1,458 research outputs found
Bi-partite entanglement entropy in massive two-dimensional quantum field theory
Recently, Cardy, Castro Alvaredo and the author obtained the first
exponential correction to saturation of the bi-partite entanglement entropy at
large region length, in massive two-dimensional integrable quantum field
theory. It only depends on the particle content of the model, and not on the
way particles scatter. Based on general analyticity arguments for form factors,
we propose that this result is universal, and holds for any massive
two-dimensional model (also out of integrability). We suggest a link of this
result with counting pair creations far in the past.Comment: 5 pages, 2 figures. v2: improved presentation of result and
calculations, section "discussion" adjusted, references adjuste
Alien Registration- Doyon, Joseph S. (Auburn, Androscoggin County)
https://digitalmaine.com/alien_docs/30899/thumbnail.jp
A new 'Conservation Space' ? Protected areas, environmental economic activities and discourses in two Yucatan biosphere reserves in Mexico
This article examines some of the local socioeconomic repercussions of two biosphere reserves on the Yucatan Peninsula-Ria Celestun and Ria Lagartos. We analyse aspects of the relationship that the residents of the six villages located within the two reserves have with their environment, by examining both the 'environmental economic activities' residents are involved in and their discourses on, and interpretations of, the notion of environment and the conservation precepts put forward by the biosphere reserves. Our research explores how the objectives of the United Nations Educational, Scientific and Cultural Organization's Man and Biosphere Programme, disseminated by biosphere reserves, are put into practice on the ground. In particular, we look at how environmental economic activities are experienced and practised without necessarily being accompanied by the integration, acceptance, and internalisation of conservation principles-and how these activities contribute, or fail to contribute, to the crystallisation of a new 'conservation space'
Infrared images of merging galaxies
Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high Infrared Astronomy Satellite (IRAS) luminosities. Infrared images have been useful in identifying double structures in the nuclei of interacting galaxies which have not even been hinted at by optical observations. A striking example of this is given by the K images of Arp 220. Graham et al. (1990) have used high resolution imaging to show that it has a double nucleus coincident with the radio sources in the middle of the dust lane. The results suggest that caution should be applied in the identification of optical bright spots as multiple nuclei in the absence of other evidence. They also illustrate the advantages of using infrared imaging to study the underlying structure in merging galaxies. The authors have begun a program to take near infrared images of galaxies which are believed to be mergers of disk galaxies because they have tidal tails and filaments. In many of these the merger is thought to have induced exceptionally luminous infrared emission (cf. Joseph and Wright 1985, Sanders et al. 1988). Although the optical images of the galaxies show spectacular dust lanes and filaments, the K images all have a very smooth distribution of light with an apparently single nucleus
Near infrared spectroscopy of starburst galaxies
(Abridged) We present new K-band spectroscopy for a sample of 48 starburst
galaxies, obtained using UKIRT in Hawaii. This constitutes a fair sample of the
most common types of starburst galaxies found in the nearby Universe. The
variety of near infrared spectral features shown by these galaxies implies
different bursts characteristics, which suggests that we survey galaxies with
different star formation histories or at different stages of their burst
evolution.
Using synthetic starburst models, we conclude that the best ensemble of
parameters which describe starburst galaxies in the nearby universe are a
constant rate of star formation, a Salpeter IMF with an upper mass cutoff equal
to 30 solar mass and bursts ages between 10 Myr and 1 Gyr. The model is fully
consistent with the differences observed in the optical and FIR between the
different types of starbursts. It suggests that HII galaxies have younger
bursts and lower metallicities than SBNGs, while LIRGs have younger bursts but
higher metallicities.
Our observations suggest that the starburst phenomenon must be a sustained or
self--sustained phenomenon: either star formation is continuous in time or
multiple bursts happen in sequence over a relatively long period of time. The
generality of our observations implies that this is a characteristic of
starburst galaxies in the nearby Universe.Comment: 19 pages, Latex, 12 encapsulated Postscript figures, Accepted for
publication in MNRA
Stochastic Approach to Non-Equilibrium Quantum Spin Systems
We investigate a stochastic approach to non-equilibrium quantum spin systems
based on recent insights linking quantum and classical dynamics. Exploiting a
sequence of exact transformations, quantum expectation values can be recast as
averages over classical stochastic processes. We illustrate this approach for
the quantum Ising model by extracting the Loschmidt amplitude and the
magnetization dynamics from the numerical solution of stochastic differential
equations. We show that dynamical quantum phase transitions are accompanied by
clear signatures in the associated classical distribution functions, including
the presence of enhanced fluctuations. We demonstrate that the method is
capable of handling integrable and non-integrable problems in a unified
framework, including those in higher dimensions.Comment: 5 pages, 5 figure
Calculus on manifolds of conformal maps and CFT
In conformal field theory (CFT) on simply connected domains of the Riemann
sphere, the natural conformal symmetries under self-maps are extended, in a
certain way, to local symmetries under general conformal maps, and this is at
the basis of the powerful techniques of CFT. Conformal maps of simply connected
domains naturally have the structure of an infinite-dimensional groupoid, which
generalizes the finite-dimensional group of self-maps. We put a topological
structure on the space of conformal maps on simply connected domains, which
makes it into a topological groupoid. Further, we (almost) extend this to a
local manifold structure based on the infinite-dimensional Frechet topological
vector space of holomorphic functions on a given domain A. From this, we
develop the notion of conformal A-differentiability at the identity. Our main
conclusion is that quadratic differentials characterizing cotangent elements on
the local manifold enjoy properties similar to those of the holomorphic
stress-energy tensor of CFT; these properties underpin the local symmetries of
CFT. Applying the general formalism to CFT correlation functions, we show that
the stress-energy tensor is exactly such a quadratic differential. This is at
the basis of constructing the stress-energy tensor in conformal loop ensembles.
