scholarly journals Path-integral renormalization group treatments for many-electron systems with long-range repulsive interactions

2008 ◽  
Vol 40 (6-7) ◽  
pp. 1071-1074 ◽  
Author(s):  
Masashi Kojo ◽  
Kikuji Hirose
Keyword(s):  
Renormalization Group ◽  
Long Range ◽  
Path Integral ◽  
Electron Systems ◽  
Group Treatments ◽  
Repulsive Interactions

HEAVY FERMIONS — THEIR MAGNETISM AND SUPERCONDUCTIVITY

1993 ◽  
Vol 07 (01n03) ◽  
pp. 2-8 ◽  
Author(s):  
F. STEGLICH ◽  
C. GEIBEL ◽  
A. LOIDL ◽  
G. SPARN ◽  
C. D. BREDL ◽  
...  
Keyword(s):  
Long Range ◽  
Heavy Fermion ◽  
Local Moment ◽  
Antiferromagnetic Order ◽  
Electron Systems ◽  
Correlated Electron Systems ◽  
Cooperative Phenomena ◽  
Correlated Electron ◽  
Highly Correlated ◽  
Heavy Fermion Superconductivity

Heavy-fermion compounds are ideally suited to study cooperative phenomena in highly correlated electron systems. We discuss local-moment magnetism and heavy-fermion band magnetism in the exemplary systems CeCu 2 Ge 2 and Ni-rich Ce(Cu 1− x Ni x )2 Ge 2, respectively. In addition, the coexistence of long-range antiferromagnetic order and heavy-fermion superconductivity in UM 2 Al 3 (M: Ni, Pd) will be addressed.

scholarly journals Scattering and Its Applications to Various Atomic Processes: Elastic Scattering, Resonances, Photoabsorption, Rydberg States, and Opacity of the Atmosphere of the Sun and Stellar Objects

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 78
Author(s):  
Anand K. Bhatia
Keyword(s):  
Elastic Scattering ◽  
Long Range ◽  
Short Range ◽  
Bound States ◽  
Rydberg States ◽  
Stellar Atmospheres ◽  
Electron Systems ◽  
Short Range Correlations ◽  
Hybrid Theory ◽  
Scattering Resonances

A scattering process can be a natural process or a process carried out in a laboratory. The scattering of particles from targets has resulted in important discoveries in physics. We discuss various scattering theories of electrons and positrons and their applications to elastic scattering, resonances, photoabsorption, excitation, and solar and stellar atmospheres. Among the most commonly employed approaches are the Kohn variational principle, close-coupling approximation, method of polarized orbitals, R-matrix formulation, and hybrid theory. In every formulation, an attempt is made to include exchange, long-range and short-range correlations, and to make the approach variationally correct. The present formulation, namely, hybrid theory, which is discussed in greater detail compared to other approximations, includes exchange, long-range correlations, and short-range correlations at the same time, and is variationally correct. It was applied to calculate the phase shifts for elastic scattering, the resonance parameters of two-electron systems, photoabsorption in two-electron systems, excitation of atomic hydrogen by an electron and positron impact, and to study the opacity of the Sun’s atmosphere. Calculations of polarizabilities, Rydberg states, and bound states of atoms are also discussed.

Strongly Correlated Electron Systems: Spin-Reflection Positivity and Some Rigorous Results

1998 ◽  
Vol 12 (07n08) ◽  
pp. 709-779 ◽  
Author(s):  
Shun-Qing Shen
Keyword(s):  
Hubbard Model ◽  
Long Range ◽  
Strongly Correlated Electron Systems ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Rigorous Results ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Generalized Hubbard Model

Theory of spin-reflection positivity developed in recent years is reviewed. This theory makes use of symmetries in an electron system and theory of matrix to investigate the ground state properties. Existences of anti- and ferromagnetic long-range orders in itinerant electron systems, and of off-diagonal long-range order are two successful applications of the theory. In this article, the author attempt to summarize exact results proved by utilizing this theory and related topics. First a general theory and basic theorems are introduced. Second, based on the band structures of conduction electrons, existences of a singlet state with strongly antiferromagnetic correlation, a state with both anti- and ferromagnetic long-range orders, and a fully saturated ferromagnetic state are proved. The theory is applied to several of the main theoretical models for strongly correlated electron systems, such as the Heisenberg model, the Hubbard model, the Anderson model, the single- and multichannel Kondo model, and the generalized Hubbard model, and a series of rigorous results are found in these models. Third, it is proved that off-diagonal long-range order and charge-density wave exist in the ground states of the attractive Hubbard model and the generalized Hubbard model. A relation between pseudospin symmetry and the uniform density theorem is introduced. Fourth, the theory is applied successfully to explain experimental observations of oscillatory interlayer magnetic coupling in ultrathin magnetic films. Finally several unsolved problems are discussed. All results introduced in this article are mathematically exact.

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