146 research outputs found
Light nuclei quasiparticle energy shift in hot and dense nuclear matter
Nuclei in dense matter are influenced by the medium. In the cluster mean
field approximation, an effective Schr\"odinger equation for the -particle
cluster is obtained accounting for the effects of the correlated medium such as
self-energy, Pauli blocking and Bose enhancement. Similar to the single-baryon
states (free neutrons and protons), the light elements (,
internal quantum state ) are treated as quasiparticles with energies
. These energies depend on the center of mass
momentum , as well as temperature and the total densities
of neutrons and protons, respectively. No equilibrium is considered so
that (or the corresponding chemical potentials ) are
fixed independently.
For the single nucleon quasiparticle energy shift, different approximate
expressions such as Skyrme or relativistic mean field approaches are well
known. Treating the -particle problem in appropriate approximations, results
for the cluster quasiparticle shifts are given. Properties of dense nuclear
matter at moderate temperatures in the subsaturation density region considered
here are influenced by the composition. This in turn is determined by the
cluster quasiparticle energies, in particular the formation of clusters at low
densities when the temperature decreases, and their dissolution due to Pauli
blocking as the density increases. Our finite-temperature Green function
approach covers different limiting cases: The low-density region where the
model of nuclear statistical equilibrium and virial expansions can be applied,
and the saturation density region where a mean field approach is possible
Monte Carlo results for the hydrogen Hugoniot
We propose a theoretical Hugoniot obtained by combining results for the
equation of state (EOS) from the Direct Path Integral Monte Carlo technique
(DPIMC) and those from Reaction Ensemble Monte Carlo (REMC) simulations. The
main idea of such proposal is based on the fact that DPMIC provides
first-principle results for a wide range of densities and temperatures
including the region of partially ionized plasmas. On the other hand, for lower
temperatures where the formation of molecules becomes dominant, DPIMC
simulations become cumbersome and inefficient. For this region it is possible
to use accurate REMC simulations where bound states (molecules) are treated on
the Born-Oppenheimer level using a binding potential calculated by Kolos and
Wolniewicz. The remaining interaction is then reduced to the scattering between
neutral particles which is reliably treated classically applying effective
potentials. The resulting Hugoniot is located between the experimental values
of Knudson {\textit{et al.}} \cite{1} and Collins {\textit{et al.}} \cite{2}.Comment: 10 pges, 2 figures, 2 table
Correlations in Hot Asymmetric Nuclear Matter
The single-particle spectral functions in asymmetric nuclear matter are
computed using the ladder approximation within the theory of finite temperature
Green's functions. The internal energy and the momentum distributions of
protons and neutrons are studied as a function of the density and the asymmetry
of the system. The proton states are more strongly depleted when the asymmetry
increases while the occupation of the neutron states is enhanced as compared to
the symmetric case. The self-consistent Green's function approach leads to
slightly smaller energies as compared to the Brueckner Hartree Fock approach.
This effect increases with density and thereby modifies the saturation density
and leads to smaller symmetry energies.Comment: 7 pages, 7 figure
Single-particle spectral function for the classical one-component plasma
The spectral function for an electron one-component plasma is calculated
self-consistently using the GW0 approximation for the single-particle
self-energy. In this way, correlation effects which go beyond the mean-field
description of the plasma are contained, i.e. the collisional damping of
single-particle states, the dynamical screening of the interaction and the
appearance of collective plasma modes. Secondly, a novel non-perturbative
analytic solution for the on-shell GW0 self-energy as a function of momentum is
presented. It reproduces the numerical data for the spectral function with a
relative error of less than 10% in the regime where the Debye screening
parameter is smaller than the inverse Bohr radius, kappa<1/a_B. In the limit of
low density, the non-perturbative self-energy behaves as n^(1/4), whereas a
perturbation expansion leads to the unphysical result of a density independent
self-energy [W. Fennel and H. P. Wilfer, Ann. Phys. Lpz._32_, 265 (1974)]. The
derived expression will greatly facilitate the calculation of observables in
correlated plasmas (transport properties, equation of state) that need the
spectral function as an input quantity. This is demonstrated for the shift of
the chemical potential, which is computed from the analytical formulae and
compared to the GW0-result. At a plasma temperature of 100 eV and densities
below 10^21 cm^-3, both approaches deviate less than 10% from each other.Comment: 14 pages, 9 figures accepted for publication in Phys. Rev. E v2:
added section V (application of presented formalism to chemical potential of
the OCP
Path integral Monte Carlo calculations of helium and hydrogen-helium plasma thermodynamics and of the deuterium shock Hugoniot
In this work we calculate the thermodynamic properties of hydrogen-helium
plasmas with different mass fractions of helium by the direct path integral
Monte Carlo method. To avoid unphysical approximations we use the path integral
representation of the density matrix. We pay special attention to the region of
weak coupling and degeneracy and compare the results of simulation with a model
based on the chemical picture. Further with the help of calculated deuterium
isochors we compute the shock Hugoniot of deuterium. We analyze our results in
comparison with recent experimental and calculated data on the deuterium
Hugoniot.Comment: 7 pages, 5 Postscript figures, accepted for publication in J. Phys.
A: Math. Ge
Маркшейдерська школа Національного гірничого університету
Викладена історія створення та розвитку маркшейдерської школи в НГУ протягом 110 років.Изложена история создания и развития маркшейдерской школы в НГУ в течение 110 лет.History of creation and development ofsurveyor school is expounded in NMU during 110 years
- …