Rapidity Profile of the Initial Energy Density in Heavy-Ion Collisions

The rapidity dependence of the initial energy density in heavy-ion collisions is calculated from a three-dimensional McLerran-Venugopalan model (3dMVn) introduced by Lam and Mahlon. This model is infrared safe since global color neutrality is enforced. In this non-boost-invariant framework, the nuclei have non-zero thickness in the longitudinal direction. This results in Bjorken-x dependent unintegrated gluon distribution functions which lead to a rapidity-dependent initial energy density after the collision. The initial energy density and its rapidity dependence are important initial conditions for the quark gluon plasma and its hydrodynamic evolution.Comment: 7 pages, 2 figures. Matches the published versio

Efficient MRF Energy Propagation for Video Segmentation via Bilateral Filters

Segmentation of an object from a video is a challenging task in multimedia applications. Depending on the application, automatic or interactive methods are desired; however, regardless of the application type, efficient computation of video object segmentation is crucial for time-critical applications; specifically, mobile and interactive applications require near real-time efficiencies. In this paper, we address the problem of video segmentation from the perspective of efficiency. We initially redefine the problem of video object segmentation as the propagation of MRF energies along the temporal domain. For this purpose, a novel and efficient method is proposed to propagate MRF energies throughout the frames via bilateral filters without using any global texture, color or shape model. Recently presented bi-exponential filter is utilized for efficiency, whereas a novel technique is also developed to dynamically solve graph-cuts for varying, non-lattice graphs in general linear filtering scenario. These improvements are experimented for both automatic and interactive video segmentation scenarios. Moreover, in addition to the efficiency, segmentation quality is also tested both quantitatively and qualitatively. Indeed, for some challenging examples, significant time efficiency is observed without loss of segmentation quality.Comment: Multimedia, IEEE Transactions on (Volume:16, Issue: 5, Aug. 2014

Photometric Variability of the mCP Star CS Vir: Evolution of the Rotation Period

The aim of this study is to accurately calculate the rotational period of CS\,Vir by using {\sl STEREO} observations and investigate a possible period variation of the star with the help of all accessible data. The {\sl STEREO} data that cover five-year time interval between 2007 and 2011 are analyzed by means of the Lomb-Scargle and Phase Dispersion Minimization methods. In order to obtain a reliable rotation period and its error value, computational algorithms such as the Levenberg-Marquardt and Monte-Carlo simulation algorithms are applied to the data sets. Thus, the rotation period of CS\,Vir is improved to be 9.29572(12) days by using the five-year of combined data set. Also, the light elements are calculated as $HJD_\mathrm{max} = 2\,454\,715.975(11) + 9_{\cdot}^\mathrm{d}29572(12) \times E + 9_{\cdot}^\mathrm{d}78(1.13) \times 10^{-8} \times E^2$ by means of the extremum times derived from the {\sl STEREO} light curves and archives. Moreover, with this study, a period variation is revealed for the first time, and it is found that the period has lengthened by 0.66(8) s y$^{-1}$, equivalent to 66 seconds per century. Additionally, a time-scale for a possible spin-down is calculated around $\tau_\mathrm{SD} \sim 10^6$ yr. The differential rotation and magnetic braking are thought to be responsible of the mentioned rotational deceleration. It is deduced that the spin-down time-scale of the star is nearly three orders of magnitude shorter than its main-sequence lifetime ($\tau_\mathrm{MS} \sim 10^9$ yr). It is, in return, suggested that the process of increase in the period might be reversible.Comment: 11 pages, 5 tables, 3 figures, the paper has been accepted for publication in PAS