47,809 research outputs found
Chain motion and viscoelasticity in highly entangled solutions of semiflexible rods
Brownian dynamics simulations are used to study highly entangled solutions of
semiflexible polymers. Bending fluctuations of semiflexible rods are
signficantly affected by entanglement only above a concentration ,
where for chains of similar length and
persistence length. For , the tube radius approaches a
dependence , and the linear viscoelastic response
develops an elastic contribution that is absent for . Experiments
on isotropic solutions of -actin span concentrations near for which
the predicted asymptotic scaling of the plateau modulus is
not yet valid.Comment: 4 pages, 5 figures, submitted to PR
Ambiguities of theoretical parameters and CP/T violation in neutrino factories
We study the optimal setup for observation of the CP asymmetry in neutrino
factory experiments --- the baseline length, the muon energy and the analysis
method. First, we point out that the statistical quantity which has been used
in previous works doesn't represent the CP asymmetry. Then we propose the more
suitable quantity, , which is sensitive to the CP
asymmetry. We investigate the behavior of with ambiguities of
the theoretical parameters. The fake CP asymmetry due to the matter effect
increases with the baseline length and hence the error in the estimation of the
fake CP asymmetry grows with the baseline length due to the ambiguities of the
theoretical parameters. Namely, we lose the sensitivity to the genuine
CP-violation effect in longer baseline.Comment: 8pages, 2figures, Talk given by J. Sato at Joint U.S. / Japan
Workshop on New Initiatives in Muon Lepton Flavor Violation and Neutrino
Oscillation with High Intense Muon and Neutrino Sources, Honolulu, Hawaii,
2-6 Oct 200
NMR relaxation rate in the field-induced octupolar liquid phase of spin-1/2 J1-J2 frustrated chains
In the spin-1/2 frustrated chain with nearest-neighbor ferromagnetic exchange
J1 and next-nearest-neighbor antiferromagnetic exchange J2 under magnetic
field, magnetic multipolar-liquid (quadrupolar, octupolar, and hexadecapolar)
phases are widely expanded from the saturation down to a low-field regime.
Recently, we have clarified characteristic temperature and field dependence of
the NMR relaxation rate 1/T_1 in the quadrupolar phase. In this paper, we
examine those of 1/T_1 in the octupolar phase combining field theoretical
method with numerical data. The relevance of the results to quasi
one-dimensional J1-J2 magnets such as PbCuSO4(OH)2, Rb2Cu2Mo3O12 and Li2ZrCuO4
is shortly discussed.Comment: 6 pages (1 column), 3 figure
Adiabatic Effective Action for Vortices in Neutral and Charged Superfluids
Adiabatic effective action for vortices in neutral and charged superfluids at
zero temperature are calculated using the topological Landau-Ginzburg theory
recently proposed by Hatsuda, Yahikozawa, Ao and Thouless, and vortex dynamics
are examined. The Berry phase term arising in the effective action naturally
yields the Magnus force in both neutral and charged superfluids.
It is shown that in neutral superfluid there is only one degree of freedom,
namely the center of vorticities, and the vortex energy is proportinal to the
sum of all vorticities so that it is finite only for the vanishing total
vorticity of the system.
