Fourth order many‐body Green’s function: Application of a simplified model to the ionization energies of N2

1987 ◽  
Vol 87 (12) ◽  
pp. 7146-7159 ◽  
Author(s):  
Pasquale Tomasello
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Fourth Order ◽  
Simplified Model ◽  
Many Body ◽  
Ionization Energies

AN INTRODUCTORY GUIDE TO GREEN’S FUNCTION METHODS IN NUCLEAR MANY-BODY PROBLEMS

1994 ◽  
Vol 03 (02) ◽  
pp. 523-589 ◽  
Author(s):  
T.T.S. KUO ◽  
YIHARN TZENG
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Green's Functions ◽  
Green’S Functions ◽  
Model Space ◽  
Many Body ◽  
Diagram Expansion ◽  
Nucleus Scattering ◽  
Many Body Systems ◽  
General Method

We present an elementary and fairly detailed review of several Green’s function methods for treating nuclear and other many-body systems. We first treat the single-particle Green’s function, by way of which some details concerning linked diagram expansion, rules for evaluating Green’s function diagrams and solution of the Dyson’s integral equation for Green’s function are exhibited. The particle-particle hole-hole (pphh) Green’s function is then considered, and a specific time-blocking technique is discussed. This technique enables us to have a one-frequency Dyson’s equation for the pphh and similarly for other Green’s functions, thus considerably facilitating their calculation. A third type of Green’s function considered is the particle-hole Green’s function. RPA and high order RPA are treated, along with examples for setting up particle-hole RPA equations. A general method for deriving a model-space Dyson’s equation for Green’s functions is discussed. We also discuss a method for determining the normalization of Green’s function transition amplitudes based on its vertex function. Some applications of Green’s function methods to nuclear structure and recent deep inelastic lepton-nucleus scattering are addressed.

Eine Approximation der Löwdinschen natürlichen Orbitale für Moleküle mit einer Green-Funktion-Methode

1972 ◽  
Vol 27 (4) ◽  
pp. 545-552 ◽  
Author(s):  
R. Albat
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Mass Operator ◽  
Ground States ◽  
Present Form ◽  
Many Body ◽  
Natural Orbitals ◽  
First Order ◽  
The Many ◽  
Closed Shells

Abstract An Approximation of Löwdin's Natural Orbitals for Molecules with a Green's Function Method The many-body-pertubation theorie of the single-particle Green's function is used to get an approximate first-order density matrix. Slightly modified SCF-orbitals form the basis for the expansion. The mass-operator in Dyson's equation is considered up to second order in the Perturbation. In the present form the method is only applicable to ground states with closed shells. The ground states of the molecules LiH and NH3 serve as examples to demonstrate the usefulness of the directly calculated natural orbitals for application in the C I-method. The natural orbitals give a much better convergence of the C I-expansion than the SCF-orbitals do.

Support Flexibility and Natural Frequencies of Pipe Mounted Thermowells

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
David S. Bartran
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Natural Frequencies ◽  
Pipe Wall ◽  
Simplified Model ◽  
Load Model ◽  
Distributed Load ◽  
Pipe Fittings ◽  
Insight Into ◽  
Design And Application

A simplified model of a pipe mounted thermowell provides a measure of insight into the design and application of intrusive pipe fittings. A combination of Fourier and Green’s function methods together with a distributed load model of the thermowell/pipe wall interface are used to calculate the support compliance and subsequently the natural frequencies of the thermowell. These are compared with limited though independent calculations. This comparison confirms a profound reduction in natural frequencies for commonly encountered thermowell installations, reductions that should not be ignored where the risk of flow-induced resonance is high.

Charge-Transfer Excited States in Aqueous DNA: Insights from Many-Body Green’s Function Theory

2014 ◽  
Vol 112 (22) ◽  
Author(s):  
Huabing Yin ◽  
Yuchen Ma ◽  
Jinglin Mu ◽  
Chengbu Liu ◽  
Michael Rohlfing
Keyword(s):  
Charge Transfer ◽  
Green’S Function ◽  
Excited States ◽  
Green's Function ◽  
Function Theory ◽  
Many Body
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