21 research outputs found
Transport theory with nonlocal corrections
A kinetic equation which combines the quasiparticle drift of Landau's
equation with a dissipation governed by a nonlocal and noninstant scattering
integral in the spirit of Snider's equation for gases is derived. Consequent
balance equations for the density, momentum and energy include quasiparticle
contributions and the second order quantum virial corrections and are proven to
be consistent with conservation laws.Comment: Proceedings of the 8th International Workshop on Atomic Physics for
Ion-Driven Fusion, Heidelberg 1997, appear in Laser and Particle Beam
Nonlocal kinetic theory
The short time behavior of a disturbed system is influenced by off-shell
motion and best characterized by the reduced density matrix possessing high
energetic tails. We present analytically the formation of correlations due to
collisions in an interacting Fermionic system with and without initial
correlation. After this short time regime the time evolution is controlled by
small gradients. This leads to a nonlocal Boltzmann equation for the
quasiparticle distribution and a functional relating the latter one to the
reduced density matrix. The nonlocalities are presented as time and space
shifts arising from gradient expansion and are leading to virial corrections in
the thermodynamical limit.Comment: Proceedings KB99 Workshop, September 20-24 1999, Rostock, German
Duration and non-locality of a nucleon-nucleon collision
For a set of realistic nucleon-nucleon potentials we evaluate microscopic
parameters of binary collisions: a time duration of the scattering state, a
mean distance and a rotation of nucleons during a collision. These parameters
enter the kinetic equation as non-instantaneous and non-local corrections of
the scattering integral, i.e., they can be experimentally tested. Being
proportional to off-shell derivatives of the scattering T-matrix,
non-instantaneous and non-local corrections make it possible to compare the
off-shell behavior of different potentials in a vicinity of the energy shell.
The Bonn one-Boson-exchange (A-C) and Paris potentials are found to yield very
close results, while the separable Paris potential differs.Comment: Phys. Rev. C su
Formation of correlations in strongly coupled plasmas
The formation of binary correlations in plasma is studied from the quantum
kinetic equation. It is shown that this formation is much faster than
dissipation due to collisions. In a hot (dense) plasma the correlations are
formed on the scale of inverse plasma frequency (Fermi energy). We derive
analytical formulae for the time dependency of the potential energy which
measures the extent of correlations. We discuss the dynamical formation of
screening and compare with the statical screened result. Comparisons are made
with molecular dynamic simulations.Comment: Proceedings of the 8th International Workshop on Atomic Physics for
Ion-Driven Fusion, Heidelberg 1997, appear in Laser and Particle Beam
Retarded versus time-nonlocal quantum kinetic equations
The finite duration of the collisions in Fermionic systems as expressed by
the retardation time in non-Markovian Levinson-type kinetic equations is
discussed in the quasiclassical limit. We separate individual contributions
included in the memory effect resulting in (i) off-shell tails of the Wigner
distribution, (ii) renormalization of scattering rates and (iii) of the
single-particle energy, (iv) collision delay and (v) related non-local
corrections to the scattering integral. In this way we transform the Levinson
equation into the Landau-Silin equation extended by the non-local corrections
known from the theory of dense gases. The derived nonlocal kinetic equation
unifies the Landau theory of quasiparticle transport with the classical kinetic
theory of dense gases. The space-time symmetry is discussed versus
particle-hole symmetry and a solution is proposed which transforms these two
exclusive pictures into each other.Comment: slightly revised, 19 page
LIME: A New Membrane Raft-associated Adaptor Protein Involved in CD4 and CD8 Coreceptor Signaling
Lymphocyte membrane rafts contain molecules critical for immunoreceptor signaling. Here, we report identification of a new raft-associated adaptor protein LIME (Lck-interacting molecule) expressed predominantly in T lymphocytes. LIME becomes tyrosine phosphorylated after cross-linking of the CD4 or CD8 coreceptors. Phospho-LIME associates with the Src family kinase Lck and its negative regulator, Csk. Ectopic expression of LIME in Jurkat T cells results in an increase of Csk in lipid rafts, increased phosphorylation of Lck and higher Ca2+ response to CD3 stimulation. Thus, LIME appears to be involved in regulation of T cell activation by coreceptors
Space-time versus particle-hole symmetry in quantum Enskog equations
The non-local scattering-in and -out integrals of the Enskog equation have
reversed displacements of colliding particles reflecting that the -in and -out
processes are conjugated by the space and time inversions. Generalisations of
the Enskog equation to Fermi liquid systems are hindered by a request of the
particle-hole symmetry which contradicts the reversed displacements. We resolve
this problem with the help of the optical theorem. It is found that space-time
and particle-hole symmetry can only be fulfilled simultaneously for the
Bruckner-type of internal Pauli-blocking while the Feynman-Galitskii form
allows only for particle-hole symmetry but not for space-time symmetry due to a
stimulated emission of Bosons