate one-loop anomalous dimensions
have to be calculated. We present the calculation of the anomalous dimensions
for all production channels of squarks and gluinos and provide numerical
predictions for the Tevatron and the LHC.Comment: 6 pages, talk given at RADCOR 2009 - 9th International Symposium on
Radiative Corrections (Applications of Quantum Field Theory to Phenomenology)
October 25-30 2009, Ascona, Switzerlan
Noncommutative Quantum Cosmology
We consider noncommutative quantum cosmology in the case of the low-energy
string effective theory. Exacts solutions are found and compared with the
commutative case.The Noncommutative quantum cosmology is considered in the case
of the low-energy string effective theory. Exacts solutions are found and
compared with the commutative case.Comment: Revtex4, 3 pages, 2 figures, to appear in Gen.Rel.Gra
Looking Beyond Inflationary Cosmology
In spite of the phenomenological successes of the inflationary universe
scenario, the current realizations of inflation making use of scalar fields
lead to serious conceptual problems which are reviewed in this lecture. String
theory may provide an avenue towards addressing these problems. One particular
approach to combining string theory and cosmology is String Gas Cosmology. The
basic principles of this approach are summarized.Comment: invited talk at "Theory Canada 1" (Univ. of British Columbia,
Vancouver, Canada, June 2 - 4, 2005) (references updated
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