111 research outputs found
Effects of mode-mode and isospin-isospin correlations on domain formation of disoriented chiral condensates
The effects of mode-mode and isospin-isospin correlations on nonequilibrium
chiral dynamics are investigated by using the method of the time dependent
variational approach with squeezed states as trial states. Our numerical
simulations show that large domains of the disoriented chiral condensate (DCC)
are formed due to the combined effect of the mode-mode and isospin-isospin
correlations. Moreover, it is found that, when the mode-mode correlation is
included, the DCC domain formation is accompanied by the amplification of the
quantum fluctuation, which implies the squeezing of the state. However, neither
the DCC domain formation nor the amplification of the quantum fluctuation is
observed if only the isospin-isospin correlation is included. This suggests
that the mode-mode coupling plays a key role in the DCC domain formation.Comment: 10 pages, 11 figures; Correction of an error in Fig.
Time-Evolution of a Collective Meson Field by the Use of a Squeezed State
A time-evolution of quantum meson fields is investigated in a linear sigma
model by means of the time-dependent variational approach with a squeezed
state. The chiral condensate, which is a mean field of the quantum meson
fields, and quantum fluctuations around it are treated self-consistently in
this approach. The attention is payed to the description of the relaxation
process of the chiral condensate, where the energy stored in the mean field
configuration flows to the fluctuation modes. It is shown that the quantum
fluctuations play an important role to describe this relaxation process.Comment: 18 pages, 22 postscript figures, uses PTPTeX.st
Nonequilibrium chiral dynamics by the time dependent variational approach with squeezed states
We investigate the inhomogeneous chiral dynamics of the O(4) linear sigma
model in 1+1 dimensions using the time dependent variational approach in the
space spanned by the squeezed states. We compare two cases, with and without
the Gaussian approximation for the Green's functions. We show that mode-mode
correlation plays a decisive role in the out-of-equilibrium quantum dynamics of
domain formation and squeezing of states.Comment: 5 pages, 4 figures. RevTex, version to appear in Phys. Rev. C. Rapid
Communicatio
Normal modes of a quasi-one-dimensional multi-chain complex plasma
We studied equally charged particles, suspended in a complex plasma, which
move in a plane and interact with a screened Coulomb potential (Yukawa type)
and with an additional external confining parabolic potential in one direction,
that makes the system quasi-one-dimensional (Q1D). The normal modes of the
system are studied in the presence of dissipation. We also investigated how a
perpendicular magnetic field couples the phonon modes with each other. Two
different ways of exciting the normal modes are discussed: 1) a uniform
excitation of the Q1D lattice, and 2) a local forced excitation of the system
in which one particle is driven by e.g. a laser. Our results are in very good
agreement with recent experimental findings on a finite single chain system
(Phys. Rev. Lett. {\bf 91}, 255003 (2003)). Predictions are made for the normal
modes of multi-chain structures in the presence of damping.Comment: 15 pages, 14 figures, accepted for publication on PR
Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal
This paper is devoted to a detailed analysis of the new type of the undulator
radiation generated by an ultra-relativistic charged particle channeling along
a crystal plane, which is periodically bent by a transverse acoustic wave, as
well as to the conditions limiting the observation of this phenomenon. This
mechanism makes feasible the generation of electromagnetic radiation, both
spontaneous and stimulated, emitted in a wide range of the photon energies,
from X- up to gamma-rays
Channeling of Positrons through Periodically Bent Crystals: on Feasibility of Crystalline Undulator and Gamma-Laser
The electromagnetic radiation generated by ultra-relativistic positrons
channelling in a crystalline undulator is discussed. The crystalline undulator
is a crystal whose planes are bent periodically with the amplitude much larger
than the interplanar spacing. Various conditions and criteria to be fulfilled
for the crystalline undulator operation are established. Different methods of
the crystal bending are described. We present the results of numeric
calculations of spectral distributions of the spontaneous radiation emitted in
the crystalline undulator and discuss the possibility to create the stimulated
emission in such a system in analogy with the free electron laser. A careful
literature survey covering the formulation of all essential ideas in this field
is given. Our investigation shows that the proposed mechanism provides an
efficient source for high energy photons, which is worth to study
experimentally.Comment: 52 pages, MikTeX, 14 figure
The effect of memory on relaxation in a scalar field theory
We derive a kinetic equation with a non-Markovian collision term which
includes a memory effect, from Kadanoff-Baym equations in theory
within the three-loop level for the two-particle irreducible (2PI) effective
action. The memory effect is incorporated into the kinetic equation by a
generalized Kadanoff-Baym ansatz.Based on the kinetic equations with and
without the memory effect, we investigate an influence of this effect on decay
of a single particle excitation with zero momentum in 3+1 dimensions and the
spatially homogeneous case. Numerical results show that, while the time
evolution of the zero mode is completely unaffected by the memory effect due to
a separation of scales in the weak coupling regime, this effect leads first to
faster relaxation than the case without it and then to slower relaxation as the
coupling constant increases.Comment: 12 pages, 6 eps figure
Development and application of radar reflectometer using micro to infrared waves
Progress in microwave and millimeter-wave technologies has made possible advanced diagnostics for application to various fields, including radio astronomy, alien substance detection, plasma diagnostics, airborne and space-borne imaging radars called as synthetic aperture radars, and living body measurements. Transmission, reflection, scattering, and radiation processes of electromagnetic waves are utilized as diagnostic principles. The diagnostics are classified as active and passive systems. Specifically, active radar reflectometry has become of importance in various applications due to the possibility of high localization and accessibility of the measurements as well as the non-invasive nature of the systems. In this paper, recent development and application of radar reflectometers are described. The key words are profile reflectometry, fluctuation reflectometry, imaging radar (optics imaging and synthetic aperture imaging), and radio-optics fusion technology in order to improve the spatial resolution
- …