Search results for "Dimension"

Complex-mass renormalization in chiral effective field theory

2009

We consider a low-energy effective field theory of vector mesons and Goldstone bosons using the complex-mass renormalization. As an application we calculate the mass and the width of the $\rho$ meson.

Robust non-Markovianity in ultracold gases

2012

We study the effect of thermal fluctuations on a probe qubit interacting with a Bose-Einstein condensed (BEC) reservoir. The zero-temperature case was studied in [Haikka P et al 2011 Phys. Rev. A 84 031602], where we proposed a method to probe the effects of dimensionality and scattering length of a BEC based on its behavior as an environment. Here we show that the sensitivity of the probe qubit is remarkably robust against thermal noise. We give an intuitive explanation for the thermal resilience, showing that it is due to the unique choice of the probe qubit architecture of our model.

Quantitative modeling of spin relaxation in quantum dots

2011

Physics Department, Harvard University, 02138 Cambridge MA, USA(Dated: December 16, 2011)We use numerically exact diagonalization to calculate the spin-orbit and phonon-induced triplet-singlet relaxation rate in a two-electron quantum dot exposed to a tilted magnetic field. Our schemeincludes a three-dimensional description of the quantum dot, the Rashba and the linear and cubicDresselhaus spin-orbit coupling, the ellipticity of the quantum dot, and the full angular descriptionof the magnetic field. We are able to find reasonable agreement with the experimental results ofMeunier et al. [Phys. Rev. Lett. 98, 126601 (2007)] in terms of the singlet-triplet energy splittingand the spin relaxation …

Interface localization transition in Ising films with competing walls: Ginzburg criterion and crossover scaling.

1996

The multifractal character of the electronic states in disordered two-dimensional systems

1995

The nature of electronic states in disordered two-dimensional (2D) systems is investigated. With this aim, we present our calculations of both density of states and d.c. conductivity for square lattices modelling the Anderson Hamiltonian with on-site energies randomly chosen from a box distribution of width W. For weak disorder (W), the eigenfunctions calculated by means of the Lanczos diagonalization algorithm display spatial fluctuations reflecting their (multi)fractal behaviour. For increasing disorder the observed increase of the curdling of the wavefunction reflects its stronger localization. However, as a function of energy, the eigenstates at energy mod E mod /V approximately=1.5 are…

The effect of reducing dimensionality on the excitonic recombination in InAs/InP heterostructures

1997

In this work we study the exciton recombination of InAs/InP self-organized quantum dots by means of photolumincscence (PL) as a function of temperature and excitation density. Well defined islands, spatially separated in most cases, and with different size distribution, make localized exciton recombination the dominant contribution to the PL spectrum. From our experimental results, we propose the co-existence of two types of islands, one with small height whose contribution to the PL spectra is important in samples with low InAs coverage (below two monolayers), and the properly 3D islands, whose dimensions and sheet concentration increase with the InAs coverage. Good quality structures are …

A study of free convection in air around horizontal cylinders of different diameters based on holographic interferometry. Temperature field equations…

2002

Abstract Holographic interferometry is used to study free convection in air around horizontal cylinders of different diameters and equal length, involving different surface temperatures, with the aim of defining the corresponding temperature fields. Interferograms were obtained to determine the temperature (T) of each point as well as its distance (x) from the surface of the cylinder. These values in turn made it possible to define functions (of an exponential nature in our case), T=f(x), that satisfactorily reproduced the temperature fields. Posteriorly, these functions were used to calculate the local convection coefficients, determining their dependency upon temperature and the direction…

Linear inverse filtering improves spatial separation of nonlinear brain dynamics: a simulation study.

2000

We examined topographic variations in nonlinear measures based on scalp voltages, which were generated by two simulated current dipoles each placed in a different hemisphere of a spherical volume conductor (three-shell model). Dipole dynamics were that of a three-torus and the x-component of the Lorenz-system and scalp voltage were calculated for a configuration of 29 electrode positions. Although estimates for correlation dimension D2 and Lyapunov exponent L1 were close to the theoretical values for the original time series, the simulated scalp voltage data showed almost no topographic resolution of dipole positions. In order to enhance topographic differentiation, we constructed linear in…

Fractal Aspects of Galaxy Clustering

2008

In the past decade, the mathematical concept of fractal has exerted a great influence in a large variety of scientific disciplines. It is very common to find recent papers on the application of fractals to different fields in Physics, Chemistry, Biology, etc. The success of the fractal geometry in the description of many systems is due to the fact that deep insights into very simple objects show how fractal measures are more natural for their study.

Searching for the scale of homogeneity

1998

We introduce a statistical quantity, known as the $K$ function, related to the integral of the two--point correlation function. It gives us straightforward information about the scale where clustering dominates and the scale at which homogeneity is reached. We evaluate the correlation dimension, $D_2$, as the local slope of the log--log plot of the $K$ function. We apply this statistic to several stochastic point fields, to three numerical simulations describing the distribution of clusters and finally to real galaxy redshift surveys. Four different galaxy catalogues have been analysed using this technique: the Center for Astrophysics I, the Perseus--Pisces redshift surveys (these two lying…