103 research outputs found
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
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
Magnetic Properties of a Bose-Einstein Condensate
Three hyperfine states of Bose-condensed sodium atoms, recently optically
trapped, can be described as a spin-1 Bose gas. We study the behaviour of this
system in a magnetic field, and construct the phase diagram, where the
temperature of the Bose condensation increases with magnetic field.
In particular the system is ferromagnetic below and the magnetization
is proportional to the condensate fraction in a vanishing magnetic field.
Second derivatives of the magnetisation with regard to temperature or magnetic
field are discontinuous along the phase boundary.Comment: 5 pages, 5 figures included, to appear in Phys. Rev.
Bose-Einstein condensation of atomic gases in a harmonic oscillator confining potential trap
We present a model which predicts the temperature of Bose-Einstein
condensation in atomic alkali gases and find excellent agreement with recent
experimental observations. A system of bosons confined by a harmonic oscillator
potential is not characterized by a critical temperature in the same way as an
identical system which is not confined. We discuss the problem of Bose-Einstein
condensation in an isotropic harmonic oscillator potential analytically and
numerically for a range of parameters of relevance to the study of low
temperature gases of alkali metals.Comment: 11 pages latex with two postscript figure
Pseudoinfarction pattern in a patient with hyperkalemia, diabetic ketoacidosis and normal coronary vessels: a case report
<p>Abstract</p> <p>Introduction</p> <p>A rare electrocardiographic finding of hyperkalemia is ST segment elevation or the so called 'pseudoinfarction' pattern. It has been suggested that hyperkalemia causes the 'pseudoinfarction' pattern not only through its direct myocardial effects, but also through other mechanisms, such as anoxia, acidosis, and coronary artery spasm.</p> <p>Case presentation</p> <p>A 33-year-old Caucasian woman with insulin-treated diabetes presented with continuous epigastric pain of four hours duration. Her coronary heart disease risk factors apart from diabetes included hypercholesterolemia and smoking. Her initial electrocardiogram revealed ST segment elevation in the anteroseptal leads consistent with anterior myocardial infarction. Blood tests revealed hyperglycemia, hyperkalemia, metabolic acidosis and urine ketones, while a bed-side cardiac echocardiogram showed no segmental wall motion abnormality. We provisionally diagnosed diabetic ketoacidosis that was possibly precipitated by acute myocardial infarction, as there were findings in favor of (epigastric pain, electrocardiogram pattern, presence of 3 coronary heart disease risk factors) and against (young age, normal echocardiogram) the diagnosis of acute myocardial infarction. We performed cardiac angiography in order to exclude an anterior acute myocardial infarction, which could lead to myocardial damage and possible severe complications should there be a delay in treatment. Angiography revealed normal coronary arteries. During the procedure, ST segment elevation in the anteroseptal leads was still present in our patient's electrocardiogram results.</p> <p>Conclusion</p> <p>ST segment elevation is a rare manifestation of hyperkalemia. In our patient, coronary spasm did not contribute to such an electrocardiography finding.</p
Magnetic Field Effects in the Pseudogap Phase: A Competing Energy Gap Scenario for Precursor Superconductivity
We study the sensitivity of T_c and T^* to low fields, H, within the
pseudogap state using a BCS-based approach extended to arbitrary coupling. We
find that T^* and T_c, which are of the same superconducting origin, have very
different H dependences. This is due to the pseudogap, \Delta_{pg}, which is
present at the latter, but not former temperature. Our results for the
coherence length \xi fit well with existing experiments.We predict that very
near the insulator \xi will rapidly increase.Comment: 4 pages, 4 figures, RevTe
Ground-State of Charged Bosons Confined in a Harmonic Trap
We study a system composed of N identical charged bosons confined in a
harmonic trap. Upper and lower energy bounds are given. It is shown in the
large N limit that the ground-state energy is determined within an accuracy of
and that the mean field theory provides a reasonable result with
relative error of less than 16% for the binding energy .Comment: 15 page
Quasicondensate and superfluid fraction in the 2D charged-boson gas at finite temperature
The Bogoliubov - de Gennes equations are solved for the Coulomb Bose gas
describing a fluid of charged bosons at finite temperature. The approach is
applicable in the weak coupling regime and the extent of its quantitative
usefulness is tested in the three-dimensional fluid, for which diffusion Monte
Carlo data are available on the condensate fraction at zero temperature. The
one-body density matrix is then evaluated by the same approach for the
two-dimensional fluid with e^2/r interactions, to demonstrate the presence of a
quasi-condensate from its power-law decay with increasing distance and to
evaluate the superfluid fraction as a function of temperature at weak coupling.Comment: 9 pages, 2 figure
Bose-Einstein condensation as symmetry breaking in compact curved spacetimes
We examine Bose-Einstein condensation as a form of symmetry breaking in the
specific model of the Einstein static universe. We show that symmetry breaking
never occursin the sense that the chemical potential never reaches its
critical value.This leads us to some statements about spaces of finite volume
in general. In an appendix we clarify the relationship between the standard
statistical mechanical approaches and the field theory method using zeta
functions.Comment: Revtex, 25 pages, 3 figures, uses EPSF.sty. To be published in Phys.
Rev.
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