2,314 research outputs found
Transplanckian energy production and slow roll inflation
In this paper we investigate how the energy density due to a non-standard
choice of initial vacuum affects the expansion of the universe during
inflation. To do this we introduce source terms in the Friedmann equations
making sure that we respect the relation between gravity and thermodynamics. We
find that the energy production automatically implies a slow rolling
cosmological constant. Hence we also conclude that there is no well defined
value for the cosmological constant in the presence of sources. We speculate
that a non-standard vacuum can provide slow roll inflation on its own.Comment: 16 pages, 2 figures, version 2: minor corrections to section 4 and
references adde
Space Noncommutativity Corrections to the Cardy-Verlinde Formula
In this letter we compute the corrections to the Cardy-Verlinde formula of
Schwarzschild black holes. These corrections stem from the space
noncommutativity. Because the Schwarzschild black holes are non rotating, to
the first order of perturbative calculations, there is no any effect on the
properties of black hole due to the noncommutativity of space.Comment: 7 pages, no figures, accepted for publication in Int. J. Mod. Phys.
Electromagnetic Corrections in Partially Quenched Chiral Perturbation Theory
We introduce photons in Partially Quenched Chiral Perturbation Theory and
calculate the resulting electromagnetic loop-corrections at NLO for the charged
meson masses and decay constants. We also present a numerical analysis to
indicate the size of the different corrections. We show that several
phenomenologically relevant quantities can be calculated consistently with
photons which couple only to the valence quarks, allowing the use of gluon
configurations produced without dynamical photons.Comment: 11 page
Black hole thermalization rate from brane anti-brane model
We develop the quasi-particle picture for Schwarzchild and far from extremal
black holes. We show that the thermalization equations of the black hole is
recovered from the model of branes and anti-branes. This can also be viewed as
a field theory explanation of the relationship between area and entropy for
these black holes. As a by product the annihilation rate of branes and
anti-branes is computed.Comment: 11 pages, late
Observing the Structure of the Landscape with the CMB Experiments
Assuming that inflation happened through a series of tunneling in the string
theory landscape, it is argued that one can determine the structure of vacua
using precise measurements of the scalar spectral index and tensor
perturbations at large scales. It is shown that for a vacuum structure where
the energy gap between the minima is constant, i.e. , one
obtains the scalar spectral index, , to be , for the modes
that exit the horizon 60 e-folds before the end of inflation. Alternatively,
for a vacuum structure in which the energy gap increases linearly with the
vacuum index, i.e. , turns out to be
. Both these two models are motivated within the string theory
landscape using flux-compactification and their predictions for scalar spectral
index are compatible with WMAP results. For both these two models, the results
for the scalar spectral index turn out to be independent of . Nonetheless,
assuming that inflation started at Planckian energies and that there had been
successful thermalization at each step, one can constrain and in these two models,
respectively. Violation of the single-field consistency relation between the
tensor and scalar spectra is another prediction of chain inflation models. This
corresponds to having a smaller tensor/scalar ratio at large scales in
comparison with the slow-roll counterparts. Similar to slow-roll inflation, it
is argued that one can reconstruct the vacuum structure using the CMB
experiments.Comment: v1: 8 pages, 2 figures; v2: grammatical typos corrected, results
unchanged v3: To be published in JCA
Squeezed States in the de Sitter Vacuum
We discuss the treatment of squeezed states as excitations in the Euclidean
vacuum of de Sitter space. A comparison with the treatment of these states as
candidate no-particle states, or alpha-vacua, shows important differences
already in the free theory. At the interacting level alpha-vacua are
inconsistent, but squeezed state excitations seem perfectly acceptable. Indeed,
matrix elements can be renormalized in the excited states using precisely the
standard local counterterms of the Euclidean vacuum. Implications for
inflationary scenarios in cosmology are discussed.Comment: 15 pages, no figures. One new citation in version 3; no other change
Inflation as a probe of new physics
In this paper we consider inflation as a probe of new physics near the string
or Planck scale. We discuss how new physics can be captured by the choice of
vacuum, and how this leads to modifications of the primordial spectrum as well
as the way in which the universe expands during inflation. Provided there is a
large number of fields contributing to the vacuum energy -- as typically is
expected in string theory -- we will argue that both types of effects can be
present simultaneously and be of observational relevance. Our conclusion is
that the ambiguity in choice of vacuum is an interesting new parameter in
serious model building.Comment: 14 page
Lectures on string theory and cosmology
In these lectures I review recent attempts to apply string theory to
cosmology, including string cosmology and various models of brane cosmology. In
addition, the review includes an introduction to inflation as well as a
discussion of transplanckian signatures. I also provide a critical discussion
of the possible role of holography. The material is based on lectures given in
January 2004 at the RTN String School in Barcelona, but also contain some
additional material.Comment: Lectures given in January 2004 at the RTN Barcelona String School, 50
pages, 9 figure
On the Moduli Space of N = 2 Supersymmetric G_2 Gauge Theory
We apply the method of confining phase superpotentials to N = 2
supersymmetric Yang-Mills theory with the exceptional gauge group G_2. Our
findings are consistent with the spectral curve of the periodic Toda lattice,
but do not agree with the hyperelliptic curve suggested previously in the
literature. We also apply the method to theories with fundamental matter,
treating both the example of SO(5) and G_2.Comment: 14 pages, LaTeX, 1 figure, reference adde
De Sitter Waves and the Zero Curvature Limit
We show that a particular set of global modes for the massive de Sitter
scalar field (the de Sitter waves) allows to manage the group representations
and the Fourier transform in the flat (Minkowskian) limit. This is in
opposition to the usual acceptance based on a previous result, suggesting the
appearance of negative energy in the limit process. This method also confirms
that the Euclidean vacuum, in de Sitter spacetime, has to be preferred as far
as one wishes to recover ordinary QFT in the flat limit.Comment: 9 pages, latex no figure, to appear in Phys. Rev.
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