Equivalence of real-space renormalization groups for quantum systems and for critical dynamics

1985 ◽  
Vol 32 (9) ◽  
pp. 6108-6109 ◽  
Author(s):  
T. Schneider ◽  
M. Zannetti
Keyword(s):  
Real Space ◽  
Quantum Systems ◽  
Critical Dynamics ◽  
Renormalization Groups

Real-space quantum renormalization groups

1992 ◽  
Vol 68 (24) ◽  
pp. 3487-3490 ◽  
Author(s):  
S. R. White ◽  
R. M. Noack
Keyword(s):  
Real Space ◽  
Renormalization Groups

scholarly journals Local Spin and Open Quantum Systems: Clarifying Misconceptions, Unifying Approaches

2020 ◽  
Author(s):  
Angel Martín Pendás ◽  
Evelio Francisco
Keyword(s):  
Quantum Control ◽  
Open Systems ◽  
Open Quantum Systems ◽  
Real Space ◽  
Quantum Systems ◽  
Spin Coupling ◽  
Molecular Systems ◽  
Open Quantum ◽  
Local Spin

<p>We now show that Clark and Davidson local spins operators are perfectly defined subsystem operators if a fragment is taken as an <i>open quantum system</i> (OQS). Open systems have become essential in quantum control and quantum computation, but have not received much attention in Chemistry. We have already shown (<i>J. Chem. Theory Comput</i>. <b>2018</b>, <i>15</i>, 1079) how real space OQSs can be defined in molecular systems and how they offer new insights relating quantum mechanical entaglement and chemical bonding. The OQS account of local spin that we offer yields a rigorous, yet easily accessible way to rationalize local spin values. A fragment is found in a mixed state direct sum of sectors characterized by different number of electrons that occur with different probabilities. The local spin is then a weighted sum of otherwise standard <i>S</i>(<i>S</i>+1) values. With OQS glasses, it is obvious that atomic or fragment spins should not vanish. Our approach thus casts doubts on any procedure used to annihilate them, like those used by Mayer and coworkers. OQS local spins allow for a fruitful use of models. One can propose easily sector probabilities for localized, covalent, ionic, zwitterionic, etc. situations, and examine their ideal local spins. We have mapped all 2c-2e cases, and shown how to do that in general multielectron cases. The role of electron correlation is also studied by tuning the Hubbard U/t parameter for H chains. Correlation induced localization changes the spin-coupling patterns even qualitatively, and show how the limiting antiferromagnet arises.</p>

Stochastic Simulation of Quantum Systems and Critical Dynamics

1984 ◽  
Vol 53 (23) ◽  
pp. 2191-2194 ◽  
Author(s):  
T. Schneider ◽  
M. Zannetti ◽  
R. Badii ◽  
H. R. Jauslin
Keyword(s):  
Stochastic Simulation ◽  
Quantum Systems ◽  
Critical Dynamics
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