pinecone/core-2020-05-10-deduplication huggingface dataset:
Towards ab initio thermodynamics of the electron gas at strong
  degeneracy

Recently a number of theoretical studies of the uniform electron gas (UEG) at
finite temperature have appeared that are of relevance for dense plasmas, warm
dense matter and laser excited solids and thermodynamic density functional
theory simulations. In particular, restricted path integral Monte Carlo (RPIMC)
results became available which, however, due to the Fermion sign problem, are
confined to moderate quantum degeneracy, i.e. low to moderate densities. We
have recently developed an alternative approach---configuration PIMC [T. Schoof
{\em et al.}, Contrib. Plasma Phys. {\bf 51}, 687 (2011)] that allows one to
study the so far not accessible high degeneracy regime. Here we present the
first step towards UEG simulations using CPIMC by studying implementation and
performance of the method for the model case of $N=4$ particles. We also
provide benchmark data for the total energy
Two-temperature pair potentials and phonon spectra for simple metals in
  the warm dense matter regime

We develop ion-ion pair potentials for Al, Na and K for densities and
temperatures relevant to the warm-dense-matter (WDM) regime. Furthermore, we
emphasize non-equilibrium states where the ion temperature $T_i$ differs from
the electron temperature $T_e$. This work focuses mainly on ultra-fast
laser-metal interactions where the energy of the laser is almost exclusively
transferred to the electron sub-system over femtosecond time scales. This
results in a two-temperature system with $T_e>T_i$ and with the ions still at
the initial room temperature $T_i=T_r$. First-principles calculations, such as
density functional theory (DFT) or quantum Monte Carlo, are as yet not fully
feasible for WDM conditions due to lack of finite-$T$ features, e.g.
pseudopotentials, and extensive CPU time requirements. Simpler methods are
needed to study these highly complex systems. We propose to use two-temperature
pair potentials $U_{ii}(r, T_i,T_e)$ constructed from linear-response theory
using the non-linear electron density $n(\mathbf{r})$ obtained from finite-$T$
DFT with a single ion immersed in the appropriate electron fluid. We compute
equilibrium phonon spectra at $T_r$ which are found to be in very good
agreement with experiments. This gives credibility to our non-equilibrium
phonon dispersion relations which are important in determining thermophysical
properties, stability, energy-relaxation mechanisms and transport coefficients.Comment: International Conf. on Strongly-Coupled Coulombo Systems (SCCS) 201
Low-density crystals in charged colloids : Comparison with Yukawa theory

Charged colloids can behave as Yukawa systems, with similar phase behaviour.
Using particle- resolved studies, we consider a system with an unusually long
Debye screening length which forms crystals at low colloid volume fraction
{\phi} ~ 0.01. We quantitatively compare this system with the Yukawa model and
find that its freezing point is compatible with the theoretical prediction but
that the crystal polymorph is not always that expected. In particular we find
body-centred cubic crystals where face-centred cubic crystals are expected.Comment: To appear in the special issue of Contributions to Plasma Physics for
  Strongly Coupled Coulomb Systems 201
Radio frequency induced and neoclassical asymmetries and their effects
  on turbulent impurity transport in a tokamak

Poloidal asymmetries in the impurity density can be generated by radio
frequency heating in the core and by neoclassical effects in the edge of
tokamak plasmas. In a pedestal case study, using global neoclassical
simulations we find that finite orbit width effects can generate significant
poloidal variation in the electrostatic potential, which varies on a small
radial scale. Gyrokinetic modeling shows that these poloidal asymmetries can be
strong enough to significantly modify turbulent impurity peaking. In the
pedestal the ExB drift in the radial electric field can give a larger
contribution to the poloidal motion of impurities than that of their parallel
streaming. Under such circumstances we find that up-down asymmetries can also
affect impurity peaking.Comment: Paper for 14th International Workshop on Plasma Edge Theory in Fusion
  Devices, revised version, submitte
Quantum hydrodynamics for plasmas -- a Thomas-Fermi theory perspective

