1,303 research outputs found
A sufficient criterion for integrability of stochastic many-body dynamics and quantum spin chains
We propose a dynamical matrix product ansatz describing the stochastic
dynamics of two species of particles with excluded-volume interaction and the
quantum mechanics of the associated quantum spin chains respectively. Analyzing
consistency of the time-dependent algebra which is obtained from the action of
the corresponding Markov generator, we obtain sufficient conditions on the
hopping rates for identifing the integrable models. From the dynamical algebra
we construct the quadratic algebra of Zamolodchikov type, associativity of
which is a Yang Baxter equation. The Bethe ansatz equations for the spectra are
obtained directly from the dynamical matrix product ansatz.Comment: 19 pages Late
The spin-1/2 XXZ Heisenberg chain, the quantum algebra U_q[sl(2)], and duality transformations for minimal models
The finite-size scaling spectra of the spin-1/2 XXZ Heisenberg chain with
toroidal boundary conditions and an even number of sites provide a projection
mechanism yielding the spectra of models with a central charge c<1 including
the unitary and non-unitary minimal series. Taking into account the
half-integer angular momentum sectors - which correspond to chains with an odd
number of sites - in many cases leads to new spinor operators appearing in the
projected systems. These new sectors in the XXZ chain correspond to a new type
of frustration lines in the projected minimal models. The corresponding new
boundary conditions in the Hamiltonian limit are investigated for the Ising
model and the 3-state Potts model and are shown to be related to duality
transformations which are an additional symmetry at their self-dual critical
point. By different ways of projecting systems we find models with the same
central charge sharing the same operator content and modular invariant
partition function which however differ in the distribution of operators into
sectors and hence in the physical meaning of the operators involved. Related to
the projection mechanism in the continuum there are remarkable symmetry
properties of the finite XXZ chain. The observed degeneracies in the energy and
momentum spectra are shown to be the consequence of intertwining relations
involving U_q[sl(2)] quantum algebra transformations.Comment: This is a preprint version (37 pages, LaTeX) of an article published
back in 1993. It has been made available here because there has been recent
interest in conformal twisted boundary conditions. The "duality-twisted"
boundary conditions discussed in this paper are particular examples of such
boundary conditions for quantum spin chains, so there might be some renewed
interest in these result
Photon polarisation entanglement from distant dipole sources
It is commonly believed that photon polarisation entanglement can only be
obtained via pair creation within the same source or via postselective
measurements on photons that overlapped within their coherence time inside a
linear optics setup. In contrast to this, we show here that polarisation
entanglement can also be produced by distant single photon sources in free
space and without the photons ever having to meet, if the detection of a photon
does not reveal its origin -- the which way information. In the case of two
sources, the entanglement arises under the condition of two emissions in
certain spatial directions and leaves the dipoles in a maximally entangled
state.Comment: 7 pages, 2 figures, revised version, accepted for publication in J.
Phys.
Limit on the Radiative Neutrinoless Double Electron Capture of Ar from GERDA Phase I
Neutrinoless double electron capture is a process that, if detected, would
give evidence of lepton number violation and the Majorana nature of neutrinos.
A search for neutrinoless double electron capture of Ar has been
performed with germanium detectors installed in liquid argon using data from
Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso
Laboratory of INFN, Italy. No signal was observed and an experimental lower
limit on the half-life of the radiative neutrinoless double electron capture of
Ar was established: 3.6 10 yr at 90 % C.I.Comment: 7 pages, 3 figure
Flux Modulations seen by the Muon Veto of the GERDA Experiment
The GERDA experiment at LNGS of INFN is equipped with an active muon veto.
The main part of the system is a water Cherenkov veto with 66~PMTs in the water
tank surrounding the GERDA cryostat. The muon flux recorded by this veto shows
a seasonal modulation. Two effects have been identified which are caused by
secondary muons from the CNGS neutrino beam (2.2 %) and a temperature
modulation of the atmosphere (1.4 %). A mean cosmic muon rate of /(sm) was found in good agreement with other experiments at
LNGS at a depth of 3500~meter water equivalent.Comment: 7 pages, 6 figure
Social media usage among wine tourism DMOs
Social media is an important tool for tourism destination promotion.
The usage and the contents published on these platforms have an important role
in visitors’ decision-making process. Information and communication technologies
are changing DMOs’ markets and communication paradigm, since they
allow the interaction between these organizations, visitors, and stakeholders.
