Atom-dimer scattering and long-lived trimers in fermionic mixtures

We consider a heteronuclear fermionic mixture on the molecular side of an interspecies Feshbach resonance and discuss atom-dimer scattering properties in uniform space and in the presence of an external confining potential, restricting the system to a quasi-2D geometry. We find that there is a peculiar atom-dimer p-wave resonance which can be tuned by changing the frequency of the confinement. Our results have implications for the ongoing experiments on Lithium-Potassium mixtures, where this mechanism allows for switching the p-wave interaction between a K atom and Li-K dimer from attractive to repulsive, and forming a weakly bound trimer with unit angular momentum. We show that such trimers are long-lived and the atom-dimer resonance does not enhance inelastic relaxation in the mixture, making it an outstanding candidate for studies of p-wave resonance effects in a many-body system.Comment: 4 pages, 2 figures, published versio

On the dual equivalence between self-dual and Maxwell-Chern-Simons models with Lorentz symmetry breaking

In this paper, we use gauge embedding procedure and master action approach to establish the equivalence between the self-dual and Maxwell-Chern-Simons models with Lorentz symmetry breaking. As a result, new kinds of Lorentz-breaking terms arise.Comment: 14 pages, minor corrections, version accepted to Physical Review

The Schwarzschild black hole as a point particle

The description of a point mass in general relativity (GR) is given in the framework of the field formulation of GR where all the dynamical fields, including the gravitational field, are considered in a fixed background spacetime. With the use of stationary (not static) coordinates non-singular at the horizon, the Schwarzschild solution is presented as a point-like field configuration in a whole background Minkowski space. The requirement of a stable $\eta$-causality stated recently in [J.B.Pitts and W.C.Schieve, Found. Phys., v. 34, 211 (2004)] is used essentially as a criterion for testing configurations.Comment: LATEX, 8 pages, no figure

Teleparallel Killing Vectors of the Einstein Universe

In this short paper we establish the definition of the Lie derivative of a second rank tensor in the context of teleparallel theory of gravity and also extend it for a general tensor of rank $p+q$. This definition is then used to find Killing vectors of the Einstein universe. It turns out that Killing vectors of the Einstein universe in the teleparallel theory are the same as in General Relativity.Comment: 9 pages, accepted for publication in Mod. Phys. Lett.

Molecular ion trap-depletion spectroscopy of BaCl+^+

We demonstrate a simple technique for molecular ion spectroscopy. BaCl$^+$ molecular ions are trapped in a linear Paul trap in the presence of a room-temperature He buffer gas and photodissociated by driving an electronic transition from the ground X$^1\Sigma^+$ state to the repulsive wall of the A$^1\Pi$ state. The photodissociation spectrum is recorded by monitoring the induced trap loss of BaCl$^+$ ions as a function of excitation wavelength. Accurate molecular potentials and spectroscopic constants are determined. Comparison of the theoretical photodissociation cross-sections with the measurement shows excellent agreement. This study represents the first spectroscopic data for BaCl$^+$ and an important step towards the production of ultracold ground-state molecular ions.Comment: 5 pages, 5 figure

VLTI/PIONIER images the Achernar disk swell

Context. The mechanism of disk formation around fast-rotating Be stars is not well understood. In particular, it is not clear which mechanisms operate, in addition to fast rotation, to produce the observed variable ejection of matter. The star Achernar is a privileged laboratory to probe these additional mechanisms because it is close, presents B-Be phase variations on timescales ranging from 6 yr to 15 yr, a companion star was discovered around it, and probably presents a polar wind or jet. Aims. Despite all these previous studies, the disk around Achernar was never directly imaged. Therefore we seek to produce an image of the photosphere and close environment of the star. Methods. We used infrared long-baseline interferometry with the PIONIER/VLTI instrument to produce reconstructed images of the photosphere and close environment of the star over four years of observations. To study the disk formation, we compared the observations and reconstructed images to previously computed models of both the stellar photosphere alone (normal B phase) and the star presenting a circumstellar disk (Be phase). Results. The observations taken in 2011 and 2012, during the quiescent phase of Achernar, do not exhibit a disk at the detection limit of the instrument. In 2014, on the other hand, a disk was already formed and our reconstructed image reveals an extended H-band continuum excess flux. Our results from interferometric imaging are also supported by several H-alpha line profiles showing that Achernar started an emission-line phase sometime in the beginning of 2013. The analysis of our reconstructed images shows that the 2014 near-IR flux extends to 1.7 - 2.3 equatorial radii. Our model-independent size estimation of the H-band continuum contribution is compatible with the presence of a circumstellar disk, which is in good agreement with predictions from Be-disk models

High-Resolution Spectroscopy of FUors

High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness, but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened and a complex shortward-displaced shell spectrum increased in strength, disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind structure of FU Ori show evidence of sporadic infall. The strength of P Cyg absorption varied cyclically with a period of 14.8 days, with phase stability maintained over 3 seasons, and is believed to be the rotation period. The structure of the photospheric lines also varies cyclically, but with a period of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has faded, the emission lines of a pre-existing low-excitation chromosphere have emerged, so we believe the `line doubling' in V1057 Cyg is produced by these central emission cores in the absorption lines, not by orbital motion in an inclined Keplerian disk. No dependence of v_eq sin i on wavelength or excitation potential was detected in either star, again contrary to expectation for a self-luminous accretion disk. Nor are critical lines in the near infrared accounted for by synthetic disk spectra. A rapidly rotating star near the edge of stability (Larson 1980), can better explain these observations. FUor eruptions may not be a property of ordinary TTS, but may be confined to a special subspecies of rapid rotators having powerful quasi-permanent winds.Comment: 41 pages (including 32 figures and 9 tables); ApJ, in press; author affiliation, figs. 3 and 9 correcte