Search results for "PERTURBATION"
showing 10 items of 811 documents
Effective theory approaches to heavy meson resonances based on non-perturbative low energy two-meson dynamics
2019
This dissertation provides a theoretical effective description of a special class of hadronic meson states with charm and bottom quark content and their associated phenomenology. The considered states are difficult to be accommodated in CQMs and are candidates to be interpreted as meson molecules. This relies on the assumption that their main properties can be described by means of an effective low energy interaction of two more fundamental mesons. We have paid special attention to the relevant symmetries of QCD and two-body unitarity to construct the low energy effective meson-meson interactions. We have investigated the predictions of the Next-to-Leading Order (NLO) Unitary Heavy Meson Ch…
Review of Particle Physics
2020
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, …
Many-particle approach to the image-charge effect
2011
Microscopical systems of molecules and atomic chains are studied to obtain information about quantum-transport phenomena. Both exact diagonalization method through second quantization and perturbation theory approach with Feynman diagrams are described, and then the energy spectra for the studied systems are calculated using the two methods.
Dissociable Effects of Reward on P300 and EEG Spectra Under Conditions of High vs. Low Vigilance During a Selective Visual Attention Task
2020
The influence of motivation on selective visual attention in states of high vs. low vigilance is poorly understood. To explore the possible differences in the influence of motivation on behavioral performance and neural activity in high and low vigilance levels, we conducted a prolonged 2 h 20 min flanker task and provided monetary rewards during the 20- to 40- and 100- to 120-min intervals of task performance. Both the behavioral and electrophysiological measures were modulated by prolonged task engagement. Moreover, the effect of reward was different in high vs. low vigilance states. The monetary reward increased accuracy and decreased the reaction time (RT) and number of omitted response…
Interaction en champ proche entre une sonde nanométrique et le champ de composants à cristal photonique:- interaction faible, microscopie spatialemen…
2008
With the improvement of fabrication techniques, the nanophotonics and more especially the photonics crystals which are periodic structure at the Wavelength scale have been recently developed. In this work, by using a scanning near-field optical microscope, we study such components. Firslty, we use the local probe to visualize the light distribution inside photonic crystal microcavities etched into semiconductor III/V. We focus us on the explanation of the near-field maps formation and on the probe influence on these maps. Thus, we have visualize degeneracy splitting of optical cavity modes and clearly observed in near-field cavity modes which were not visible in far-field. Moreover, in the …
Computational Structures and SAPT Interaction Energies of HXeSH···H2Y (Y=O or S) Complexes
2018
Ab initio calculations of the structures, vibrational spectra and supermolecular and symmetry-adapted perturbation theory (SAPT) interaction energies of the HXeOH and HXeSH complexes with H2O and H2S molecules are presented. Two minima already reported in the literature were reproduced and ten new ones were found together with some transition states. All complexes show blue shift in Xe&ndash
Application of time-dependent many-body perturbation theory to excitation spectra of selected finite model systems
2016
In this thesis, an approximate method introduced to solve time-dependent many-body problems known as time-dependent many-body perturbation theory is studied. Many-body perturbation theory for interacting electrons and phonons is reviewed. In particular, the electron propagator G and an unconventional two-component phonon propagator, which satisfy coupled integral Dyson equations, are introduced. In practice, the associated integral kernels known as the electron Σ and phonon self-energies need to be approximated. The conserving approximations known as the Hartree (-Fock) and the first and second Born approximations, which respect the continuity equation between the electron density and curren…
The linearized Calderón problem for polyharmonic operators
2023
In this article we consider a linearized Calderón problem for polyharmonic operators of order 2m (m ≥ 2) in the spirit of Calderón’s original work [7]. We give a uniqueness result for determining coefficients of order ≤ 2m − 1 up to gauge, based on inverting momentum ray transforms. peerReviewed
Merging Features from Green's Functions and Time Dependent Density Functional Theory: A Route to the Description of Correlated Materials out of Equil…
2016
We propose a description of nonequilibrium systems via a simple protocol that combines exchange-correlation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double counting of interactions, is tested against exact results in Hubbard-type systems, with respect to interaction strength, perturbation speed and inhomogeneity, and system dimensionality and size. In many regimes, we find significant improvement over adiabatic time dependent density functional theory or second Born nonequilibrium Green's function approximations. We briefly discuss the reasons for the residual discrepancies, and directions for future work.
Open-source QCD analysis of nuclear parton distribution functions at NLO and NNLO
2019
We present new sets of nuclear parton distribution functions (nPDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). Our analyses are based on deeply inelastic scattering data with charged-lepton and neutrino beams on nuclear targets. In addition, a set of proton baseline PDFs is fitted within the same framework with the same theoretical assumptions. The results of this global QCD analysis are compared to existing nPDF sets and to the fitted cross sections. Also, the uncertainties resulting from the limited constraining power of the included experimental data are presented. The published work is based on an open-source tool, xFitter, which has been modified to be ap…