The idea to describe quantum systems within a hydrodynamic framework (quantum
hydrodynamics, QHD) goes back to Madelung and Bohm. While such a description is
formally exact for a single particle, more recently the concept has been
applied to many-particle systems by Manfredi and Haas [Phys. Rev. B {\bf 64},
075316 (2001)] and received high popularity in parts of the quantum plasma
community. Thereby, often the applicability limits of these equations are
ignored, giving rise to unphysical predictions. Here we demonstrate that
modified QHD equations for plasmas can be derived from Thomas-Fermi theory
including gradient corrections. This puts QHD on firm grounds. At the same time
this derivation yields a different prefactor, $\gamma=(D-2/3D)$, in front of
the quantum (Bohm) potential which depends on the system dimensionality $D$.
Our approach allows one to identify the limitations of QHD and to outline
systematic improvements
A New Scheme for High-Intensity Laser-Driven Electron Acceleration in a
  Plasma 2

We propose a new approach to high-intensity relativistic laser-driven
electron acceleration in a plasma. Here, we demonstrate that a plasma wave
generated by a stimulated forward-scattering of an incident laser pulse can be
in the longest acceleration phase with injected relativistic beam electrons.
This is why the plasma wave has the maximum amplification coefficient which is
determined by the acceleration time and the breakdown (overturn) electric field
in which the acceleration of the injected beam electrons occurs. We must note
that for the longest acceleration phase the relativity of the injected beam
electrons plays a crucial role in our scheme. We estimate qualitatively the
acceleration parameters of relativistic electrons in the field of a plasma wave
generated at the stimulated forward-scattering of a high-intensity laser pulse
in a plasma.Comment: 4 pages. arXiv admin note: substantial text overlap with
  arXiv:1404.658
Complex Plasma Research under Microgravity Conditions: PK-3 Plus Laboratory on the International Space Station

Complex (dusty) plasmas are composed of weakly ionised gas and charged microparticles and represent the\ud
plasma state of soft matter. Due to the ”heavy” component — the microparticles — and the low density of the\ud
surrounding medium, the rarefied gas and plasma, it is necessary to perform experiments under microgravity\ud
conditions to cover a broad range of experimental parameters which are not available on ground. The investigations have been performed onboard the International Space Station (ISS) with the help of the ”Plasma Crystal-3 Plus” (PK-3 Plus) laboratory. It was perfectly suited for the formation of large stable liquid and crystalline Systems and provided interesting insights into processes like crystallisation and melting, laning in binary mixtures, electrorheological effects due to ac electric fields and projectile interaction with a strongly coupled complex\ud
plasma cloud
Free Energy of the Uniform Electron Gas: Testing Analytical Models
  against First Principle Results

The uniform electron gas is a key model system in the description of matter,
including dense plasmas and solid state systems. However, the simultaneous
occurence of quantum, correlation, and thermal effects makes the theoretical
description challenging. For these reasons, over the last half century many
analytical approaches have been developed the accuracy of which has remained
unclear. We have recently obtained the first \textit{ab initio} data for the
exchange correlation free energy of the uniform electron gas [T. Dornheim
\textit{et al.}, Phys.~Rev.~Lett.~\textbf{117}, 156403 (2016)] which now
provides the opportunity to assess the quality of the mentioned approaches and
parametrizations. Particular emphasis is put on the warm dense matter regime,
where we find significant discrepancies between the different approaches
Improved Equation of State for Finite-Temperature Spin-Polarized
  Electron Liquids on the Basis of Singwi-Tosi-Land-Sjolander Approximation

An accurate expression for the exchange-correlation free energy f_{xc} of
homogeneous electron fluids at finite temperatures is presented on the basis of
Singwi-Tosi-Land-Sjolander (STLS) approximation. In addition to the derivation
for the paramagnetic state, that for the ferromagnetic state is newly carried
out in which a correction in the strong Coulomb coupling regime is incorporated
into the construction of analytic expression as a function of the coupling
constant and the Fermi degeneracy. The fitting formula for f_{xc} is then
extended over any degree of spin polarization with the aid of available
interpolation scheme. The proposed equation of state, called iSTLS formula,
shows reasonable agreements with the existing quantum Monte Carlo evaluations
at finite temperatures in the paramagnetic state, thus giving a consensus for
the thermodynamic functions between many-body theories and computer
simulations. On the other hand, the current status for the agreement among
various evaluations of f_{xc} is relatively unsatisfactory in the ferromagnetic
state, suggesting the necessity of further investigations.Comment: 19 page manuscript, 13 figures, and Supplemental Material; Submitted
  to Contrib. Plasma Phy
Core-SOL Modelling of Neon Seeded JET Discharges with the ITER-like Wall

