4,508 research outputs found
Combining Full-Shape and BAO Analyses of Galaxy Power Spectra: A 1.6% CMB-independent constraint on H0
We present cosmological constraints from a joint analysis of the pre- and
post-reconstruction galaxy power spectrum multipoles from the final data
release of the Baryon Oscillation Spectroscopic Survey (BOSS). Geometric
constraints are obtained from the positions of BAO peaks in reconstructed
spectra, analyzed in combination with the unreconstructed spectra in a
full-shape (FS) likelihood using a joint covariance matrix, giving stronger
parameter constraints than FS-only or BAO-only analyses. We introduce a new
method for obtaining constraints from reconstructed spectra based on a
correlated theoretical error, which is shown to be simple, robust, and
applicable to any flavor of density-field reconstruction. Assuming CDM
with massive neutrinos, we analyze data from two redshift bins
and obtain constraints on the Hubble
constant , using only a single prior on the current baryon density
from Big Bang Nucleosynthesis (BBN) and no knowledge of the power
spectrum slope . This gives , with the inclusion of BAO
data sharpening the measurement by , representing one of the strongest
current constraints on independent of cosmic microwave background data.
Restricting to the best-fit slope from Planck (but without additional
priors on the spectral shape), we obtain a measurement of . We find strong constraints on the
cosmological parameters from a joint analysis of the FS, BAO, and Planck data.
This sets new bounds on the sum of neutrino masses (at confidence) and the effective number of
relativistic degrees of freedom , though
contours are not appreciably narrowed by the inclusion of BAO data.Comment: 42 pages, 12 figures, accepted by JCAP, likelihoods available at
https://github.com/Michalychforever/lss_montepython (minor typo corrected
Spherically Symmetric Solutions in M\o ller's Tetrad Theory of Gravitation
The general solution of M\o ller's field equations in case of spherical
symmetry is derived. The previously obtained solutions are verified as special
cases of the general solution.Comment: LaTeX2e with AMS-LaTeX 1.2, 8 page
Quantum transport of strongly interacting photons in a one-dimensional nonlinear waveguide
We present a theoretical technique for solving the quantum transport problem
of a few photons through a one-dimensional, strongly nonlinear waveguide. We
specifically consider the situation where the evolution of the optical field is
governed by the quantum nonlinear Schr\"odinger equation (NLSE). Although this
kind of nonlinearity is quite general, we focus on a realistic implementation
involving cold atoms loaded in a hollow-core optical fiber, where the atomic
system provides a tunable nonlinearity that can be large even at a
single-photon level. In particular, we show that when the interaction between
photons is effectively repulsive, the transmission of multi-photon components
of the field is suppressed. This leads to anti-bunching of the transmitted
light and indicates that the system acts as a single-photon switch. On the
other hand, in the case of attractive interaction, the system can exhibit
either anti-bunching or bunching, which is in stark contrast to semiclassical
calculations. We show that the bunching behavior is related to the resonant
excitation of bound states of photons inside the system.Comment: 22 pages, 24 figure
Cluster magnetic fields from large-scale-structure and galaxy-cluster shocks
The origin of the micro-Gauss magnetic fields in galaxy clusters is one of
the outstanding problem of modern cosmology. We have performed
three-dimensional particle-in-cell simulations of the nonrelativistic Weibel
instability in an electron-proton plasma, in conditions typical of cosmological
shocks. These simulations indicate that cluster fields could have been produced
by shocks propagating through the intergalactic medium during the formation of
large-scale structure or by shocks within the cluster. The strengths of the
shock-generated fields range from tens of nano-Gauss in the intercluster medium
to a few micro-Gauss inside galaxy clusters.Comment: 4 pages, 2 color figure
New Path Equations in Absolute Parallelism Geometry
The Bazanski approach, for deriving the geodesic equations in Riemannian
geometry, is generalized in the absolute parallelism geometry. As a consequence
of this generalization three path equations are obtained. A striking feature in
the derived equations is the appearance of a torsion term with a numerical
coefficients that jumps by a step of one half from equation to another. This is
tempting to speculate that the paths in absolute parallelism geometry might
admit a quantum feature.Comment: 4 pages Latex file Journal Reference: Astrophysics and space science
228, 273, (1995
Robust nonparametric detection of objects in noisy images
We propose a novel statistical hypothesis testing method for detection of
objects in noisy images. The method uses results from percolation theory and
random graph theory. We present an algorithm that allows to detect objects of
unknown shapes in the presence of nonparametric noise of unknown level and of
unknown distribution. No boundary shape constraints are imposed on the object,
only a weak bulk condition for the object's interior is required. The algorithm
has linear complexity and exponential accuracy and is appropriate for real-time
systems. In this paper, we develop further the mathematical formalism of our
method and explore important connections to the mathematical theory of
percolation and statistical physics. We prove results on consistency and
algorithmic complexity of our testing procedure. In addition, we address not
only an asymptotic behavior of the method, but also a finite sample performance
of our test.Comment: This paper initially appeared in 2010 as EURANDOM Report 2010-049.
