2,452 research outputs found
Quantum corrections to dynamical holographic thermalization: entanglement entropy and other non-local observables
We investigate the thermalization time scale in the planar limit of the SU(N)
N=4 SYM plasma at strong yet finite 't Hooft coupling by considering its
supergravity dual description, including the full O(alpha'^3) type IIB string
theory corrections. We also discuss on the effects of the leading non-planar
corrections. We use extended geometric probes in the bulk which are dual to
different non-local observables in the N=4 SYM theory. This is carried out
within the framework of dynamical holographic thermalization.Comment: 19 pages, 4 figures. V2: References added, 1 figure added, 1 figure
corrected, enlarged discussions about extended probes, typos corrected.
Published versio
Dynamics of holographic thermalization
Dynamical evolution of thin shells composed by different kinds of degrees of
freedom collapsing within asymptotically AdS spaces is explored with the aim of
investigating models of holographic thermalization of strongly coupled systems.
From the quantum field theory point of view this corresponds to considering
different thermal quenches. We carry out a general study of the thermalization
time scale using different parameters and space-time dimensions, by calculating
renormalized space-like geodesic lengths and rectangular minimal area surfaces
as extended probes of thermalization, which are dual to two-point functions and
rectangular Wilson loops. Different kinds of degrees of freedom in the shell
are described by their corresponding equations of state. We consider a scalar
field, as well as relativistic matter, a pressureless massive fluid and
conformal matter, which can be compared with the collapse of an AdS-Vaidya thin
shell. Remarkably, for conformal matter, the thermalization time scale becomes
much larger than the others. Furthermore, in each case we also investigate
models where the cosmological constants of the inner and outer regions
separated by the shell are different. We found that in this case only a scalar
field shell collapses, and that the thermalization time scale is also much
larger than the AdS-Vaidya case.Comment: 25 pages, 4 figures. V2: published versio
Strings and D-branes in curved space-time
In this thesis we study the AdS3 Wess-Zumino-Novikov-Witten model. We compute
the Operator Product Expansion of primary fields as well as their images under
the spectral flow automorphism in all sectors of the model by considering it as
a Wick rotation of the H3+ coset model. We argue that the symmetries of the
affine algebra require a truncation which establishes the closure of the fusion
rules on the Hilbert space of the theory. These results are then used to
discuss the factorization of four point functions by applying the bootstrap
approach.
We also study the modular properties of the model. Although the Euclidean
partition function is modular invariant, the characters on the Euclidean torus
diverge and the regularization proposed in the literature removes information
on the spectrum, so that the usual one to one map between characters and
representations of rational models is lost. Reconsidering the characters
defined on the Lorentzian torus and focusing on their structure as
distributions, we obtain expressions that recover those properties. We then
study their generalized modular properties and use them to discuss the relation
between modular data and one point functions associated to symmetric D-branes,
generalizing some results from Rational Conformal Field Theories in the
particular cases of point like and dS2 branes, such as Cardy type solutions or
Verlinde like formulas.Comment: 167 pages, PhD. Thesis, defended 15/03/2012, 9 figure
The generalized Bergshoeff-de Roo identification II
We recently introduced a T-duality covariant mechanism to compute all-order
higher-derivative interactions in the heterotic string. Here we extend the
formalism to account for a two-parameter family of corrections that also
include the bosonic string and HSZ theory. We use our result to compute the
full second order Double Field Theory (DFT) for generic values of the
parameters, including the generalized Green-Schwarz transformation and its
invariant action.Comment: 46 page
Uplifting non-compact gauged supergravities
We provide the M-theory uplift of de Sitter vacua of SO(5,3) and SO(4,4)
gaugings of maximal supergravity in 4 dimensions. We find new non-compact
backgrounds that are squashed hyperboloids with non-trivial flux for the 3-form
potential. The uplift requires a new non-linear ansatz for the 11-dimensional
metric and for the 3-form potential that reduces to the known one leading to
the 7-sphere solution in the case of the SO(8) gauging.Comment: 28 pages. v2: font fixed and clarified some points. JHEP versio
On supersymmetric - systems with magnetic fields
We study systems of and branes with non zero world-volume
magnetic fields in the weak coupling limit. We find two configurations for
which the conditions for absence of tachyons in the spectra coincide exactly
with those found in the low energy effective theory approach, for the systems
to preserve 1/8 of the supersymmetries of the Type string theory vacuum.