It also clarifies the relation between Cardy's boundary conditions for CFT on
simply connected domains, and the expression of the stress-energy tensor in
terms of metric variations.Comment: v1: 51 pages, 5 figures. v2: 56 pages, corrections and
clarifications. v3: 53 pages, one substantial addition (groupoid structure),
discussion further clarified and simplified. v4: 59 pages, introduction
improved, with a discussion on the relations with previous works. Published
versio
Evolution of Genes Neighborhood Within Reconciled Phylogenies: An Ensemble Approach
Context
The reconstruction of evolutionary scenarios for whole genomes in terms of genome rearrangements is a fundamental problem in evolutionary and comparative genomics. The DeCo algorithm, recently introduced by BĂ©rard et al., computes parsimonious evolutionary scenarios for gene adjacencies, from pairs of reconciled gene trees. However, as for many combinatorial optimization algorithms, there can exist many co-optimal, or slightly sub-optimal, evolutionary scenarios that deserve to be considered.
Contribution
We extend the DeCo algorithm to sample evolutionary scenarios from the whole solution space under the Boltzmann distribution, and also to compute Boltzmann probabilities for specific ancestral adjacencies.
Results
We apply our algorithms to a dataset of mammalian gene trees and adjacencies, and observe a significant reduction of the number of syntenic conflicts observed in the resulting ancestral gene adjacencies
Finite Temperature Dynamical Correlations in Massive Integrable Quantum Field Theories
We consider the finite-temperature frequency and momentum dependent two-point
functions of local operators in integrable quantum field theories. We focus on
the case where the zero temperature correlation function is dominated by a
delta-function line arising from the coherent propagation of single particle
modes. Our specific examples are the two-point function of spin fields in the
disordered phase of the quantum Ising and the O(3) nonlinear sigma models. We
employ a Lehmann representation in terms of the known exact zero-temperature
form factors to carry out a low-temperature expansion of two-point functions.
We present two different but equivalent methods of regularizing the divergences
present in the Lehmann expansion: one directly regulates the integral
expressions of the squares of matrix elements in the infinite volume whereas
the other operates through subtracting divergences in a large, finite volume.
Our central results are that the temperature broadening of the line shape
exhibits a pronounced asymmetry and a shift of the maximum upwards in energy
("temperature dependent gap"). The field theory results presented here describe
the scaling limits of the dynamical structure factor in the quantum Ising and
integer spin Heisenberg chains. We discuss the relevance of our results for the
analysis of inelastic neutron scattering experiments on gapped spin chain
systems such as CsNiCl3 and YBaNiO5.Comment: 54 pages, 10 figure
Conformal loop ensembles and the stress-energy tensor
We give a construction of the stress-energy tensor of conformal field theory
(CFT) as a local "object" in conformal loop ensembles CLE_\kappa, for all
values of \kappa in the dilute regime 8/3 < \kappa <= 4 (corresponding to the
central charges 0 < c <= 1, and including all CFT minimal models). We provide a
quick introduction to CLE, a mathematical theory for random loops in simply
connected domains with properties of conformal invariance, developed by
Sheffield and Werner (2006). We consider its extension to more general regions
of definition, and make various hypotheses that are needed for our construction
and expected to hold for CLE in the dilute regime. Using this, we identify the
stress-energy tensor in the context of CLE. This is done by deriving its
associated conformal Ward identities for single insertions in CLE probability
functions, along with the appropriate boundary conditions on simply connected
domains; its properties under conformal maps, involving the Schwarzian
derivative; and its one-point average in terms of the "relative partition
function." Part of the construction is in the same spirit as, but widely
generalizes, that found in the context of SLE_{8/3} by the author, Riva and
Cardy (2006), which only dealt with the case of zero central charge in simply
connected hyperbolic regions. We do not use the explicit construction of the
CLE probability measure, but only its defining and expected general properties.Comment: 49 pages, 3 figures. This is a concatenated, reduced and simplified
version of arXiv:0903.0372 and (especially) arXiv:0908.151
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