3,335 research outputs found
BRST cohomologies for symplectic reflection algebras and quantizations of hypertoric varieties
a
phi-meson in Nuclear Matter
-meson mass in nuclear matter () is investigated using an
effective Lagrangian of interacting with octet baryons.
decreases by a few \% in nuclear matter due to the current conservation and
effective nucleon/hyperon masses. Its implication to the p-A and A-A collisions
are briefly discussed.Comment: 7 pages, latex, 3 postscript figures, submitted to Prog. Theor. Phy
Localization of affine W-algebras
We introduce the notion of an asymptotic algebra of chiral differential
operators. We then construct, via a chiral Hamiltonian reduction, one such
algebra over a resolution of the intersection of the Slodowy slice with the
nilpotent cone. We compute the space of global sections of this algebra thereby
proving a localization theorem for affine W-algebras at the critical level.Comment: 36 page
The Acceleration Mechanism of Resistive MHD Jets Launched from Accretion Disks
We analyzed the results of non-linear resistive magnetohydrodynamical (MHD)
simulations of jet formation to study the acceleration mechanism of
axisymmetric, resistive MHD jets. The initial state is a constant angular
momentum, polytropic torus threaded by weak uniform vertical magnetic fields.
The time evolution of the torus is simulated by applying the CIP-MOCCT scheme
extended for resistive MHD equations. We carried out simulations up to 50
rotation period at the innermost radius of the disk created by accretion from
the torus. The acceleration forces and the characteristics of resistive jets
were studied by computing forces acting on Lagrangian test particles. Since the
angle between the rotation axis of the disk and magnetic field lines is smaller
in resistive models than in ideal MHD models, magnetocentrifugal acceleration
is smaller. The effective potential along a magnetic field line has maximum
around in resistive models, where is the radius where the
density of the initial torus is maximum. Jets are launched after the disk
material is lifted to this height by pressure gradient force. Even in this
case, the main acceleration force around the slow magnetosonic point is the
magnetocentrifugal force. The power of the resistive MHD jet is comparable to
the mechanical energy liberated in the disk by mass accretion. Joule heating is
not essential for the formation of jets.Comment: 15 pages, 15 figures, 1 table, accepted for publication in Ap
Resistive Magnetohydrodynamics of Jet Formation and Magnetically Driven Accretion
We carried out 2.5-dimensional resistive magnetohydrodynamic simulations to
study the effects of magnetic diffusivity on magnetically driven mass accretion
and jet formation. We found that (1) when the normalized magnetic diffusivity,
is small, mass accretion and jet formation take place intermittently; (2) when
diffusivity is middle, the system evolves toward a quasi-steady state; and the
system evolves toward a quasi-steady state; and (3) when diffusivity is large,
the accretion/mass outflow rate decreases with diffusivity and approaches 0.
The results of these simulations indicate magnetic braking provide a mass
accretion rate which is sufficient to explain the activity of AGNs.Comment: 24 pages, LaTex, 15 jpg figures include, accepted for PAS
Extra-large crystal emulsion detectors for future large-scale experiments
Photographic emulsion is a particle tracking device which features the best
spatial resolution among particle detectors. For certain applications, for
example muon radiography, large-scale detectors are required. Therefore, a huge
surface has to be analyzed by means of automated optical microscopes. An
improvement of the readout speed is then a crucial point to make these
applications possible and the availability of a new type of photographic
emulsions featuring crystals of larger size is a way to pursue this program.
This would allow a lower magnification for the microscopes, a consequent larger
field of view resulting in a faster data analysis. In this framework, we
developed new kinds of emulsion detectors with a crystal size of 600-1000 nm,
namely 3-5 times larger than conventional ones, allowing a 25 times faster data
readout. The new photographic emulsions have shown a sufficient sensitivity and
a good signal to noise ratio. The proposed development opens the way to future
large-scale applications of the technology, e.g. 3D imaging of glacier bedrocks
or future neutrino experiments.Comment: Version accepted for publication in JINS
Parker-Jeans Instability of Gaseous Disks Including the Effect of Cosmic Rays
We use linear analysis to examine the effect of cosmic rays (CRs) on the
Parker-Jeans instability of magnetized self-gravitating gaseous disks. We adopt
a slab equilibrium model in which the gravity (including self-gravity) is
perpendicular to the mid-plane, the magnetic field lies along the slab. CR is
described as a fluid and only along magnetic field lines diffusion is
considered. The linearised equations are solved numerically. The system is
susceptible to Parker-Jeans instability. In general the system is less unstable
when the CR diffusion coefficient is smaller (i.e., the coupling between the
CRs and plasma is stronger). The system is also less unstable if CR pressure is
larger. This is a reminiscence of the fact that Jeans instability and Parker
instability are less unstable when the gas pressure is larger (or temperature
is higher). Moreover, for large CR diffusion coefficient (or small CR
pressure), perturbations parallel to the magnetic field are more unstable than
those perpendicular to it. The other governing factor on the growth rate of the
perturbations in different directions is the thickness of the disk or the
strength of the external pressure on the disk. In fact, this is the determining
factor in some parameter regimes.Comment: 19pages, 14figures submitted to Ap
A Glassless Stereo-Type Visualization System for 3D MHD Real-Time Earthâs Magnetosphere Simulator
- âŠ