Dynamics of gap solitons in a dipolar Bose-Einstein condensate on a three-dimensional optical lattice

We suggest and study the stable disk- and cigar-shaped gap solitons of a dipolar Bose-Einstein condensate of $^{52}$Cr atoms localized in the lowest band gap by three optical-lattice (OL) potentials along orthogonal directions. The one-dimensional version of these solitons of experimental interest confined by an OL along the dipole moment direction and harmonic traps in transverse directions is also considered. Important dynamics of (i) breathing oscillation of a gap soliton upon perturbation and (ii) dragging of a gap soliton by a moving lattice along axial $z$ direction demonstrates the stability of gap solitons. A movie clip of dragging of three-dimensional gap soliton is included.Comment: To see the dragging movie clip please download sourc

X-ray observations of the hot phase in Sgr~A*

We analyze 134 ks Chandra ACIS-I observations of the Galactic Centre (GC) performed in July 2011. The X-ray image with the field of view $17' \times 17'$ contains the hot plasma surrounding the Sgr~A*. The obtained surface brightness map allow us to fit Bondi hot accretion flow to the innermost hot plasma around the GC. We have fitted spectra from region up to $5"$ from Sgr~A* using a thermal bremsstrahlung model and four Gaussian profiles responsible for K$_{\alpha}$ emission lines of Fe, S, Ar, and Ca. The X-ray surface brightness profile up to $3"$ from Sgr~A* found in our data image, was successfully fitted with the dynamical model of Bondi spherical accretion. By modelling the surface brightness profile, we derived the temperature and number density profiles in the vicinity of the black hole. The best fitted model of spherical Bondi accretion shows that this type of flow works only up to $3"$ and implies outer plasma density and temperature to be: $n_{\rm e}^{\rm out}=18.3 \pm {0.1}$ cm$^{-3}$ and $T_{\rm e}^{\rm out}= 3.5 \pm {0.3}$ keV respectively. We show that the Bondi flow can reproduce observed surface brightness profile up to $3"$ from Sgr~A* in the Galactic Center. This result strongly suggests the position of stagnation radius in the complicated dynamics around GC. The Faraday rotation computed from our model towards the pulsar PSR J1745-2900 near the GC agrees with the observed one, recently reported.Comment: 10 pages, 7 figures, accepted for publication in A&

Dynamics of quasi-one-dimensional bright and vortex solitons of a dipolar Bose-Einstein condensate with repulsive atomic interaction

By numerical and variational analysis of the three-dimensional Gross-Pitaevskii equation we study the formation and dynamics of bright and vortex-bright solitons in a cigar-shaped dipolar Bose-Einstein condensate for large repulsive atomic interactions. Phase diagram showing the region of stability of the solitons is obtained. We also study the dynamics of breathing oscillation of the solitons as well as the collision dynamics of two solitons at large velocities. Two solitons placed side-by-side at rest coalesce to form a stable bound soliton molecule due to dipolar attraction.Comment: To obtain the included video clips S1, S2, S3 and S4, please download sourc

Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density

The requirement of intermediate line component in the recently observed spectra of several AGNs points to possibility of the existence of a physically separate region between broad line region (BLR) and narrow line region (NLR). In this paper we explore the emission from intermediate line region (ILR) by using the photoionization simulations of the gas clouds distributed radially from the AGN center. The gas clouds span distances typical for BLR, ILR and NLR, and the appearance of dust at the sublimation radius is fully taken into account in our model. Single cloud structure is calculated under the assumption of the constant pressure. We show that the slope of the power law cloud density radial profile does not affect the existence of ILR in major types of AGN. We found that the low ionization iron line, Fe~II, appears to be highly sensitive for the presence of dust and therefore becomes potential tracer of dust content in line emitting regions. We show that the use of disk-like cloud density profile computed at the upper part of the accretion disc atmosphere reproduces the observed properties of the line emissivities. In particular, the distance of H${\beta}$ line inferred from our model agrees with that obtained from the reverberation mapping studies in Sy1 galaxy NGC 5548.Comment: 15 pages, 13 figure

The intermediate line region in active galactic nuclei

We show that the recently observed suppression of the gap between the broad line region (BLR) and the narrow line region (NLR) in some AGN can be fully explained by an increase of the gas density in the emitting region. Our model predicts the formation of the intermediate line region (ILR) that is observed in some Seyfert galaxies by the detection of emission lines with intermediate velocity full width half maximum (FWHM) $\sim$ 700 - 1200 km s$^{-1}$. These lines are believed to be originating from an ILR located somewhere between the BLR and NLR. As it was previously proved, the apparent gap is assumed to be caused by the presence of dust beyond the sublimation radius. Our computations with the use of {\sc cloudy} photoionization code, show that the differences in the shape of spectral energy distribution (SED) from the central region of AGN, do not diminish the apparent gap in the line emission in those objects. A strong discontinuity in the line emission vs radius exists for all lines at the dust sublimation radius. However, increasing the gas density to $\sim$ 10$^{11.5}$ cm$^{-3}$ at the sublimation radius provides the continuous line emission vs radius and fully explains the recently observed lack of apparent gap in some AGN. We show that such a high density is consistent with the density of upper layers of an accretion disk atmosphere. Therefore, the upper layers of the disk atmosphere can give rise to the formation of observed emission line clouds.Comment: 9 pages, 6 figures, accepted for publication in Ap

Quantum scattering in one dimension

A self-contained discussion of nonrelativistic quantum scattering is presented in the case of central potentials in one space dimension, which will facilitate the understanding of the more complex scattering theory in two and three dimensions. The present discussion illustrates in a simple way the concept of partial-wave decomposition, phase shift, optical theorem and effective-range expansion.Comment: 8 page