1,496 research outputs found
Finite-Temperature Gluon Condensate with Renormalization Group Flow Equations
Within a self-consistent proper-time Renormalization Group (RG) approach we
investigate an effective QCD trace anomaly realization with dilatons and
determine the finite-temperature behavior of the gluon condensate. Fixing the
effective model at vanishing temperature to the glueball mass and the bag
constant a possible gluonic phase transition is explored in detail. Within the
RG framework the full non-truncated dilaton potential analysis is compared with
a truncated potential version.Comment: 22 pages, 11 figures, LaTeX2e; revised version accepted for
publication in Phys. Rev.
Model of molecular bonding based on the Bohr-Sommerfeld picture of atoms
We develop a model of molecular binding based on the Bohr-Sommerfeld
description of atoms together with a constraint taken from conventional quantum
mechanics. The model can describe the binding energy curves of H2, H3 and other
molecules with striking accuracy. Our approach treats electrons as point
particles with positions determined by extrema of an algebraic energy function.
Our constrained model provides a physically appealing, accurate description of
multi-electron chemical bonds.Comment: 5 pages, 7 figures, to appear in Physics Letters
Electron correlations in two-dimensional small quantum dots
We consider circular and elliptic quantum dots with parabolic external
confinement, containing 0 - 22 electrons and with values of r_s in the range 0
< r_s < 3. We perform restricted and unrestricted Hartree-Fock calculations,
and further take into account electron correlations using second-order
perturbation theory. We demonstrate that in many cases correlations
qualitatively change the spin structure of the ground state from that obtained
under Hartree-Fock and spin-density-functional calculations. In some cases the
correlation effects destroy Hund's rule. We also demonstrate that the
correlations destroy static spin-density waves observed in Hartree-Fock and
spin-density-functional calculations.Comment: 11 pages, 9 figures. This replacement contains new content. Results
have been recalculated for dots with zero effective thickness (true 2D). For
6 electrons, results have been compared with configuration interaction
results from the literatur
The Friedrichs-Model with fermion-boson couplings II
In this work we present a formal solution of the extended version of the
Friedrichs Model. The Hamiltonian consists of discrete and continuum bosonic
states, which are coupled to fermions. The simultaneous treatment of the
couplings of the fermions with the discrete and continuous sectors of the
bosonic degrees of freedom leads to a system of coupled equations, whose
solutions are found by applying standard methods of representation of bound and
resonant states.Comment: 13 page
A simple and surprisingly accurate approach to the chemical bond obtained from dimensional scaling
We present a new dimensional scaling transformation of the Schrodinger
equation for the two electron bond. This yields, for the first time, a good
description of the two electron bond via D-scaling. There also emerges, in the
large-D limit, an intuitively appealing semiclassical picture, akin to a
molecular model proposed by Niels Bohr in 1913. In this limit, the electrons
are confined to specific orbits in the scaled space, yet the uncertainty
principle is maintained because the scaling leaves invariant the
position-momentum commutator. A first-order perturbation correction,
proportional to 1/D, substantially improves the agreement with the exact ground
state potential energy curve. The present treatment is very simple
mathematically, yet provides a strikingly accurate description of the potential
energy curves for the lowest singlet, triplet and excited states of H_2. We
find the modified D-scaling method also gives good results for other molecules.
It can be combined advantageously with Hartree-Fock and other conventional
methods.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Letter
Effects due to Resonant and Continuum States on the Neutrino-Nucleus Cross Section
Estimates of the neutrino-nucleus cross section, for the charged-current
process nu+208Pb-> e+208Bi, are presented. The nuclear structure calculations
have been performed by considering bound, resonant, and continuum states in the
single-particle basis used to construct correlated proton-particle neutron-hole
configurations. The observed features of the spectrum of 208Bi have been
reproduced, as accurately as possible, by diagonalizing a phenomenological
multipole-multipole interaction. Calculations of the cross section, for values
of q 200 $ MeV, were performed, and the dependence of the results upon the
choice of the residual proton-neutron interaction was investigated. It is found
that the inclusion of resonant states in the calculation of the nuclear wave
functions increases the neutrino-nucleus cross section, and that the
contribution of the continuum is negligible.Comment: 15 pages, 6 figures, 2 tables, 39 references. submitted to Physical
Review
Two-proton radioactivity and three-body decay. IV. Connection to quasiclassical formulation
We derive quasiclassical expressions for the three-body decay width and
define the ``preexponential'' coefficients for them. The derivation is based on
the integral formulae for the three-body width obtained in the semianalytical
approach with simplified three-body Hamiltonian [L.V. Grigorenko and M.V.\
Zhukov, arXiv:0704.0920v1]. The model is applied to the decays of the first
excited state of Ne and ground state of Fe.
Various qualitative aspects of the model and relations with the other
simplified approaches to the three-body decays are discussed.Comment: 9 Pages, 2 figure
Nuclear shape dependence of Gamow-Teller distributions in neutron-deficient Pb isotopes
We study Gamow-Teller strength distributions in the neutron-deficient even
isotopes (184-194)Pb in a search for signatures of deformation. The microscopic
formalism used is based on a deformed quasiparticle random phase approximation
(QRPA) approach, which involves a self-consistent quasiparticle deformed Skyrme
Hartree-Fock (HF) basis and residual spin-isospin forces in both the
particle-hole and particle-particle channels. By analyzing the sensitivity of
the Gamow-Teller strength distributions to the various ingredients in the
formalism, we conclude that the beta-decay of these isotopes could be a useful
tool to look for fingerprints of nuclear deformation.Comment: 20 pages, 11 figures. To be published in Physical Review
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