6,489 research outputs found
Radiative Symmetry Breaking and Dynamical Origin of Cosmological Constant in Theory with Non-Linear Curvature Coupling
A scalar self-interacting theory non-linearly coupled with some power of the
curvature have a possibility to explain the current smallness of the
cosmological constant. Here one concentrate on a massless scalar field in the
four-dimensional Fridmann-Robertson-Walker (FRW) spacetime with flat spatial
part. One show the phase structure of radiative symmetry breaking and review a
dynamical resolution of the cosmological constant problem.Comment: 9 pages. To appear in the proceedings of 7th Workshop on Quantum
Field Theory Under the Influence of External Conditions (QFEXT 05),
Barcelona, Catalonia, Spain, 5-9 Sep 200
Aharonov-Bohm Effect at liquid-nitrogen temperature: Frohlich superconducting quantum device
The Aharonov-Bohm (AB) effect has been accepted and has promoted
interdisciplinary scientific activities in modern physics. To observe the AB
effect in condensed matter physics, the whole system needs to maintain phase
coherence, in a tiny ring of the diameter 1 micrometer and at low temperatures
below 1 K. We report that AB oscillations have been measured at high
temperature 79 K by use of charge-density wave (CDW) loops in TaS3 ring
crystals. CDW condensate maintained macroscopic quantum coherence, which
extended over the ring circumference 85 micrometer. The periodicity of the
oscillations is h/2e in accuracy within a 10 percent range. The observation of
the CDW AB effect implies Frohlich superconductivity in terms of macroscopic
coherence and will provide a novel quantum interference device running at room
temperature.Comment: 11 pages, 4 figure
Inhomogeneous Quasi-stationary States in a Mean-field Model with Repulsive Cosine Interactions
The system of N particles moving on a circle and interacting via a global
repulsive cosine interaction is well known to display spatially inhomogeneous
structures of extraordinary stability starting from certain low energy initial
conditions. The object of this paper is to show in a detailed manner how these
structures arise and to explain their stability. By a convenient canonical
transformation we rewrite the Hamiltonian in such a way that fast and slow
variables are singled out and the canonical coordinates of a collective mode
are naturally introduced. If, initially, enough energy is put in this mode, its
decay can be extremely slow. However, both analytical arguments and numerical
simulations suggest that these structures eventually decay to the spatially
uniform equilibrium state, although this can happen on impressively long time
scales. Finally, we heuristically introduce a one-particle time dependent
Hamiltonian that well reproduces most of the observed phenomenology.Comment: to be published in J. Phys.
and mesons at finite temperature and density in the NJL model with dimensional regularization
Dynamical Symmetry breaking and meson masses are studied in the
Nambu-Jona-Lasinio (NJL) model at finite temperature and chemical potential
using the dimensional regularization. Since the model is not renormalizable in
four space-time dimensions, physical results and parameters depend on the
regularization method. Following the imaginary time formalism, we introduce the
temperature, and the chemical potential, . The parameters in the model
are fixed by calculating the pion mass and decay constant in the dimensional
regularization at .Comment: 28 pages, 9 figures, v2: a few points corrected and references adde
Space-time evolution induced by spinor fields with canonical and non-canonical kinetic terms
We study spinor field theories as an origin to induce space-time evolution.
