4,447 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
Modelling the measured local time evolution of strongly nonlinear heat pulses in the Large Helical Device
In some magnetically confined plasmas, an applied pulse of rapid edge cooling can trigger either a positive or negative excursion in the core electron temperature from its steady state value. We present a new model which captures the time evolution of the transient, non-diffusive local dynamics in the core plasma. We show quantitative agreement between this model and recent spatially localized measurements (Inagaki et al 2010 Plasma Phys. Control. Fusion 52 075002) of the local time-evolving temperature pulse in cold pulse propagation experiments in the Large Helical Device
Stochastic Gravitational Wave Background originating from Halo Mergers
The stochastic gravitational wave background (GWB) from halo mergers is
investigated by a quasi-analytic method. The method we employ consists of two
steps. The first step is to construct a merger tree by using the Extended
Press-Schechter formalism or the Sheth & Tormen formalism, with Monte-Carlo
realizations. This merger tree provides evolution of halo masses. From -body
simulation of two-halo mergers, we can estimate the amount of gravitational
wave emission induced by the individual merger process. Therefore the second
step is to combine this gravitaional wave emission to the merger tree and
obtain the amplitude of GWB. We find for Hz, where is the energy density of the GWB. It
turns out that most of the contribution on the GWB comes from halos with masses
below and mergers at low redshift, i.e., .Comment: 5 pages, 8 figures. Accepted for publication in Physical Review
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
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.
Chiral Properties of QCD Vacuum in Magnetars- A Nambu-Jona-Lasinio Model with Semi-Classical Approximation
The breaking of chiral symmetry of light quarks at zero temperature in
presence of strong quantizing magnetic fiels is studied using
Nambu-Jona-Lasinio (NJL) model with Thomas-Fermi type semi-classical formalism.
It is found that the dynamically generated light quark mass can never become
zero if the Landau levels are populated and the mass increases with the
increase of magnetic field strength.Comment: REVTEX 11 Pages, One .eps figure (included
Schwinger-Dyson Analysis of Dynamical Symmetry Breaking on a Brane with Bulk Yang-Mills Theory
The dynamically generated fermion mass is investigated in the flat brane
world with (4+delta)-dimensional bulk space-time, and in the Randall-Sundrum
(RS) brane world. We consider the bulk Yang-Mills theory interacting with the
fermion confined on a four-dimensional brane. Based on the effective theory
below the reduced cutoff scale on the brane, we formulate the Schwinger-Dyson
equation of the brane fermion propagator. By using the improved ladder
approximation we numerically solve the Schwinger-Dyson equation and find that
the dynamical fermion mass is near the reduced cutoff scale on the brane for
the flat brane world with delta >= 3 and for the RS brane world. In RS brane
world KK excited modes of the bulk gauge field localized around the y = pi R
brane and it enhances the dynamical symmetry breaking on the brane. The decay
constant of the fermion and the anti-fermion composite operator can be taken to
be the order of the electroweak scale much smaller than the Planck scale.
Therefore electroweak mass scale can be realized from only the Planck scale in
the RS brane world due to the fermion and the anti-fermion pair condensation.
That is a dynamical realization of Randall-Sundrum model which solves the
weak-Planck hierarchy problem.Comment: 21 pages, 12 figures; typos corrected, references added and updated,
footnotes adde
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
Symmetry structure and phase transitions
We study chiral symmetry structure at finite density and temperature in the
presence of external magnetic field and gravity, a situation relevant in the
early Universe and in the core of compact stars.
We then investigate the dynamical evolution of phase transition in the
expanding early Universe and possible formation of quark nuggets and their
survival.Comment: Plenary talk given at the 4th. ICPAQGP held at Jaipur, India from Nov
26-30, 2001.laTex 2e file with 8 ps figures and 12 page
- âŠ