35,795 research outputs found
On the Two Obstacles Problem in Orlicz-Sobolev Spaces and Applications
We prove the Lewy-Stampacchia inequalities for the two obstacles problem in
abstract form for T-monotone operators. As a consequence for a general class of
quasi-linear elliptic operators of Ladyzhenskaya-Uraltseva type, including
p(x)-Laplacian type operators, we derive new results of
regularity for the solution. We also apply those inequalities to obtain new
results to the N-membranes problem and the regularity and monotonicity
properties to obtain the existence of a solution to a quasi-variational problem
in (generalized) Orlicz-Sobolev spaces
A method for evaluating models that use galaxy rotation curves to derive the density profiles
There are some approaches, either based on General Relativity (GR) or
modified gravity, that use galaxy rotation curves to derive the matter density
of the corresponding galaxy, and this procedure would either indicate a partial
or a complete elimination of dark matter in galaxies. Here we review these
approaches, clarify the difficulties on this inverted procedure, present a
method for evaluating them, and use it to test two specific approaches that are
based on GR: the Cooperstock-Tieu (CT) and the Balasin-Grumiller (BG)
approaches. Using this new method, we find that neither of the tested
approaches can satisfactorily fit the observational data without dark matter.
The CT approach results can be significantly improved if some dark matter is
considered, while for the BG approach no usual dark matter halo can improve its
results.Comment: 11 pages, 2 figures, 4 tables. v2: diverse text improvements, no
changes in the conclusions. Version accepted in MNRA
The runaway black hole GRO J1655-40
We have used the Hubble Space Telescope to measure the motion in the sky and
compute the galactocentric orbit of the black hole X-ray binary GRO J1655-40.
The system moves with a runaway space velocity of km s in a
highly eccentric () orbit. The black hole was formed in the
disk at a distance greater than 3 kpc from the Galactic centre and must have
been shot to such an eccentric orbit by the explosion of the progenitor star.
The runaway linear momentum and kinetic energy of this black hole binary are
comparable to those of solitary neutron stars and millisecond pulsars. GRO
J1655-40 is the first black hole for which there is evidence for a runaway
motion imparted by a natal kick in a supernova explosion.Comment: Published in Astronomy and Astrophysics. 5 pages, 2 color figures.
Color figure and animation can be found at
http://www.iafe.uba.ar/astronomia/mirabel/mirabel.html or
ftp://ftp.cea.fr/incoming/y2k01/mirabe
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