3,159 research outputs found
Nuclear Masses, Chaos, and the Residual Interaction
We interpret the discrepancy between semiempirical nuclear mass formulas and
actual nuclear masses in terms of the residual interaction. We show that
correlations exist among all binding energies and all separation energies
throughout the valley of stability. We relate our approach to chaotic motion in
nuclei.Comment: 9 page
Finite element optimizations for efficient non-linear electrical tomography reconstruction
Electrical Tomography can produce accurate results only if the underlying 2D or 3D volume discretization is chosen suitably for the applied numerical algorithm. We give general indications where and how to optimize a finite element discretization of a volume under investigation to enable efficient computation of potential distributions and the reconstruction of materials. For this, we present an error estimator and material-gradient indicator as a driver for adaptive mesh refinement and show how finite element mesh properties affect the efficiency and accuracy of the solutions
Spreading Widths of Doorway States
As a function of energy E, the average strength function S(E) of a doorway
state is commonly assumed to be Lorentzian in shape and characterized by two
parameters, the peak energy E_0 and the spreading width Gamma. The simple
picture is modified when the density of background states that couple to the
doorway state changes significantly in an energy interval of size Gamma. For
that case we derive an approximate analytical expression for S(E). We test our
result successfully against numerical simulations. Our result may have
important implications for shell--model calculations.Comment: 13 pages, 7 figure
Interaction of Regular and Chaotic States
Modelling the chaotic states in terms of the Gaussian Orthogonal Ensemble of
random matrices (GOE), we investigate the interaction of the GOE with regular
bound states. The eigenvalues of the latter may or may not be embedded in the
GOE spectrum. We derive a generalized form of the Pastur equation for the
average Green's function. We use that equation to study the average and the
variance of the shift of the regular states, their spreading width, and the
deformation of the GOE spectrum non-perturbatively. We compare our results with
various perturbative approaches.Comment: 26 pages, 9 figure
Shear Viscosity of Quark Matter
We consider the shear viscosity of a system of quarks and its ratio to the
entropy density above the critical temperature for deconfinement. Both
quantities are derived and computed for different modeling of the quark
self-energy, also allowing for a temperature dependence of the effective mass
and width. The behaviour of the viscosity and the entropy density is argued in
terms of the strength of the coupling and of the main characteristics of the
quark self-energy. A comparison with existing results is also discussed.Comment: 15 pages, 4 figure
On the modeling of neural cognition for social network applications
In this paper, we study neural cognition in social network. A stochastic
model is introduced and shown to incorporate two well-known models in Pavlovian
conditioning and social networks as special case, namely Rescorla-Wagner model
and Friedkin-Johnsen model. The interpretation and comparison of these model
are discussed. We consider two cases when the disturbance is independent
identical distributed for all time and when the distribution of the random
variable evolves according to a markov chain. We show that the systems for both
cases are mean square stable and the expectation of the states converges to
consensus.Comment: submitted to IEEE CCAT 201
Mesonic correlation functions at finite temperature and density in the Nambu-Jona-Lasinio model with a Polyakov loop
We investigate the properties of scalar and pseudo-scalar mesons at finite
temperature and quark chemical potential in the framework of the
Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with
the aim of taking into account features of both chiral symmetry breaking and
deconfinement. The mesonic correlators are obtained by solving the
Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field)
quark propagator at finite temperature and density. In the phase of broken
chiral symmetry a narrower width for the sigma meson is obtained with respect
to the NJL case; on the other hand, the pion still behaves as a Goldstone
boson. When chiral symmetry is restored, the pion and sigma spectral functions
tend to merge. The Mott temperature for the pion is also computed.Comment: 24 pages, 9 figures, version to appear in Phys. Rev.
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