Five ELMy H-mode Ne seeded JET pulses have been simulated with the self-consistent core-SOL model COREDIV. In this five pulse series only the Ne seeding rate was changed shot by shot, allowing a thorough study of the effect of Ne seeding on the total radiated power and of its distribution between core and SOL tobe made. The increase in the simulations of the Ne seeding rate level above that achieved in experiments shows saturation of the total radiated power at a relatively low radiated-heating power ratio (frad = 0.60) and a further increase of the ratio of SOL to core radiation, in agreement with the reduction of W release at high Ne seeding level. In spite of the uncertainties caused by the simplified SOL model of COREDIV (neutral model, absence of ELMs and slab model for the SOL), the increase of the perpendicular transport in the SOL with increasing Ne seeding rate, which allows to reproduce numerically the experimental distribution core-SOL of the radiated power, appears to be of general applicability
Temperature Anisotropy Relaxation of the One-Component Plasma

The relaxation rate of a Maxwellian velocity distribution function that has
an initially anisotropic temperature $(T_\parallel \neq T_\perp)$ is an
important physical process in space and laboratory plasmas. It is also a
canonical example of an energy transport process that can be used to test
theory. Here, this rate is evaluated using molecular dynamics simulations of
the one-component plasma. Results are compared with the predictions of four
kinetic theories; two treating the weakly coupled regime (1) the Landau
equation, and (2) the Lenard-Balescu equation, and two that attempt to extend
the theory into the strongly coupled regime (3) the effective potential theory
and (4) the generalized Lenard-Balescu theory. The role of dynamic screening is
studied, and is found to have a negligible influence on this transport rate.
Oscillations and a delayed relaxation onset in the temperature profiles are
observed at strong coupling, which are not described by the kinetic theories.Comment: 15 pages, 7 figures, to be published in Contributions to Plasma
  Physic
Time Reversal Invariance of quantum kinetic equations II: Density
  operator formalism

Time reversal symmetry is a fundamental property of many quantum mechanical
systems. The relation between statistical physics and time reversal is subtle
and not all statistical theories conserve this particular symmetry, most
notably hydrodynamic equations and kinetic equations such as the Boltzmann
equation. Here we consider quantum kinetic generalizations of the Boltzmann
equation by using the method of reduced density operators leading to the
quantum generalization of the BBGKY-(Bogolyubov, Born, Green, Kirkwood, Yvon)
hierachy. We demonstrate that all commonly used approximations, including
Vlasov, Hartree-Fock and the non-Markovian generalizations of the Landau,
T-matrix and Lenard-Balescu equations are originally time-reversal invariant,
and we formulate a general criterion for time reversibility of approximations
to the quantum BBGKY-hierarchy. Finally, we illustrate, on the example of the
Born approximation, how irreversibility is introduced into quantum kinetic
theory via the Markov limit, making the connection with the standard Boltzmann
equation. This paper is a complement to paper I [Scharnke {\it et al.},
submitted to J. Math. Phys., arXiv:1612.08033] where time-reversal invariance
of quantum-kinetic equations was analyzed in the frame of the independent
nonequilibrium Green functions formalism
Modulational Instability and Generation of Envelope Solitons in Four
  Component Space Plasmas

