Search results for "Observable"
showing 10 items of 634 documents
The behavior of correlation functions in trans-polyacetylene: quantum Monte Carlo study
2002
We present results of a quantum Monte Carlo simulation of the one-dimensional half-filled Hubbard model to study different correlation functions in the trans-polyacetylene (t-PA) polymer. Magnetic structure of the model in t-PA is studied for a different range values of the Hubbard repulsion interactions, U and V ,w here U 4t , with V ∈[ U/2 ,U ] (t is the hopping matrix elements). In this work, we investigate the behavior of the magnetic correlation functions for different phases transitions between different ordering (antiferromagnetic and ferromagnetic) by varying the nearest-neighbor interactions U and V between different atomic sites. Our results indicate that there is a presence of a …
Monte Carlo Methods for the Sampling of Free Energy Landscapes
2019
In this chapter, we return to classical statistical mechanics, wherein the canonical ensemble averages of an observable \(A(\overrightarrow{x})\), where \(\overrightarrow{x} \) stands symbolically for the “microstate” coordinate in the configurational part of the phase space of the system, are given by (cf. Sect. 2.1.1)
Quasi-Lie Brackets and the Breaking of Time-Translation Symmetry for Quantum Systems Embedded in Classical Baths
2018
Many open quantum systems encountered in both natural and synthetic situations are embedded in classical-like baths. Often, the bath degrees of freedom may be represented in terms of canonically conjugate coordinates, but in some cases they may require a non-canonical or non-Hamiltonian representation. Herein, we review an approach to the dynamics and statistical mechanics of quantum subsystems embedded in either non-canonical or non-Hamiltonian classical-like baths which is based on operator-valued quasi-probability functions. These functions typically evolve through the action of quasi-Lie brackets and their associated Quantum-Classical Liouville Equations, or through quasi-Lie brackets a…
Cascading dust inflation in Born-Infeld gravity
2015
In the framework of Born-Infeld inspired gravity theories, which deviates from General Relativity (GR) in the high curvature regime, we discuss the viability of Cosmic Inflation without scalar fields. For energy densities higher than the new mass scale of the theory, a gravitating dust component is shown to generically induce an accelerated expansion of the Universe. Within such a simple scenario, inflation gracefully exits when the GR regime is recovered, but the Universe would remain matter dominated. In order to implement a reheating era after inflation, we then consider inflation to be driven by a mixture of unstable dust species decaying into radiation. Because the speed of sound gravi…
Differential branching fraction and angular analysis of the decay $B^{0} \to K^{*0} \mu^{+}\mu^{-}$
2013
The angular distribution and differential branching fraction of the decay B-0 -> K*(0)mu(+)mu(-) are studied using a data sample, collected by the LHCb experiment in pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.0 fb(-1). Several angular observables are measured in bins of the dimuon invariant mass squared, q(2). A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q(0)(2) = 4.9 +/- 0.9 GeV2/c(4), where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
Geneses of Labour Market Turnover: Job Search and Entrepreneurial Aspirations On-the-job
2005
In this paper we study the labour market behavior of employed individuals that have entrepreneurial aspirations in addition to aspirations to switch job. We analyze empirically these two “search processes” side-by-side and report three main findings: First, neither entrepreneurial aspirations nor aspirations to switch job are uncommon, but only few are engaged in both search processes. Second, the two processes are not alike: It is more difficult to empirically explain entrepreneurial aspirations than aspirations to switch job. Only few observable characteristics of the employed are related to both processes. Varied experience and job dissatisfaction are directly related to the probability …
Left-handed neutrino disappearance probe of neutrino mass and character
1996
We explore the sensitivity to a non vanishing neutrino mass offered by dynamical observables, i.e., branching ratios and polarizations. The longitudinal polarization in the C.M. frame decreases by a 4% for $D^+ \rightarrow \tau^+ \nu_\tau$ and $m_{\nu_\tau}=24$ MeV. Taking advantage of the fact that the polarization is a Lorentz variant quantity, we study the polarization effects in a boosted frame. By means of a neutrino beam, produced by a high velocity boosted parent able to flip the neutrino helicity, we find that an enhanced left-handed neutrino deficit, induced by a Wigner rotation, appears.
Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$
2021
Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce. Purpose: This paper presents details of a virtual Compton scattering (VCS) experiment, performed at the A1 setup at the Mainz Microtron by studying the $e p \to e p \gamma$ reaction. The article focuses on selected aspects of the analysis. Method: The experiment extracted the $P_{LL} -P_{TT} / \epsilon$ and $P_{LT}$ structure functions, as well as the electric and magnetic GPs of the proton, at three new values of the four-momentum transfer squared $Q^2$: 0.10, 0.20 and 0.45 GeV$^2$. Results: We emphasize the importance of the ca…
Number of observable features in the acoustic-Raman spectra of nanocrystals
2012
Low-frequency Raman scattering spectra are presented for gold nanocrystals with diameters 3.5 and 13 nm. The frequencies of the Raman peaks but also their number are shown to vary with the nanocrystal size. These results are analyzed using both the continuous elastic medium approximation and an atomistic approach. We show that the number of atoms in the nanocrystal determines an upper limit of the number of observable Raman features. The frequency range in which the continuous elastic medium approximation is valid is defined by comparison with the calculations based on the atomistic approach.
Roadmap on quantum nanotechnologies
2021
Quantum phenomena are typically observable at length and time scales smaller than those of our everyday experience, often involving individual particles or excitations. The past few decades have seen a revolution in the ability to structure matter at the nanoscale, and experiments at the single particle level have become commonplace. This has opened wide new avenues for exploring and harnessing quantum mechanical effects in condensed matter. These quantum phenomena, in turn, have the potential to revolutionize the way we communicate, compute and probe the nanoscale world. Here, we review developments in key areas of quantum research in light of the nanotechnologies that enable them, with a …