4,332 research outputs found
Nonperturbative aspects of the QCD analytic invariant charge
In the framework of the analytic approach to Quantum Chromodynamics a new
model for the strong running coupling has recently been developed. Its
underlying idea is to impose the analyticity requirement on the perturbative
expansion of the renormalization group function for restoring the
correct analytic properties of the latter. The proposed model possesses a
number of appealing features. Namely, the analytic invariant charge has no
unphysical singularities at any loop level; it contains no free parameters; it
has universal behavior both in ultraviolet and infrared regions at any loop
level; and it possesses a fair higher loop and scheme stability. The extension
of this model to the timelike region revealed the asymmetrical behavior of the
running coupling in the intermediate- and low-energy domains of spacelike and
timelike regions, that is essential when one handles the experimental data. The
developed approach enables one to describe, in a consistent way, various strong
interaction processes both of perturbative and intrinsically nonperturbative
nature.Comment: Talk given at Tenth International QCD Conference (QCD 03), 2 - 9 July
2003, Montpellier, France; LaTeX2e, 4 pages, 4 EPS figure
Scattering of solitary waves in granular media
A detailed numerical study of the scattering of solitary waves by a barrier,
in a granular media with Hertzian contact, shows the existence of secondary
multipulse structures generated at the interface of two "sonic vacua", which
have a similar structure as the one previously found by Nesterenko and
coworkers.Comment: 4 pages, 9 figures (fig 5, replaced). Submitted to PR
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
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