Search results for "Computer Science Applications"

Transparent Boundary Condition for Oseen-Frank Model. Application for NLC Cells With Patterned Electrodes

2015

In the present work a novel application of Transparent Boundary Conditions (TBC) to nematic liquid crystal cells (NLCC) with planar alignment and a patterned electrode is studied. This device is attracting great interest since it allows soliton steering by optically and externally induced waveguides. We employ the continuum Oseen-Frank theory to find the tilt and twist angle distributions in the cell under the one-constant approximation. The electric field distribution takes into account the whole 2D permittivity tensor for the transverse coordinates. Standard finite difference time domain methods together with an iterative method is applied to find an approximate solution to our coupled pr…

A first-principles time-dependent density functional theory framework for spin and time-resolved angular-resolved photoelectron spectroscopy in perio…

2017

We present a novel theoretical approach to simulate spin, time, and angular-resolved photoelectron spectroscopy (ARPES) from first-principles that is applicable to surfaces, thin films, few layer systems, and low-dimensional nanostructures. The method is based on a general formulation in the framework of time-dependent density functional theory (TDDFT) to describe the real time-evolution of electrons escaping from a surface under the effect of any external (arbitrary) laser field. By extending the so-called t-SURFF method to periodic systems one can calculate the final photoelectron spectrum by collecting the flux of the ionization current trough an analyzing surface. The resulting approach…

EnCurv: Simple Technique of Maintaining Global Membrane Curvature in Molecular Dynamics Simulations.

2021

The EnCurv method for maintaining membrane curvature in molecular dynamics simulations is introduced. The method allows maintaining any desired curvature in a sector of lipid membrane bent in a single plane without adding any unphysical interactions into the system and without restrictions on lateral and transversal lipid diffusion and distribution. The current implementation is limited to the membranes curved in a single plane but generalization to arbitrary curvature and membrane topology is possible. The method is simple, easy to implement, and scales linearly with the system size. EnCurv is agnostic to the force field, simulation parameters, and membrane composition. The proof of princi…

Extracting the impact parameter dependence of the nPDFs from the EKS98 and EPS09 global fits

2013

As all the globally fitted nuclear PDFs (nPDFs) have been so far impact parameter independent, it has not been possible to calculate the hard process cross sections in different centrality classes consistently with the global analyses. In \cite{Helenius:2012wd} we have offered a solution to this problem by determining two spatially dependent nPDF sets, \texttt{EPS09s} and \texttt{EKS98s}, using the $A$-systematics of the earlier global fits EPS09 and EKS98 and an assumption that the spatial dependence can be written as a power series of the nuclear thickness function. For a data comparison, we have calculated the nuclear modification factor of inclusive neutral pion production in d+Au colli…

Calibration of a camera-projector monochromatic system

2015

Camera–projector systems are increasingly being used in many different applications, including object reconstruction. In recent years, a number of approaches have been proposed to calibrate such devices; in this paper a calibration method is presented which can be used with monochromatic systems. The method is based on open-source code, makes use of planar calibration patterns, is fully automatic, easy to use and fast. Additionally, no initial information regarding the camera interior orientation is needed, and both sensors (camera and projector) are fully calibrated during the process. The method is validated by a series of tests, where root mean square errors (RMSEs) in image space are ke…

A simple method for limiting the quadrature oscillator amplitude

1981

Quark-model study of the hadron structure and the hadron-hadron interaction

2011

Recent results of hadron spectroscopy and hadron-hadron interaction within a quark model framework are reviewed. Higher order Fock space components are considered based on new experimental data on low-energy hadron phenomenology. The purpose of this study is to obtain a coherent description of the low-energy hadron phenomenology to constrain QCD phenomenological models and try to learn about low-energy realizations of the theory.

Theoretical overview of kaon decays

2014

Kaon decays are an important testing ground of the electroweak flavour theory. They can provide new signals of CP violation and, perhaps, a window into physics beyond the Standard Model. At the same time, they exhibit an interesting interplay of long-distance QCD effects in flavour-changing transitions. A brief overview is presented, focusing on a few selected topics of particular interest. A more detailed and comprehensive review can be found in arXiv:1107.6001.

Small violations of 3 × 3 unitarity, the phase inB0s–B̄0smixing and visiblet → cZdecays at the LHC

2009

We show that it is possible to accommodate the observed size of the phase in Bs0?s0 mixing in the framework of a model with violation of 3 ? 3 unitarity. This violation is associated to the presence of a new Q = 2/3 isosinglet quark T, which mixes both with t and c and has a mass not exceeding 500 GeV. The crucial point is the fact that this framework allows for ? ? arg(?VtsVcbV*tbV*cs) of order ?, to be contrasted with the situation in the Standard Model, where ? is constrained to be of order ?2. We point out that this scenario implies rare top decays t?cZ at a rate observable at the LHC and |Vtb| significantly different from unity. In this framework, one may also account for the observed …

Charge asymmetries of top quarks: a window to new physics at hadron colliders

2009

With the next start of LHC, a huge production of top quarks is expected. There are several models that predict the existence of heavy colored resonances decaying to top quarks in the TeV energy range. A peak in the differential cross section could reveal the existence of such a resonance, but this is experimentally challenging, because it requires selecting data samples where top and antitop quarks are highly boosted. Nonetheless, the production of such resonances might generate a sizable charge asymmetry of top versus antitop quarks. We consider a toy model with general flavour independent couplings of the resonance to quarks, of both vector and axial-vector kind. The charge asymmetry turn…