340 research outputs found
Comment on "General Non-Markovian Dynamics of Open Quantum Systems"
The existence of a "non-Markovian dissipationless" regime, characterized by
long lived oscillations, was recently reported for a class of quantum open
systems (Zhang et al, PRL, 109, 170402, (2012)). It is claimed this could
happen in the strong coupling regime, a surprising result which has attracted
some attention. We show that this regime exists if and only if the total
Hamiltonian is unbounded from below, casting serious doubts on the usefulness
of this result
Using Gene Ontology to describe the role of the neurexin-neuroligin-SHANK complex in human, mouse and rat and its relevance to autism
People with an autistic spectrum disorder (ASD) display a variety of characteristic behavioral traits, including impaired social interaction, communication difficulties and repetitive behavior. This complex neurodevelopment disorder is known to be associated with a combination of genetic and environmental factors. Neurexins and neuroligins play a key role in synaptogenesis and neurexin-neuroligin adhesion is one of several processes that have been implicated in autism spectrum disorders
Rapidly-converging methods for the location of quantum critical points from finite-size data
We analyze in detail, beyond the usual scaling hypothesis, the finite-size
convergence of static quantities toward the thermodynamic limit. In this way we
are able to obtain sequences of pseudo-critical points which display a faster
convergence rate as compared to currently used methods. The approaches are
valid in any spatial dimension and for any value of the dynamic exponent. We
demonstrate the effectiveness of our methods both analytically on the basis of
the one dimensional XY model, and numerically considering c = 1 transitions
occurring in non integrable spin models. In particular, we show that these
general methods are able to locate precisely the onset of the
Berezinskii-Kosterlitz-Thouless transition making only use of ground-state
properties on relatively small systems.Comment: 9 pages, 2 EPS figures, RevTeX style. Updated to published versio
Charmed Baryons with
The width of a recently discovered excited charmed-strange baryon, a
candidate for a state with spin 3/2, is calculated. In the absence of
configuration mixing between the ground-state (spin-1/2) charmed-strange baryon
and the spin-1/2 state lying about 95 MeV above it,
one finds and , where the tilde denotes the partial
width with kinematic factors removed. Assuming a kinematic factor for P-wave
decay of , one predicts MeV, while the channel is closed. Some
suggestions are given for detecting the , the spin-3/2 charmed
nonstrange baryon, and the , the spin-3/2 charmed doubly-strange
baryon.Comment: 11 pages, latex, 2 uuencoded figures sent separatel
Spin-1 Antiferromagnetic Heisenberg Chains in an External Staggered Field
We present in this paper a nonlinear sigma-model analysis of a spin-1
antiferromagnetic Heisenberg chain in an external commensurate staggered
magnetic field. After rediscussing briefly and extending previous results for
the staggered magnetization curve, the core of the paper is a novel
calculation, at the tree level, of the Green functions of the model. We obtain
precise results for the elementary excitation spectrum and in particular for
the spin gaps in the transverse and longitudinal channels. It is shown that,
while the spectral weight in the transverse channel is exhausted by a single
magnon pole, in the longitudinal one, besides a magnon pole a two-magnon
continuum appears as well whose weight is a stedily increasing function of the
applied field, while the weight of the magnon decreases correspondingly. The
balance between the two is governed by a sum rule that is derived and
discussed. A detailed comparison with the present experimental and numerical
(DMRG) status of the art as well as with previous analytical approaches is also
made.Comment: 23 pages, 3 figures, LaTe
Analytical Concentrations of Some Elements in Seeds and Crude Extracts from Aesculus hippocastanum, by ICP-OES Technique
The metal content in some samples of horse chestnut seeds (Aesculus hippocastanum) was monitored over time (years 2016, 2017, 2018, 2019) considering the two most common and representative Mediterranean varieties: the pure species (AHP, which gives white flowers) and a hybrid one (AHH, which gives pink flowers). The selected elemental composition of the samples was determined by applying the ICP-OES technique.
Several samples obtained from different preliminary treatments of the peeled seeds were examined, such as: i) floury samples (wild type) mineralized with the wet method; ii) the ashes of both AHP and AHH varieties; iii) the fraction of total inorganic soluble salts (TISS).