Link to the abstract at EURANDOM repository:
http://www.eurandom.tue.nl/reports/2010/049-abstract.pdf Link to the paper at
EURANDOM repository: http://www.eurandom.tue.nl/reports/2010/049-report.pd
Towards the Gravity Dual of Quarkonium in the Strongly Coupled QCD Plasma
We build a "bottom-up" holographic model of charmonium by matching the
essential spectral data. We argue that this data must include not only the
masses but also the decay constants of the J/psi and psi' mesons. Relative to
the "soft-wall" models for light mesons, such a matching requires two new
features in the holographic potential: an overall upward shift as well as a
narrow "dip" near the holographic boundary. We calculate the spectral function
as well as the position of the complex singularities (quasinormal frequencies)
of the retarded correlator of the charm current at finite temperatures. We
further extend this analysis by showing that the residues associated with these
singularities are given by the boundary derivative of the appropriately
normalized quasinormal mode. We find that the "melting" of the J/psi spectral
peak occurs at a temperature of about 540 MeV, or 2.8 T_c, in good agreement
with lattice results.Comment: 13 pages, 9 figure
Ruled Laguerre minimal surfaces
A Laguerre minimal surface is an immersed surface in the Euclidean space
being an extremal of the functional \int (H^2/K - 1) dA. In the present paper,
we prove that the only ruled Laguerre minimal surfaces are up to isometry the
surfaces R(u,v) = (Au, Bu, Cu + D cos 2u) + v (sin u, cos u, 0), where A, B, C,
D are fixed real numbers. To achieve invariance under Laguerre transformations,
we also derive all Laguerre minimal surfaces that are enveloped by a family of
cones. The methodology is based on the isotropic model of Laguerre geometry. In
this model a Laguerre minimal surface enveloped by a family of cones
corresponds to a graph of a biharmonic function carrying a family of isotropic
circles. We classify such functions by showing that the top view of the family
of circles is a pencil.Comment: 28 pages, 9 figures. Minor correction: missed assumption (*) added to
Propositions 1-2 and Theorem 2, missed case (nested circles having nonempty
envelope) added in the proof of Pencil Theorem 4, missed proof that the arcs
cut off by the envelope are disjoint added in the proof of Lemma
Number of Common Sites Visited by N Random Walkers
We compute analytically the mean number of common sites, W_N(t), visited by N
independent random walkers each of length t and all starting at the origin at
t=0 in d dimensions. We show that in the (N-d) plane, there are three distinct
regimes for the asymptotic large t growth of W_N(t). These three regimes are
separated by two critical lines d=2 and d=d_c(N)=2N/(N-1) in the (N-d) plane.
For d<2, W_N(t)\sim t^{d/2} for large t (the N dependence is only in the
prefactor). For 2<d<d_c(N), W_N(t)\sim t^{\nu} where the exponent \nu=
N-d(N-1)/2 varies with N and d. For d>d_c(N), W_N(t) approaches a constant as
t\to \infty. Exactly at the critical dimensions there are logaritmic
corrections: for d=2, we get W_N(t)\sim t/[\ln t]^N, while for d=d_c(N),
W_N(t)\sim \ln t for large t. Our analytical predictions are verified in
numerical simulations.Comment: 5 pages, 3 .eps figures include
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