Initial States and Time Evolution in Nonequilibrium Quantum Field Theory

2007 ◽  
Vol 785 (1-2) ◽  
pp. 218-221
Author(s):  
R.F. Álvarez-Estrada
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Time Evolution ◽  
Quantum Field ◽  
Initial States

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.

Simulating Equilibrium Behavior of Quantum Fields with Time-evolving Classical Fields

2021 ◽  
Vol 1 ◽  
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Real Time ◽  
Time Evolution ◽  
Equations Of Motion ◽  
Quantum Field ◽  
Quantum Fields ◽  
Equilibrium Behavior ◽  
Classical Fields

A set of field configurations (replicas) reaches equilibrium of quantum field theory after real-time evolution obeying classical equations of motion.

scholarly journals FIELD THEORY APPROACH TO $K^0-\overline{K^0}$ AND $B^0-\overline{B^0}$ SYSTEMS

1998 ◽  
Vol 13 (20) ◽  
pp. 3587-3600 ◽  
Author(s):  
M. BEUTHE ◽  
J. PESTIEAU ◽  
G. LÓPEZ CASTRO
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Cp Violation ◽  
Time Evolution ◽  
Theory Approach ◽  
Quantum Field ◽  
Unstable Particles ◽  
Mixed Systems

Quantum field theory provides a consistent framework to deal with unstable particles. We present here an approach based on field theory to describe the production and decay of unstable [Formula: see text] and [Formula: see text] mixed systems. The formalism is applied to compute the time evolution amplitudes of K0 and [Formula: see text] studied in DAPHNE and CPLEAR experiments. We also introduce a new set of parameters that describe CP violation in K→ππ decays without recourse to isospin decomposition of the decay amplitudes.

scholarly journals Probing the Planck scale: the modification of the time evolution operator due to the quantum structure of spacetime

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
T. Padmanabhan
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Matrix Element ◽  
Time Evolution ◽  
Single Particle ◽  
Evolution Operator ◽  
Planck Scale ◽  
Position Operator ◽  
Quantum Field ◽  
Time Evolution Operator

Abstract The propagator which evolves the wave-function in non-relativistic quantum mechanics, can be expressed as a matrix element of a time evolution operator: i.e. GNR(x) = 〈x2|UNR(t)|x1〉 in terms of the orthonormal eigenkets |x〉 of the position operator. In quantum field theory, it is not possible to define a conceptually useful single-particle position operator or its eigenkets. It is also not possible to interpret the relativistic (Feynman) propagator GR(x) as evolving any kind of single-particle wave-functions. In spite of all these, it is indeed possible to express the propagator of a free spinless particle, in quantum field theory, as a matrix element 〈x2|UR(t)|x1〉 for a suitably defined time evolution operator and (non-orthonormal) kets |x〉 labeled by spatial coordinates. At mesoscopic scales, which are close but not too close to Planck scale, one can incorporate quantum gravitational corrections to the propagator by introducing a zero-point-length. It turns out that even this quantum-gravity-corrected propagator can be expressed as a matrix element 〈x2|UQG(t)|x1〉. I describe these results and explore several consequences. It turns out that the evolution operator UQG(t) becomes non-unitary for sub-Planckian time intervals while remaining unitary for time interval is larger than Planck time. The results can be generalized to any ultrastatic curved spacetime.

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