A four component space plasma system (consisting of immobile positive ions,
inertial cold positrons as well as hot electrons and positrons following
Cairns' nonthermal distribution function is considered. The nonlinear
propagation of the positron-acoustic (PA) waves, in which the inertia
(restoring force) is provided by the cold positron species (nonthermal pressure
of both hot electron and positron species) has been theoretically investigated
by deriving the nonlinear Schr\"odinger (NLS) equation. It is found from the
numerical analysis of this NLS equation that the space plasma system under
consideration supports the existence of both dark and bright envelope solitons
associated with PA waves, and that the dark (bright) envelope solitons are
modulationally stable (unstable). It is also observed that the basic properties
(viz. stable regime and unstable regime with growth rate) of the PA envelope
solitions are significantly modified by related plasma parameters (viz. number
densities and temperature of plasma species), which correspond to different
realistic space plasma situations.Comment: 9 figures, 1 manuscript. arXiv admin note: text overlap with
  arXiv:1706.0563
\textit{Ab Initio} results for the Static Structure Factor of the Warm
  Dense Electron Gas

The uniform electron gas at finite temperature is of high current interest
for warm dense matter research. The complicated interplay of quantum degeneracy
and Coulomb coupling effects is fully contained in the pair distribution
function or, equivalently, the static strucutre factor. By combining exact
quantum Monte Carlo results for large wave vectors with the long-range behavior
from the Singwi-Tosi-Land-Sj\"olander approximation, we are able to obtain
highly accurate data for the static structure factor over the entire $k$-range.
This allows us to gauge the accuracy of previous approximations and discuss
their respective shortcomings. Further, our new data will serve as valuable
input for the computation of other quantities
On the Kubo-Greenwood Model for Electron Conductivity

Currently, the most common method to calculate transport properties for
materials under extreme conditions is based on the phenomenological
Kubo-Greenwood method. The results of an inquiry into the justification and
context of that model are summarized here. Specifically, the basis for its
connection to equilibrium DFT and the assumption of static ions are discussed
briefly.Comment: Submitted to Contributions to Plasma Physics for the 2017 Strongly
  Coupled Coulombs Systems conference proceeding
Ion Potential in Non-ideal Dense Quantum Plasmas

The screened ion potential in non-ideal dense quantum plasmas is investigated
by invoking the Singwi-Tosi-Land-Sj\"olander approximation for the electronic
local field correction at densities $r_s\lesssim 2$ and degeneracy parameters
$\theta\lesssim 1$, where $r_s$ is the ratio of the mean inter-particle
distance to the first Bohr radius, and $\theta$ is the ratio of the thermal
energy to the Fermi energy of the electrons. Various cross-checks with ion
potentials obtained from ground state quantum Monte-Carlo data, the random
phase approximation, as well as with existing analytical models are presented.
Further, the importance of the electronic correlation effects for the dynamics
in strongly coupled ionic subsystems for $0.1\leq r_s\leq 2$ is discussed
Gradient correction and Bohm potential for 2D and 1D electron gases at a
  finite temperature

From the static polarization function of electrons in the random phase
approximation the quantum Bohm potential for the quantum hydrodynamic
description of electrons, and the density gradient correction to the
Thomas-Fermi free energy at a finite temperature for the 2D and 1D cases are
derived. The behavior of the Bohm potential and of the density gradient
correction as a function of the degeneracy parameter is discussed. Based on
recent developments in the fluid description of quantum plasmas, the Bohm
potential for the high frequency domain is presented
Ionization potential depression and optical spectra in a Debye plasma
  model

We show how optical spectra in dense plasmas are determined by the shift of
energy levels as well as the broadening owing to collisions with the plasma
particles. In lowest approximation, the interaction with the plasma particles
is described by the RPA dielectric function, leading to the Debye shift of the
continuum edge. The bound states remain nearly un-shifted, their broadening is
calculated in Born approximation. The role of ionization potential depression
as well as the Inglis-Teller effect are shown. The model calculations have to
be improved going beyond the lowest (RPA) approximation when applying to WDM
spectra
Simultaneous effect of an external magnetic field and gas-induced
  friction on the caging of particles in two-dimensional Yukawa systems

We investigate the simultaneous effect of a static homogeneous external
magnetic field and a background gas medium on the quasi-localization of the
dust particles -- characterized quantitatively by cage correlation functions --
in strongly coupled two-dimensional Yukawa systems. We apply the Langevin
dynamics computer simulation method in which the frictional and Lorentz forces
are taken into account. Both the presence of the magnetic field or the friction
originating from the background gas, when acting alone, increase the caging
time. When present simultaneously, however, we find that their effects combine
in a nontrivial manner and act against each other within a window of the
parameter values
Local structure in dense hydrogen at the liquid-liquid phase transition
  by Coupled Electron-Ion Monte Carlo

