10 research outputs found
Two-Dimensional Electron Gas with Cold Atoms in Non-Abelian Gauge Potentials
Motivated by the possibility of creating non-Abelian fields using cold atoms
in optical lattices, we explore the richness and complexity of non-interacting
two-dimensional electron gases (2DEGs) in a lattice, subjected to such fields.
In the continuum limit, a non-Abelian system characterized by a two-component
"magnetic flux" describes a harmonic oscillator existing in two different
charge states (mimicking a particle-hole pair) where the coupling between the
states is determined by the non-Abelian parameter, namely the difference
between the two components of the "magnetic flux." A key feature of the
non-Abelian system is a splitting of the Landau energy levels, which broaden
into bands, as the spectrum depends explicitly on the transverse momentum.
These Landau bands result in a coarse-grained "moth," a continuum version of
the generalized Hofstadter butterfly. Furthermore, the bands overlap, leading
to effective relativistic effects. Importantly, similar features also
characterize the corresponding two-dimensional lattice problem when at least
one of the components of the magnetic flux is an irrational number. The lattice
system with two competing "magnetic fluxes" penetrating the unit cell provides
a rich environment in which to study localization phenomena. Some unique
aspects of the transport properties of the non-Abelian system are the
possibility of inducing localization by varying the quasimomentum, and the
absence of localization of certain zero-energy states exhibiting a linear
energy-momentum relation. Furthermore, non-Abelian systems provide an
interesting localization scenario where the localization transition is
accompanied by a transition from relativistic to non-relativistic theory.Comment: A version with higher resolution figures is available at
http://physics.gmu.edu/~isatija/NALFinal.pd
Phantom thermodynamics
This paper deals with the thermodynamic properties of a phantom field in a
flat Friedmann-Robertson-Walker universe. General expressions for the
temperature and entropy of a general dark-energy field with equation of state
are derived from which we have deduced that, whereas the
temperature of a cosmic phantom fluid () is definite negative, its
entropy is always positive. We interpret that result in terms of the intrinsic
quantum nature of the phantom field and apply it to (i) attain a consistent
explanation for some recent results concerning the evolution of black holes
which,induced by accreting phantom energy, gradually loss their mass to finally
vanish exactly at the big rip, and (ii) introduce the concept of cosmological
information and its relation with life and the anthropic principle. Some
quantum statistical-thermodynamic properties of the quantum quantum field are
also considered that include a generalized Wien law and the prediction of some
novel phenomena such as the stimulated absorption of phantom energy and the
anti-laser effect.Comment: 19 pages, LaTex, 2 figures, accepted for publication in Nuclear
Physics