361 research outputs found
Molecular formations in ultracold mixtures of interacting and noninteracting atomic gases
Atom-molecule equilibrium for molecular formation processes is discussed for
boson-fermion, fermion-fermion, and boson-boson mixtures of ultracold atomic
gases in the framework of quasichemical equilibrium theory. After presentation
of the general formulation, zero-temperature phase diagrams of the
atom-molecule equilibrium states are calculated analytically; molecular, mixed,
and dissociated phases are shown to appear for the change of the binding energy
of the molecules. The temperature dependences of the atom or molecule densities
are calculated numerically, and finite-temperature phase structures are
obtained of the atom-molecule equilibrium in the mixtures. The transition
temperatures of the atom or molecule Bose-Einstein condensations are also
evaluated from these results. Quantum-statistical deviations of the law of mass
action in atom-molecule equilibrium, which should be satisfied in mixtures of
classical Maxwell-Boltzmann gases, are calculated, and the difference in the
different types of quantum-statistical effects is clarified. Mean-field
calculations with interparticle interactions (atom-atom, atom-molecule, and
molecule-molecule) are formulated, where interaction effects are found to give
the linear density-dependent term in the effective molecular binding energies.
This method is applied to calculations of zero-temperature phase diagrams,
where new phases with coexisting local-equilibrium states are shown to appear
in the case of strongly repulsive interactions.Comment: 35 pages, 14 figure
Intake, Digestibility and Rate of Passage of Grass in Grazing by Light Breed Horses on Different Pastures
In a previous study, grazing light breed horses could ingest CP and DE requirements for maintenance without supplements. However, their grazing behaviour, such as biting and chewing efficiency, which related to the passage rate of forage in the digestive tract and fibre digestibility, was affected by the pasture conditions (Kawai et al., 2004). In this study, the DM intake, digestibility and mean retention time (MRT) of grass in light breed horses were determined and compared in spring, summer and autumn on an improved pasture
A compact magnetic bearing for gimballed momentum wheel
A three axis controlled magnetic bearing and its application to a momentum wheel are described. The four divided stators provide a momentum wheel with high reliability, low weight, large angular momentum storage capacity, and gimbal control. Those characteristics are desirable for spacecraft attitude control
Meson Condensation in Dense Matter Revisited
The results for meson condensation in the literature vary markedly depending
on whether one uses chiral perturbation theory or the current-algebra-plus-PCAC
approach. To elucidate the origin of this discrepancy, we re-examine the role
of the sigma-term in meson condensation. We find that the resolution of the
existing discrepancy requires a knowledge of terms in the Lagrangian that are
higher order in density than hitherto considered.Comment: 10pages, USC(NT)-94-
Diquark Bose-Einstein condensation
Bose-Einstein condensation (BEC) of composite diquarks in quark matter (the
color superconductor phase) is discussed using the quasi-chemical equilibrium
theory at a relatively low density region near the deconfinement phase
transition, where dynamical quark-pair fluctuations are assumed to be described
as bosonic degrees of freedom (diquarks). A general formulation is given for
the diquark formation and particle-antiparticle pair-creation processes in the
relativistic flamework, and some interesting properties are shown, which are
characteristic for the relativistic many-body system. Behaviors of transition
temperature and phase diagram of the quark-diquark matter are generally
presented in model parameter space, and their asymptotic behaviors are also
discussed. As an application to the color superconductivity, the transition
temperatures and the quark and diquark density profiles are calculated in case
with constituent/current quarks, where the diquark is in bound/resonant state.
We obtained MeV for constituent quarks and MeV
for current quarks at a moderate density (). The method
is also developed to include interdiquark interactions into the quasi-chemical
equilibrium theory within a mean-field approximation, and it is found that a
possible repulsive diquark-diquark interaction lowers the transition
temperature by nearly 50%.Comment: 21 pages, 23 figure
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
Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure
In these lectures the three flavor soliton approach for baryons is reviewed.
Effects of flavor symmetry breaking in the baryon wave--functions on axial
current matrix elements are discussed. A bosonized chiral quark model is
considered to outline the computation of spin dependent nucleon structure
functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry
and Spin, Prague, 2001, to appear in the proceedings. References correcte
Dissipative Field Theory with Caldeira-Leggett Method and its Application to Disoriented Chiral Condensation
The effective field theory including the dissipative effect is developed
based on the Caldeira-Leggett theory at the classical level. After the
integration of the small field fluctuations considered as the field radiation,
the integro-differential field equation is given and shown to include the
dissipative effects. In that derivation, special cares should be taken for the
boundary condition of the integration. Application to the linear sigma model is
given, and the decay process of the chiral condensate is calculated with it,
both analytically in the linear approximation and numerically. With these
results, we discuss the stability of chiral condensates within the quenched
approximation.Comment: 16pages, ReV-Te
Collective ferromagnetism in two-component Fermi-degenerate gas trapped in finite potential
Spin asymmetry of the ground states is studied for the trapped
spin-degenerate (two-component) gases of the fermionic atoms with the repulsive
interaction between different components, and, for large particle number, the
asymmetric (collective ferromagnetic) states are shown to be stable because it
can be energetically favorable to increase the fermi energy of one component
rather than the increase of the interaction energy between up-down components.
We formulate the Thomas-Fermi equations and show the algebraic methods to solve
them. From the Thomas-Fermi solutions, we find three kinds of ground states in
finite system: 1) paramagnetic (spin-symmetric), 2) ferromagnetic (equilibrium)
and 3) ferromagnetic (nonequilibrium) states. We show the density profiles and
the critical atom numbers for these states obtained analytically, and, in
ferromagnetic states, the spin-asymmetries are shown to occur in the central
regions of the trapped gas, and grows up with increasing particle number. Based
on the obtained results, we discuss the experimental conditions and current
difficulties to realize the ferromagnetic states of the trapped atom gas, which
should be overcome.Comment: submit to PR
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