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- SCL Seminar by Ricardo Carretero

San Diego State University USA presents a seminar talk entitled Vortex rings nature physics mathematics and computations Abstract In this talk we will explore the beautiful and complex world of vortex rings A vortex ring is formed when a vortex line a twister is looped back onto itself creating a close ring that carries vorticity Vortex rings are commonplace in fluids For example in liquids many species of marine mammals know how to create them play with them and even use them to catch prey Smoke rings in gases are also common In fact not only people can make smoke rings but volcanoes and chimneys are also at it We will focus on the occurrence of vortex rings in superfluids fluids without viscosity described by the nonlinear Schrödinger equation We showcase some of their phenomenology including internal excitation waves Kelvin modes their mutual interactions collisions and scattering scenarios We also briefly discuss an efficient computational implementation for solving the ensuing partial differential equations using GPU accelerated codes that allow for numerical integration runs of vortex rings in real time News 12 February 2016 SCL Seminar by Jelena Smiljanic 12 January 2016 In memoriam Nikola Buric 28 December 2015 SCL Seminar

Original URL path: http://www.scl.rs/news/931-scl-seminar-by-ricardo-carretero (2016-02-10)

Open archived version from archive - SCL Seminar by Carlos A. R. Sa de Melo

quantum phase transitions in superfluids with non s wave order parameters have been conjectured theoretically for p wave and d wave systems for many years but never observed experimentally due to the absence of tunable parameters However Zeeman or spin orbit fields and interactions can be tuned in the context of ultra cold atoms and allow for the visitation of several different phases For systems with zero Zeeman field the evolution from BCS to BEC superfluidity in the presence of spin orbit effects is only a crossover 1 as the system remains fully gapped even though a triplet component of the order parameter emerges In contrast for finite Zeeman fields spin orbit coupling induces a triplet component in the order parameter that produces nodes in the quasiparticle excitation spectrum leading to bulk topological phase transitions of the Lifshitz type 2 Additionally a fully gapped phase exists where a crossover from indirect to direct gap occurs For spin orbit couplings with equal Rashba and Dresselhaus strengths the nodal quasi particles are Dirac fermions that live at and in the vicinity of rings of nodes Transitions from and to nodal phases can occur via the emergence of zero mode Majorana fermions at phase boundaries where rings of nodes of Dirac fermions annihilate 3 Lastly we will characterize different phases via spectroscopic and thermodynamic properties and conclude that Lifshitz is the Lord of the Rings 4 1 Li Han C A R Sá de Melo Evolution from BCS to BEC superfluidity in the presence of spin orbit coupling Phys Rev A 85 011606 R 2012 see also arXiv 1106 3613v1 2 Kangjun Seo Li Han and C A R Sá de Melo Topological phase transitions in ultra cold Fermi superfluids the evolution from BCS to BEC under artificial spin orbit fields Phys Rev

Original URL path: http://www.scl.rs/news/932-scl-seminar-by-carlos-a-r-sa-de-melo (2016-02-10)

Open archived version from archive - SCL Seminar by Bosiljka Tadic

science these research activities provided evidence for the emergence of new collective phenomena on the Web from sharing common emotion to coordinated efforts and cooperation leading to the collective knowledge The source of all these phenomena is in human to human interactions with shared values where multiple factors such as the subject of communications motivation to cooperate as well as technology that enables or limits it play a significant role In this multidisciplinary strategies the concepts of statistical physics are of fundamental importance Firstly physics theory provides with understanding the underlying stochastic processes through which the collective behavior arises from interactions at microscopic scale and secondly the ways to quantify the emergent phenomena in analogy to the complex dynamical systems in the physics laboratory In this seminar we illustrate some of the potentials of this approach in the actual case of the online chats data that concern a specific content cognition In the analysed example the concepts of non equilibrium statistical physics are complemented with the methods of text analysis and graph theory Besides an agent based model of the online chat systems with an emotional robot is designed in order to explain the underlying dynamics further and demonstrate the