These conditions give rise to a four-parameter family of solutions in each
case. We present further evidence of the stability of these systems by
computing the lowest order interaction amplitude, verifying the no force
condition as well as the supersymmetric character of the spectrum.Comment: Latex file, no figures, 11 pages, references added, to be published
in Physics Letters
Fusion rules and four-point functions in the AdS3 WZNW model
We study the operator product expansion in the AdS WZNW model. The OPE of
primary fields and their spectral flow images is computed from the analytic
continuation of the expressions in the H WZNW model, adding spectral
flow. We argue that the symmetries of the affine algebra require a truncation
which establishes the closure of the fusion rules on the Hilbert space of the
theory. Although the physical mechanism determining the decoupling is not
completely understood, we present several consistency checks on the results. A
preliminary analysis of factorization allows to obtain some properties of
four-point functions involving fields in generic sectors of the theory, to
verify that they agree with the spectral flow selection rules and to show that
the truncation must be realized in physical amplitudes for consistency.Comment: 37 pages, 5 figures, version to appear in Physical Review
FUSE Observation of the Narrow-line Seyfert 1 Galaxy RE 1034+39
We present analysis from simultaneous FUSE, ASCA, and EUVE observations, as
well as a reanalysis of archival HST spectra, from the extreme Narrow-line
Seyfert 1 Galaxy RE 1034+39 (KUG 1031+398). RE 1034+39 has an unusually hard
spectral energy distribution (SED) that peaks in the soft X-rays. Its emission
lines are unusual in that they can all be modelled as a Lorentzian centered at
the rest wavelength with only a small range in velocity widths. In order to
investigate whether the unusual SED influences the emission line ratios and
equivalent widths, we present three complementary types of photoionization
analysis. The FUSE spectrum was particularly important because it includes the
high-ionization line OVI. First, we use the photoionization code Cloudy and the
SED developed from the coordinated observations to confirm that the emission
lines are consistent with observed hard SED. The best model parameters were an
ionization parameter log(U) ~ -2 and a hydrogen number density log(n_H)=9.75
[cm^-2]. Second, we present a Locally Optimally-emitting Cloud model. This
model produced enhanced OVI as observed, but also yielded far too strong MgII.
Third, we develop a series of semi-empirical SEDs, run Cloudy models, and
compare the results with the measured values using a figure of merit (FOM). The
FOM minimum indicates similar SED and gas properties as were inferred from the
one-zone model using the RE 1034+39 continuum. Furthermore, the FOM increases
sharply toward softer continua, indicating that a hard SED is required by the
data in the context of a one-zone model.Comment: 65 pages 20 figure
Transient Receptor Potential Channel Polymorphisms Are Associated with the Somatosensory Function in Neuropathic Pain Patients
Transient receptor potential channels are important mediators of thermal and mechanical stimuli and play an important role in neuropathic pain. The contribution of hereditary variants in the genes of transient receptor potential channels to neuropathic pain is unknown. We investigated the frequency of transient receptor potential ankyrin 1, transient receptor potential melastin 8 and transient receptor potential vanilloid 1 single nucleotide polymorphisms and their impact on somatosensory abnormalities in neuropathic pain patients. Within the German Research Network on Neuropathic Pain (Deutscher Forscbungsverbund Neuropathischer Schmerz) 371 neuropathic pain patients were phenotypically characterized using standardized quantitative sensory testing. Pyrosequencing was employed to determine a total of eleven single nucleotide polymorphisms in transient receptor potential channel genes of the neuropathic pain patients and a cohort of 253 German healthy volunteers. Associations of quantitative sensory testing parameters and single nucleotide polymorphisms between and within groups and subgroups, based on sensory phenotypes, were analyzed. Single nucleotide polymorphisms frequencies did not differ between both the cohorts. However, in neuropathic pain patients transient receptor potential ankyrin 1 710G>A (rs920829, E179K) was associated with the presence of paradoxical heat sensation (p = 0.03), and transient receptor potential vanilloid 1 1911A>G (rs8065080, I585V) with cold hypoalgesia (p = 0.0035). Two main subgroups characterized by preserved (1) and impaired (2) sensory function were identified. In subgroup 1 transient receptor potential vanilloid 1 1911A>G led to significantly less heat hyperalgesia, pinprick hyperalgesia and mechanical hypaesthesia (p = 0.006, p = 0.005 and p<0.001) and transient receptor potential vanilloid 1 1103C>G (rs222747, M315I) to cold hypaesthesia (p = 0.002), but there was absence of associations in subgroup 2. In this study we found no evidence that genetic variants of transient receptor potential channels are involved in the expression of neuropathic pain, but transient receptor potential channel polymorphisms contributed significantly to the somatosensory abnormalities of neuropathic pain patients
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