2,771 research outputs found
Exact description of D-branes in K-matrix theory
We summarize how to describe D-branes in a matrix theory based on unstable
D-instantons, which we call K-matrix theory, and explicity show that D-branes
can be constructed as bound states of infinitly many unstable D-instantons. We
examine the fluctuations around Dp-brane solutions in the matrix theory and
show that they correctly reproduce fields on the Dp-brane world-volume.
Plugging them into the action of the matrix theory, we precisely obtain the
Dp-brane action as the effective action of the fluctuations.Comment: 19 pages, Talk given by S.S. at the 17th Nishinomiya-Yukawa Memorial
Symposium, Nishinomiya, November, 200
Equilibrium magnetisation structures in ferromagnetic nanorings
The ground state of the ring-shape magnetic nanoparticle is studied.
Depending on the geometrical and magnetic parameters of the nanoring, there
exist different magnetisation configurations (magnetic phases): two phases with
homogeneous magnetisation (easy-axis and easy-plane phases) and two
inhomogeneous (planar vortex phase and out-of-plane one). The existence of a
new intermediate out-of-plane vortex phase, where the inner magnetisation is
not strongly parallel to the easy axis, is predicted. Possible transitions
between different phases are analysed using the combination of analytical
calculations and micromagnetic simulations.Comment: LaTeX, 19 pages, 11 figure
X-ray Emission from the Type Ic Supernova 1994I Observed with Chandra
We present two high-resolution Chandra X-ray observations of supernova (SN)
1994I which show, for the first time, that the interaction of the blast wave
from a Type Ic SN with its surrounding circumstellar material (CSM) can give
rise to soft X-ray emission. Given a 0.3-2 keV band X-ray luminosity of L_x ~ 1
x 10^{37} ergs/s between six and seven years after the outburst of SN 1994I,
and assuming the X-ray emission arises from the shock-heated CSM, we derive a
pre-SN mass-loss rate of \dot{M} ~ 1 x 10^{-5} M_sun/yr (v_w/10 km/s).
Combining the results with earlier ROSAT observations, we construct the X-ray
lightcurve of SN 1994I. A best-fit X-ray rate of decline of L_x \propto t^{-s}
with index s~1 and a CSM density profile of rho_csm \propto r^{-1.9\pm0.1} are
inferred, consistent with what is expected for a constant mass-loss rate and
constant wind velocity profile for the SN progenitor (rho_csm \propto r^{-2}).Comment: 5 pages, 3 figures, accepted for publication in the Astrophysical
Journal Letter
Five-dimensional SYM from undeformed ABJM
We expand undeformed ABJM theory around the vacuum solution that was found in
arxiv:0909.3101. This solution can be interpreted as a circle-bundle over a
two-dimensional plane with a singularity at the origin. By imposing periodic
boundary conditions locally far away from the singularity, we obtain a local
fuzzy two-torus over which we have a circle fibration. By performing
fluctuation analysis we obtain five-dimensional SYM with the precise value on
the coupling constant that we would obtain by compactifying multiple M5 branes
on the vacuum three-manifold. In the resulting SYM theory we also find a
coupling to a background two-form.Comment: 23 page
Bell's inequality with Dirac particles
We study Bell's inequality using the Bell states constructed from four
component Dirac spinors. Spin operator is related to the Pauli-Lubanski pseudo
vector which is relativistic invariant operator. By using Lorentz
transformation, in both Bell states and spin operator, we obtain an observer
independent Bell's inequality, so that it is maximally violated as long as it
is violated maximally in the rest frame.Comment: 7 pages. arXiv admin note: text overlap with arXiv:quant-ph/0308156
by other author
Radiatively Inefficient Accretion Flow in the Nucleus of NGC 1097
We present a model for the accretion flow around the supermassive black hole
in the LINER nucleus of NGC 1097 which fits the optical to X-ray spectral
energy distribution (SED). The X-ray segment of the SED is based on
observations with the Chandra X-Ray Observatory, which are reported here for
the first time. The inner part of the flow is modeled as a radiatively
inefficient accretion flow (RIAF) and the outer part as a standard thin disk.
The value of the transition radius (~225 Schwarzschild radii) between the RIAF
and outer thin disk was obtained from our previous fitting of the double-peaked
Balmer emission line profile, which originates in the thin disk. The black hole
mass was inferred from measurements of the stellar velocity dispersion in the
host galaxy. When these parameters are used in the accretion flow model, the
SED can be successfully reproduced, which shows that the line profile model and
the accretion flow model are consistent with each other. A small remaining
excess in the near-UV is accounted by the contribution of an obscured starburst
located within 9 pc from the nucleus, as we reported in an earlier paper. The
radio flux is consistent with synchrotron emission of a relativistic jet
modeled by means of the internal shock scenario. In an appendix we also analyze
the Chandra X-ray observations of the ~1 kpc circumnuclear star-forming ring
and of an ultraluminous compact X-ray source located outside the ring.Comment: 10 pages and 6 figures formatted with emulateapj, accepted for
publication in Ap
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