7,652 research outputs found
Parametric resonance at the critical temperature in high energy heavy ion collisions
Parametric resonance in soft modes at the critical temperature () in
high energy heavy ion collisions is studied in the case when the temperature
() of the system is almost constant for a long time. By deviding the fields
into three parts, zero mode (condensate), soft modes and hard modes and
assuming that the hard modes are in thermal equilibrium, we derive the equation
of motion for soft modes at . Enhanced modes are extracted by
comparing with the Mathieu equation for the condensate oscillating along the
sigma axis at . It is found that the soft mode of fields at
about 174 MeV is enhanced.Comment: 8 pages, 1 figure Some statements and equations are modified to
clarif
Parametric amplification with a friction in heavy ion collisions
We study the effects of the expansion of the system and the friction on the
parametric amplification of mesonic fields in high energy heavy ion collisions
within the linear model . The equation of motion which is similar to
Mathieu equation is derived to describe the time development of classical
fields in the last stage of a heavy ion collision after the freezeout time. The
enhanced mode is extracted analytically by comparison with Mathieu equation and
the equation of motion is solved numerically to examine whether soft modes will
be enhanced or not. It is found that the strong peak appears around 267 MeV in
the pion transverse momentum distribution in cases with weak friction and high
maximum temperature. This enhancement can be extracted by taking the ratio
between different modes in the pion transverse momentum distribution.Comment: 10 pages, 9 figures LaTeX: appendix adde
Topology Change of Coalescing Black Holes on Eguchi-Hanson Space
We construct multi-black hole solutions in the five-dimensional
Einstein-Maxwell theory with a positive cosmological constant on the
Eguchi-Hanson space, which is an asymptotically locally Euclidean space. The
solutions describe the physical process such that two black holes with the
topology of S^3 coalesce into a single black hole with the topology of the lens
space L(2;1)=S^3/Z_2. We discuss how the area of the single black hole after
the coalescence depends on the topology of the horizon.Comment: 10 pages, Some comments are added. to be published as a letter in
Classical and Quantum Gravit
Two-photon nonlinearity in general cavity QED systems
We have investigated the two-photon nonlinearity at general cavity QED
systems, which covers both weak and strong coupling regimes and includes
radiative loss from the atom. The one- and two-photon propagators are obtained
in analytic forms. By surveying both coupling regimes, we have revealed the
conditions on the photonic wavepacket for yielding large nonlinearity depending
on the cavity Q-value. We have also discussed the effect of radiative loss on
the nonlinearity.Comment: 8 pages, 5 figure
Theoretical framework of entangled-photon generation from biexcitons in nano-to-bulk crossover regime with planar geometry
We have constructed a theoretical framework of the biexciton-resonant
hyperparametric scattering for the pursuit of high-power and high-quality
generation of entangled photon pairs. Our framework is applicable to
nano-to-bulk crossover regime where the center-of-mass motion of excitons and
biexcitons is confined. Material surroundings and the polarization correlation
of generated photons can be considered. We have analyzed the entangled-photon
generation from CuCl film, by which ultraviolet entangled-photon pairs are
generated, and from dielectric microcavity embedding a CuCl layer. We have
revealed that in the nano-to-bulk crossover regime we generally get a high
performance from the viewpoint of statistical accuracy, and the generation
efficiency can be enhanced by the optical cavity with maintaining the high
performance. The nano-to-bulk crossover regime has a variety of degrees of
freedom to tune the entangled-photon generation, and the scattering spectra
explicitly reflect quantized exciton-photon coupled modes in the finite
structure.Comment: 18 pages, 10 figure
Magnetic Ordering, Orbital Ordering and Resonant X-ray Scattering in Perovskite Titanates
The effective Hamiltonian for perovskite titanates is derived by taking into
account the three-fold degeneracy of orbitals and the strong
electron-electron interactions. The magnetic and orbital ordered phases are
studied in the mean-field approximation applied to the effective Hamiltonian. A
large degeneracy of the orbital states in the ferromagnetic phase is found in
contrast to the case of the doubly degenerate orbitals. Lifting of this
orbital degeneracy due to lattice distortions and spin-orbit coupling is
examined. A general form for the scattering cross section of the resonant x-ray
scattering is derived and is applied to the recent experimental results in
YTiO. The spin wave dispersion relation in the orbital ordered YTiO is
also studied.Comment: 10 pages, 6 figure
Interaction between dust grains near a conducting wall
The effect of the conducting electrode on the interaction of dust grains in a
an ion flow is discussed. It is shown that two grains levitating above the
electrode at the same height may attract one another. This results in the
instability of a dust layer in a plasma sheath.Comment: 9 pages. 3 figures. Submitted to Plasma Physics Report
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