28,019 research outputs found
Static, massive fields and vacuum polarization potential in Rindler space
In Rindler space, we determine in terms of special functions the expression
of the static, massive scalar or vector field generated by a point source. We
find also an explicit integral expression of the induced electrostatic
potential resulting from the vacuum polarization due to an electric charge at
rest in the Rindler coordinates. For a weak acceleration, we give then an
approximate expression in the Fermi coordinates associated with the uniformly
accelerated observer.Comment: 11 pages, latex, no figure
The {\alpha}-Decay Chains of the Isotopes using Relativistic Mean Field Theory
We study the binding energy, root-mean-square radius and quadrupole
deformation parameter for the synthesized superheavy element Z = 115, within
the formalism of relativistic mean field theory. The calculation is dones for
various isotopes of Z = 115 element, starting from A = 272 to A = 292. A
systematic comparison between the binding energies and experimental data is
made.The calculated binding energies are in good agreement with experimental
result. The results show the prolate deformation for the ground state of these
nuclei. The most stable isotope is found to be 282115 nucleus (N = 167) in the
isotopic chain. We have also studied Q{\alpha} and T{\alpha} for the
{\alpha}-decay chains of 115.Comment: 12 Pages 6 Figures 3 Table
High-Dimensional Stochastic Design Optimization by Adaptive-Sparse Polynomial Dimensional Decomposition
This paper presents a novel adaptive-sparse polynomial dimensional
decomposition (PDD) method for stochastic design optimization of complex
systems. The method entails an adaptive-sparse PDD approximation of a
high-dimensional stochastic response for statistical moment and reliability
analyses; a novel integration of the adaptive-sparse PDD approximation and
score functions for estimating the first-order design sensitivities of the
statistical moments and failure probability; and standard gradient-based
optimization algorithms. New analytical formulae are presented for the design
sensitivities that are simultaneously determined along with the moments or the
failure probability. Numerical results stemming from mathematical functions
indicate that the new method provides more computationally efficient design
solutions than the existing methods. Finally, stochastic shape optimization of
a jet engine bracket with 79 variables was performed, demonstrating the power
of the new method to tackle practical engineering problems.Comment: 18 pages, 2 figures, to appear in Sparse Grids and
Applications--Stuttgart 2014, Lecture Notes in Computational Science and
Engineering 109, edited by J. Garcke and D. Pfl\"{u}ger, Springer
International Publishing, 201
Entropy Driven Dimerization in a One-Dimensional Spin-Orbital Model
We study a new version of the one-dimensional spin-orbital model with spins
S=1 relevant to cubic vanadates. At small Hund's coupling J_H we discover
dimerization in a pure electronic system solely due to a dynamical spin-orbital
coupling. Above a critical value J_H, a uniform ferromagnetic state is
stabilized at zero temperature. More surprisingly, we observe a temperature
driven dimerization of the ferrochain, which occurs due to a large entropy
released by dimer states. This dynamical dimerization seems to be the mechanism
driving the peculiar intermediate phase of YVO_3.Comment: 5 pages, 4 figure
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