Original URL path: http://www.scl.rs/news/936-scl-seminar-by-bosiljka-tadic (2016-02-10)

Open archived version from archive - SCL Seminar by Wassilij Kopylov

talk we will present an application of the time delayed Pyragas control scheme to the dissipative Dicke model via a modulation of the atom field coupling The feedback creates an infinite sequence of non equilibrium phases with fixed points and limit cycles in the primary superradiant regime We will analyse this Hopf bifurcation scenario as a function of delay time and feedback strength and determine analytical conditions for the phase

Original URL path: http://www.scl.rs/news/937-scl-seminar-by-wassilij-kopylov (2016-02-10)

Open archived version from archive - SCL Seminar by Darko Hric

Finland presents a seminar talk entitled Community detection in networks structural versus annotated clusters Abstract Detecting communities in networks is one of the most popular topics of network science Communities or clusters are usually conceived as subgraphs of a network with a high density of links within the subgraphs and a comparatively lower density between them Algorithms to find communities in networks rely just on structural information and search for cohesive subsets of nodes On the other hand most scholars implicitly or explicitly assume that structural communities represent groups of nodes with similar non topological properties or functions This hypothesis could not be verified so far because of the lack of network datasets with information on the classification of the nodes We show that traditional community detection methods fail to find the annotated clusters in many large networks Our results show that there is a marked separation between structural and annotated clusters in line with recent findings That means that either our current modeling of community structure has to be substantially modified or that annotated clusters may not be recoverable from topology alone News 12 February 2016 SCL Seminar by Jelena Smiljanic 12 January 2016 In memoriam Nikola Buric 28

Original URL path: http://www.scl.rs/news/938-scl-seminar-by-darko-hric (2016-02-10)

Open archived version from archive - SCL Seminar by Marko Rancic

materials like GaAs and InAs do not have stable zero nuclear spin isotopes and therefore the nuclear spins must be dynamically polarized DNP or dynamically decoupled In this talk we will give a detailed overview of methods developed to overcome the nuclear spin induced decoherence of the two electron double quantum dot system DQD with a special emphasis on our recent results In our recent study we explore the interplay of spin orbit and hyperfine effects on the nuclear preparation schemes in two electron DQDs in InGaAs The quantity of utmost interest is the electron spin decoherence time in dependence of the number of sweeps through the electron spin singlet triplet anti crossing Decoherence of the electron spin is caused by the difference field induced by the nuclear spins We study the case where a singlet S 2 0 is initialized in which both electrons are in the left dot Subsequently the system is driven repeatedly through the anti crossing and back using linear electrical bias sweeps In the second part of the talk we will give an overview of dynamical decoupling methods with a special emphasis on recent dynamical decoupling experiments conducted in GaAs DQDs in the Yacobi group

Original URL path: http://www.scl.rs/news/940-scl-seminar-by-marko-rancic (2016-02-10)

Open archived version from archive - SCL Seminar by Jelena Stajic

00 in the library of the Institute of Physics Belgrade Jelena Stajic Associte Editor Science presents a seminar talk entitled Publishing physics in Science from an editor s perspective News 12 February 2016 SCL Seminar by Jelena Smiljanic 12 January 2016 In memoriam Nikola Buric 28 December 2015 SCL Seminar by Milos Radonjic 25 December 2015 SCL Seminar by Milan Radonjic 18 December 2015 SCL Seminar by Nenad Vukmirovic 11

Original URL path: http://www.scl.rs/news/941-scl-seminar-by-jelena-stajic (2016-02-10)

Open archived version from archive - SCL Seminar by Vladimir V. Klinshov

implementation low dimension and possibility for theoretical analysis Recently pulse coupled phase oscillators have been shown to be especially useful for study of the networks with coupling delays It has been proven that networks of phase oscillators with time delay pulsatile coupling can be reduced to finite dimensional maps under quite general conditions With the help of this technique we investigate dynamics of networks of various configurations The studied phenomena

Original URL path: http://www.scl.rs/news/942-scl-seminar-by-vladimir-v-klinshov (2016-02-10)

Open archived version from archive