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Synchronized and Desynchronized Phases of Exciton-Polariton Condensates in the Presence of Disorder  [PDF]
A. Baas,K. G. Lagoudakis,M. Richard,R. Andre,Le Si Dang,B. Deveaud-Pledran
Physics , 2007, DOI: 10.1103/PhysRevLett.100.170401
Abstract: Condensation of exciton-polaritons in semiconductor microcavities takes place despite in plane disorder. Below the critical density the inhomogeneity of the potential seen by the polaritons strongly limits the spatial extension of the ground state. Above the critical density, in presence of weak disorder, this limitation is spontaneously overcome by the non linear interaction, resulting in an extended synchronized phase. This mechanism is clearly evidenced by spatial and spectral studies, coupled to interferometric measurements. In case of strong disorder, several non phase-locked (independent) condensates can be evidenced. The transition from synchronized phase to desynchronized phase is addressed considering multiple realizations of the disorder.
Physiological Responses in Relation to Performance during Competition in Elite Synchronized Swimmers  [PDF]
Lara Rodríguez-Zamora, Xavier Iglesias, Anna Barrero, Diego Chaverri, Pau Erola, Ferran A. Rodríguez
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049098
Abstract: Purpose We aimed to characterize the cardiovascular, lactate and perceived exertion responses in relation to performance during competition in junior and senior elite synchronized swimmers. Methods 34 high level senior (21.4±3.6 years) and junior (15.9±1.0) synchronized swimmers were monitored while performing a total of 96 routines during an official national championship in the technical and free solo, duet and team competitive programs. Heart rate was continuously monitored. Peak blood lactate was obtained from serial capillary samples during recovery. Post-exercise rate of perceived exertion was assessed using the Borg CR-10 scale. Total competition scores were obtained from official records. Results Data collection was complete in 54 cases. Pre-exercise mean heart rate (beats·min?1) was 129.1±13.1, and quickly increased during the exercise to attain mean peak values of 191.7±8.7, with interspersed bradycardic events down to 88.8±28.5. Mean peak blood lactate (mmol·L?1) was highest in the free solo (8.5±1.8) and free duet (7.6±1.8) and lowest at the free team (6.2±1.9). Mean RPE (0–10+) was higher in juniors (7.8±0.9) than in seniors (7.1±1.4). Multivariate analysis revealed that heart rate before and minimum heart rate during the routine predicted 26% of variability in final total score. Conclusions Cardiovascular responses during competition are characterized by intense anticipatory pre-activation and rapidly developing tachycardia up to maximal levels with interspersed periods of marked bradycardia during the exercise bouts performed in apnea. Moderate blood lactate accumulation suggests an adaptive metabolic response as a result of the specific training adaptations attributed to influence of the diving response in synchronized swimmers. Competitive routines are perceived as very to extremely intense, particularly in the free solo and duets. The magnitude of anticipatory heart rate activation and bradycardic response appear to be related to performance variability.
Competition of languages in the presence of a barrier  [PDF]
Christian Schulze,Dietrich Stauffer
Physics , 2007, DOI: 10.1016/j.physa.2007.02.071
Abstract: Using the Schulze model for Monte Carlo simulations of language competition, we include a barrier between the top half and the bottom half of the lattice. We check under which conditions two different languages evolve as dominating in the two halves.
Shark scavenging behavior in the presence of competition  [cached]
Shannon P. GERRY, Andrea J. SCOTT
Current Zoology , 2010,
Abstract: The distribution of organisms within a community can often be determined by the degree of plasticity or degree of specialization of resource acquisition. Resource acquisition is often based on the morphology of an organism, behavior, or a combination of both. Performance tests of feeding can identify the possible interactions that allow one species to better exploit a prey item. Scavenging behaviors in the presence or absence of a competitor were investigated by quantifying prey selection in a trophic generalist, spiny dogfish Squalus acanthias, and a trophic specialist, smooth-hounds Mustelus canis, in order to determine if each shark scavenged according to its jaw morphology. The diet of dogfish consists of small fishes, squid, ctenophores, and bivalves; they are expected to be nonselective predators. Smooth-hounds primarily feed on crustaceans; therefore, they are predicted to select crabs over other prey types. Prey selection was quantified by ranking each prey item according to the order it was consumed. Dietary shifts were analyzed by comparing the percentage of each prey item selected during solitary versus competitive scavenging. When scavenging alone, dogfish prefer herring and squid, which are easily handled by the cutting dentition of dogfish. Dogfish shift their diet to include a greater number of prey types when scavenging with a competitor. Smooth-hounds scavenge on squid, herring, and shrimp when alone, but increase the number of crabs in the diet when scavenging competitively. Competition causes smooth-hounds to scavenge according to their jaw morphology and locomotor abilities, which enables them to feed on a specialized resource [Current Zoology 56 (1): 100–108 2010].
Prisoners' Dilemma in Presence of Collective Dephasing  [PDF]
Ahmad Nawaz
Mathematics , 2013, DOI: 10.1088/1751-8113/45/19/195304
Abstract: We quantize prisoner dilemma in presence of collective dephasing with dephasing rate $\gamma $. It is shown that for two parameters set of strategies $Q\otimes Q$ is Nash equilibrium below a cut-off value of time. Beyond this cut-off it bifurcates into two new Nash equilibria $Q\otimes D$ and $D\otimes Q$. Furthermore for maximum value of decoherence \ $C\otimes D$ and $D\otimes C$ also become Nash equilibria. At this stage the game has four Nash equilibria. On the other hand for three parameters set of strategies there is no pure strategy Nash equilibrium however there is mixed strategy (non unique) Nash equilibrium that is not affected by collective dephasing..
