Bistability and instability of dark-antidark solitons in the cubic-quintic nonlinear Schroedinger equation

We characterize the full family of soliton solutions sitting over a background plane wave and ruled by the cubic-quintic nonlinear Schroedinger equation in the regime where a quintic focusing term represents a saturation of the cubic defocusing nonlinearity. We discuss existence and properties of solitons in terms of catastrophe theory and fully characterize bistability and instabilities of the dark-antidark pairs, revealing new mechanisms of decay of antidark solitons.Comment: 8 pages, 10 figures, accepted in PR

Sequential deformation of plains along Tessera boundaries on Venus: Evidence from Alpha Regio

Tesserae are regions of elevated terrain characterized by two or more sets of ridges and grooves that intersect orthogonally. Tesserae comprise 15-20 percent of the surface of Venus, but the nature of their formation and evolution is not well understood; processes proposed to account for their characteristics are many and varied. Two types of tessera boundaries have been described: type 1 are generally embayed by plains; and type 2 boundaries are characterized by being linear at the 100-km scale and often associated with steep scarps or tectonic features. Margins such as the western edge of Alpha have been described as type 2. Some of the tessera have boundaries that display deformation of both the edge of the tessera and the adjoining plains. This study focuses on the western edge of Alpha Regio in an effort to characterize on occurrence of this type of boundary and assess the implications of the style in general. Using Magellan SAR imagery, lineament lengths, orientations, and spacing were measured for ten 50 x 60 km areas spanning 500 km of the western boundary. Structural characteristics and orientations were compared to stratigraphic units in order to assess the sequence and style of deformation

Faint dwarf galaxies in nearby clusters

Besides giant elliptical galaxies, a number of low-mass stellar systems inhabit the cores of galaxy clusters, such as dwarf elliptical galaxies (dEs/dSphs), ultra-compact dwarf galaxies (UCDs), and globular clusters. The detailed morphological examination of faint dwarf galaxies has, until recently, been limited to the Local Group (LG) and the two very nearby galaxy clusters Virgo and Fornax. Here, we compare the structural parameters of a large number of dEs/dSphs in the more distant clusters Hydra I and Centaurus to other dynamically hot stellar systems.Comment: 2 pages, 1 figure; to appear in "A Universe of Dwarf Galaxies: Observations, Theories, Simulations", held in Lyon, France (June 14-18, 2010), eds. M. Koleva, P. Prugniel & I. Vauglin, EAS Series (Paris: EDP

Generalized coherent states are unique Bell states of quantum systems with Lie group symmetries

We consider quantum systems, whose dynamical symmetry groups are semisimple Lie groups, which can be split or decay into two subsystems of the same symmetry. We prove that the only states of such a system that factorize upon splitting are the generalized coherent states. Since Bell's inequality is never violated by the direct product state, when the system prepared in the generalized coherent state is split, no quantum correlations are created. Therefore, the generalized coherent states are the unique Bell states, i.e., the pure quantum states preserving the fundamental classical property of satisfying Bell's inequality upon splitting.Comment: 4 pages, REVTeX, amssymb style. More information on http://www.technion.ac.il/~brif/science.htm

The Absence of Extra-Tidal Structure in the Sculptor Dwarf Spheroidal Galaxy

The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy are presented. Our aims were to obtain an accurate map of the outer structure of Sculptor, and to determine the level of interaction between this system and the Galaxy. Photometry was obtained in two colours down to the magnitude limits of V=20 and I=19, covering a 3.1 times 3.1 square deg area centred on Sculptor. The resulting colour-magnitude data were used as a mask to select candidate horizontal branch and red giant branch stars for this system. Previous work has shown that the red horizontal branch (HB) stars are more concentrated than the blue HB stars. We have determined the radial distributions of these two populations and show that the overall Sculptor density profile is well described by a two component model based on a combination of these radial distributions. Additionally, spectra of the Ca ii triplet region were obtained for over 700 candidate red giant stars over the 10 square deg region using the 2dF instrument on the Anglo-Australian Telescope. These spectra were used to remove foreground Galactic stars based on radial velocity and Ca ii triplet strength. The final list of Sculptor members contained 148 stars, seven of which are located beyond the nominal tidal radius. Both the photometric and spectroscopic datasets indicate no significant extra-tidal structure. These results support at most a mild level of interaction between this system and the Galaxy, and we have measured an upper mass limit for extra-tidal material to be 2.3 +/- 0.6% of the Sculptor luminous mass. This lack of tidal interaction indicates that previous velocity dispersion measurements (and hence the amount of dark matter detected) in this system are not strongly influenced by the Galactic tidal field.Comment: 53 pages, 23 figures. Accepted for publication in the Astronomical Journal. Some figures are reduced in size, and a full version is available at: ftp://ftp.mso.anu.edu.au/pub/coleman/sculptor.pd

