Revival of oscillation from mean-field-induced death : Theory and experiment

Submitted ACKNOWLEDGMENTS T. B. acknowledges the financial support from SERB, Department of Science and Technology (DST), India [Project Grant No.: SB/FTP/PS-005/2013]. D. G. acknowledges DST, India, for providing support through the INSPIRE fellowship. J. K. acknowledges Government of the Russian Federation (Agreement No. 14.Z50.31.0033 with Institute of Applied Physics RAS).Peer reviewedPreprin

Networks of coupled oscillators: From phase to amplitude chimeras

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Chaos 28, 113124 (2018) and may be found at https://doi.org/10.1063/1.5054181.We show that amplitude-mediated phase chimeras and amplitude chimeras can occur in the same network of nonlocally coupled identical oscillators. These are two different partial synchronization patterns, where spatially coherent domains coexist with incoherent domains and coherence/incoherence referring to both amplitude and phase or only the amplitude of the oscillators, respectively. By changing the coupling strength, the two types of chimera patterns can be induced. We find numerically that the amplitude chimeras are not short-living transients but can have a long lifetime. Also, we observe variants of the amplitude chimeras with quasiperiodic temporal oscillations. We provide a qualitative explanation of the observed phenomena in the light of symmetry breaking bifurcation scenarios. We believe that this study will shed light on the connection between two disparate chimera states having different symmetry-breaking properties. Chimera states are emergent dynamical patterns in networks of coupled oscillators where coherent and incoherent domains coexist due to spontaneous symmetry-breaking. In oscillators that exhibit both phase and amplitude dynamics, two types of distinct chimera patterns exist, namely, amplitude-mediated phase chimeras (AMCs) and amplitude chimeras (ACs). In the AMC state coherent and incoherent regions are distinguished by different mean phase velocities: all coherent oscillators have the same phase velocity, however, the incoherent oscillators have disparate phase velocities. In contrast to AMC, in the AC state, all the oscillators have the same phase velocity, however, the oscillators in the incoherent domain show periodic oscillations with randomly shifted center of mass. Surprisingly, in all the previous studies on chimeras, a given network of continuous-time dynamical systems seems to show either AMC or AC: they never occur in the same network. In this paper, for the first time, we identify a network of coupled oscillators where both AMC and AC are observed in the same system, and we also provide a qualitative explanation of the observation based on symmetry-breaking bifurcations.DFG, 163436311, SFB 910: Kontrolle selbstorganisierender nichtlinearer Systeme: Theoretische Methoden und Anwendungskonzept

Transition from homogeneous to inhomogeneous limit cycles : Effect of local filtering in coupled oscillators

10 pages, 8 FigsPeer reviewedPublisher PD

Constraining the equation of state of hybrid stars using recent information from multidisciplinary physics

At the ultra-high densities existing in the core of neutron stars, it is expected that a phase transition from baryonic to deconfined quark matter may occur. Such a phase transition would affect the underlying equation of state (EoS) as well as the observable astrophysical properties of neutron stars. Comparison of EoS model predictions with astronomical data from multi-messenger signals then provides us an opportunity to probe the behaviour of dense matter. In this work, we restrict the allowed parameter space of EoS models in neutron stars for both nucleonic (relativistic mean field model) and quark matter (bag model) sectors by imposing state-of-the-art constraints from nuclear calculations, multi-messenger astrophysical data and perturbative QCD (pQCD). We systematically investigate the effect of each constraint on the parameter space of uncertainties using a cut-off filter scheme, as well as the correlations among the parameters and with neutron star astrophysical observables. Using the constraints, we obtain limits for maximum NS mass, maximum central density, as well as for NS radii and tidal deformability. Although pQCD constraints are only effective at very high densities, they significantly reduce the parameter space of the quark model. We also conclude that astrophysical data supports high values of the bag parameter B and disfavors the existence of a pure quark matter core in hybrid stars.Comment: 16 pages, 11 figures, 2 table

PDMS/ceramic composite membrane synthesis and evaluation of ciprofloxacin removal efficiency

The present study employs an unexplored, one-step route for remediation of ciprofloxacin, an emerging contaminant, using hydrophobically modified ceramic membranes. Hydrophobic interaction between the membrane and the target contaminant, i.e., ciprofloxacin, is the governing factor responsible for its removal. The hydrophilic surface of hollow, single channel, macroporous clay-alumina membranes was made hydrophobic using cross-linked polydimethylsiloxane. The influencing parameters-concentration of polymer, cross-linking agent, catalyst and coating time-were optimized by Taguchi analysis to yield a membrane with enhanced ciprofloxacin rejection and high permeate flux. The synthesized membrane was characterized for its contact angle, clean water permeability, degree of swelling, degree of cross-linking, X-Ray diffraction, atomic fluorescence microscopy, field emission scanning electron microscopy. Effect of various operating parameters-cross flow velocity, transmembrane pressure, filtration time, solution pH-was investigated upon removal of ciprofloxacin in cross flow membrane filtration. Maximum rejection of 99.3% was obtained by the hydrophobic membrane having contact angle of 138.5 degrees for 5 mg/L feed solution. The stability of the membrane was judged in terms of change in ciprofloxacin rejection upon filtration for five consecutive cycles, each cycle being 180 min. The developed PDMS/ceramic composite membranes could have great prospect for long-term application in removal of emerging contaminants from water

g-mode Oscillations in Neutron Stars with Hyperons

A common alternative to the standard assumption of nucleonic composition of matter in the interior of a neutron star is to include strange baryons, particularly hyperons. Any change in composition of the neutron star core has an effect on g-mode oscillations of neutron stars, through the compositional dependence of the equilibrium and adiabatic sound speeds. We study the core g-modes of a neutron star contaning hyperons, using a variety of relativistic mean field models of dense matter that satisfy observational constraints on global properties of neutron stars. Our selected models predict a sharp rise in the g-mode frequencies upon the onset of strange baryons. Should g-modes be observed in the near future, their frequency could be used to test the presence of hyperonic matter in the core of neutron stars.Comment: 17 pages, 7 figure