We present a study of the local structure of high pressure hydrogen around
the liquid-liquid transition line based on results from the Coupled
Electron-Ion Monte Carlo method. We report results for the Equation of State,
for the radial distribution function between protons g(r) and results from a
cluster analysis to detect the possible formation of stable molecular ions
beyond the transition line, as well as above the critical temperature. We
discuss various estimates for the molecular fraction in both phases and show
that, although the presence of $H_3^+$ ions is suggested by the form of the
g(r) they are not stable against thermal fluctuations.Comment: 13 pages, 7 figures, submitted to Contributions to Plasma Physics for
  the proceedings of SCCS201
Power Balance in the ITER Plasma and Divertor

It is planned to use atomic processes to spread out most of the heating power
over the first wall and side walls to reduce the heat loads on the plasma
facing components in ITER to ~ 50 MW. Calculations indicate that there will be
100 MW in bremstrahlung radiation from the plasma center, 50 MW of radiation
from the plasma edge inside the separatrix and 100 MW of radiation from the
scrape-off layer and divertor plasma, leaving 50 MW of power to be deposited on
the divertor plates. The radiation losses are enhanced by the injection of
impurities such as Neon or Argon at acceptably low levels (~0.1 % Argon, etc.)Comment: Preprint for the Plasma Edge Theory Conference, Monterey, Dec.4-6,
  1995, 5 pages, gzipped postscrip
Debye-Onsager-Relaxation-Effect beyond linear Response and Antiscreening
  in Plasma Systems

The quantum kinetic equation for charged particles in strong electric fields
is derived and analyzed with respect to the particle flux. It is found that the
applied electric field is screened nonlinearly. The relaxation field is
calculated completely quantum mechanically and up to any order in the applied
field. The classical limit is given in analytical form. In the range of weak
fields the deformation of the screening cloud is responsible for the
Debye-Onsager relaxation effect. The result beyond linear response presented
here allows to investigate a field regime where no screening cloud is present.
The descreening field is determined as a function of thermal energy density of
the plasma. For stronger fields the moving charge is accelerated by accumulated
opposite charges in front of the particle. This can be understood in analogue
to the accoustic Doppler effect. A critical field strength is presented up to
which value a thermalized plasma is possible. The range of applicability of the
treatment is discussed with respect to applied field strength and space
gradients.Comment: text and 2 figures appear in Contrib. to Plasma Physic
Accurate first-principle equation of state for the One-Component Plasma

Accurate "first-principle" expressions for the excess free energy $F_{ex}$
and internal energy $U_{ex}$ of the classical one-component plasma (OCP) are
obtained. We use the Hubbard-Schofield transformation that maps the OCP
Hamiltonian onto the Ising-like Hamiltonian, with coefficients expressed in
terms of equilibrium correlation functions of a reference system. We use the
ideal gas as a reference system for which all the correlation functions are
known. Explicit calculations are performed with the high-order terms in the
Ising-like Hamiltonian omitted. For small values of the plasma parameter
$\Gamma$ the Debye-Huckel result for $F_{ex}$ and $U_{ex}$ is recovered. For
large $\Gamma$ these depend linearly on $\Gamma$ in accordance with the Monte
Carlo findings for the OCP. The MC data for the internal energy are reproduced
fairly well by the obtained analytical expression.Comment: 15 pages, 2 figures, to appear in Contrib. Plasma Phys., v.38 N4,
  (1998
One-particle spectral function of electrons in a hot and dense plasma

A self-consistent determination of the spectral function and the self-energy
of electrons in a hot and dense plasma is reported. The self-energy is
determined within the approximation of the screened potential. It is shown,
that the quasi-particle concept is not an adequate concept for hot and dense
plasmas, since the width of the spectral function has to be considered. As an
example, the solar core plasma is discussed. An effective quasi-particle
picture is introduced and results for the solar core plasma as well as for ICF
plasmas are presented.Comment: latex, 5 pages, 5 figures in eps forma