2,456 research outputs found
Extracting the bulk metric from boundary information in asymptotically AdS spacetimes
We use geodesic probes to recover the entire bulk metric in certain
asymptotically AdS spacetimes. Given a spectrum of null geodesic endpoints on
the boundary, we describe two remarkably simple methods for recovering the bulk
information. After examining the issues which affect their application in
practice, we highlight a significant advantage one has over the other from a
computational point of view, and give some illustrative examples. We go on to
consider spacetimes where the methods cannot be used to recover the complete
bulk metric, and demonstrate how much information can be recovered in these
cases.Comment: 33 pages, 11 figures; v2 references adde
Ultimate pH values and bacteriological condition of meat and stress metabolites in blood of transported reindeer bulls
Twenty-three reindeer bulls, aged 2-3 years, fed during two winter months at the Vuolda reindeer research station in Arjeplog, Sweden, were used in the study. The first group of eight reindeer was moved from their feeding corral to a selection corral, captured by lasso and stunned with a captive bolt outside the selection corral. The second group of seven reindeer was moved to the selection corral, captured by lasso and restrained, after which they were loaded onto a lorry- and transported for 1 hour and then slaughtered. The third group of eight reindeer was moved to the selection corral and herded directly onto the lorry, without any manual handling. They were transported for 5 h and then slaughtered. In both transport groups, four reindeer were fitted with pre-programmed automatic blood sampling equipment (ABSE). ABSE sampled blood at predetermined times via a jugular vein catheter. Ultimate pH-values in three muscles (Mm. longissimus, triceps brachii and biceps femoris) were significantly lower in the group carefully handled and transported for 5 h compared with the other two groups. The physiological mechanisms behind these results are discussed. Samples from M. semimembranosus were collected at slaughter and after 2, 6 and 10 days of refrigerated storage (+4 °C). The samples were analysed for total counts of aerobic bacteria (pour-plated in Tryptone Glucose Extract Agar, Difco, incubated at 20 °C and 30 °C, respectively for 72 h), coliform bacteria 37 °C (pour-plated in Violet Red Bile Agar, Oxoid, incubated at 37 °C for 24 h), Enterococci (surface-plated onto Slantez and Bartley Agar, Oxoid, incubated at 44 °C for 48 h) and Bacillus cereus (surface-plated onto Blood Agar Plates (Blood Agar Base, Difco, supplemented with 5% defibrinated horse blood) 30 °C for 24 h). All samples fell in the range 'fit for consumption'. At slaughter, there was no difference in ASAT activity, urea and Cortisol concentrations between the two transported groups. However, the plasma ASAT activity and urea concentrations at slaughter were significantly lower in the non-transported group. In both transport groups, the plasma Cortisol concentrations increased during loading onto and unloading from the lorry. Abomasal lesions were observed in all treatment groups. It was concluded that reindeer showed an acute stress response to manual handling and transport
Conformal Field Theory Interpretation of Black Hole Quasi-normal Modes
We obtain exact expressions for the quasi-normal modes of various spin for
the BTZ black hole. These modes determine the relaxation time of black hole
perturbations. Exact agreement is found between the quasi-normal frequencies
and the location of the poles of the retarded correlation function of the
corresponding perturbations in the dual conformal field theory. This then
provides a new quantitative test of the AdS/CFT correspondence.Comment: 4 pages, RevTeX, references adde
Miracles and complementarity in de Sitter space
In this paper we consider a scenario, consisting of a de Sitter phase
followed by a phase described by a scale factor , where
, which can be viewed as an inflationary toy model. It is argued that
this scenario naively could lead to an information paradox. We propose that the
phenomenon of Poincar\'{e} recurrences plays a crucial role in the resolution
of the paradox. We also comment on the relevance of these results to inflation
and the CMBR.Comment: 13 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
CMB quadrupole suppression: II. The early fast roll stage
Within the effective field theory of inflation, an initialization of the
classical dynamics of the inflaton with approximate equipartition between the
kinetic and potential energy of the inflaton leads to a brief fast roll stage
that precedes the slow roll regime. The fast roll stage leads to an attractive
potential in the wave equations for the mode functions of curvature and tensor
perturbations. The evolution of the inflationary perturbations is equivalent to
the scattering by this potential and a useful dictionary between the scattering
data and observables is established.Implementing methods from scattering theory
we prove that this attractive potential leads to a suppression of the
quadrupole moment for CMB and B-mode angular power spectra. The scale of the
potential is determined by the Hubble parameter during slow roll. Within the
effective field theory of inflation at the grand unification (GUT) energy scale
we find that if inflation lasts a total number of efolds N_{tot} ~ 59, there is
a 10-20% suppression of the CMB quadrupole and about 2-4% suppression of the
tensor quadrupole. The suppression of higher multipoles is smaller, falling off
as 1/l^2. The suppression is much smaller for N_{tot} > 59, therefore if the
observable suppression originates in the fast roll stage, there is the upper
bound N_{tot} ~ 59.Comment: Some comments and references adde
A black hole hologram in de Sitter space
In this paper we show that the entropy of de Sitter space with a black hole
in arbitrary dimension can be understood using a modified Cardy-Verlinde
entropy formula. We also comment on the observer dependence of the de Sitter
entropy.Comment: 13 pages. Final version accepted for publication in JHEP. Added
references and improved presentatio
Excursions beyond the horizon: Black hole singularities in Yang-Mills theories (I)
We study black hole singularities in the AdS/CFT correspondence. These
singularities show up in CFT in the behavior of finite-temperature correlation
functions. We first establish a direct relation between space-like geodesics in
the bulk and momentum space Wightman functions of CFT operators of large
dimensions. This allows us to probe the regions inside the horizon and near the
singularity using the CFT. Information about the black hole singularity is
encoded in the exponential falloff of finite-temperature correlators at large
imaginary frequency. We construct new gauge invariant observables whose
divergences reflect the presence of the singularity. We also find a UV/UV
connection that governs physics inside the horizon. Additionally, we comment on
the possible resolution of the singularity.Comment: 34 page, 10 figures, uses harvmac, references adde
Stability Constraints on Classical de Sitter Vacua
We present further no-go theorems for classical de Sitter vacua in Type II
string theory, i.e., de Sitter constructions that do not invoke
non-perturbative effects or explicit supersymmetry breaking localized sources.
By analyzing the stability of the 4D potential arising from compactification on
manfiolds with curvature, fluxes, and orientifold planes, we found that
additional ingredients, beyond the minimal ones presented so far, are necessary
to avoid the presence of unstable modes. We enumerate the minimal setups for
(meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde
Black Hole Thermodynamics and Heavy Fermion Metals
Heavy fermion alloys at critical doping typically exhibit non-Fermi-liquid
behavior at low temperatures, including a logarithmic or power law rise in the
ratio of specific heat to temperature as the temperature is lowered. Anomalous
specific heat of this type is also observed in a simple class of gravitational
dual models that exhibit anisotropic scaling with dynamical critical exponent z
> 1.Comment: 17 pages, 4 figures; v2: added references; v3: matches published
versio
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