33,556 research outputs found
Ground-states of spin-1 bosons in asymmetric double-wells
In this work we investigate the different states of a system of spin-1 bosons
in two potential wells connected by tunneling, with spin-dependent interaction.
The model utilizes the well-known Bose-Hubbard Hamiltonian, adding a local
interaction term that depends on the modulus of the total spin in a well,
favoring a high- or low-spin state for different signs of the coupling
constant. We employ the concept of fidelity to detect critical values of
parameters for which the ground state undergoes significant changes. The nature
of the states is investigated through evaluation of average occupation numbers
in the wells and of spin correlations. A more detailed analysis is done for a
two-particle system, but a discussion of the three-particle case and some
results for larger numbers are also presented.Comment: 7 pages, 10 figure
Anderson localization on the Falicov-Kimball model with Coulomb disorder
The role of Coulomb disorder is analysed in the Anderson-Falicov-Kimball
model. Phase diagrams of correlated and disordered electron systems are
calculated within dynamical mean-field theory applied to the Bethe lattice, in
which metal-insulator transitions led by structural and Coulomb disorders and
correlation can be identified. Metallic, Mott insulator, and Anderson insulator
phases, as well as the crossover between them are studied in this perspective.
We show that Coulomb disorder has a relevant role in the phase-transition
behavior as the system is led towards the insulator regime
The Role of Fermions in Bubble Nucleation
We present a study of the role of fermions in the decay of metastable states
of a scalar field via bubble nucleation. We analyze both one and
three-dimensional systems by using a gradient expansion for the calculation of
the fermionic determinant. The results of the one-dimensional case are compared
to the exact results of previous work.Comment: 15 pages, revtex, 9 figure
White dwarfs with a surface electrical charge distribution: Equilibrium and stability
The equilibrium configuration and the radial stability of white dwarfs
composed of charged perfect fluid are investigated. These cases are analyzed
through the results obtained from the solution of the hydrostatic equilibrium
equation. We regard that the fluid pressure and the fluid energy density follow
the relation of a fully degenerate electron gas. For the electric charge
distribution in the object, we consider that it is centralized only close to
the white dwarfs' surfaces. We obtain larger and more massive white dwarfs when
the total electric charge is increased. To appreciate the effects of the
electric charge in the structure of the star, we found that it must be in the
order of with which the electric field is about
. For white dwarfs with electric fields close to the
Schwinger limit, we obtain masses around . We also found that in
a system constituted by charged static equilibrium configurations, the maximum
mass point found on it marks the onset of the instability. This indicates that
the necessary and sufficient conditions to recognize regions constituted by
stable and unstable equilibrium configurations against small radial
perturbations are respectively and .Comment: This is a preprint. The original paper will be published in EPJ
Holonomy Transformation in the FRW Metric
In this work we investigate loop variables in Friedman-Robertson-Walker
spacetime. We analyze the parallel transport of vectors and spinors in several
paths in this spacetime in order to classify its global properties. The band
holonomy invariance is analysed in this background.Comment: 8 page
Translational research into gut microbiota: new horizons on obesity treatment: updated 2014
Obesity is currently a pandemic of worldwide proportions affecting millions of people. Recent studies have proposed the hypothesis that mechanisms not directly related to the human genome could be involved in the genesis of obesity, due to the fact that, when a population undergoes the same nutritional stress, not all individuals present weight gain related to the diet or become hyperglycemic. The human intestine is colonized by millions of bacteria which form the intestinal flora, known as gut flora. Studies show that lean and overweight human may present a difference in the composition of their intestinal flora; these studies suggest that the intestinal flora could be involved in the development of obesity. Several mechanisms explain the correlation between intestinal flora and obesity. The intestinal flora would increase the energetic extraction of non-digestible polysaccharides. In addition, the lipopolysaccharide from intestinal flora bacteria could trigger a chronic sub-clinical inflammatory process, leading to obesity and diabetes. Another mechanism through which the intestinal flora could lead to obesity would be through the regulation of genes of the host involved in energy storage and expenditure. In the past five years data coming from different sources established causal effects between intestinal microbiota and obesity/insulin resistance, and it is clear that this area will open new avenues of therapeutic to obesity, insulin resistance and DM2.Obesity is currently a pandemic of worldwide proportions affecting millions of people. Recent studies have proposed the hypothesis that mechanisms not directly related to the human genome could be involved in the genesis of obesity, due to the fact that, when a population undergoes the same nutritional stress, not all individuals present weight gain related to the diet or become hyperglycemic. The human intestine is colonized by millions of bacteria which form the intestinal flora, known as gut flora. Studies show that lean and overweight human may present a difference in the composition of their intestinal flora; these studies suggest that the intestinal flora could be involved in the development of obesity. Several mechanisms explain the correlation between intestinal flora and obesity. The intestinal flora would increase the energetic extraction of non-digestible polysaccharides. In addition, the lipopolysaccharide from intestinal flora bacteria could trigger a chronic sub-clinical inflammatory process, leading to obesity and diabetes. Another mechanism through which the intestinal flora could lead to obesity would be through the regulation of genes of the host involved in energy storage and expenditure. In the past five years data coming from different sources established causal effects between intestinal microbiota and obesity/insulin resistance, and it is clear that this area will open new avenues of therapeutic to obesity, insulin resistance and DM259215416
Quantum computing with incoherent resources and quantum jumps
Spontaneous emission and the inelastic scattering of photons are two natural
processes usually associated with decoherence and the reduction in the capacity
to process quantum information. Here we show that when suitably detected, these
photons are sufficient to build all the fundamental blocks needed to perform
quantum computation in the emitting qubits while protecting them from
deleterious dissipative effects. We exemplify by showing how to teleport an
unknown quantum state and how to efficiently prepare graph states for the
implementation of measurement-based quantum computation.Comment: 5 pages, 5 figure
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