2,336 research outputs found
The electromagnetic self-force on a charged spherical body slowly undergoing a small, temporary displacement from a position of rest
The self-force of classical electrodynamics on a charged "rigid" body of
radius R is evaluated analytically for the body undergoing a slow (i.e., with a
speed v<<c), slight (i.e., small compared to R), and temporary displacement
from an initial position of rest. The results are relevant to the
Bohr-Rosenfeld analysis of the measurability of the electromagnetic field,
which has been the subject of a recent controversy.Comment: REVTeX, 15 pages, 3 figures, accepted by J. Phys.
Comment on 'Self-dressing and radiation reaction in classical electrodynamics'
Using the canonical formalism, Compagno and Persico [J. Phys. A: Math. Gen.
35 (2002) 3629--45] have calculated the 'radiation-reaction' force on a uniform
spherical charge moving rigidly, slowly and slightly from its position at the
time when the transverse electric field is assumed to vanish. This force is
shown to result in the same time-averaged self-force as that which has been
obtained by different means for the test charge of a Bohr--Rosenfeld
field-measurement procedure and which Compagno and Persico claimed to be
incorrect.Comment: REVTeX, 4 pages; this version has some cosmetic changes to agree
fully with the published version. Reply to this Comment is in G. Compagno and
F. Persico, J. Phys. A: Math. Gen. 35, 8965 (2002); response to the Reply is
in physics/021005
Fission Decay Widths for Heavy-Ion Fusion-Fission Reactions
Cross-section and neutron-emission data from heavy-ion fusion-fission
reactions are consistent with a Kramers-modified statistical model which takes
into account the collective motion of the system about the ground state; the
temperature dependence of the location of fission transition points; and the
orientation degree of freedom. We see no evidence to suggest that the nuclear
viscosity departs from the surface-plus-window dissipation model. The strong
increase in the nuclear viscosity above a temperature of ~1 MeV deduced by
others is an artifact generated by an inadequate fission model.Comment: 14 pg, 6 fig, submitted to Physical Revie
Distribution of occupation numbers in finite Fermi-systems and role of interaction in chaos and thermalization
New method is developed for calculation of single-particle occupation numbers
in finite Fermi systems of interacting particles. It is more accurate than the
canonical distribution method and gives the Fermi-Dirac distribution in the
limit of large number of particles. It is shown that statistical effects of the
interaction are absorbed by an increase of the effective temperature. Criteria
for quantum chaos and statistical equilibrium are considered. All results are
confirmed by numerical experiments in the two-body random interaction model.Comment: 4 pages, Latex, 4 figures in the form of PS-file
Two-phonon -vibrational states in rotating triaxial odd- nuclei
Distribution of the two phonon vibrational collectivity in the
rotating triaxial odd- nucleus, Nb, that is one of the three
nuclides for which experimental data were reported recently, is calculated in
the framework of the particle vibration coupling model based on the cranked
shell model plus random phase approximation. This framework was previously
utilized for analyses of the zero and one phonon bands in other mass region and
is applied to the two phonon band for the first time. In the present
calculation, three sequences of two phonon bands share collectivity almost
equally at finite rotation whereas the state is the purest at zero
rotation.Comment: 15 pages, 3 figures, accepted for publication in Physical Review
Geometric factors in the Bohr--Rosenfeld analysis of the measurability of the electromagnetic field
The Geometric factors in the field commutators and spring constants of the
measurement devices in the famous analysis of the measurability of the
electromagnetic field by Bohr and Rosenfeld are calculated using a
Fourier--Bessel method for the evaluation of folding integrals, which enables
one to obtain the general geometric factors as a Fourier--Bessel series. When
the space region over which the factors are defined are spherical, the
Fourier--Bessel series terms are given by elementary functions, and using the
standard Fourier-integral method of calculating folding integrals, the
geometric factors can be evaluated in terms of manageable closed-form
expressions.Comment: 21 pages, REVTe
Quadrupole collective variables in the natural Cartan-Weyl basis
The matrix elements of the quadrupole collective variables, emerging from
collective nuclear models, are calculated in the natural Cartan-Weyl basis of
O(5) which is a subgroup of a covering structure. Making
use of an intermediate set method, explicit expressions of the matrix elements
are obtained in a pure algebraic way, fixing the -rotational structure
of collective quadrupole models.Comment: submitted to Journal of Physics
On the area operators of the Husain-Kuchar-Rovelli model and Canonical/Loop Quantum Gravity
I investigate the relation between an operative definition of the area of a
surface specified by matter fields and the area operators recently introduced
in the canonical/loop approach to Quantum Gravity and in Rovelli's variant of
the Husain-Kuchar Quantum-Gravity toy model. The results suggest that the
discreteness of the spectra of the area operators might not be observable.Comment: LaTex, 8 page
Exponential increase of energy level density in atoms: Th and Th II
We present analytical estimates and numerical calculations showing that the
energy level density in open-shell atoms increases exponentially with increase
of excitation energy. As an example, we use the relativistic Hartree-Fock and
configuration interaction methods to calculate the density of states of Th and
Th II. The result is used to estimate the effect of electrons on the nuclear
transition which is considered for the use in a nuclear clock.Comment: 4 pages, 1 figure, 3 tables
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
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