Nuclear symmetry energy in a modified quark meson coupling model

We study nuclear symmetry energy and the thermodynamic instabilities of asymmetric nuclear matter in a self-consistent manner by using a modified quark-meson coupling model where the confining interaction for quarks inside a nucleon is represented by a phenomenologically averaged potential in an equally mixed scalar-vector harmonic form. The nucleon-nucleon interaction in nuclear matter is then realized by introducing additional quark couplings to $\sigma$, $\omega$, and $\rho$ mesons through mean-field approximations. We find an analytic expression for the symmetry energy ${\cal E}_{sym}$ as a function of its slope $L$. Our result establishes a linear correlation between $L$ and ${\cal E}_{sym}$. We also analyze the constraint on neutron star radii in $(pn)$ matter with $\beta$ equilibrium

Pentaquarks in the medium in the quark-meson coupling model

We calculate the properties of the pentaquarks $\Theta^+$ and $\Xi^{--,0}$ in symmetric nuclear matter using the quark meson coupling model (QMC). The stability of the $\Theta^+$ in the medium with respect to the channel $\Theta^+\to NK^+$ is discussed.Comment: 6 pages, 5 figures, revte

Service employee adaptiveness : exploring the impact of role-stress and managerial control approaches

The research aims to explore the relationships between managerial control strategies, role stress and employee adaptiveness among call center employees. Based on a conceptual model, a questionnaire based survey methodology is adopted. Data was collected from call center employees in India and the data was analysed through PLS methodology. The study finds that Outcome control and activity control increase role stress while capability control does not have a significant impact. The interaction between outcome control and activity control also tends to impact role stress of employees. Role stress felt by employees have significant negative impact on employee adaptiveness The sampling approach was convenience based affecting the generalizability of the results. The papers provides guidelines for utilising managerial control approaches in a service setting. The paper looks at managerial control approaches in a service setting – a topic not quite researched before

Reconstruction methods — P‾ANDA focussing-light guide disc DIRC

The Focussing-Lightguide Disc DIRC will provide crucial Particle Identification (PID) information for the P‾ANDA experiment at FAIR, GSI. This detector presents a challenging environment for reconstruction due to the complexity of the expected hit patterns and the operating conditions of the P‾ANDA experiment. A discussion of possible methods to reconstruct PID from this detector is given here. Reconstruction software is currently under development

Non-Abelian symmetries and disorder: a broad non-ergodic regime and anomalous thermalization

Symmetries play a central role in single-particle localization. Recent research focused on many-body localized (MBL) systems, characterized by new kind of integrability, and by the area-law entanglement of eigenstates. We investigate the effect of a non-Abelian $SU(2)$ symmetry on the dynamical properties of a disordered Heisenberg chain. While $SU(2)$ symmetry is inconsistent with the conventional MBL, a new non-ergodic regime is possible. In this regime, the eigenstates exhibit faster than area-law, but still a strongly sub-thermal scaling of entanglement entropy. Using exact diagonalization, we establish that this non-ergodic regime is indeed realized in the strongly disordered Heisenberg chains. We use real-space renormalization group (RSRG) to construct approximate excited eigenstates, and show their accuracy for systems of size up to $L=26$. As disorder strength is decreased, a crossover to the thermalizing phase occurs. To establish the ultimate fate of the non-ergodic regime in the thermodynamic limit, we develop a novel approach for describing many-body processes that are usually neglected by RSRG, accessing systems of size $L>2000$. We characterize the resonances that arise due to such processes, finding that they involve an ever growing number of spins as the system size is increased. The probability of finding resonances grows with the system size. Even at strong disorder, we can identify a large lengthscale beyond which resonances proliferate. Presumably, this eventually would drive the system to a thermalizing phase. However, the extremely long thermalization time scales indicate that a broad non-ergodic regime will be observable experimentally. Our study demonstrates that symmetries control dynamical properties of disordered, many-body systems. The approach introduced here provides a versatile tool for describing a broad range of disordered many-body systems.Comment: 25 pages, 21 figure

Squeezed Fermions at Relativistic Heavy Ion Colliders

Large back-to-back correlations of observable fermion -- anti-fermion pairs are predicted to appear, if the mass of the fermions is modified in a thermalized medium. The back-to-back correlations of protons and anti-protons are experimentally observable in ultra-relativistic heavy ion collisions, similarly to the Andreev reflection of electrons off the boundary of a superconductor. While quantum statistics suppresses the probability of observing pairs of fermions with nearby momenta, the fermionic back-to-back correlations are positive and of similar strength to bosonic back-to-back correlations.Comment: LaTeX, ReVTeX 12 pages, uses epsf.sty, 2 eps figures, improved presentatio

Electronic States in Diffused Quantum Wells

In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, $sp^3 s^*$ spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengths $L_{D}=20\div100$ {\AA} the transition (C3-HH3) is not sensitive to the diffusion length, but the transitions (C1-HH1), (C1-LH1), (C2-HH2) and (C2-LH2) display large "blue shifts" as L_{D} increases. For diffusion lengths $L_{D}=0\div20$ {\AA} the transitions (C1-HH1) and (C1-LH1) are less sensitive to the L_{D} changes than the (C3-HH3) transition. The observed dependence is explained in terms of the bound states spatial distributions.Comment: ReVTeX file, 7pp., no macros, 4 figures available on the reques

Neutron star matter in an effective model

We study the equation of state (EOS) for dense matter in the core of the compact star with hyperons and calculate the star structure in an effective model in the mean field approach. With varying incompressibility and effective nucleon mass, we analyse the resulting EOS with hyperons in beta equilibrium and its underlying effect on the gross properties of the compact star sequences. The results obtained in our analysis are compared with predictions of other theoretical models and observations. The maximum mass of the compact star lies in the range $1.21-1.96 ~M_{\odot}$ for the different EOS obtained, in the model.Comment: 10 pages, 14 figures as appeared in PRC 74, 055803, (2006

Back-to-Back Correlations for Finite Expanding Fireballs

Back-to-Back Correlations of particle-antiparticle pairs are related to the in-medium mass-modification and squeezing of the quanta involved. They are predicted to appear when hot and dense hadronic matter is formed in high energy nucleus-nucleus collisions. The survival and magnitude of the Back-to-Back Correlations of boson-antiboson pairs generated by in-medium mass modifications are studied here in the case of a thermalized, finite-sized, spherically symmetric expanding medium. We show that the BBC signal indeed survives the finite-time emission, as well as the expansion and flow effects, with sufficient intensity to be observed at RHIC.Comment: 24 pages, 4 figure