2,532 research outputs found
Dynamics of Coherent States in Regular and Chaotic Regimes of the Non-integrable Dicke Model
The quantum dynamics of initial coherent states is studied in the Dicke model
and correlated with the dynamics, regular or chaotic, of their classical limit.
Analytical expressions for the survival probability, i.e. the probability of
finding the system in its initial state at time , are provided in the
regular regions of the model. The results for regular regimes are compared with
those of the chaotic ones. It is found that initial coherent states in regular
regions have a much longer equilibration time than those located in chaotic
regions. The properties of the distributions for the initial coherent states in
the Hamiltonian eigenbasis are also studied. It is found that for regular
states the components with no negligible contribution are organized in
sequences of energy levels distributed according to Gaussian functions. In the
case of chaotic coherent states, the energy components do not have a simple
structure and the number of participating energy levels is larger than in the
regular cases.Comment: Contribution to the proceedings of the Escuela Latinoamericana de
F\'isica (ELAF) Marcos Moshinsky 2017. (9 pages, 4 figures
Effects of Bacillus thuringiensis Cry Toxins on Developmental and Reproductive Characteristics of the Predator Orius albidipennis (Hemiptera: Anthocoridae) Under Laboratory Conditions
The effects of Cry toxins from Bacillus thuringiensis (Berliner) (Bt) on the anthocorid
Orius albidipennis Reuter were studied under laboratory conditions. Tritrophic experiments were
performed, in which Orius nymphs were fed Helicoverpa armigera (Hu¨bner) larvae reared on a diet
with Cry1Ac, Cry1Ab, or Cry2Ab toxins at different concentrations (0, 1, and 10 g/ml), when
supplemented with Ephestia kuehniella Zeller eggs. In complementary experiments, the Bt Cry1Ac
toxin was directly fed to Orius nymphs at a very high concentration (1 mg/ml). No effects on prey
consumption, developmental time, nymph survival, fecundity, and egg hatching of O. albidipennis
were found in either experiment. It can be concluded that the toxins tested do not seem to pose a risk
for the anthocorid O. albidipennis, especially when it is exposed through the pre
Optimization of curing cycle in carbon fiber-reinforced laminates: Void distribution and mechanical properties
A strategy is presented to optimize out-of-autoclave processing of quasi-isotropic carbon fiber-reinforced
laminates. Square panels of 4.6 mm nominal thickness with very low porosity Ă°6 0:2%Ăž were manufactured
by compression molding at low pressure (0.2 MPa) by careful design of the temperature cycle to
maximize the processing window. The mechanisms of void migration during processing were ascertained
by means of X-ray microtomography and the effect of ply clustering on porosity and on void shape was
explained. Finally, the effect of porosity and ply clustering on the compressive strength before and after
impact was studied
Nonlinear field theories during homogeneous spatial dilation
The effect of a uniform dilation of space on stochastically driven nonlinear
field theories is examined. This theoretical question serves as a model problem
for examining the properties of nonlinear field theories embedded in expanding
Euclidean Friedmann-Lema\^{\i}tre-Robertson-Walker metrics in the context of
cosmology, as well as different systems in the disciplines of statistical
mechanics and condensed matter physics. Field theories are characterized by the
speed at which they propagate correlations within themselves. We show that for
linear field theories correlations stop propagating if and only if the speed at
which the space dilates is higher than the speed at which correlations
propagate. The situation is in general different for nonlinear field theories.
In this case correlations might stop propagating even if the velocity at which
space dilates is lower than the velocity at which correlations propagate. In
particular, these results imply that it is not possible to characterize the
dynamics of a nonlinear field theory during homogeneous spatial dilation {\it a
priori}. We illustrate our findings with the nonlinear Kardar-Parisi-Zhang
equation
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