9,306 research outputs found
Non-Markovian generalization of the Lindblad theory of open quantum systems
A systematic approach to the non-Markovian quantum dynamics of open systems
is given by the projection operator techniques of nonequilibrium statistical
mechanics. Combining these methods with concepts from quantum information
theory and from the theory of positive maps, we derive a class of correlated
projection superoperators that take into account in an efficient way
statistical correlations between the open system and its environment. The
result is used to develop a generalization of the Lindblad theory to the regime
of highly non-Markovian quantum processes in structured environments.Comment: 10 pages, 1 figure, replaced by published versio
Final excitation energy of fission fragments
We study how the excitation energy of the fully accelerated fission fragments
is built up. It is stressed that only the intrinsic excitation energy available
before scission can be exchanged between the fission fragments to achieve
thermal equilibrium. This is in contradiction with most models used to
calculate prompt neutron emission where it is assumed that the total excitation
energy of the final fragments is shared between the fragments by the condition
of equal temperatures. We also study the intrinsic excitation-energy partition
according to a level density description with a transition from a
constant-temperature regime to a Fermi-gas regime. Complete or partial
excitation-energy sorting is found at energies well above the transition
energy.Comment: 8 pages, 3 figure
Energy and momentum deposited into a QCD medium by a jet shower
Hard partons moving through a dense QCD medium lose energy by radiative
emissions and elastic scatterings. Deposition of the radiative contribution
into the medium requires rescattering of the radiated gluons. We compute the
total energy loss and its deposition into the medium self-consistently within
the same formalism, assuming perturbative interaction between probe and medium.
The same transport coefficients that control energy loss of the hard parton
determine how the energy is deposited into the medium; this allows a parameter
free calculation of the latter once the former have been computed or extracted
from experimental energy loss data. We compute them for a perturbative medium
in hard thermal loop (HTL) approximation. Assuming that the deposited
energy-momentum is equilibrated after a short relaxation time, we compute the
medium's hydrodynamical response and obtain a conical pattern that is strongly
enhanced by showering.Comment: 4 pages, 3 figures, revtex4, intro modified, typos correcte
Stability of atoms and molecules in an ultrarelativistic Thomas-Fermi-Weizsaecker model
We consider the zero mass limit of a relativistic Thomas-Fermi-Weizsaecker
model of atoms and molecules. We find bounds for the critical nuclear charges
that ensure stability.Comment: 8 pages, LaTe
Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions
Recently reported transverse momentum distributions of strange hadrons
produced in Pb(158AGeV) on Pb collisions and corresponding results from the
relativistic quantum molecular dynamics (RQMD) approach are examined. We argue
that the experimental observations favor a scenario in which multi-strange
hadrons are formed and decouple from the system rather early at large energy
densities (around 1 GeV/fm). The systematics of the strange and non-strange
particle spectra indicate that the observed transverse flow develops mainly in
the late hadronic stages of these reactions.Comment: 4 pages, 4 figure
Lattice Gauge Description of Colliding Nuclei
We propose a novel formalism for simultaneously describing both, the hard and
soft parton dynamics in ultrarelativistic collisions of nuclei. The emission of
gluons from the initially coherent parton configurations of the colliding
nuclei and low- color coherence effects are treated in the framework of a
Yang-Mills transport equation on a coupled lattice-particle system. A collision
term is added to the transport equation to account for the remaining
intermediate and high- interactions in an infrared finite manner.Comment: 8 page
Entropy production by resonance decays
We investigate entropy production for an expanding system of particles and
resonances with isospin symmetry -- in our case pions and mesons --
within the framework of relativistic kinetic theory. A cascade code to simulate
the kinetic equations is developed and results for entropy production and
particle spectra are presented.Comment: 17 pages, 10 ps-figures included, only change: preprint number adde
Fluctuations of particle ratios and the abundance of hadronic resonances
In this letter we will argue that the event-by-event fluctuations of the
ratio of positively over negatively charged pions provides a measurements of
the number of rho and omega mesons right after hadronization. This finding can
be utilized to put the hypothesis of chemical equilibration in relativistic
heavy ion collisions to a test.Comment: 4 pages. No figure. Uses revtex with prl, aps, and multicol style
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