779 research outputs found
New analytic running coupling in QCD: higher loop levels
The properties of the new analytic running coupling are investigated at the
higher loop levels. The expression for this invariant charge, independent of
the normalization point, is obtained by invoking the asymptotic freedom
condition. It is shown that at any loop level the relevant function has
the universal behaviors at small and large values of the invariant charge. Due
to this feature the new analytic running coupling possesses the universal
asymptotics both in the ultraviolet and infrared regions irrespective of the
loop level. The consistency of the model considered with the general definition
of the QCD invariant charge is shown.Comment: LaTeX 2.09, 12 pages with 5 EPS figures, uses mpla1.sty; enlarged
version is accepted for publication in Mod. Phys. Lett.
Anomalous wave reflection from the interface of two strongly nonlinear granular media
Granular materials exhibit a strongly nonlinear behaviour affecting the
propagation of information in the medium. Dynamically self-organized strongly
nonlinear solitary waves are the main information carriers in granular chains.
Here we report the first experimental observation of the dramatic change of
reflectivity from the interface of two granular media triggered by a noncontact
magnetically induced initial precompression. It may be appropriate to name this
phenomenon the "acoustic diode" effect. Based on numerical simulations, we
explain this effect by the high gradient of particle velocity near the
interface.Comment: 14 pages, 3 figure
Boundary conditions at spatial infinity for fields in Casimir calculations
The importance of imposing proper boundary conditions for fields at spatial
infinity in the Casimir calculations is elucidated.Comment: 8 pages, 1 figure, submitted to the Proceedings of The Seventh
Workshop QFEXT'05 (Barcelona, September 5-9, 2005
Extended analytic QCD model with perturbative QCD behavior at high momenta
In contrast to perturbative QCD, the analytic QCD models have running
coupling whose analytic properties correctly mirror those of spacelike
observables. The discontinuity (spectral) function of such running coupling is
expected to agree with the perturbative case at large timelike momenta;
however, at low timelike momenta it is not known. In the latter regime, we
parametrize the unknown behavior of the spectral function as a sum of (two)
delta functions; while the onset of the perturbative behavior of the spectral
function is set to be 1.0-1.5 GeV. This is in close analogy with the "minimal
hadronic ansatz" used in the literature for modeling spectral functions of
correlators. For the running coupling itself, we impose the condition that it
basically merges with the perturbative coupling at high spacelike momenta. In
addition, we require that the well-measured nonstrange semihadronic (V+A) tau
decay ratio value be reproduced by the model. We thus obtain a QCD framework
which is basically indistinguishable from perturbative QCD at high momenta (Q >
1 GeV), and at low momenta it respects the basic analyticity properties of
spacelike observables as dictated by the general principles of the local
quantum field theories.Comment: 15 pages, 6 figures; in v2 Sec.IV is extended after Eq.(48) and
refs.[51-52] added; v2 published in Phys.Rev.D85,114043(2012
Self-Consistent Separable Rpa Approach for Skyrme Forces: Axial Nuclei
The self-consistent separable RPA (random phase approximation) method is
formulated for Skyrme forces with pairing. The method is based on a general
self-consistent procedure for factorization of the two-body interaction. It is
relevant for various density- and current-dependent functionals. The
contributions of the time-even and time-odd Skyrme terms as well as of the
Coulomb and pairing terms to the residual interaction are taken
self-consistently into account. Most of the expression have a transparent
analytical form, which makes the method convenient for the treatment and
analysis. The separable character of the residual interaction allows to avoid
diagonalization of high-rank RPA matrices and thus to minimize the calculation
effort. The previous studies have demonstrated high numerical accuracy and
efficiency of the method for spherical nuclei. In this contribution, the method
is specified for axial nuclei. We provide systematic and detailed presentation
of formalism and discuss different aspects of the model.Comment: 42 page
Observation of the novel type of ordering: Spontaneous ferriquadrupolar order
Using Raman and infrared spectroscopies the spontaneous ferriquadrupolar
ordering has been observed in the rare-earth-based system KDy(MoO).
Ordered quadrupoles in the electron subsystem attend non-equivalent distortions
of rare-earth ions in the ordered phase. The mean field theory explaining the
onset of such a type of ordering has been constructed.Comment: 6 pages, 4 figure
How Hertzian solitary waves interact with boundaries in a 1-D granular medium
We perform measurements, numerical simulations, and quantitative comparisons
with available theory on solitary wave propagation in a linear chain of beads
without static preconstrain. By designing a nonintrusive force sensor to
measure the impulse as it propagates along the chain, we study the solitary
wave reflection at a wall. We show that the main features of solitary wave
reflection depend on wall mechanical properties. Since previous studies on
solitary waves have been performed at walls without these considerations, our
experiment provides a more reliable tool to characterize solitary wave
propagation. We find, for the first time, precise quantitative agreements.Comment: Proof corrections, ReVTeX, 11 pages, 3 eps (Focus and related papers
on http://www.supmeca.fr/perso/jobs/
An elementary proof of the irrationality of Tschakaloff series
We present a new proof of the irrationality of values of the series
in both qualitative and
quantitative forms. The proof is based on a hypergeometric construction of
rational approximations to .Comment: 5 pages, AMSTe
Deformation effects in Giant Monopole Resonance
The isoscalar giant monopole resonance (GMR) in Samarium isotopes (from
spherical Sm to deformed Sm) is investigated within the
Skyrme random-phase-approximation (RPA) for a variety of Skyrme forces. The
exact RPA and its separable version (SRPA) are used for spherical and deformed
nuclei, respectively. The quadrupole deformation is shown to yield two effects:
the GMR broadens and attains a two-peak structure due to the coupling with the
quadrupole giant resonance.Comment: 6 pages, 4 figures, proceedings of 11th Intern. Spring Seminar on
Nuclear Physics (Ischia, Italy, May 12-16, 2014
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