4 research outputs found
Reaction-diffusion processes in zero transverse dimensions as toy models for high-energy QCD
We examine numerically different zero-dimensional reaction-diffusion
processes as candidate toy models for high-energy QCD evolution. Of the models
examined -- Reggeon Field Theory, Directed Percolation and Reversible Processes
-- only the latter shows the behaviour commonly expected, namely an increase of
the scattering amplitude with increasing rapidity. Further, we find that
increasing recombination terms, quantum loops and the heuristic inclusion of a
running of the couplings, generically slow down the evolution.Comment: 17 pages, 7 figure
Long Range Hops and the Pair Annihilation Reaction A+A->0: Renormalization Group and Simulation
A simple example of a non-equilibrium system for which fluctuations are
important is a system of particles which diffuse and may annihilate in pairs on
contact. The renormalization group can be used to calculate the time dependence
of the density of particles, and provides both an exact value for the exponent
governing the decay of particles and an epsilon-expansion for the amplitude of
this power law. When the diffusion is anomalous, as when the particles perform
Levy flights, the critical dimension depends continuously on the control
parameter for the Levy distribution. The epsilon-expansion can then become an
expansion in a small parameter. We present a renormalization group calculation
and compare these results with those of a simulation.Comment: As-published version; two significant errors fixed, two references
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Tilt Modulus and Angle-Dependent Flux Lattice Melting in the Lowest Landau Level Approximation
For a clean high-T superconductor, we analyze the Lawrence-Doniach free
energy in a tilted magnetic field within the lowest Landau level (LLL)
approximation. The free energy maps onto that of a strictly -axis field, but
with a reduced interlayer coupling. We use this result to calculate the tilt
modulus of a vortex lattice and vortex liquid. The vortex contribution
to can be expressed in terms of the squared -axis Josephson plasmon
frequency . The transverse component of the field has very
little effect on the position of the melting curve.Comment: 8 pages, 2 figures, accepted for publication in Physical Review B
(Rapid Communications