scholarly journals Random phase approximation up to the melting point: Impact of anharmonicity and nonlocal many-body effects on the thermodynamics of Au

2015 ◽  
Vol 91 (20) ◽  
Author(s):  
B. Grabowski ◽  
S. Wippermann ◽  
A. Glensk ◽  
T. Hickel ◽  
J. Neugebauer
Keyword(s):  
Melting Point ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Phase Approximation ◽  
Many Body ◽  
Many Body Effects

scholarly journals Fundamental nuclear structure symmetries in double beta decay processes

2020 ◽  
Vol 9 ◽  
pp. 211
Author(s):  
O. Civitarese
Keyword(s):  
Nuclear Structure ◽  
Beta Decay ◽  
Random Phase Approximation ◽  
Body Problem ◽  
Random Phase ◽  
Double Beta Decay ◽  
Phase Approximation ◽  
Many Body ◽  
Quasiparticle Random Phase Approximation ◽  
Fundamental Symmetries

The nuclear structure physics of double beta decay transitions is reviewed starting from the consideration of fundamental symmetries of the nuclear many body problem. The problems found in the use of the Quasiparticle Random Phase Approximation (QRPA) and related approximations, in dealing with the calculation of nuclear double beta decay observables, are understood in terms of the mixing between isospin collective and intrinsic variables.

scholarly journals Random Phase Approximation Applied to Many-Body Noncovalent Systems

2019 ◽  
Vol 16 (1) ◽  
pp. 427-442 ◽  
Author(s):  
Marcin Modrzejewski ◽  
Sirous Yourdkhani ◽  
Jiří Klimeš
Keyword(s):  
Random Phase Approximation ◽  
Random Phase ◽  
Phase Approximation ◽  
Many Body

Ab-Initio Calculations for the Electronic Spectra of Cubic and Hexagonal Boron Nitride

2004 ◽  
Vol 829 ◽  
Author(s):  
Guido Satta ◽  
Giancarlo Cappellini ◽  
Valerio Olevano ◽  
Lucia Reining
Keyword(s):  
Boron Nitride ◽  
Random Phase Approximation ◽  
Density Functional ◽  
Hexagonal Boron Nitride ◽  
Random Phase ◽  
Optical Spectra ◽  
Many Body ◽  
Self Energy ◽  
Many Body Effects ◽  
Excitonic Effects

ABSTRACTWe present state of the art fist-principles calculations for the optical spectra and the loss functions of bulk boron nitride in the cubic (c-BN) and in the hexagonal (h-BN) phases. We start from a DFT-LDA density functional Khon-Sham bandstructure to investigate the influence of many-body effects beyond the Random Phase Approximation (RPA) on the optical spectra through the inclusion of self-energy and excitonic effects by a GW calculation and the solution of the Bethe-Salpeter equation. For the loss function we only perform RPA calculations. We show to which extent the description of many-body effects is important for a meaningiful comparison with experiment, and when they can be neglected.

scholarly journals Random-Phase Approximation in Many-Body Noncovalent Systems: Methane in a Dodecahedral Water Cage

2021 ◽  
Vol 17 (2) ◽  
pp. 804-817
Author(s):  
Marcin Modrzejewski ◽  
Sirous Yourdkhani ◽  
Szymon Śmiga ◽  
Jiří Klimeš
Keyword(s):  
Random Phase Approximation ◽  
Random Phase ◽  
Phase Approximation ◽  
Many Body

Dielectric response of metallic crystal made up of highly polarisable molecules: the semi-classical approach

Open Physics ◽  
2009 ◽  
Vol 7 (4) ◽  
Author(s):  
Željana Bonačić Lošić ◽  
Paško Županović
Keyword(s):  
Dielectric Function ◽  
Dielectric Response ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Collective Modes ◽  
Classical Approach ◽  
Phase Approximation ◽  
Many Body ◽  
Band Insulator ◽  
The Many

AbstractThe dielectric response is considered within models of a one-band metal, a two-band insulator and a two-band metal using the semi-classical approximation. Corresponding dielectric functions are found. The dielectric function of two-band metal is found to be the interpolation between the Sellmeyer and Lorenz-Lorentz expressions, respectively. The frequencies of the collective modes are identified as the zeroes of the dielectric functions. The correspondence between the semi-classical approach used in this paper and the many-body calculation within the random-phase approximation is established.

scholarly journals Hartree–Fock and random phase approximation theories in a many-fermion solvable model

2015 ◽  
Vol 30 (36) ◽  
pp. 1550196 ◽  
Author(s):  
Giampaolo Co’ ◽  
Stefano De Leo
Keyword(s):  
Random Phase Approximation ◽  
Random Phase ◽  
Solvable Model ◽  
Phase Approximation ◽  
Many Body ◽  
Hartree Fock ◽  
Ideal System ◽  
The Many ◽  
Effective Theories ◽  
Number Of Particles

We present an ideal system of interacting fermions where the solutions of the many-body Schrödinger equation can be obtained without making approximations. These exact solutions are used to test the validity of two many-body effective approaches, the Hartree–Fock and the random phase approximation theories. The description of the ground state done by the effective theories improves with increasing number of particles.

RANDOM PHASE APPROXIMATION FOR ALLOWED AND PARITY NON-CONSERVING ELECTRIC DIPOLE TRANSITION AMPLITUDES AND ITS CONNECTION WITH MANY-BODY PERTURBATION THEORY AND COUPLED-CLUSTER THEORY

2006 ◽  
Vol 05 (04) ◽  
pp. 945-956
Author(s):  
GEETHA GOPAKUMAR ◽  
CHIRANJIB SUR ◽  
BHANU PRATAP DAS ◽  
RAJAT K. CHAUDHURI ◽  
DEBASHIS MUKHERJEE ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Electric Dipole ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Coupled Cluster ◽  
Phase Approximation ◽  
Many Body ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Many Body Perturbation Theory

The connections between the Random Phase Approximation (RPA) and Many-Body Perturbation Theory (MBPT) and its all order generalization, the Coupled-Cluster Theory (CCT), have been explored. Explicit expressions have been derived for the electric dipole amplitudes for allowed and forbidden transitions induced by the parity non-conserving neutral weak interaction. The Goldstone diagrams associated with the RPA terms in both cases are shown to arise in MBPT and CCT, and the numerical verification of this relationship is made for the allowed electric dipole transitions.

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