2,560 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
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.
On Thermalization in de Sitter Space
We discuss thermalization in de Sitter space and argue, from two different
points of view, that the typical time needed for thermalization is of order
, where is the radius of the de Sitter space in question.
This time scale gives plenty of room for non-thermal deviations to survive
during long periods of inflation. We also speculate in more general terms on
the meaning of the time scale for finite quantum systems inside isolated boxes,
and comment on the relation to the Poincar\'{e} recurrence time.Comment: 14 pages, 2 figures, latex, references added. Improved discussion in
section 3 adde
Holographic Superconductors with Lifshitz Scaling
Black holes in asymptotically Lifshitz spacetime provide a window onto finite
temperature effects in strongly coupled Lifshitz models. We add a Maxwell gauge
field and charged matter to a recently proposed gravity dual of 2+1 dimensional
Lifshitz theory. This gives rise to charged black holes with scalar hair, which
correspond to the superconducting phase of holographic superconductors with z >
1 Lifshitz scaling. Along the way we analyze the global geometry of static,
asymptotically Lifshitz black holes at arbitrary critical exponent z > 1. In
all known exact solutions there is a null curvature singularity in the black
hole region, and, by a general argument, the same applies to generic Lifshitz
black holes.Comment: 23 pages, 4 figures; v2: added references; v3: matches published
versio
Type 0A 2D Black Hole Thermodynamics and the Deformed Matrix Model
Recently, it has been proposed that the deformed matrix model describes a
two-dimensional type 0A extremal black hole. In this paper, the thermodynamics
of 0A charged non-extremal black holes is investigated. We observe that the
free energy of the deformed matrix model to leading order in 1/q can be seen to
agree to that of the extremal black hole. We also speculate on how the deformed
matrix model is able to describe the thermodynamics of non-extremal black
holes.Comment: 12 page
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
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
Analysis of Higher Spin Field Equations in Four Dimensions
The minimal bosonic higher spin gauge theory in four dimensions contains
massless particles of spin s=0,2,4,.. that arise in the symmetric product of
two spin 0 singletons. It is based on an infinite dimensional extension of the
AdS_4 algebra a la Vasiliev. We derive an expansion scheme in which the
gravitational gauge fields are treated exactly and the gravitational curvatures
and the higher spin gauge fields as weak perturbations. We also give the
details of an explicit iteration procedure for obtaining the field equations to
arbitrary order in curvatures. In particular, we highlight the structure of all
the quadratic terms in the field equations.Comment: Latex, 30 pages, several clarifications and few references adde
Holographic Superconductor for a Lifshitz fixed point
We consider the gravity dual of strongly coupled system at a Lifshitz-fixed
point and finite temperature, which was constructed in a recent work
arXiv:0909.0263. We construct an Abelian Higgs model in that background and
calculate condensation and conductivity using holographic techniques. We find
that condensation happens and DC conductivity blows up when temperature turns
below a critical value.Comment: 14 pages, 4 figures, v4: improved version, references adde
Scalar Synchrotron Radiation in the Schwarzschild-anti-de Sitter Geometry
We present a complete relativistic analysis for the scalar radiation emitted
by a particle in circular orbit around a Schwarzschild-anti-de Sitter black
hole. If the black hole is large, then the radiation is concentrated in narrow
angles- high multipolar distribution- i.e., the radiation is synchrotronic.
However, small black holes exhibit a totally different behavior: in the small
black hole regime, the radiation is concentrated in low multipoles. There is a
transition mass at , where is the AdS radius. This behavior is
new, it is not present in asymptotically flat spacetimes.Comment: 13 pages, 6 figures, published version. References adde
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