Rajeev Singh

Indian Institute of Technology (Banaras Hindu University) Varanasi | BHU · Department of Physics

Differential excitatory and inhibitory interactions, specifically lateral inhibition, between the constituent elements of complex systems underlie a wide range of spatiotemporal patterns in nature. Here, we show that when systems of relaxation oscillators, whose dynamics involve widely separate timescales, are coupled primarily through diffusion of...

We propose a method for generation of genuine multipartite entangled states in a short-range Ising spin chain with periodic global pulses of magnetic field. We consider an integrable and a nonintegrable Floquet system that is periodic in time and has constant quasienergy gaps with degeneracies. We start with all spins polarized along one direction...

The collective dynamics seen in a wide variety of chemical, biological and ecological systems involve interactions between relaxation oscillators that typically involve fast activation process coupled with a slower inactivation. In this paper, we show that systems of such oscillators having distinct kinetics governing local dynamical behavior and w...

We propose a method for generation of multiparty entangled states in an Ising spin chain with nearest neighbour interactions and periodic global pulses of magnetic field. We consider an integrable and a nonintegrable Floquet system that are periodic in time and have constant quasi-energy gaps with degeneracies. We start with simple product initial...

The magneto-transport properties of Bi2Se3–ySy were investigated. Magnetoresistance (MR) decreases with an increase in the S content, and finally, for 7% (i.e., y = 0.21) S doping, the magnetoresistance becomes negative. This negative MR is unusual as it is observed when a magnetic field is applied in the perpendicular direction to the plane of the...

The magneto-transport properties in Sulfur doped Bi2Se3 are investigated. The magnetoresistance (MR) decreases with increase of S content and finally for 7% (i.e. y=0.21) S doping the magnetoresistance becomes negative. This negative MR is unusual as it is observed when magnetic field is applied with the perpendicular direction to the plane of the...

Localization in interacting systems caused by disorder, known as many-body localization (MBL), has attracted a lot of attention in recent years. Most systems studied in this context also show single-particle localization, and the question of MBL is whether the phenomena survives the effects of interactions. It is intriguing to consider a system wit...

We numerically investigate the dynamics of entanglement in a chain of spinless fermions with nonrandom but long-range hopping and interactions, and with random on-site energies. For moderate disorder in the absence of interactions, the chain hosts delocalized states at the top of the band which undergo a delocalization-localization transition with...

Mixed states of a quantum system, represented by density operators, can be decomposed as a statistical mixture of pure states in a number of ways where each decomposition can be viewed as a different preparation recipe. However the fact that the density matrix contains full information about the ensemble makes it impossible to estimate the preparat...

Mixed states of a quantum system, represented by density operators, can be decomposed as a statistical mixture of pure states in a number of ways where each decomposition can be viewed as a different preparation recipe. However the fact that the density matrix contains full information about the ensemble makes it impossible to estimate the preparat...

The many-body localization transition is a dynamical quantum phase transition between a localized and an extended phase. We study this transition in the XXZ model with disordered magnetic field and focus on the time evolution following a global quantum quench. While the dynamics of the bipartite entanglement and spin fluctuations are already known...

We propose to apply spin noise spectroscopy (SNS) to detect many-body localization (MBL) in disordered spin systems. The SNS methods are relatively non-invasive technique to probe spontaneous spin fluctuations. We here show that the spin noise signals obtained by cross-correlation SNS with two probe beams can be used to separate the MBL phase from...

The spontaneous emergence of contraction-inducing electrical activity in the uterus at the beginning of labor remains poorly understood, partly due to the seemingly contradictory observation that isolated uterine cells are not spontaneously active. It is known, however, that the expression of gap junctions increases dramatically in the approach to...

Non-equilibrium systems are characterized by a rich variety of dynamical behaviors, which may sensitively depend on control parameters. Here, we investigate and provide a quantitative analysis of the role of disorder on the transitions between different dynamical regimes in extended heterogeneous systems of excitable and passive cells, induced by v...

In many complex systems, the dynamical evolution of the different components can result in adaptation of the connections between them. We consider the problem of how a fully connected network of discrete-state dynamical elements which can interact via positive or negative links, approaches structural balance by evolving its links to be consistent w...

Every choice of orthonormal frame in the Hilbert space of a bipartite system corresponds to one set of all mutually commuting density matrices or, equivalently, classical state space of the system; the quantum state space itself can thus be profitably viewed as an orbit of classical state spaces, one for each orthonormal frame. We exploit this conn...

Non-equilibrium processes which convert chemical energy into mechanical motion enable the motility of organisms. Bundles of inextensible filaments driven by energy transduction of molecular motors form essential components of micron-scale motility engines like cilia and flagella. The mimicry of cilia-like motion in recent experiments on synthetic a...

Hydrodynamic instabilities provide a generic route to spontaneous biomimetic oscillations in chemomechanically active filaments : Supplementary Information

Planar flexible periodic beating of clamped active filament with flowfield

Aplanar corkscrew-like rigid rotation of clamped active filament with flowfield

Hopf bifurcation in clamped active filament

Recent experiments have highlighted how collective dynamics in networks of brain regions affect behavior and cognitive function. In this paper we show that a simple, homogeneous system of densely connected oscillators representing the aggregate activity of local brain regions can exhibit a rich variety of dynamical patterns emerging via spontaneous...

A variety of complex spatial patterns relevant to chemical and biological systems can be generated through reaction-diffusion mechanisms. In this paper, we show that diffusive coupling through the inactivating component in a system of relaxation oscillators extends such complexity to the temporal domain, generating remarkable spatiotemporal phenome...

We examine the conjectured asymptotic shape of the three dimensional corner growth model [Olejarz et. al.,PRL, 108, 016102 (2012)] by mapping the model onto a restricted solid on solid model on a triangular lattice. By choosing appropriate boundary conditions, we are able to obtain high precision numerical results for the growth velocity using Mont...

Coherent oscillatory activity can arise spontaneously as a result of increased coupling in a system of excitable and passive cells, each being quiescent in isolation. This can potentially explain the appearance of spontaneous rhythmic contractions in the pregnant uterus close to term. We investigate the transition to periodic activity using a model...

Synchronized oscillations are of critical functional importance in many biological systems. We show that such oscillations can arise without centralized coordination in a disordered system of electrically coupled excitable and passive cells. Increasing the coupling strength results in waves that lead to coherent periodic activity, exhibiting cluste...

The geometry of the generalized Bloch sphere $\Omega_3$, the state space of a qutrit is studied. Closed form expressions for $\Omega_3$, its boundary $\partial \Omega_3$, and the set of extremals $\Omega_3^{\rm ext}$ are obtained by use of an elementary observation. These expressions and analytic methods are used to classify the 28 two-sections and...

Homogeneous populations of oscillators have recently been shown to exhibit stable coexistence of coherent and incoherent regions. Generalizing the concept of chimera states to the context of order-disorder transition in systems at thermal equilibrium, we show analytically that such complex ordering can appear in a system of Ising spins, possibly th...

The Belousov-Zhabotinsky reaction is the prototypical reaction for chemical oscillations. This system has been studied extensively. Periodic oscillations are observed for suitable parameter values. Experiments have also been done in thin tubes wherein travelling chemical waves are observed. This corresponds to a reaction- diffusion system in one di...