scholarly journals Study of simulation method of time evolution of atomic and molecular systems by quantum electrodynamics

2014 ◽  
Vol 114 (23) ◽  
pp. 1567-1580 ◽  
Author(s):  
Kazuhide Ichikawa ◽  
Masahiro Fukuda ◽  
Akitomo Tachibana
Keyword(s):  
Time Evolution ◽  
Quantum Electrodynamics ◽  
Simulation Method ◽  
Molecular Systems

Time evolution in quantum electrodynamics

1991 ◽  
Vol 44 (9) ◽  
pp. 5407-5413 ◽  
Author(s):  
K. Pachucki
Keyword(s):  
Time Evolution ◽  
Quantum Electrodynamics

scholarly journals Non-Equilibrium Quantum Electrodynamics in Open Systems as a Realizable Representation of Quantum Field Theory of the Brain

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 43 ◽  
Author(s):  
Akihiro Nishiyama ◽  
Shigenori Tanaka ◽  
Jack A. Tuszynski
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Time Evolution ◽  
Central Region ◽  
Quantum Electrodynamics ◽  
Quantum Tunneling ◽  
Evolution Equations ◽  
Open Systems ◽  
Quantum Field ◽  
The Brain

We derive time evolution equations, namely the Klein–Gordon equations for coherent fields and the Kadanoff–Baym equations in quantum electrodynamics (QED) for open systems (with a central region and two reservoirs) as a practical model of quantum field theory of the brain. Next, we introduce a kinetic entropy current and show the H-theorem in the Hartree–Fock approximation with the leading-order (LO) tunneling variable expansion in the 1st order approximation for the gradient expansion. Finally, we find the total conserved energy and the potential energy for time evolution equations in a spatially homogeneous system. We derive the Josephson current due to quantum tunneling between neighbouring regions by starting with the two-particle irreducible effective action technique. As an example of potential applications, we can analyze microtubules coupled to a water battery surrounded by a biochemical energy supply. Our approach can be also applied to the information transfer between two coherent regions via microtubules or that in networks (the central region and the N res reservoirs) with the presence of quantum tunneling.

Molecular quantum electrodynamics

1971 ◽  
Vol 321 (1547) ◽  
pp. 557-572 ◽  
Keyword(s):  
Electromagnetic Field ◽  
Quantum Electrodynamics ◽  
Unitary Transformation ◽  
Charged Particles ◽  
Gauge Condition ◽  
Binding Energies ◽  
Quantum Mechanical ◽  
Supplementary Condition ◽  
Molecular Systems ◽  
Hamiltonian Theory

A comparison is made of the conventional quantum mechanical hamiltonian for the interaction of molecular systems with the electromagnetic field and the alternative multipole formulation given recently (Atkins & Woolley 1970). The conventional hamiltonian is first derived by using Dirac’s generalized hamiltonian theory in which the Coulomb gauge condition is introduced as a supplementary condition. We analyse further the interpretation of the unitary transformation that connects the two hamiltonians in terms of the arbitrariness of the phase of the wavefunctions of charged particles in the presence of the electromagnetic field, and finally examine the problem of exhibiting explicitly the binding energies of the molecular systems.

Estimation of Equivalent Permeability in Magnetorheological Fluid Considering Cluster Formation of Particles

2004 ◽  
Vol 71 (2) ◽  
pp. 201-207 ◽  
Author(s):  
Toshihiko Shiraishi ◽  
Shin Morishita ◽  
Henri P. Gavin
Keyword(s):  
Time Evolution ◽  
Magnetic Permeability ◽  
Cluster Formation ◽  
Simulation Method ◽  
Magnetic Flux Density ◽  
Magnetic Characteristics ◽  
The Finite Element Method ◽  
Mr Fluid ◽  
Equivalent Permeability ◽  
Mr Fluids

This paper describes a simulation method for the equivalent magnetic permeability of mangetorheological (MR) fluids considering cluster formation of suspended particles. The cluster formation under a magnetic field is simulated by cellular automata (CA). Simulated cluster structures are qualitatively equivalent to those observed experimentally. Considering this structure, magnetic permeability analysis is conducted on a representative MR fluid by the finite element method. The equivalent permeability in the MR fluid was obtained from the average magnetic flux density and field. The time evolution of the magnetic characteristics of the MR fluid is shown to correspond to the time evolution of cluster formation.

scholarly journals Derivation of the stationary fluorescence spectrum formula for molecular systems from the perspective of quantum electrodynamics

2021 ◽  
Vol 61 (2) ◽  
Author(s):  
Y. Braver ◽  
L. Valkunas ◽  
A. Gelzinis
Keyword(s):  
Fluorescence Spectrum ◽  
Quantum Electrodynamics ◽  
Fluorescence Spectra ◽  
Photon Emission ◽  
Mathematical Treatment ◽  
Matrix Formalism ◽  
Physical Content ◽  
Molecular Systems ◽  
Standard Textbook ◽  
Density Matrix Formalism

Numerical simulations of stationary fluorescence spectra of molecular systems usually rely on the relation between the photon emission rate and the system’s dipole–dipole correlation function. However, research papers usually take this relation for granted, and standard textbook expositions of the theory of fluorescence spectra also tend to leave out this important relation. In order to help researchers with less theoretical training gain a deeper understanding of the emission process, we perform a step-by-step derivation of the expression for the fluorescence spectrum, focusing on rigorous mathematical treatment and the underlying physical content. Right from the start, we employ quantum description of the electromagnetic field, which provides a clear picture of emission that goes beyond the phenomenological treatment in terms of the Einstein A coefficient. Having obtained the final expression, we discuss the relation of the latter to the present level of theory by studying a simple two-level system. From the technical perspective, the present work also aims at familiarizing the reader with the density matrix formalism and with the application of the double-sided Feynman diagrams.

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