Self-interacting spinor fields with canonical and non-canonical kinetic terms
are considered in a Friedman-Robertson-Walker universe. The deceleration
parameter is calculated by solving the equation of motion and the Friedman
equation, simultaneously. It is shown that the spinor fields can accelerate and
decelerate the universe expansion. To construct realistic models we discuss the
contributions from the dynamical symmetry breaking.Comment: 16 pages, 19 figure
Phase Structure of a Four- and Eight-Fermion Interaction Model at Finite Temperature and Chemical Potential in Arbitrary Dimensions
The phase structure of a four- and eight-fermion interaction model is
investigated at finite temperature and chemical potential in arbitrary
space-time dimensions, . The effective potential and the gap
equation are calculated in the leading order of the 1/N expansion. If the first
order phase transition takes place, the phase boundary dividing the symmetric
and the broken phase is modified by the eight-fermion interaction.Comment: 20 pages, 26 figures; revised argument and added reference for
section
Dynamical symmetry breaking in the external gravitational and constant magnetic fields
We investigate the effects of the external gravitational and constant
magnetic fields to the dynamical symmetrybreaking. As simple models of the
dynamical symmetry breaking we consider the Nambu-Jona-Lasinio (NJL) model and
the supersymmetric Nambu-Jona-Lasinio (SUSY NJL) model non-minimally
interacting with the external gravitational field and minimally interacting
with constant magnetic field. The explicit expressions for the scalar and
spinor Green functions are found up to the linear terms on the spacetime
curvature and exactly for a constant magnetic field. We obtain the effective
potential of the above models from the Green functions in the magnetic field in
curved spacetime. Calculating the effective potential numerically with the
varying curvature and/or magnetic fields we show the effects of the external
gravitational and magnetic fields to the phase structure of the theories. In
particular, increase of the curvature in the spontaneously broken chiral
symmetry phase due to the fixed magnetic field makes this phase to be less
broken. On the same time strong magnetic field quickly induces chiral symmetry
breaking even at the presence of fixed gravitational field within nonbroken
phase.Comment: 23 pages, Latex, epic.sty and eepic.sty are use
Superconducting Fluctuations in a Multi-Band 1D Hubbard Model
A renormalization-group and bosonization approach for a multi-band Hubbard
Hamiltonian in one dimension is described. Based on the limit of many bands, it
is argued that this Hamiltonian with bare repulsive electron-electron
interactions is scaled under specific conditions to a model in which
superconducting fluctuations dominate.Comment: 12 pages + 1 fig, Revtex, Preprint - Los Alamo
Phase diagram of Nambu-Jona-Lasinio model with dimensional regularization
We investigate the phase diagram on temperature-chemical potential plane in
the Nambu-Jona-Lasinio model with the dimensional regularization. While the
structure of the resulting diagram shows resemblance to the one in the
frequently used cutoff regularization, some results of our study indicate
striking difference between these regularizations. The diagram in the
dimensional regularization exhibits strong tendency of the first order phase
transition.Comment: 9 pages, 9 figure
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Attitudes toward depression among Japanese non-psychiatric medical doctors: A cross-sectional study
Abstract
Background: Under-recognition of depression is common in many countries. Education of medical staff, focusing on their attitudes towards depression, may be necessary to change their behavior and enhance recognition of depression. Several studies have previously reported on attitudes toward depression among general physicians. However, little is known about attitudes of non-psychiatric doctors in Japan. In the present study, we surveyed nonpsychiatric doctorsâ attitude toward depression.
Methods: The inclusion criteria of participants in the present study were as follows: 1) Japanese non-psychiatric doctors and 2) attendees in educational opportunities regarding depression care. We conveniently approached two populations: 1) a workshop to depression care for non-psychiatric doctors and 2) a general physician-psychiatrist (GP)network group. We contacted 367 subjects. Attitudes toward depression were measured using the Depression Attitude Questionnaire (DAQ), a 20-item self-report questionnaire developed for general physicians. We report scores of each DAQ item and factors derived from exploratory factor analysis.
Results: We received responses from 230 subjects, and we used DAQ data from 187 non-psychiatric doctors who met the inclusion criteria. All non-psychiatric doctors (n = 187) disagreed with "I feel comfortable in dealing with depressed patients' needs," while 60 % (n = 112) agreed with "Working with depressed patients is heavy going." Factor analysis indicated these items comprised a factor termed "Depression should be treated by psychiatrists" - to which 54 % of doctors (n = 101) agreed. Meanwhile, 67 % of doctors (n = 126) thought that nurses could be useful in depressed patient support. The three factors derived from the Japanese DAQ differed from models previously derived from British GP samples. The attitude of Japanese non-psychiatric doctors concerning whether depression should be treated by psychiatrists was markedly different to that of British GPs.
Conclusions: Japanese non-psychiatric doctors believe that depression care is beyond the scope of their duties. It is suggested that educational programs or guidelines for depression care developed in other countries such as the UK are not directly adaptable for Japanese non-psychiatric doctors. Developing a focused educational program that motivates non-psychiatric doctors to play a role in depression care is necessary to enhance recognition and treatment of depression in Japan
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