6,819 research outputs found
Identification of a high-velocity compact nebular filament 2.2 arcsec south of the Galactic Centre
The central parsec of the Milky Way is a very special region of our Galaxy;
it contains the supermassive black hole associated with Sgr A* as well as a
significant number of early-type stars and a complex structure of streamers of
neutral and ionized gas, within two parsecs from the centre, representing a
unique laboratory. We report the identification of a high velocity compact
nebular filament 2.2 arcsec south of Sgr A*. The structure extends over ~1
arcsec and presents a strong velocity gradient of ~200 km s^{-1} arcsec^{-1}.
The peak of maximum emission, seen in [Fe III] and He I lines, is located at
d{\alpha} = +0.20 +/- 0.06 arcsec and d{\delta} = -2.20 +/- 0.06 arcsec with
respect to Sgr A*. This position is near the star IRS 33N. The velocity at the
emission peak is Vr = -267 km s^{-1}. The filament has a position angle of PA =
115{\degr} +/- 10{\degr}, similar to that of the Bar and of the Eastern Arm at
that position. The peak position is located 0.7 arcsec north of the binary
X-ray and radio transient CXOGX J174540.0-290031, a low-mass X-ray binary with
an orbital period of 7.9 hr. The [Fe III] line emission is strong in the
filament and its vicinity. These lines are probably produced by shock heating
but we cannot exclude some X-ray photoionization from the low-mass X-ray
binary. Although we cannot rule out the idea of a compact nebular jet, we
interpret this filament as a possible shock between the Northern and the
Eastern Arm or between the Northern Arm and the mini-spiral "Bar".Comment: 7 pages, 4 figures, published online in MNRA
Convergence of numerical schemes for short wave long wave interaction equations
We consider the numerical approximation of a system of partial differential
equations involving a nonlinear Schr\"odinger equation coupled with a
hyperbolic conservation law. This system arises in models for the interaction
of short and long waves. Using the compensated compactness method, we prove
convergence of approximate solutions generated by semi-discrete finite volume
type methods towards the unique entropy solution of the Cauchy problem. Some
numerical examples are presented.Comment: 31 pages, 7 figure
Noncommutative Particles in Curved Spaces
We present a formulation in a curved background of noncommutative mechanics,
where the object of noncommutativity is considered as an
independent quantity having a canonical conjugate momentum. We introduced a
noncommutative first-order action in D=10 curved spacetime and the covariant
equations of motions were computed. This model, invariant under diffeomorphism,
generalizes recent relativistic results.Comment: 1+15 pages. Latex. New comments and results adde
Thermodynamics of quantum crystalline membranes
We investigate the thermodynamic properties and the lattice stability of
two-dimensional crystalline membranes, such as graphene and related compounds,
in the low temperature quantum regime . A key role is played by
the anharmonic coupling between in-plane and out-of plane lattice modes that,
in the quantum limit, has very different consequences than in the classical
regime. The role of retardation, namely of the frequency dependence, in the
effective anharmonic interactions turns out to be crucial in the quantum
regime. We identify a crossover temperature, , between classical and
quantum regimes, which is K for graphene. Below , the
heat capacity and thermal expansion coefficient decrease as power laws with
decreasing temperature, tending to zero for as required by the
third law of thermodynamics.Comment: 13 pages, 1 figur
Grid-Brick Event Processing Framework in GEPS
Experiments like ATLAS at LHC involve a scale of computing and data
management that greatly exceeds the capability of existing systems, making it
necessary to resort to Grid-based Parallel Event Processing Systems (GEPS).
Traditional Grid systems concentrate the data in central data servers which
have to be accessed by many nodes each time an analysis or processing job
starts. These systems require very powerful central data servers and make
little use of the distributed disk space that is available in commodity
computers. The Grid-Brick system, which is described in this paper, follows a
different approach. The data storage is split among all grid nodes having each
one a piece of the whole information. Users submit queries and the system will
distribute the tasks through all the nodes and retrieve the result, merging
them together in the Job Submit Server. The main advantage of using this system
is the huge scalability it provides, while its biggest disadvantage appears in
the case of failure of one of the nodes. A workaround for this problem involves
data replication or backup.Comment: 6 pages; document for CHEP'03 conferenc
Reply to 'Comment on "Thermodynamics of quantum crystalline membranes"'
In this note, we reply to the comment made by E.I.Kats and V.V.Lebedev
[arXiv:1407.4298] on our recent work "Thermodynamics of quantum crystalline
membranes" [Phys. Rev. B 89, 224307 (2014)]. Kats and Lebedev question the
validity of the calculation presented in our work, in particular on the use of
a Debye momentum as a ultra-violet regulator for the theory. We address and
counter argue the criticisms made by Kats and Lebedev to our work.Comment: 5 pages, 4 figure
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