1,588 research outputs found
Existence and Stability of standing waves for supercritical NLS with a Partial Confinement
We prove the existence of orbitally stable ground states to NLS with a
partial confinement together with qualitative and symmetry properties. This
result is obtained for nonlinearities which are -supercritical, in
particular we cover the physically relevant cubic case. The equation that we
consider is the limit case of the cigar-shaped model in BEC.Comment: Revised version, accepted on Comm. Math. Physic
Junctions of anyonic Luttinger wires
We present an extended study of anyonic Luttinger liquids wires jointing at a
single point. The model on the full line is solved with bosonization and the
junction of an arbitrary number of wires is treated imposing boundary
conditions that preserve exact solvability in the bosonic language. This allows
to reach, in the low momentum regime, some of the critical fixed points found
with the electronic boundary conditions. The stability of all the fixed points
is discussed.Comment: 16 pages, 2 figures, typos corrected, Refs adde
Detection of a population gradient in the Sagittarius Stream
We present a quantitative comparison between the Horizontal Branch morphology
in the core of the Sagittarius dwarf spheroidal galaxy (Sgr) and in a wide
field sampling a portion of its tidal stream (Sgr Stream), located tens of kpc
away from the center of the parent galaxy. We find that the Blue Horizontal
Branch (BHB) stars in that part of the Stream are five times more abundant than
in the Sgr core, relative to Red Clump stars. The difference in the ratio of
BHB to RC stars between the two fields is significant at the 4.8 sigma level.
This indicates that the old and metal-poor population of Sgr was preferentially
stripped from the galaxy in past peri-Galactic passages with respect to the
intermediate-age metal rich population that presently dominates the bound core
of Sgr, probably due to a strong radial gradient that was settled within the
galaxy before its disruption. The technique adopted in the present study allows
to trace population gradients along the whole extension of the Stream.Comment: 4 pages, 3 .ps figures (fig. 1 at low resolution); Accepted for
publication by A&A Letter
A dwarf galaxy remnant in Canis Major: the fossil of an in-plane accretion onto the Milky Way
We present an analysis of the asymmetries in the population of Galactic
M-giant stars present in the 2MASS All Sky catalogue. Several large-scale
asymmetries are detected, the most significant of which is a strong
elliptical-shaped stellar over-density, close to the Galactic plane at (l=240,
b=-8), in the constellation of Canis Major. A small grouping of globular
clusters (NGC 1851, NGC 1904, NGC 2298, and NGC 2808), coincident in position
and radial velocity, surround this structure, as do a number of open clusters.
The population of M-giant stars in this over-density is similar in number to
that in the core of the Sagittarius dwarf galaxy. We argue that this object is
the likely dwarf galaxy progenitor of the ring-like structure that has recently
been found at the edge of the Galactic disk. A numerical study of the tidal
disruption of an accreted dwarf galaxy is presented. The simulated debris fits
well the extant position, distance and velocity information on the ``Galactic
Ring'', as well as that of the M-giant over-densities, suggesting that all
these structures are the consequence of a single accretion event. The disrupted
dwarf galaxy stream orbits close to the Galactic Plane, with a pericentre at
approximately the Solar circle, an orbital eccentricity similar to that of
stars in the Galactic thick disk, as well as a vertical scale height similar to
that of the thick disk. This finding strongly suggests that the Canis Major
dwarf galaxy is a building block of the Galactic thick disk, that the thick
disk is continually growing, even up to the present time, and that thick disk
globular clusters were accreted onto the Milky Way from dwarf galaxies in
co-planar orbits.Comment: 13 pages, 18 figures (2 in colour), accepted for publication in MNRA
On the orbital stability for a class of nonautonomous NLS
Following the original approach introduced by T. Cazenave and P.L. Lions in
\cite{CaLi} we prove the existence and the orbital stability of standing waves
for the following class of NLS: \label{intr1} i\partial_t u+ \Delta u - V(x) u
+ Q(x) u|u|^{p-2}=0, \hbox{} (t,x) \in \R\times \R^n, \hbox{} 2<p<2+\frac 4n
and \label{intr2} i\partial_t u - \Delta^2 u - V(x) u + Q(x) u|u|^{p-2}=0,
\hbox{} (t,x) \in \R\times \R^n, \hbox{} 2<p<2+\frac 8n under suitable
assumptions on the potentials and . More precisely we assume
and for
a suitable . The main point is the analysis of the compactness of
minimiziang sequences to suitable constrained minimization problems related to
\eqref{intr1} and \eqref{intr2}
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