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Djordjevic M.,Institute of Physics Belgrade
Journal of Physics: Conference Series | Year: 2016

High momentum suppression of light and heavy flavor observables is considered to be an excellent probe of jet-medium interactions in QCD matter created at RHIC and LHC. Utilizing this tool requires accurate suppression predictions for different experiments, probes and experimental conditions, and their unbiased comparison with experimental data. We developed the dynamical energy loss formalism which takes into account both radiative and collision energy loss computed within the same theoretical framework, dynamical (as opposed to static) scattering centers, finite magnetic mass, running coupling and uses no free parameters in comparison with experimental data. Within this formalism, we provide predictions, and a systematic comparison with the experimental data, for a diverse set of probes, various centrality ranges and various collision energies at RHIC and LHC. We also provide clear qualitative and quantitative predictions for the upcoming LHC experiments. A comprehensive agreement between our predictions and experimental results suggests that our dynamical energy loss formalism can well explain the jet-medium interactions in QGP, which will be further tested by the obtained predictions for the upcoming data. Source


Jovanovic R.,Institute of Physics Belgrade | Tuba M.,Megatrend University | Simian D.,Lucian Blaga University
WSEAS Transactions on Computers | Year: 2010

The aim of this paper is compare the effect of using different topologies or connections between separate colonies in island based parallel implementations of the Ant Colony Optimization applied to the Minimum Weight Vertex Cover Problem. We investigated the sequential Ant Colony Optimization algorithms applied to the Minimum Weight Vertex Cover Problem before. Parallelization of population based algorithms using the island model is of great importance because it often gives super linear increase in performance. We observe the behavior of different parallel algorithms corresponding to several topologies and communication rules like fully connected, replace worst, ring and independent parallel runs. We also propose a variation of the algorithm corresponding to the ring topology that maintains the diversity of the search, but still moves to areas with better solutions and gives slightly better results even on a single processor with threads. Source


Jovanovic R.,Institute of Physics Belgrade | Tuba M.,Megatrend University
Applied Soft Computing Journal | Year: 2011

The minimum weight vertex cover problem is an interesting and applicable NP-hard problem that has been investigated from many different aspects. The ant colony optimization metaheuristic is a relatively new technique that was successfully adjusted and applied to many hard combinatorial optimization problems, including the minimum weight vertex cover problem. Some kind of hybridization or exploitation of the knowledge about specific problem often greatly improves the performance of standard evolutionary algorithms. In this article we propose a pheromone correction heuristic strategy that uses information about the best-found solution to exclude suspicious elements from it. Elements are suspicious if they have some undesirable properties that make them unlikely members of the optimal solution. This hybridization improves pure ant colony optimization algorithm by avoiding early trapping in local convergence. We tested our algorithm on numerous test-cases that were used in the previous research of the same problem and our algorithm uniformly performed better, giving slightly better results in significantly shorter time. © 2011 Elsevier B.V. All rights reserved. Source


Ali Sekh G.,Institute of Physics Belgrade
Pramana - Journal of Physics | Year: 2013

Matter-wave bright solitons in bichromatic lattice potentials are considered and their dynamics for different lattice environments are studied. Bichromatic potentials are created from superpositions of (i) two linear optical lattices and (ii) a linear and a nonlinear optical lattice. Effective potentials are found for the solitons in both bichromatic lattices and a comparative study is done on the dynamics of solitons with respect to the effective potentials. The effects of dispersion on solitons in bichromatic lattices are studied and it is found that the dispersive spreading can be minimized by appropriate combinations of lattice and interaction parameters. Stability of nondispersive matter-wave solitons is checked from phase portrait analysis. © Indian Academy of Sciences. Source


Kono M.,Chuo University | Vranjes J.,Institute of Physics Belgrade
Physical Review Letters | Year: 2014

Complicated wave behavior observed in the cylindrical pair-ion (fullerene) experiments by Oohara and co-workers are now identified to be low harmonic ion cyclotron waves combined with ion plasma oscillations inherent to kinetic theory. The electrostatic dispersion equation derived is based on an approximation for the current from the exact solutions of the characteristic cylindrical geometry form of the Vlasov plasma equation in a uniform magnetized plasma cylinder surrounded by a larger metal boundary outside a vacuum gap, which thus differs from that in unbounded plasmas. Positive and negative ions, differing only in the sign of their charge, respond to a potential in the same time scale and cooperate to reflect the enhanced kinetic orbital behaviors to the macroscopic propagation characteristics. In addition, the experimental value of the Larmor radius (comparable to the discharge radius but small enough to make the analytic approximation useful) makes higher harmonic ion cyclotron effects both observable and calculable with the appropriate approximation for the kinetic theory. © 2014 American Physical Society. Source

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