Diagrammatic perturbation theory. The ground state of the carbon monosulfide molecule

1977 ◽  
Vol 67 (10) ◽  
pp. 4491-4497 ◽  
Author(s):  
Stephen Wilson
Keyword(s):  
Perturbation Theory ◽  
Ground State ◽  
Carbon Monosulfide ◽  
Diagrammatic Perturbation Theory

van der Waals perturbation theory for fermion and boson ground-state matter

1987 ◽  
Vol 35 (9) ◽  
pp. 3901-3910 ◽  
Author(s):  
V. C. Aguilera-Navarro ◽  
R. Guardiola ◽  
C. Keller ◽  
M. de Llano ◽  
M. Popovic ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Ground State ◽  
Van Der Waals

REMARKS ON THE GROUND STATE ENERGY OF THE SPIN-BOSON MODEL: AN APPLICATION OF THE WIGNER–WEISSKOPF MODEL

2001 ◽  
Vol 13 (02) ◽  
pp. 221-251 ◽  
Author(s):  
MASAO HIROKAWA
Keyword(s):  
Perturbation Theory ◽  
Spectral Analysis ◽  
Ground State Energy ◽  
Ground State ◽  
Spectral Properties ◽  
State Energy ◽  
Regularity Condition ◽  
Infrared Singularity ◽  
Regular Perturbation ◽  
Boson Model

For the ground state energy of the spin-boson (SB) model, we give a new upper bound in the case with infrared singularity condition (i.e. without infrared cutoff), and a new lower bound in the case of massless bosons with infrared regularity condition. We first investigate spectral properties of the Wigner–Weisskopf (WW) model, and apply them to SB model to achieve our purpose. Then, as an extra result of the spectral analysis for WW model, we show that a non-perturbative ground state appears, and its ground state energy is so low that we cannot conjecture it by using the regular perturbation theory.

The direct calculation of the first-order density matrix for atoms

1965 ◽  
Vol 283 (1393) ◽  
pp. 194-202 ◽  
Keyword(s):  
Perturbation Theory ◽  
Density Matrix ◽  
Ground State ◽  
Direct Calculation ◽  
Molecular Orbitals ◽  
Natural Orbitals ◽  
Mean Values ◽  
First Order ◽  
Order Contribution

The theory of isoelectronic sequences of atoms has been developed as a perturbation theory and is extended here to the calculation of the first-order density matrix. It is shown that the calculation of the first-order contribution to this matrix can be reduced to the solution of a number of one-electron equations. These equations have been solved for the helium ground state, the helium 3 S state and the lithium ground state. From the density matrix, mean values of one-electron operators can be derived by integration. A variety of these mean values is quoted and the significance of the stable values discussed. From the density matrix the natural orbitals can be derived and these are found to be identical with the unrestricted molecular orbitals to terms of zero and first order.

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