Therefore, social media are increasing their relevance on DMOs’ marketing
strategies. This purpose of this study is to analyze comparatively social media
platforms’ usage by six wine tourism DMOs. The results were provided by the
analysis of secondary data available on these platforms and DMOs posts on the
four most popular social media platforms to tourism industry: Facebook,
Instagram, Twitter, and YouTube. Results indicate that DMOs use their official
accounts on these platforms on different ways. This study also reveals that
Facebook is more interactive than other platforms, and YouTube achieves less
engagement levels.info:eu-repo/semantics/publishedVersio
Manejo de Riego por Goteo en Uva de Mesa cv. Thompson Seedless Cultivada en Suelos de Textura Fina
The objective of this trial was to evaluate the effect of three drip
irrigation frequencies on table grapes (Vitis vinifera L.) cv. Thompson
Seedless planted on a clay loam textured soil (Fluventic Haploxeroll).
The drip irrigation frequencies were established considering daily crop
evapotranspiration (ETc), estimated by evaporation pan and adjusted
using a crop coefficient (Kc). The treatments corresponded to a water
application each time the accumulated daily ETc was equivalent to 6 h
(T6), 12 h (T12), and 18 h of irrigation (T18). The largest soil wet
bulb size was obtained with T18. This treatment also produced greater
berry weight and size. Stem water potential was higher in T18 (P 64
0.05) than in the other treatments. These results can be explained,
given the soil texture characteristics (clay loam), by a better
water/air balance with a less frequent irrigation regime.El objetivo de este ensayo fue evaluar el efecto de tres frecuencias de
riego por goteo sobre un parronal de uva de mesa (Vitis vinifera L.),
cv. Thompson Seedless, plantado en un suelo de textura franco arcillosa
(Fluventic Haploxeroll). Las frecuencias de riego se establecieron
considerando la evapotranspiraci\uf3n (ETc) acumulada del cultivo,
determinada por el m\ue9todo de la evaporaci\uf3n de bandeja y
corregida por un coeficiente de cultivo (Kc), y expresada como
acumulaci\uf3n de horas de riego equivalentes. Los tratamientos
correspondieron a regar cada vez que la ETc acumulada correspondiera a
6 h (T6), 12 h (T12) y 18 h de riego (T18). El mayor tama\uf1o de
bulbo de suelo h\ufamedo se obtuvo con el T18. Este tratamiento
present\uf3 mayor peso de poda y calibre de bayas a la cosecha. El
potencial h\ueddrico xilem\ue1tico fue m\ue1s alto (P 640,05)
en el tratamiento T18 que en los otros tratamientos. Estos resultados
se podr\uedan explicar, dadas las caracter\uedsticas texturales del
suelo, por un mejor equilibrio agua-aire en el suelo en el tratamiento
regado con menos frecuencia
The Polarised Valence Quark Distribution from semi-inclusive DIS
The semi-inclusive difference asymmetry A^{h^{+}-h^{-}} for hadrons of
opposite charge has been measured by the COMPASS experiment at CERN. The data
were collected in the years 2002-2004 using a 160 GeV polarised muon beam
scattered off a large polarised ^6LiD target and cover the range 0.006 < x <
0.7 and 1 < Q^2 < 100 (GeV/c)^2. In leading order QCD (LO) the asymmetry
A_d^{h^{+}-h^{-}} measures the valence quark polarisation and provides an
evaluation of the first moment of Delta u_v + Delta d_v which is found to be
equal to 0.40 +- 0.07 (stat.) +- 0.05 (syst.) over the measured range of x at
Q^2 = 10 (GeV/c)^2. When combined with the first moment of g_1^d previously
measured on the same data, this result favours a non-symmetric polarisation of
light quarks Delta u-bar = - Delta d-bar at a confidence level of two standard
deviations, in contrast to the often assumed symmetric scenario Delta u-bar =
Delta d-bar = Delta s-bar = Delta s.Comment: 7 pages, 3 figures, COMPASS, revised: details added, author list
update
Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target
Multiplicities of charged pions and unidentified hadrons produced in
deep-inelastic scattering were measured in bins of the Bjorken scaling variable
, the relative virtual-photon energy and the relative hadron energy .
Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and
an isoscalar target (LiD). They cover the kinematic domain in the photon
virtuality > 1(GeV/c, , and . In addition, a leading-order pQCD analysis was performed using the
pion multiplicity results to extract quark fragmentation functions
Large Anomalous Hall effect in a silicon-based magnetic semiconductor
Magnetic semiconductors are attracting high interest because of their
potential use for spintronics, a new technology which merges electronics and
manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently
emerged as the most popular materials for this new technology. While Curie
temperatures are rising towards room temperature, these materials can only be
fabricated in thin film form, are heavily defective, and are not obviously
compatible with Si. We show here that it is productive to consider transition
metal monosilicides as potential alternatives. In particular, we report the
discovery that the bulk metallic magnets derived from doping the narrow gap
insulator FeSi with Co share the very high anomalous Hall conductance of
(GaMn)As, while displaying Curie temperatures as high as 53 K. Our work opens
up a new arena for spintronics, involving a bulk material based only on
transition metals and Si, and which we have proven to display a variety of
large magnetic field effects on easily measured electrical properties.Comment: 19 pages with 5 figure
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