129 research outputs found
Phase Transition in Strongly Degenerate Hydrogen Plasma
Direct fermionic path-integral Monte-Carlo simulations of strongly coupled
hydrogen are presented. Our results show evidence for the hypothetical plasma
phase transition. Its most remarkable manifestation is the appearance of
metallic droplets which are predicted to be crucial for the electrical
conductivity allowing to explain the rapid increase observed in recent shock
compression measurments.Comment: 1 LaTeX file using jetpl.cls (included), 5 ps figures. Manuscript
submitted to JETP Letter
Interacting electrons in a one-dimensional random array of scatterers - A Quantum Dynamics and Monte-Carlo study
The quantum dynamics of an ensemble of interacting electrons in an array of
random scatterers is treated using a new numerical approach for the calculation
of average values of quantum operators and time correlation functions in the
Wigner representation. The Fourier transform of the product of matrix elements
of the dynamic propagators obeys an integral Wigner-Liouville-type equation.
Initial conditions for this equation are given by the Fourier transform of the
Wiener path integral representation of the matrix elements of the propagators
at the chosen initial times. This approach combines both molecular dynamics and
Monte Carlo methods and computes numerical traces and spectra of the relevant
dynamical quantities such as momentum-momentum correlation functions and
spatial dispersions. Considering as an application a system with fixed
scatterers, the results clearly demonstrate that the many-particle interaction
between the electrons leads to an enhancement of the conductivity and spatial
dispersion compared to the noninteracting case.Comment: 10 pages and 8 figures, to appear in PRB April 1
Hole crystallization in semiconductors
When electrons in a solid are excited to a higher energy band they leave
behind a vacancy (hole) in the original band which behaves like a positively
charged particle. Here we predict that holes can spontaneously order into a
regular lattice in semiconductors with sufficiently flat valence bands. The
critical hole to electron effective mass ratio required for this phase
transition is found to be of the order of 80.Comment: accepted for publication in J. Phys. A: Math. Ge
Quantum simulations of strongly coupled quark-gluon plasma
A strongly coupled quark-gluon plasma (QGP) of heavy constituent
quasiparticles is studied by a path-integral Monte-Carlo method, which improves
the corresponding classical simulations by extending them to the quantum
regime. It is shown that this method is able to reproduce the lattice equation
of state and also yields valuable insight into the internal structure of the
QGP. The results indicate that the QGP reveals liquid-like rather than gas-like
properties. At temperatures just above the critical one it was found that bound
quark-antiquark states still survive. These states are bound by effective
string-like forces. Quantum effects turned out to be of prime importance in
these simulations.Comment: 8 pages, 10 figures, revised version of the contribution to
proceedings of "Int. Workshop on High Density Nuclear Matter", Cape Town,
5-10 Apr., 201
Thermodynamics of hot dense H-plasmas: Path integral Monte Carlo simulations and analytical approximations
This work is devoted to the thermodynamics of high-temperature dense hydrogen
plasmas in the pressure region between and Mbar. In particular
we present for this region results of extensive calculations based on a
recently developed path integral Monte Carlo scheme (direct PIMC). This method
allows for a correct treatment of the thermodynamic properties of hot dense
Coulomb systems. Calculations were performed in a broad region of the
nonideality parameter and degeneracy parameter . We give a comparison with a few available results from
other path integral calculations (restricted PIMC) and with analytical
calculations based on Pade approximations for strongly ionized plasmas. Good
agreement between the results obtained from the three independent methods is
found.Comment: RevTex file, 21 pages, 5 ps-figures include
Thermodynamic Properties of Correlated Strongly Degenerate Plasmas
An efficient numerical approach to equilibrium properties of strongly coupled
systems which include a subsystem of fermionic quantum particles and a
subsystem of classical particles is presented. It uses an improved path
integral representation of the many-particle density operator and allows to
describe situations of strong coupling and strong degeneracy, where analytical
theories fail. A novel numerical method is developed, which allows to treat
degenerate systems with full account of the spin scatistics. Numerical results
for thermodynamic properties such as internal energy, pressure and pair
correlation functions are presented over a wide range of degeneracy parameter.Comment: 8 pages, 4 figures, uses sprocl.sty (included) to be published in
"Progress in Nonequilibrium Green's functions", M. Bonitz (Ed.), World
Scientific 200
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