Length scale competition in soliton bearing equations: A collective coordinate approach  [PDF]
Sara Cuenda,Angel Sanchez
Physics , 2004, DOI: 10.1063/1.1876632
Abstract: We study the phenomenon of length scale competition, an instability of solitons and other coherent structures that takes place when their size is of the same order of some characteristic scale of the system in which they propagate. Working on the framework of nonlinear Klein-Gordon models as a paradigmatic example, we show that this instability can be understood by means of a collective coordinate approach in terms of soliton position and width. As a consequence, we provide a quantitative, natural explanation of the phenomenon in much simpler terms than any previous treatment of the problem. Our technique allows to study the existence of length scale competition in most soliton bearing nonlinear models and can be extended to coherent structures with more degrees of freedom, such as breathers.
Collective Decision Dynamics in the Presence of External Drivers  [PDF]
Danielle S. Bassett,David L. Alderson,Jean M. Carlson
Physics , 2012, DOI: 10.1103/PhysRevE.86.036105
Abstract: We develop a sequence of models describing information transmission and decision dynamics for a network of individual agents subject to multiple sources of influence. Our general framework is set in the context of an impending natural disaster, where individuals, represented by nodes on the network, must decide whether or not to evacuate. Sources of influence include a one-to-many externally driven global broadcast as well as pairwise interactions, across links in the network, in which agents transmit either continuous opinions or binary actions. We consider both uniform and variable threshold rules on the individual opinion as baseline models for decision-making. Our results indicate that 1) social networks lead to clustering and cohesive action among individuals, 2) binary information introduces high temporal variability and stagnation, and 3) information transmission over the network can either facilitate or hinder action adoption, depending on the influence of the global broadcast relative to the social network. Our framework highlights the essential role of local interactions between agents in predicting collective behavior of the population as a whole.
Collective Chemotactic Dynamics in the Presence of Self-Generated Fluid Flows  [PDF]
Enkeleida Lushi,Raymond E. Goldstein,Michael J. Shelley
Physics , 2012, DOI: 10.1103/PhysRevE.86.040902
Abstract: In micro-swimmer suspensions locomotion necessarily generates fluid motion, and it is known that such flows can lead to collective behavior from unbiased swimming. We examine the complementary problem of how chemotaxis is affected by self-generated flows. A kinetic theory coupling run-and-tumble chemotaxis to the flows of collective swimming shows separate branches of chemotactic and hydrodynamic instabilities for isotropic suspensions, the first driving aggregation, the second producing increased orientational order in suspensions of "pushers" and maximal disorder in suspensions of "pullers". Nonlinear simulations show that hydrodynamic interactions can limit and modify chemotactically-driven aggregation dynamics. In puller suspensions the dynamics form aggregates that are mutually-repelling due to the non-trivial flows. In pusher suspensions chemotactic aggregation can lead to destabilizing flows that fragment the regions of aggregation.
Competition between Kondo and RKKY correlations in the presence of strong randomness  [PDF]
Minh-Tien Tran,Ki-Seok Kim
Physics , 2011, DOI: 10.1088/0953-8984/23/42/425602
Abstract: We propose that competition between Kondo and magnetic correlations results in a novel universality class for heavy fermion quantum criticality in the presence of strong randomness. Starting from an Anderson lattice model with disorder, we derive an effective local field theory in the dynamical mean-field theory (DMFT) approximation, where randomness is introduced into both hybridization and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Performing the saddle-point analysis in the U(1) slave-boson representation, we reveal its phase diagram which shows a quantum phase transition from a spin liquid state to a local Fermi liquid phase. In contrast with the clean limit of the Anderson lattice model, the effective hybridization given by holon condensation turns out to vanish, resulting from the zero mean value of the hybridization coupling constant. However, we show that the holon density becomes finite when variance of hybridization is sufficiently larger than that of the RKKY coupling, giving rise to the Kondo effect. On the other hand, when the variance of hybridization becomes smaller than that of the RKKY coupling, the Kondo effect disappears, resulting in a fully symmetric paramagnetic state, adiabatically connected with the spin liquid state of the disordered Heisenberg model. ......
Propagation of collective pair excitations in disordered Bose superfluids  [PDF]
Samuel Lellouch,Lih-King Lim,Laurent Sanchez-Palencia
Physics , 2015, DOI: 10.1103/PhysRevA.92.043611
Abstract: We study the effect of disorder on the propagation of collective excitations in a disordered Bose superfluid. We incorporate local density depletion induced by strong disorder at the meanfield level, and formulate the transport of the excitations in terms of a screened scattering problem. We show that the competition of disorder, screening, and density depletion induces a strongly non-monotonic energy dependence of the disorder parameter. In three dimensions, it results in a rich localization diagram with four different classes of mobility spectra, characterized by either no or up to three mobility edges. Implications on experiments with disordered ultracold atoms are discussed.
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