8,002 research outputs found
Coherent Structure of Zonal Flow and Onset of Turbulent Transport
Excitation of the turbulence in the range of drift wave frequency and zonal flow in magnetized plasmas is analyzed. Nonlinear stabilization effect on zonal flow drive is introduced, and the steady state solution is obtained. The condition for the onset of turbulent transport is obtained and partition ratio of fluctuation energy into turbulence and zonal flows is derived. The turbulent transport coefficient, which includes the effect of zonal flow, is also obtained. Analytic result and direct numerical simulation show a good agreemen
Pole dynamics for the Flierl-Petviashvili equation and zonal flow
We use a systematic method which allows us to identify a class of exact
solutions of the Flierl-Petvishvili equation. The solutions are periodic and
have one dimensional geometry. We examine the physical properties and find that
these structures can have a significant effect on the zonal flow generation.Comment: Latex 40 pages, seven figures eps included. Effect of variation of
g_3 is studied. New references adde
Optical polarisation variability of radio loud narrow line Seyfert 1 galaxies. Search for long rotations of the polarisation plane
Narrow line Seyfert 1 galaxies (NLSy1s) constitute the AGN subclass
associated with systematically smaller black hole masses. A few radio loud ones
have been detected in MeV -- GeV energy bands by Fermi and evidence for the
presence of blazar-like jets has been accumulated. In this study we wish to
quantify the temporal behaviour of the optical polarisation, fraction and
angle, for a selected sample of radio loud NLSy1s. We also search for rotations
of the polarisation plane similar to those commonly observed in blazars. We
have conducted R-band optical polarisation monitoring of a sample of 10 RL
NLSy1s 5 of which have been previously detected by Fermi. The dataset includes
observations with the RoboPol, KANATA, Perkins and Steward polarimeters. In the
cases where evidences for long rotations of the polarisation plane are found,
we carry out numerical simulations to assess the probability that they are
caused by intrinsically evolving EVPAs instead of observational noise. Even our
moderately sampled sources show indications of variability, both in
polarisation fraction and angle. For the four best sampled objects in our
sample we find multiple periods of significant polarisation angle variability.
In the two best sampled cases, namely J1505+0326 and J0324+3410, we find
indications for three long rotations. We show that although noise can induce
the observed behaviour, it is much more likely that the apparent rotation is
caused by intrinsic evolution of the EVPA. To our knowledge this is the very
first detection of such events in this class of sources. In the case of the
largest dataset (J0324+3410) we find that the EVPA concentrates around a
direction which is at 49.3\degr to the 15-GHz radio jet implying a projected
magnetic field at an angle of 40.7\degr to that axis.Comment: Accepted for publication in section 2. Astrophysical processes of
Astronomy and Astrophysic
Tunnel magnetoresistance and interfacial electronic state
We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the -levels of impurities,
based on reduction in the spin-dependent -electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.Comment: 5 pages, 4 figures, 2 column revtex4 format, ICMFS 2002 (Kyoto
Dynamical Generation of Fermion Mass and Magnetic Field in Three-Dimensional QED with Chern-Simons Term
We study dynamical symmetry breaking in three-dimensional QED with a
Chern-Simons (CS) term, considering the screening effect of flavor
fermions. We find a new phase of the vacuum, in which both the fermion mass and
a magnetic field are dynamically generated, when the coefficient of the CS term
equals . The resultant vacuum becomes the finite-density
state half-filled by fermions. For , we find the fermion
remains massless and only the magnetic field is induced. For ,
spontaneous magnetization does not occur and should be regarded as an external
field.Comment: 8 pages, no figure, to be published in Phys. Rev. Let
The Supersymmetric Ward-Takahashi Identity in 1-Loop Lattice Perturbation Theory. I. General Procedure
The one-loop corrections to the lattice supersymmetric Ward-Takahashi
identity (WTi) are investigated in the off-shell regime. In the Wilson
formulation of the N=1 supersymmetric Yang-Mills (SYM) theory, supersymmetry
(SUSY) is broken by the lattice, by the Wilson term and is softly broken by the
presence of the gluino mass. However, the renormalization of the supercurrent
can be realized in a scheme that restores the continuum supersymmetric WTi
(once the on-shell condition is imposed). The general procedure used to
calculate the renormalization constants and mixing coefficients for the local
supercurrent is presented. The supercurrent not only mixes with the gauge
invariant operator . An extra mixing with other operators coming from
the WTi appears. This extra mixing survives in the continuum limit in the
off-shell regime and cancels out when the on-shell condition is imposed and the
renormalized gluino mass is set to zero. Comparison with numerical results are
also presented.Comment: 16 pages, 2 figures. Typos error correcte
Exact Bond-Located Spin Ground State in the Hubbard Chain with Off-Diagonal Coulomb Interactions
We show the existence of an exact ground state in certain parameter regimes
of one-dimensional half-filled extended Hubbard model with site-off-diagonal
interactions. In this ground state, the bond-located spin correlation exhibits
a long-range order. In the case when the spin space is SU(2) symmetric, this
ground state degenerates with higher spin states including a fully
ferromagnetic state. We also discuss the relation between the exact
bond-ordered ground state and the critical bond-spin-density-wave phase.Comment: 4 pages, 4 eps figure
Gauge Symmetry Enhancement and Radiatively Induced Mass in the Large N Nonlinear Sigma Model
We consider a hybrid of nonlinear sigma models in which two complex
projective spaces are coupled with each other under a duality. We study the
large N effective action in 1+1 dimensions. We find that some of the
dynamically generated gauge bosons acquire radiatively induced masses which,
however, vanish along the self-dual points where the two couplings
characterizing each complex projective space coincide. These points correspond
to the target space of the Grassmann manifold along which the gauge symmetry is
enhanced, and the theory favors the non-Abelian ultraviolet fixed point.Comment: 11 pages, REVTEX, typos are corrected, version to appear in Phys.
Rev.
Ni-substituted sites and the effect on Cu electron spin dynamics of YBa2Cu{3-x}NixO{7-\delta}
We report Cu nuclear quadrupole resonance experiment on magnetic impurity
Ni-substituted YBaCuNiO. The distribution of
Ni-substituted sites and its effect on the Cu electron spin dynamics are
investigated. Two samples with the same Ni concentration =0.10 and nearly
the same oxygen content but different 's were prepared: One is an
as-synthesized sample (7-=6.93) in air (), and the
other is a quenched one (7-=6.92) in a reduced oxygen atmosphere
(). The plane-site Cu(2) nuclear spin-lattice
relaxation for the quenched sample was faster than that for the as-synthesized
sample, in contrast to the Cu(1) relaxation that was faster for the
as-synthesized sample. This indicates that the density of plane-site Ni(2) is
higher in the quenched sample, contrary to the chain-site Ni(1) density which
is lower in the quenched sample. From the analysis in terms of the Ni-induced
nuclear spin-lattice relaxation, we suggest that the primary origin of
suppression of is associated with nonmagnetic depairing effect of the
plane-site Ni(2).Comment: 7 pages, 5 figure
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