On the other hand the effective mass and the vortex energy for a vortex in
charged superfluids are defined individually as expected. The effects of the
vortex core on these quantities are also estimated. The possible depinning
scenario which is governed by the Magnus force and the inertial mass is also
discussed.Comment: 26 page
On the Magnetic Excitation Spectra of High Tc Cu Oxides up to the Energies far above the Resonance Energy
Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy and La214 systems have been
studied. For La1.88Sr0.12CuO4, c"(q,w) have been measured up to ~30 meV and
existing data have been analyzed up to the energy w~150 meV by using the
phenomenological expression of the generalized magnetic susceptibility
c(q,w)=c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is the susceptibility of the
electrons without the exchange coupling J(q) among them. In the relatively low
energy region up to slightly above the resonance energy Er, it has been
reported by the authors' group that the expression can explain characteristics
of the q- and w-dependence of the spectra of YBa2Cu3Oy (YBCO or YBCOy). Here,
it is also pointed out that the expression can reproduce the rotation of four
incommensurate peaks of c"(q,w) within the a*-b* plane about (p/a, p/a) {or
so-called (p, p)} point by 45 degree, which occurs as w goes to the energy
region far above Er from E below Er. For La2-xSrxCuO4 and La2-xBaxCuO4,
agreements between the observed results and the calculations are less
satisfactory than for YBCO, indicating that we have to take account of the
existence of the "stripes" to consistently explain the observed c"(q,w) of
La214 system especially near x=1/8.Comment: 14 pages, 5 figure
Canonical Theory of 2+1 Gravity
Recently 2+1 dimensional gravity theory, especially has been
studied extensively. It was shown to be equivalent to the 2+1 Chern-Simon
theory and has been investigated to understand the black hole thermodynamics,
i.e. Hawking temperature and others. The purpose of this report is to
investigate the canonical formalism of the original 2+1 Einstein gravity theory
instead of the Chern-Simon theory. For the spherically symmetric space-time,
local conserved quantities(local mass and angular momentum) are introduced and
using them canonical quantum theory is defined. Constraints are imposed on
state vectors and solved analytically. The strategy to obtain the solution is
followed by our previous work.Comment: 6 pages, talk given at LLWI-2000: From Particles to Universe,
Alberta, 20-26 February 200
A chemically driven fluctuating ratchet model for actomyosin interaction
With reference to the experimental observations by T. Yanagida and his
co-workers on actomyosin interaction, a Brownian motor of fluctuating ratchet
kind is designed with the aim to describe the interaction between a Myosin II
head and a neighboring actin filament. Our motor combines the dynamics of the
myosin head with a chemical external system related to the ATP cycle, whose
role is to provide the energy supply necessary to bias the motion. Analytical
expressions for the duration of the ATP cycle, for the Gibbs free energy and
for the net displacement of the myosin head are obtained. Finally, by
exploiting a method due to Sekimoto (1997, J. Phys. Soc. Jpn., 66, 1234), a
formula is worked out for the amount of energy consumed during the ATP cycle.Comment: 15 pages. 1 figur
Infrared/optical - X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506
We investigate the origin of short X-ray flares which are occasionally
observed in early stages of afterglows of gamma-ray bursts (GRBs). We observed
two events, GRB 071112C and GRB 080506, before the start of X-ray flares in the
optical and near-infrared (NIR) bands with the 1.5-m Kanata telescope. In
conjunction with published X-ray and optical data, we analyzed densely sampled
light curves of the early afterglows and spectral energy distributions (SEDs)
in the NIR-X-ray ranges. We found that the SEDs had a break between the optical
and X-ray bands in the normal decay phases of both GRBs regardless of the model
for the correction of the interstellar extinction in host galaxies of GRBs. In
the X-ray flares, X-ray flux increased by 3 and 15 times in the case of GRB
071112C and 080506, respectively, and the X-ray spectra became harder than
those in the normal decay phases. No significant variation in the optical-NIR
range was detected together with the X-ray flares. These results suggest that
the X-ray flares were associated with either late internal shocks or external
shocks from two-component jets.Comment: 10 pages, 5 figures, accepted to Astronomy and Astrophysic
Direct Observation of Non-Monotonic dx2-y2-Wave Superconducting Gap in Electron-Doped High-Tc Superconductor Pr0.89LaCe0.11CuO4
We performed high-resolution angle-resolved photoemission spectroscopy on
electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4 to study the
anisotropy of the superconducting gap. The observed momentum dependence is
basically consistent with the dx2-y2-wave symmetry, but obviously deviates from
the monotonic dx2-y2 gap function. The maximum gap is observed not at the zone
boundary, but at the hot spot where the antiferromagnetic spin fluctuation
strongly couples to the electrons on the Fermi surface. The present
experimental results unambiguously indicate the spin-mediated pairing mechanism
in electron-doped high-Tc superconductors.Comment: 4 pages, 4 figure
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