109 research outputs found
Correlations and synchronization in a Bose-Fermi mixture
We study a Bose-Fermi mixture within the framework of the mean-field theory,
including three possible regimes for the fermionic species: fully polarized,
BCS, and unitarity. Starting from the 3D description and using the variational
approximation (VA), we derive 1D and 2D systems of equations, under the
corresponding confining potentials. This method produces a pair of nonlinear
Schr\"{o}dinger (NLS) equations coupled to algebraic equations for the
transverse widths of the confined state. The equations incorporate interactions
between atoms of the same species and between the species, assuming that the
latter can be manipulated by means of the Feshbach resonance (FR). As an
application, we explore spatial density correlations in the ground state (GS)
between the species, concluding that they strongly depend on the sign and
strength of the inter-species interaction. Also studied are the dynamics of the
mixture in a vicinity of the GS and the corresponding spatiotemporal
inter-species correlation. The correlations are strongly affected by the
fermionic component, featuring the greatest variation in the unitary regime.
Results produced by the VA are verified by comparison with full numerical
solutions.Comment: Journal of Physics B: Atomic, Molecular and Optical Physics, in pres
The variational reduction for low-dimensional Fermi gases and Bose - Fermi mixtures: A brief review
We present a summary of some recent theoretical results for matter-wave
patterns in Fermi and Bose-Fermi degenerate gases, obtained in the framework of
the quasi-mean-field approximation. We perform a dimensional reduction from the
three-dimensional (3D) equations of motion to 2D and 1D effective equations. In
both cases, comparison of the low-dimensional reductions to the full model is
performed, showing very good agreement for ground-state solutions. Some complex
dynamical regimes are reported too for the corresponding 1D systems.Comment: Condensed Matter, accepted. arXiv admin note: text overlap with
arXiv:1502.0131
Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin
The Kibble-Zurek mechanism in a subcritical bifurcation
We present the study of the freezing dynamics of topological defects in a subcritical system by testing the Kibble-Zurek (KZ) mechanism while crossing a tri-stable region in a one-dimensional quintic complex Ginzburg-Landau equation. The critical exponents of the KZ mechanism and the horizon (KZ-scaling regime) are predicted from the quasistatic study, and are in full accordance with the quenched study. The correlation length, in the KZ freezing regime, is corroborated from the number of topological defects and from the spatial correlation function of the order parameter. Furthermore, we characterize the dynamics to differentiate three out-of-equilibrium regimes: the adiabatic, the impulse and the free-relaxation. We show that the impulse regime shares a common temporal domain with a fast exponential increase of the order parameter
Satellite-derived UV climatology at Escudero station, Antarctic Peninsula
We have used data from the Ozone Monitoring Instrument (OMI) aboard NASA's Earth Observing System (EOS) Aura satellite over the period 2004-11 to describe the characteristics of surface ultraviolet (UV) irradiance at Escudero Station (62°12′S, 58°57′W). The station is located on King George Island (northern Antarctic Peninsula). Temperatures in summer are frequently above 0°C, and the surrounding ocean is typically ice-free. We found that the UV irradiance at Escudero is driven by the Antarctic ozone hole (which annually in spring leads to significant variations in the ozone) and by clouds (which are more frequent and have a larger optical depth compared with other Antarctic sites). The combined effect of ozone and clouds led to significant variations in the surface UV. The variability (taken as the standard deviation of the UV estimates retrieved from OMI) is typically greater than 30% at Escudero, but may reach values greater than 50% in spring. The consistency of OMI-derived data was checked by using ground-based spectral measurements carried out under controlled conditions in January 2011. © 2013 Antarctic Science Ltd
- …