2,584 research outputs found
Quantum Hertz entropy increase in a quenched spin chain
The classical Hertz entropy is the logarithm of the volume of phase space
bounded by the constant energy surface; its quantum counterpart, the quantum
Hertz entropy, is , where the quantum operator specifies the number of states with energy below a given energy eigenstate.
It has been recently proved that, when an isolated quantum mechanical system is
driven out of equilibrium by an external driving, the change in the expectation
of its quantum Hertz entropy cannot be negative, and is null for adiabatic
driving. This is in full agreement with the Clausius principle. Here we test
the behavior of the expectation of the quantum Hertz entropy in the case when
two identical XY spin chains initially at different temperatures are quenched
into a single XY chain. We observed no quantum Hertz entropy decrease. This
finding further supports the statement that the quantum Hertz entropy is a
proper entropy for isolated quantum systems. We further quantify how far the
quenched chain is from thermal equilibrium and the temperature of the closest
equilibrium.Comment: 9 pages, 5 figure
Fluctuation theorems for continuously monitored quantum fluxes
It is shown that quantum fluctuation theorems remain unaffected if
measurements of any kind and number of observables are performed during the
action of a force protocol. That is, although the backward and forward
probabilities entering the fluctuation theorems are both altered by these
measurements, their ratio remains unchanged. This observation allows to
describe the measurement of fluxes through interfaces and, in this way, to
bridge the gap between the current theory, based on only two measurements
performed at the beginning and end of the protocol, and experiments that are
based on continuous monitoring.Comment: 4 pages, 1 figure. Accepted in Physical Review Letter
Work statistics, irreversible heat and correlations build-up in joining two spin chains
We investigate the influences of quantum many-body effects, such as
criticality and the existence of factorisation fields, in the thermodynamic
cost of establishing a bonding link between two independent quantum spin
chains. We provide a physical interpretation of the behavior of irreversible
work spent in such process by linking the phenomenology of such quantities to
the properties of the spectrum of the systemComment: 9 pages, 8 figures. Contribution to the FQMT13 special volum
Investor sentiment and trading behavior
The aim of this paper is to model trading decisions of financial investors based on a sentiment index. For this purpose, we analyse a dynamical model which includes the sentiment index in the agents' trading behavior. We consider the set up of a Discrete Dynamical System, assuming that in financial markets transactions take place between two groups of fundamentalists that differ in their perception of fundamental value. The proportion of fundamentalists in the two groups is assumed to depend on the sentiment index. The sentiment index used is related to the risk asymmetry index (RAX) enabling us to consider both the variance and the asymmetry of the prediction error between the two groups of fundamentalists.
We identify the equilibria of the model and conduct a numerical analysis in order to capture stylized facts documented empirically in the financial literature
Fundamentalists heterogeneity and the role of the sentiment indicator
This paper is a contribution to the literature on the role of the sentiment indices in heterogeneous asset pricing models. We propose a new sentiment index in a financial market where we assume that transactions take place between two groups of fundamentalists that differentiate on the perception of the fundamental value. We assume that the fraction of fundamentalists in the two groups depends on the sentiment index. After studying the analytical properties of the deterministic discrete dynamical system we compare the new index with a previous index introduced in financial literature. For this purpose, by adding stochastic components to the fundamentalist' demands, we measure the performance of our model under different sentiment indices and we test its explanatory power to reproduce the stylized facts of financial data relying on the S&P500 index
Geometric magnetism in open quantum systems
An isolated classical chaotic system, when driven by the slow change of
several parameters, responds with two reaction forces: geometric friction and
geometric magnetism. By using the theory of quantum fluctuation relations we
show that this holds true also for open quantum systems, and provide explicit
expressions for those forces in this case. This extends the concept of Berry
curvature to the realm of open quantum systems. We illustrate our findings by
calculating the geometric magnetism of a damped charged quantum harmonic
oscillator transported along a path in physical space in presence of a magnetic
field and a thermal environment. We find that in this case the geometric
magnetism is unaffected by the presence of the heat bath.Comment: 7 pages. Signs corrected. v3 Accepted in Phys. Rev.
Human Papillomavirus (HPV) Detection in Keratotic Variants of Oral Lichen Planus: Negative Results in a Preliminary Open Study
Background During the last few decades, several researches have been identified HPV genomic sequences in Head Neck Squamous Cell Carcinomas (HNSCC) and in Oral Potentially Malignant Disorders (OPMD) hypothesizing a possible viral etiological role. However, the reported prevalence of HPV-DNA (varying from 0% to 100%) in these lesions result still very discordant.
Objective Human papillomavirus (HPV) infection in Oral Lichen Planus (OLP) has been largely investigated but not so extensively with respect to its morphological/histopathological features. The possible influence of hyper-keratosis/parakeratosis in HPV detection for keratotic variants of OLP is here proposed and investigated.
Materials and methods A total of 45 individuals with keratotic variants of OLP, clinically and histologically confirmed, were consecutively enrolled, before starting any treatment, and underwent oral brushing for HPV investigation. Viral DNA was extracted from oral brushed cells and HPV DNA researched by the combined use of the INNO-LiPA HPV Genotyping system (Innogenetics) and a PCR assay coupled with genome sequencing.
Results None of cytological samples collected resulted HPV-positive.
Conclusions In this preliminary study, oral HPV infection, investigated by means of a non-invasive oral sampling procedure and a standardized approach for HPV DNA detection, was not showed in any of the investigated cases. The presence of epithelial hyper-keratosis/parakeratosis in some variants of OLP could be a possible cause of impenetrability and/or difficult detection of the virus. Indeed, in case of keratotic variants of OLP, the possible potential false-negative results of HPV investigation by cytological procedure might be possible; on consequence, an alternative approach for viral detection (i.e. by histological sampling) should be considered
Novel non-invasive adjunctive techniques for early oral cancer diagnosis and oral lesions examination
Oral cancer is a potentially fatal disease with an increasing incidence and an unchanged 5-year mortality rate. Unfortunately, oral cancer is often still late diagnosed, which leads to an increase in the likelihood of functional impairment due to treatment and mortality rate. Definitive diagnosis of oral cancer must be confirmed by scalpel biopsy and histological assessment. However despite its benefits, scalpel biopsy is invasive and it is burdened by a potential morbidity. Furthermore, previous studies have suggested a high degree of intraobserver and interobserver variability regarding the histological evaluation of malignancy. As a consequence, in recent years there has been a growing and persisting demand towards developing new non-invasive, practical diagnostic tools that might facilitate the early detection of oral cancer. The most investigated non-invasive adjunctive techniques are vital staining, autofluorescence, chemiluminescence, narrow band imaging, and exfoliative cytology. Aim of the review is to critically describe these adjunctive aids and, after considering the literature data, an expert opinion on the effectiveness and the possible use of each technique will be provided
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