Furthermore, the hydroalcoholic crude extracts (as a tincture) were obtained according to the official Pharmacopoeia methods, and the relevant results were compared with those of a commercial sample, an herbal product - food supplement of similar characteristics. The main characteristics of this research work underline that the two botanical varieties give different distinctive characters, due to the Fe content (80.05 vs 1.42 mg / 100 g d.s., for AHP and AHH - wild type flour samples, respectively), along with K, Ca, Mn, Ni and Cu, which are more abundant in the AHP samples. Furthermore, the PCA analysis was applied to the experimental dataset in order to classify and discriminate the samples, in relation to their similar botanical origin, but different for the color of the bloom. These results can be useful for the traceability of raw materials potentially intended for the production of auxiliary systems of pharmacological interest.The metal content in some samples of horse chestnut seeds (Aesculus hippocastanum) was monitored over time (years 2016–2019) considering the two most common and representative Mediterranean varieties: the pure species (AHP, which gives white flowers) and a hybrid one (AHH, which gives pink flowers). The selected elemental composition of the samples was determined by applying the Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) technique. Several samples obtained from different preliminary treatments of the peeled seeds were examined, such as: (i) floury samples (wild-type) mineralized with the wet method; (ii) the ashes of both AHP and AHH varieties; (iii) the fraction of total inorganic soluble salts (TISS). Furthermore, the hydroalcoholic crude extracts (as a tincture) were obtained according to the official Pharmacopoeia methods, and the relevant results were compared with those of a commercial sample, an herbal product-food supplement of similar characteristics. The main characteristics of this research work underline that the two botanical varieties give different distinctive characters, due to the Fe content (80.05 vs. 1.42 mg/100 g d.s., for AHP and AHH wild-type flour samples, respectively), along with K, Ca, Mn, Ni and Cu, which are more abundant in the AHP samples. Furthermore, the Principal Component Analysis (PCA) was applied to the experimental dataset in order to classify and discriminate the samples, in relation to their similar botanical origin, but different for the color of the bloom. These results can be useful for the traceability of raw materials potentially intended for the production of auxiliary systems of pharmacological interest
Stripe Ansatzs from Exactly Solved Models
Using the Boltzmann weights of classical Statistical Mechanics vertex models
we define a new class of Tensor Product Ansatzs for 2D quantum lattice systems,
characterized by a strong anisotropy, which gives rise to stripe like
structures. In the case of the six vertex model we compute exactly, in the
thermodynamic limit, the norm of the ansatz and other observables. Employing
this ansatz we study the phase diagram of a Hamiltonian given by the sum of XXZ
Hamiltonians along the legs coupled by an Ising term. Finally, we suggest a
connection between the six and eight-vertex Anisotropic Tensor Product Ansatzs,
and their associated Hamiltonians, with the smectic stripe phases recently
discussed in the literature.Comment: REVTEX4.b4 file, 10 pages, 2 ps Figures. Revised version to appear in
PR
Stable particles in anisotropic spin-1 chains
Motivated by field-theoretic predictions we investigate the stable
excitations that exist in two characteristic gapped phases of a spin-1 model
with Ising-like and single-ion anisotropies. The sine-Gordon theory indicates a
region close to the phase boundary where a stable breather exists besides the
stable particles, that form the Haldane triplet at the Heisenberg isotropic
point. The numerical data, obtained by means of the Density Matrix
Renormalization Group, confirm this picture in the so-called large-D phase for
which we give also a quantitative analysis of the bound states using standard
perturbation theory. However, the situation turns out to be considerably more
intricate in the Haldane phase where, to the best of our data, we do not
observe stable breathers contrarily to what could be expected from the
sine-Gordon model, but rather only the three modes predicted by a novel
anisotropic extension of the Non-Linear Sigma Model studied here by means of a
saddle-point approximation.Comment: 8 pages, 7 eps figures, svjour clas
Scalar mesons in the Nambu--Jona-Lasinio model with 't Hooft interaction
We calculate the mass spectra of the pseudoscalar and scalar meson nonets in
the Nambu--Jona-Lasinio model with the 't Hooft interaction. We obtain
satisfactory result for the pseudoscalar mesons. For the scalar mesons, the 't
Hooft interaction somewhat increases the values of the masses. However, it is
not sufficient to explain the whole scalar mass spectrum. The situation could
be improved for the and mesons through mixing with the glueball
state. For the description of the masses of and \kstar mesons, it is
necessary to involve the other models. The strong decay widths of the scalar
mesons are described.Comment: LaTeX text, 8 page
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