438 research outputs found
Hidden symmetry and knot solitons in a charged two-condensate Bose system
We show that a charged two-condensate Ginzburg-Landau model or equivalently a
Gross-Pitaevskii functional for two charged Bose condensates, can be mapped
onto a version of the nonlinear O(3) -model. This implies in particular
that such a system possesses a hidden O(3) symmetry and allows for the
formation of stable knotted solitons. The results, in particular, should be
relevant to the superconducting MgB_2.Comment: This version will appear in Phys. Rev. B, added a comment on the case
when condensates in two bands do not independently conserve, also added a
figure and references to experimental papers on MgB_2 (for which our study is
relevant). Miscellaneous links on knot solitons are also available at the
homepage of one of the authors http://www.teorfys.uu.se/PEOPLE/egor/ .
Animations of knot solitons are available at
http://users.utu.fi/h/hietarin/knots/c45_p2.mp
Renormalization of the P- and T-odd nuclear potentials by the strong interaction and enhancement of P-odd effective field
Approximate analytical formulas for the self-consistent renormalization of
P,T-odd and P-odd weak nuclear potentials by the residual nucleon-nucleon
strong interaction are derived. The contact spin-flip nucleon-nucleon
interaction reduces the constant of the P,T-odd potential 1.5 times for the
proton and 1.8 times for the neutron. Renormalization of the P-odd potential is
caused by the velocity dependent spin-flip component of the strong interaction.
In the standard variant of -exchange, the conventional strength
values lead to anomalous enhancement of the P-odd potential. Moreover, the
-meson exchange contribution seems to be large enough to generate an
instability (pole) in the nuclear response to a weak potential.Comment: 5 pages, Revtex3, no figure
Streamer Wave Events Observed in Solar Cycle 23
In this paper we conduct a data survey searching for well-defined streamer
wave events observed by the Large Angle and Spectrometric Coronagraph (LASCO)
on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle
23. As a result, 8 candidate events are found and presented here. We compare
different events and find that in most of them the driving CMEs ejecta are
characterized by a high speed and a wide angular span, and the CME-streamer
interactions occur generally along the flank of the streamer structure at an
altitude no higher than the bottom of the field of view of LASCO C2. In
addition, all front-side CMEs have accompanying flares. These common
observational features shed light on the excitation conditions of streamer wave
events.
We also conduct a further analysis on one specific streamer wave event on 5
June 2003. The heliocentric distances of 4 wave troughs/crests at various
exposure times are determined; they are then used to deduce the wave properties
like period, wavelength, and phase speeds. It is found that both the period and
wavelength increase gradually with the wave propagation along the streamer
plasma sheet, and the phase speed of the preceding wave is generally faster
than that of the trailing ones. The associated coronal seismological study
yields the radial profiles of the Alfv\'en speed and magnetic field strength in
the region surrounding the streamer plasma sheet. Both quantities show a
general declining trend with time. This is interpreted as an observational
manifestation of the recovering process of the CME-disturbed corona. It is also
found that the Alfv\'enic critical point is at about 10 R where the
flow speed, which equals the Alfv\'en speed, is 200 km s
Effects of T- and P-odd weak nucleon interaction in nuclei: renormalizations due to residual strong interaction, matrix elements between compound states and their correlations with P-violating matrix elements
Manifestations of P-,T-odd weak interaction between nucleons in nucleus are
considered. Renormalization of this interaction due to residual strong
interaction is studied. Mean squared matrix elements of P-,T-odd weak
interaction between compound states are calculated. Correlators between
P-,T-odd and P-odd, T-even weak interaction matrix elements between compound
states are considered and estimates for these quantities are obtained.Comment: Submitted to Phys. Rev. C; 21 pages, REVTEX 3, no figure
New hadrons as ultra-high energy cosmic rays
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly
distributed astrophysical sources contradict the energy spectrum measured by
both the AGASA and HiRes experiments, assuming the small scale clustering of
UHECR observed by AGASA is caused by point-like sources. In that case, the
small number of sources leads to a sharp exponential cutoff at the energy
E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve
this cutoff problem. For the first time we discuss the production of such
hadrons in proton collisions with infrared/optical photons in astrophysical
sources. This production mechanism, in contrast to proton-proton collisions,
requires the acceleration of protons only to energies E<10^{21} eV. The diffuse
gamma-ray and neutrino fluxes in this model obey all existing experimental
limits. We predict large UHE neutrino fluxes well above the sensitivity of the
next generation of high-energy neutrino experiments. As an example we study
hadrons containing a light bottom squark. These models can be tested by
accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Observation of the Charmed Baryon Decays to , , and
We have observed two new decay modes of the charmed baryon into
and using data collected with the
CLEO II detector. We also present the first measurement of the branching
fraction for the previously observed decay mode . The branching fractions for these three modes relative to
are measured to be , , and , respectively.Comment: 12 page uuencoded postscript file, postscript file also available
through http://w4.lns.cornell.edu/public/CLN
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