1,460 research outputs found
Nonequilibrium Fock space for the electron transport problem
Based on the formalism of thermo field dynamics we propose a concept of
nonequilibrium Fock space and nonequilibrium quasiparticles for quantum
many-body system in nonequilibrium steady state. We develop a general theory as
well as demonstrate the utility of the approach on the example of electron
transport through the interacting region. The proposed approach is compatible
with advanced methods of electronic structure calculations such as coupled
cluster theory and configuration interaction
Noncommutative Thermofield Dynamics
The real-time operator formalism for thermal quantum field theories,
thermofield dynamics, is formulated in terms of a path-integral approach in
non-commutative spaces. As an application, the two-point function for a thermal
non-commutative theory is derived at the one-loop level. The
effect of temperature and the non-commutative parameter, competing with one
another, is analyzed.Comment: 13 pages; to be published in IJMP-A
Pion-Nucleon Scattering in Kadyshevsky Formalism: I Meson Exchange Sector
In a series of two papers we present the theoretical results of /meson-baryon scattering in the Kadyshevsky formalism. In this paper the
results are given for meson exchange diagrams. On the formal side we show, by
means of an example, how general couplings, i.e. couplings containing multiple
derivatives and/or higher spin fields, should be treated. We do this by
introducing and applying the Takahashi-Umezawa and the Gross-Jackiw method. For
practical purposes we introduce the method. We also show how the
Takashashi-Umezawa method can be derived using the theory of Bogoliubov and
collaborators and the Gross-Jackiw method is also used to study the
-dependence of the Kadyshevsky integral equation. Last but not least we
present the second quantization procedure of the quasi particle in Kadyshevsky
formalism.Comment: 29 page
Spectra of Quarkonia at Finite Temperature
Finite-temperature spectra of heavy quarkonia are calculated by combining
potential model and thermofield dynamics formalisms. The mass spectra of the
heavy quarkonia with various quark contents are calculated. It is found that
binding mass of the quarkonium decreases as temperature increases.Comment: 12 pages, 1 figure. To appear Mod.Phys.Lett.
Influence of modal loss on the quantum state generation via cross-Kerr nonlinearity
In this work we investigate an influence of decoherence effects on quantum
states generated as a result of the cross-Kerr nonlinear interaction between
two modes. For Markovian losses (both photon loss and dephasing), a region of
parameters when losses still do not lead to destruction of non-classicality is
identified. We emphasize the difference in impact of losses in the process of
state generation as opposed to those occurring in propagation channel. We show
moreover, that correlated losses in modern realizations of schemes of large
cross-Kerr nonlinearity might lead to enhancement of non-classicality.Comment: To appear in PR
Three-body problem at finite temperature and density
We derive practical three-body equations for the equal-time three-body Green
function in matter. Our equations describe both bosons and fermions at finite
density and temperature, and take into account all possible two-body
sub-processes allowed by the underlying Hamiltonian.Comment: 24 pages, revtex
Thermal Bogoliubov transformation in nuclear structure theory
Thermal Bogoliubov transformation is an essential ingredient of the thermo
field dynamics -- the real time formalism in quantum field and many-body
theories at finite temperatures developed by H. Umezawa and coworkers. The
approach to study properties of hot nuclei which is based on the extension of
the well-known Quasiparticle-Phonon Model to finite temperatures employing the
TFD formalism is presented. A distinctive feature of the QPM-TFD combination is
a possibility to go beyond the standard approximations like the thermal
Hartree-Fock or the thermal RPA ones.Comment: 8 pages, Proceedings of the International Bogolyubov Conference
"Problems of Theoretical and Mathematical Physics", August 23 -- 27, 2009,
Dubna, Russi
Lepton charge and neutrino mixing in pion decay processes
We consider neutrino mixing and oscillations in quantum field theory and
compute the neutrino lepton charge in decay processes where neutrinos are
generated. We also discuss the proper definition of flavor charge and states
and clarify the issues of the possibility of different mass parameters in field
mixing.Comment: 13 page
QED symmetries in real-time thermal field theory
We study the discrete and gauge symmetries of Quantum Electrodynamics at
finite temperature within the real-time formalism.
The gauge invariance of the complete generating functional leads to the
finite temperature Ward identities. These Ward identities relate the eight
vertex functions to the elements of the self-energy matrix. Combining the
relations obtained from the and the gauge symmetries of the theory we
find that only one out of eight longitudinal vertex functions is independent.
As a consequence of the Ward identities it is shown that some elements of the
vertex function are singular when the photon momentum goes to zero.Comment: New version as it will appear in Phys RevD 19 pages, RevTex, 1figur
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