1,928 research outputs found
Redshift-space Distortions of the Power Spectrum of Cosmological Objects on a Light Cone : Explicit Formulations and Theoretical Implications
We examine the effects of the linear and the cosmological redshift-space
distortions on the power spectrum of cosmological objects on a light cone. We
develop theoretical formulae for the power spectrum in linear theory of density
perturbations in a rigorous manner starting from first principle corresponding
to Fourier analysis. Approximate formulae, which are useful properly to
incorporate the redshift-space distortion effects into the power spectrum are
derived, and the validity is examined. Applying our formulae to galaxy and
quasar samples which roughly match the SDSS survey, we will show how the
redshift-space distortions distort the power spectrum on the light cone
quantitatively.Comment: 30 pages, Accepted for publication in the Astrophysical Journal
Supplement Serie
Stoner gap in the superconducting ferromagnet UGe2
We report the temperature () dependence of ferromagnetic Bragg peak
intensities and dc magnetization of the superconducting ferromagnet UGe2 under
pressure (). We have found that the low- behavior of the uniform
magnetization can be explained by a conventional Stoner model. A functional
analysis of the data produces the following results: The ferromagnetic state
below a critical pressure can be understood as the perfectly polarized state,
in which heavy quasiparticles occupy only majority spin bands. A Stoner gap
decreases monotonically with increasing pressure and increases
linearly with magnetic field. We show that the present analysis based on the
Stoner model is justified by a consistency check, i.e., comparison of density
of states at the Fermi energy deduced from the analysis with observed
electronic specific heat coeffieients. We also argue the influence of the
ferromagnetism on the superconductivity.Comment: 5 pages, 4 figures. to be published in Phys. Rev.
The BTZ black hole with a time-dependent boundary
The non-rotating BTZ solution is expressed in terms of coordinates that allow
for an arbitrary time-dependent scale factor in the boundary metric. We provide
explicit expressions for the coordinate transformation that generates this form
of the metric, and determine the regions of the complete Penrose diagram that
are convered by our parametrization. This construction is utilized in order to
compute the stress-energy tensor of the dual CFT on a time-dependent
background. We study in detail the expansion of radial null geodesic
congruences in the BTZ background for various forms of the scale factor of the
boundary metric. We also discuss the relevance of our construction for the
holographic calculation of the entanglement entropy of the dual CFT on
time-dependent backgrounds.Comment: 14 pages, 13 figures, title changed in journal, conformal diagrams
added, references added, final version to appear in Classical and Quantum
Gravit
The cosmological light-cone effect on the power spectrum of galaxies and quasars in wide-field redshift surveys
We examine observational consequences of the cosmological light-cone effect
on the power spectrum of the distribution of galaxies and quasars from upcoming
redshift surveys. First we derive an expression for the power spectrum of
cosmological objects in real space on a light cone, , which is exact in linear theory of density perturbations. Next we
incorporate corrections for the nonlinear density evolution and redshift-space
distortion in the formula in a phenomenological manner which is consistent with
recent numerical simulations. On the basis of this formula, we predict the
power spectrum of galaxies and quasars on the light cone for future redshift
surveys taking account of the selection function properly. We demonstrate that
this formula provides a reliable and useful method to compute the power
spectrum on the light cone given an evolution model of bias.Comment: 18 pages, 3 figures, to be published in the Astrophysical Journa
Nonperturbative aspects of ABJM theory
Using the matrix model which calculates the exact free energy of ABJM theory
on S^3 we study non-perturbative effects in the large N expansion of this
model, i.e., in the genus expansion of type IIA string theory on AdS4xCP^3. We
propose a general prescription to extract spacetime instanton actions from
general matrix models, in terms of period integrals of the spectral curve, and
we use it to determine them explicitly in the ABJM matrix model, as exact
functions of the 't Hooft coupling. We confirm numerically that these
instantons control the asymptotic growth of the genus expansion. Furthermore,
we find that the dominant instanton action at strong coupling determined in
this way exactly matches the action of an Euclidean D2-brane instanton wrapping
RP^3.Comment: 26 pages, 14 figures. v2: small corrections, final version published
in JHE
Holographic Studies of Entanglement Entropy in Superconductors
We present the results of our studies of the entanglement entropy of a
superconducting system described holographically as a fully back-reacted
gravity system, with a stable ground state. We use the holographic prescription
for the entanglement entropy. We uncover the behavior of the entropy across the
superconducting phase transition, showing the reorganization of the degrees of
freedom of the system. We exhibit the behaviour of the entanglement entropy
from the superconducting transition all the way down to the ground state at
T=0. In some cases, we also observe a novel transition in the entanglement
entropy at intermediate temperatures, resulting from the detection of an
additional length scale.Comment: 21 pages, 14 figures. v2:Clarified some remarks concerning stability.
v3: Updated to the version that appears in JHE
An exact formula for the radiation of a moving quark in N=4 super Yang Mills
We derive an exact formula for the cusp anomalous dimension at small angles.
This is done by relating the latter to the computation of certain 1/8 BPS
Wilson loops which was performed by supersymmetric localization. This function
of the coupling also determines the power emitted by a moving quark in N=4
super Yang Mills, as well as the coefficient of the two point function of the
displacement operator on the Wilson loop. By a similar method we compute the
near BPS expansion of the generalized cusp anomalous dimension.Comment: 22 pages, 5 figures. v2: references added, typos correcte
- …