29 research outputs found
A theory of -dissipative solvers for scalar conservation laws with discontinuous flux
We propose a general framework for the study of contractive semigroups
of solutions to conservation laws with discontinuous flux. Developing the ideas
of a number of preceding works we claim that the whole admissibility issue is
reduced to the selection of a family of "elementary solutions", which are
certain piecewise constant stationary weak solutions. We refer to such a family
as a "germ". It is well known that (CL) admits many different contractive
semigroups, some of which reflects different physical applications. We revisit
a number of the existing admissibility (or entropy) conditions and identify the
germs that underly these conditions. We devote specific attention to the
anishing viscosity" germ, which is a way to express the "-condition" of
Diehl. For any given germ, we formulate "germ-based" admissibility conditions
in the form of a trace condition on the flux discontinuity line (in the
spirit of Vol'pert) and in the form of a family of global entropy inequalities
(following Kruzhkov and Carrillo). We characterize those germs that lead to the
-contraction property for the associated admissible solutions. Our
approach offers a streamlined and unifying perspective on many of the known
entropy conditions, making it possible to recover earlier uniqueness results
under weaker conditions than before, and to provide new results for other less
studied problems. Several strategies for proving the existence of admissible
solutions are discussed, and existence results are given for fluxes satisfying
some additional conditions. These are based on convergence results either for
the vanishing viscosity method (with standard viscosity or with specific
viscosities "adapted" to the choice of a germ), or for specific germ-adapted
finite volume schemes
Charmed particle production in hadron-hadron collision
In the framework of Quark--Gluon--String Model developed recently in ITEP we
calculate spectra of charmed particles , , , ,
in hadron--hadron collisions taking into account the decays of
--wave resonances like , , , , ,
, and . We describe the bulk of the existing data on ,
, and production in and collisions and predict
the yield of charmed particles in and reactions at hyperon
beam energies of and . Because of significant
production of baryon resonances our predictions for unfavored fragmentation
differ from predictions of other models which do not take resonance production
into account.Comment: Latex,19 pages, 12figs. can be received by reques
Tau Polarization Asymmetry in
Rare decays provide an opportunity to probe for new physics beyond the
Standard Model. In this paper, we propose to measure the tau polarization in
the inclusive decay and discuss how it can be used, in
conjunction with other observables, to completely determine the parameters of
the flavor-changing low-energy effective Hamiltonian. Both the Standard Model
and several new physics scenarios are examined. This process has a large enough
branching fraction, , such that sufficient
statistics will be provided by the B-Factories currently under construction.Comment: 11 pages, LaTex file with psfig. Figures included via uufiles.
Lengthened version. Includes new calculation of Monte Carlo fit to Wilson
coefficient
K-Shell photodetachment of Liâ: Experiment and theory
We have measured the first and second moments of the hadronic mass-squared distribution in BâXclv, for Plepton>1.5 GeV/c. We find(MX 2âMD â2)= 0.251 ± 0.66 GeV2,((MX 2âMX 2)2)=0.576 ± 0.170 GeV4, where MÂŻ Dis the spin-averaged D meson mass. From that first moment and the first moment of the photon energy spectrum in bâs Îł, we find the heavy quark effective theory parameter λ1(in the modified minimal subtraction renormalization scheme, to order 1/MB 3and Îł0αs 2) to be â0.24±0.11GeV2. Using these first moments and the B semileptonic width, and assuming parton-hadron duality, we obtain|Vcb|=0.0404±0.0013
Improved upper limits on the flavor-changing neutral current decays BâKâ+â- and BâK*(892)â+â-
We have searched a sample of 9.6Ă106 BÂŻB events for the flavor-changing neutral current decays BâKâ+â- and BâK*(892)â+â-. We subject the latter decay to the requirement that the dilepton mass mââ exceed 0.5 GeV. There is no indication of a signal. We obtain the 90% confidence level upper limits B(BâKâ+â-) 0.5Gev0.5Gev < 1.5Ă10-6. The weighted-average limit is only 50% above the standard model prediction
Micromorphic vs. phase field approaches for gradient viscoplasticity and phase transformations
International audienceStrain gradient models and generalized continua are increasingly used to introduce characteristic lengths in the mechanical behavior of materials with microstructure. On the other hand, phase-field models have proved to be efficient tools to simulate microstructure evolution due to thermodynamical processes in the presence of mechanical deformation. It is shown that both methods have strong connections from the point of view of thermomechanical field theory. A general formulation of thermomechanics with additional degrees of freedom is presented that encompasses both applications as special cases. It is based on the introduction of additional power of internal forces introducing generalized stresses. The current knowledge in the formulation of physically non-linear constitutive equations is used to develop strongly coupled elastoviscoplastic material models involving phase transformation and moving boundaries