10,380 research outputs found
Identifying through its decay modes
We study how to assign the recently observed meson to an
appropriate level of the spectrum by the analysis of its decay modes
in final states comprising a light pseudoscalar meson. We use an effective
lagrangian approach with heavy quark and chiral symmetries, obtaining that the
measurement of the decay width would allow to distinguish between two
possible assignments.Comment: RevTex, 6 pages - references adde
Simulation of time evolution with the MERA
We describe an algorithm to simulate time evolution using the Multi-scale
Entanglement Renormalization Ansatz (MERA) and test it by studying a critical
Ising chain with periodic boundary conditions and with up to L ~ 10^6 quantum
spins. The cost of a simulation, which scales as L log(L), is reduced to log(L)
when the system is invariant under translations. By simulating an evolution in
imaginary time, we compute the ground state of the system. The errors in the
ground state energy display no evident dependence on the system size. The
algorithm can be extended to lattice systems in higher spatial dimensions.Comment: final version with data improvement (precision and size), 4.1 pages,
4 figures + extra on X
X-ray sources and their optical counterparts in the globular cluster M 22
Using XMM-Newton EPIC imaging data, we have detected 50 low-luminosity X-ray
sources in the field of view of M 22, where 5 +/- 3 of these sources are likely
to be related to the cluster. Using differential optical photometry, we have
identified probable counterparts to those sources belonging to the cluster.
Using X-ray spectroscopic and timing studies, supported by the optical colours,
we propose that the most central X-ray sources in the cluster are cataclysmic
variables, millisecond pulsars, active binaries and a blue straggler. We also
identify a cluster of galaxies behind this globular cluster.Comment: 11 pages, 7 figures, accepted for publication in A&
Phase Diagram of the Bose-Hubbard Model with T_3 symmetry
In this paper we study the quantum phase transition between the insulating
and the globally coherent superfluid phases in the Bose-Hubbard model with T_3
structure, the "dice lattice". Even in the absence of any frustration the
superfluid phase is characterized by modulation of the order parameter on the
different sublattices of the T_3 structure. The zero-temperature critical point
as a function of a magnetic field shows the characteristic "butterfly" form. At
fully frustration the superfluid region is strongly suppressed. In addition,
due to the existence of the Aharonov-Bohm cages at f=1/2, we find evidence for
the existence of an intermediate insulating phase characterized by a zero
superfluid stiffness but finite compressibility. In this intermediate phase
bosons are localized due to the external frustration and the topology of the
T_3 lattice. We name this new phase the Aharonov-Bohm (AB) insulator. In the
presence of charge frustration the phase diagram acquires the typical
lobe-structure. The form and hierarchy of the Mott insulating states with
fractional fillings, is dictated by the particular topology of the T_3 lattice.
The results presented in this paper were obtained by a variety of analytical
methods: mean-field and variational techniques to approach the phase boundary
from the superconducting side, and a strongly coupled expansion appropriate for
the Mott insulating region. In addition we performed Quantum Monte Carlo
simulations of the corresponding (2+1)D XY model to corroborate the analytical
calculations with a more accurate quantitative analysis. We finally discuss
experimental realization of the T_3 lattice both with optical lattices and with
Josephson junction arrays.Comment: 16 pages, 17 figure
A direct kinematical derivation of the relativistic Sagnac effect for light or matter beams
The Sagnac time delay and the corresponding Sagnac phase shift, for
relativistic matter and electromagnetic beams counter-propagating in a rotating
interferometer, are deduced on the ground of relativistic kinematics. This
purely kinematical approach allows to explain the ''universality'' of the
effect, namely the fact that the Sagnac time difference does not depend on the
physical nature of the interfering beams. The only prime requirement is that
the counter-propagating beams have the same velocity with respect to any
Einstein synchronized local co-moving inertial frame.Comment: 10 pages, 1 EPS figure, to appear in General Relativity and
Gravitatio
Charged Particles and the Electro-Magnetic Field in Non-Inertial Frames of Minkowski Spacetime: II. Applications: Rotating Frames, Sagnac Effect, Faraday Rotation, Wrap-up Effect
We apply the theory of non-inertial frames in Minkowski space-time, developed
in the previous paper, to various relevant physical systems. We give the 3+1
description without coordinate-singularities of the rotating disk and the
Sagnac effect, with added comments on pulsar magnetosphere and on a
relativistic extension of the Earth-fixed coordinate system. Then we study
properties of Maxwell equations in non-inertial frames like the wrap-up effect
and the Faraday rotation in astrophysics.Comment: This paper and the second one are an adaptation of arXiv 0812.3057
for publication on Int.J.Geom. Methods in Modern Phys. 36
Automated reduction of submillimetre single-dish heterodyne data from the James Clerk Maxwell Telescope using ORAC-DR
With the advent of modern multi-detector heterodyne instruments that can
result in observations generating thousands of spectra per minute it is no
longer feasible to reduce these data as individual spectra. We describe the
automated data reduction procedure used to generate baselined data cubes from
heterodyne data obtained at the James Clerk Maxwell Telescope. The system can
automatically detect baseline regions in spectra and automatically determine
regridding parameters, all without input from a user. Additionally it can
detect and remove spectra suffering from transient interference effects or
anomalous baselines. The pipeline is written as a set of recipes using the
ORAC-DR pipeline environment with the algorithmic code using Starlink software
packages and infrastructure. The algorithms presented here can be applied to
other heterodyne array instruments and have been applied to data from
historical JCMT heterodyne instrumentation.Comment: 18 pages, 13 figures, submitted to Monthly Notices of the Royal
Astronomical Societ
Reference frames and rigid motions in relativity: Applications
The concept of rigid reference frame and of constricted spatial metric, given
in the previous work [\emph{Class. Quantum Grav.} {\bf 21}, 3067,(2004)] are
here applied to some specific space-times: In particular, the rigid rotating
disc with constant angular velocity in Minkowski space-time is analyzed, a new
approach to the Ehrenfest paradox is given as well as a new explanation of the
Sagnac effect. Finally the anisotropy of the speed of light and its measurable
consequences in a reference frame co-moving with the Earth are discussed.Comment: 13 pages, 1 figur
Optical Strain Gauge for High Temperature Plastic Deformation Measurement
Nondestructive evaluation techniques for aging components are becoming very important methods for identification of material degradation, life assessment and development of inspection strategies. In this frame a laser system suited for measurement of permanent deformations in power plant pipes has been designed, built-up and in-field tested
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