Scaling Laws for Incipient Cavitation Noise

The noise produced by the motion or a body through a liquid differs from that produced by the motion of a body through a gas because of the possibility or cavitation in the liquid case. An adequate theory or cavitation and cavitation noise is not yet available, but the application or dimensional analysis together with the theoretical information so far obtained can yield scaling laws for this flow situation. In section II, a brief dissussion will be given or the scaling laws for hydrodynamic noise in some cases of non-cavitating flow; this discussion is included tor oompleteness. In section III, a summary or the present information on the scaling law. for incipient cavitation noise will be presented

Deep Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 1316: Evidence for Dynamical Evolution of Second-Generation Globular Clusters

The Advanced Camera for Surveys on board the Hubble Space Telescope has been used to obtain deep high-resolution images of the giant early-type galaxy NGC 1316 which is an obvious merger remnant. These observations supersede previous, shallower observations which revealed the presence of a population of metal-rich globular clusters of intermediate age (~ 3 Gyr). We detect a total of 1496 cluster candidates, almost 4 times as many as from the previous WFPC2 images. We confirm the bimodality of the color distribution of clusters, even in V-I, with peak colors 0.93 and 1.06. The large number of detected clusters allows us to evaluate the globular cluster luminosity functions as a function of galactocentric radius. We find that the luminosity function of the inner 50% of the intermediate-age, metal-rich (`red') population of clusters differs markedly from that of the outer 50%. In particular, the luminosity function of the inner 50% of the red clusters shows a clear flattening consistent with a turnover that is about 1.0 mag fainter than the turnover of the blue clusters. This constitutes the first direct evidence that metal-rich cluster populations formed during major mergers of gas-rich galaxies can evolve dynamically (through disruption processes) into the red, metal-rich cluster populations that are ubiquitous in `normal' giant ellipticals.Comment: Accepted for publication in ApJ Letters; 4 pages in emulateapj style. 3 figure

Disentangling the Hercules stream

Using high-resolution spectra of nearby F and G dwarf stars, we have investigated the detailed abundance and age structure of the Hercules stream. We find that the stars in the stream have a wide range of stellar ages, metallicities, and element abundances. By comparing to existing samples of stars in the solar neighbourhood with kinematics typical of the Galactic thin and thick disks we find that the properties of the Hercules stream distinctly separate into the abundance and age trends of the two disks. Hence, we find it unlikely that the Hercules stream is a unique Galactic stellar population, but rather a mixture of thin and thick disk stars. This points toward a dynamical origin for the Hercules stream, probably caused by the Galactic bar.Comment: Accepted for publication in ApJ Letter

d=4 Attractors, Effective Horizon Radius and Fake Supergravity

We consider extremal black hole attractors (both BPS and non-BPS) for N=3 and N=5 supergravity in d=4 space-time dimensions. Attractors for matter-coupled N=3 theory are similar to attractors in N=2 supergravity minimally coupled to Abelian vector multiplets. On the other hand, N=5 attractors are similar to attractors in N=4 pure supergravity, and in such theories only 1\N-BPS non-degenerate solutions exist. All the above mentioned theories have a simple interpretation in the first order (fake supergravity) formalism. Furthermore, such theories do not have a d=5 uplift. Finally we comment on the "duality" relations among the attractor solutions of N\geq2 supergravities sharing the same full bosonic sector.Comment: 1+47 pages, 2 Tables. v2: Eqs. (2.3),(2.4) and Footnote 3 added; minor cosmetic changes; to appear in PR

Calculation of the unitary part of the Bures measure for N-level quantum systems

We use the canonical coset parameterization and provide a formula with the unitary part of the Bures measure for non-degenerate systems in terms of the product of even Euclidean balls. This formula is shown to be consistent with the sampling of random states through the generation of random unitary matrices