751 research outputs found
Monte Carlo simulation for radiative kaon decays
For high precision measurements of K decays, the presence of radiated photons
cannot be neglected. The Monte Carlo simulations must include the radiative
corrections in order to compute the correct event counting and efficiency
calculations. In this paper we briefly describe a method for simulating such
decays.Comment: 11 pages, 1 figur
Non-extensive resonant reaction rates in astrophysical plasmas
We study two different physical scenarios of thermonuclear reactions in
stellar plasmas proceeding through a narrow resonance at low energy or through
the low energy wing of a wide resonance at high energy. Correspondingly, we
derive two approximate analytical formulae in order to calculate thermonuclear
resonant reaction rates inside very coupled and non ideal astrophysical plasmas
in which non-extensive effects are likely to arise. Our results are presented
as simple first order corrective factors that generalize the well known
classical rates obtained in the framework of Maxwell-Boltzmann statistical
mechanics. As a possible application of our results, we calculate the
dependence of the total corrective factor with respect to the energy at which
the resonance is located, in an extremely dense and non ideal carbon plasma.Comment: 5 pages, 1 figur
Full separability criterion for tripartite quantum systems
In this paper, an intuitive approach is employed to generalize the full
separability criterion of tripartite quantum states of qubits to the
higher-dimensional systems (Phys. Rev. A \textbf{72}, 022333 (2005)). A
distinct characteristic of the present generalization is that less restrictive
conditions are needed to characterize the properties of full separability.
Furthermore, the formulation for pure states can be conveniently extended to
the case of mixed states by utilizing the kronecker product approximate
technique. As applications, we give the analytic approximation of the criterion
for weakly mixed tripartite quantum states and investigate the full
separability of some weakly mixed states.Comment: 5 pages. To be published in Europ. J.
Evolution of coupled fermions under the influence of an external axial-vector field
The evolution of coupled fermions interacting with external axial-vector
fields is described with help of the classical field theory. We formulate the
initial conditions problem for the system of two coupled fermions in
(3+1)-dimensional space-time. This problem is solved using the perturbation
theory. We obtain in the explicit form the expressions for the leading and next
to the leading order terms in the expansion over the strength of external
fields. It is shown that in the relativistic limit the intensity of the fermion
field coincides with the transition probability in the two neutrinos system
interacting with moving and polarized matter.Comment: RevTeX4, 8 pages, 1 eps figure; revised variant, neutral currents
interactions of flavor neutrinos are included, some typos corrected, 1
reference added; accepted for publication in Eur.Phys.J.
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Modulational instabilities in Josephson oscillations of elongated coupled condensates
We study the Josephson oscillations of two coupled elongated condensates.
Linearized calculations show that the oscillating mode uniform over the length
of the condensates (uniform Josephson mode) is unstable : modes of non zero
longitudinal momentum grow exponentially. In the limit of strong atom
interactions, we give scaling laws for the instability time constant and
unstable wave vectors. Beyond the linearized approach, numerical calculations
show a damped recurrence behavior : the energy in the Josephson mode presents
damped oscillations. Finally, we derive conditions on the confinement of the
condensates to prevent instabilities
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