11,834 research outputs found
Properties of Accretion Shocks in Viscous Flows with Cooling Effects
Low angular momentum accretion flows can have standing and oscillating shock
waves. We study the region of the parameter space in which multiple sonic
points occur in viscous flows in presence of various cooling effects such as
bremsstrahlung and Comptonization. We also quantify the parameter space in
which shocks are steady or oscillating. We find that cooling induces effects
opposite to heating by viscosity even in modifying the topology of the
solutions, though one can never be exactly balanced by the other due to their
dissimilar dependence on dynamic and thermodynamic parameters. We show that
beyond a critical value of cooling, the flow ceases to contain a shock wave.Comment: 18 pages, 12 figures, Accepted for Publication in Int. J. Mod. Phys.
Generalized -conformal change and special Finsler spaces
In this paper, we investigate the change of Finslr metrics which we refer to as a
generalized -conformal change. Under this change, we study some special
Finsler spaces, namely, quasi C-reducible, semi C-reducible, C-reducible,
-like, -like and -like Finsler spaces. We also obtain the
transformation of the T-tensor under this change and study some interesting
special cases. We then impose a certain condition on the generalized
-conformal change, which we call the b-condition, and investigate the
geometric consequences of such condition. Finally, we give the conditions under
which a generalized -conformal change is projective and generalize some
known results in the literature.Comment: References added, some modifications are performed, LateX file, 24
page
Estimating the spectrum of a density matrix with LOCC
The problem of estimating the spectrum of a density matrix is considered.
Other problems, such as bipartite pure state entanglement, can be reduced to
spectrum estimation. A local operations and classical communication (LOCC)
measurement strategy is shown which is asymptotically optimal. This means that,
for a very large number of copies, it becomes unnecessary to perform collective
measurements which should be more difficult to implement in practice.Comment: 12 pages, uses iopart.cls and iopart10.clo. Improved version. v3:
Reference updated, added journal referenc
Simulation of I-V Hysteresis Branches in An Intrinsic Stack of Josephson Junctions in High Superconductors
I-V characteristics of the high T superconductor
BiSrCaCO shows a strong hysteresis, producing many
branches. The origin of hysteresis jumps is studied by use of the model of
multi-layered Josephson junctions proposed by one of the authors (T. K.). The
charging effect at superconducting layers produces a coupling between the next
nearest neighbor phase-differences, which determines the structure of
hysteresis branches. It will be shown that a solution of phase motions is
understood as a combination of rotating and oscillating phase-differences, and
that, at points of hysteresis jumps, there occurs a change in the number of
rotating phase-differences. Effects of dissipation are analyzed. The
dissipation in insulating layers works to damp the phase motion itself, while
the dissipation in superconducting layers works to damp relative motions of
phase-differences. Their effects to hysteresis jumps are discussed.Comment: 18 pages, Latex, 8 figures. To be appear in Phys.Rev.B Vol.60(1999
Numerical Renormalization Group Study of Kondo Effect in Unconventional Superconductors
Orbital degrees of freedom of a Cooper pair play an important role in the
unconventional superconductivity. To elucidate the orbital effect in the Kondo
problem, we investigated a single magnetic impurity coupled to Cooper pairs
with a () symmetry using the numerical
renormalization group method. It is found that the ground state is always a
spin doublet. The analytical solution for the strong coupling limit explicitly
shows that the orbital dynamics of the Cooper pair generates the spin 1/2 of
the ground state.Comment: 4 pages, 2 figures, JPSJ.sty, to be published in J. Phys. Soc. Jpn.
70 (2001) No. 1
Accurate Neutralino Relic Density Computations in Supergravity Models
We investigate the question of the proper thermal averaging of neutralino
annihilation amplitudes which possess poles and thresholds, as they impact on
the calculated neutralino relic density and therefore on the cosmological
viability of supersymmetric models. We focus on two typical resonances, namely
the boson and the lightest Higgs boson (). In the context of
supergravity models with radiative electroweak symmetry breaking, an
exploration of the whole parameter space of the model is possible and the
overall relevance of these sophisticated analyses can be ascertained. As an
example we chose the minimal supergravity model since the presence of
such poles is essential to obtain a cosmologically acceptable model. We find
that the proper thermal averaging is important for individual points in
parameter space and that the fraction of cosmologically acceptable points is
increased somewhat by the accurate procedure. However, qualitatively the new
set of points is very similar to that obtained previously using the usual
series approximations to the thermal average. We conclude that all
phenomenological analyses based on the previously determined cosmologically
allowed set remain valid.Comment: 15 pages, 9 figures (available upon request as uuencoded file or
separate ps files), tex (harvmac) CTP-TAMU-14/9
Physics Beyond the Standard Model and Cosmological Connections: A Summary from LCWS 06
The International Linear Collider (ILC) is likely to provide us important
insights into the sector of physics that may supersede our current paradigm
viz., the Standard Model. In anticipation of the possibility that the ILC may
come up in the middle of the next decade, several groups are vigourously
investigating its potential to explore this new sector of physics. The Linear
Collider Workshop in Bangalore (LCWS06) had several presentations of such
studies which looked at supersymmetry, extra dimensions and other exotic
possibilities which the ILC may help us discover or understand. Some papers
also looked at the understanding of cosmology that may emerge from studies at
the ILC. This paper summarises these presentations.Comment: 8 pages (including cover page) LaTeX, Summary talk presented at the
International Linear Collider Workshop in Bangalore, India in March 200
Mutual first order coherence of phase-locked lasers
We argue that (first-order) coherence is a relative, and not an absolute,
property. It is shown how feedforward or feedback can be employed to make two
(or more) lasers relatively coherent. We also show that after the relative
coherence is established, the two lasers will stay relatively coherent for some
time even if the feedforward or feedback loop has been turned off, enabling,
e.g., demonstration of unconditional quantum teleportation using lasers.Comment: 9 pages, 6 figure
Collapse of Rotating Magnetized Molecular Cloud Cores and Mass Outflows
Collapse of the rotating magnetized molecular cloud core is studied with the
axisymmetric magnetohydrodynamical (MHD) simulations. Due to the change of the
equation of state of the interstellar gas, the molecular cloud cores experience
several different phases as collapse proce eds. In the isothermal run-away
collapse (), a pseudo-disk is formed and
it continues to contract till the opaque core is fo rmed at the center. In this
disk, a number of MHD fast and slow shock pairs appear running parallelly to
the disk. After the equation of state becomes hard, an adiabatic core is
formed, which is separated from the isothermal contracting pseudo-disk by the
accretion shock front facing radially outwards. By the effect of the magnetic
tension, the angular momentum is transferred from the disk mid-plane to the
surface. The gas with excess angular momentum near the surface is finally
ejected, which explains the molecular bipolar outflow. Two types of outflows
are observed. When the poloidal magnetic field is strong (magnetic energy is
comparable to the thermal one), a U-shaped outflow is formed in which fast
moving gas is confined to the wall whose shape looks like a capit al letter U.
The other is the turbulent outflow in which magnetic field lines and velocity
fi elds are randomly oriented. In this case, turbulent gas moves out almost
perpendicularly from the disk. The continuous mass accretion leads to the
quasistatic contraction of the first core. A second collapse due to
dissociation of H in the first core follows. Finally another quasistatic
core is again formed by atomic hydrogen (the second core). It is found that
another outflow is ejected around the second atomic core, which seems to
correspond to the optical jets or the fast neutral winds.Comment: submitted to Ap
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