The emerging popular scheme of fourth generation wireless communication, orthogonal frequency-division multiplexing, is mapped onto a variant of a random field Ising Hamiltonian and results in an efficient physical intercarrier interference (ICI) cancellation decoding scheme. This scheme is based on Monte Carlo (MC) dynamics at zero temperature as well as at the Nishimori temperature and demonstrates improved bit error rate (BER) and robust convergence time compared to the state of the art ICI cancellation decoding scheme. An optimal BER performance is achieved with MC dynamics at the Nishimori temperature but with a substantial computational cost overhead. The suggested ICI cancellation scheme also supports the transmission of biased signals.

The generalized elastic model (GEM) provides the evolution equation which governs the stochastic motion of several many-body systems in nature, such as polymers, membranes, and growing interfaces. On the other hand a probe (tracer) particle in these systems performs a fractional Brownian motion due to the spatial interactions with the other system’s components. The tracer’s anomalous dynamics can be described by a fractional Langevin equation (FLE) with a space-time correlated noise. We demonstrate that the description given in terms of GEM coincides with that furnished by the relative FLE, by showing that the correlation functions of the stochastic field obtained within the FLE framework agree with the corresponding quantities calculated from the GEM. Furthermore we show that the Fox $H$-function formalism appears to be very convenient to describe the correlation properties within the FLE approach.

Using the percolation theory, we study the underlying mechanism in the formation of single-walled nanotube bundles with uniform diameter. By applying the cluster repulsion process to stick percolation, we find that the transition becomes explosive. To understand the transition nature, we first investigate the scaling behavior of transition interval $\Delta$. By comparing the results with loopless and loop-allowed bond percolations, we find that the loops crucially affect the scaling behavior of $\Delta$, and $\Delta$ is not universal. Moreover, the scaling behavior of $\Delta$ for the present nanostick systems is the same as that for loopless bond percolation. For more systematic studies on the transition nature, we also measure the changes in order parameter during the stick removal process and show that there exists a hysteresis. The results more clearly show that the transition of the stick system with cluster repulsion is discontinuous.

The large-deviation method can be used to study the measurement trajectories of open quantum systems. For optical arrangements this formalism allows to describe the long time properties of the (nonequilibrium) photon counting statistics in the context of a (equilibrium) thermodynamic approach defined in terms of dynamical phases and transitions between them in the trajectory space [J. P. Garrahan and I. Lesanovsky, Phys. Rev. Lett. 104, 160601 (2010)]. In this paper, we study the thermodynamic approach for fluorescent systems coupled to complex reservoirs that induce stochastic fluctuations in their dynamical parameters. In a fast modulation limit the thermodynamics corresponds to that of a Markovian two-level system. In a slow modulation limit, the thermodynamic properties are equivalent to those of a finite system that in an infinite-size limit is characterized by a first-order transition. The dynamical phases correspond to different intensity regimes, while the size of the system is measured by the transition rate of the bath fluctuations. As a function of a dimensionless intensive variable, the first and second derivatives of the thermodynamic potential develop an abrupt change and a narrow peak, respectively. Their scaling properties are consistent with a double-Gaussian probability distribution of the associated extensive variable.

Phase states in sodium lauryl sulphate–water–1-decanol lyotropic liquid-crystalline system have been investigated for different temperature ranges. The dependence of triangle phase diagram types, phase boundaries, and sequence of lyotropic mesophases vs temperature has been found. The thermomorphologic, thermotropic, and magnetomorphologic properties of hexagonal E, lamellar D, nematic-calamitic ${\text{N}}_{\text{C}}$, nematic-discotic ${\text{N}}_{\text{D}}$, and biaxial nematic ${\text{N}}_{\text{bx}}$ mesophases have been studied in detail. Dynamics of transformations of magnetically induced textures has been investigated. Peculiarities of typical and magnetically induced textures have been investigated in detail. Triangle phase diagrams of sodium lauryl sulphate–water–1-decanol lyotropic liquid-crystalline system for different temperatures and typical and magnetically induced textures of E, D, ${\text{N}}_{\text{C}}$, ${\text{N}}_{\text{D}}$, and ${\text{N}}_{\text{bx}}$ mesophases are presented.

We consider two interacting semiflexible charged chains of length $L_c$ under shape fluctuations, where the interplay of electric and mechanical properties is found to yield rigidity-sensitive charge modulation and interdistance-dependent persistence length ${\ell }_p$. The resulting conformation is characterized by equilibrium force between the chains and their fractal dimensions. It turns out that ${\ell }_p$ and $L_c$ emerge as critical factors to determine the force nature as well as chain shapes. We show that conformational fluctuations cause the repulsion of nonsteric origin, and its competition with charge fluctuation effects yields the interchain force modulated by the length scales and counterion valence. As a result, it is predicted that flexible short chains can be more strongly repulsive than rigid long chains, although they carry smaller amount of net charges.

We study the critical behavior of the $d=3$ Ising model with bond randomness through extensive Monte Carlo simulations and finite-size scaling techniques. Our results indicate that the critical behavior of the random-bond model is governed by the same universality class as the site- and bond-diluted models, clearly distinct from that of the pure model, thus providing a complete set of universality in disordered systems.

The existence of gas-liquid coexistence in dipolar fluids with no other contribution to attractive interaction than dipole-dipole interaction is a basic and open question in the theory of fluids. Here we compute the gas-liquid critical point in a system of dipolar soft spheres subject to an external electric field using molecular dynamics computer simulation. Tracking the critical point as the field strength is approaching zero we find the following limiting values: $T_c=0.063$ and ${\rho }_c=0.0033$ (dipole moment $\mu =1$). These values are confirmed by independent simulation at zero field strength.

We report the experimental demonstration of chaotic phase synchronization (CPS) in unidirectionally coupled time-delay systems using electronic circuits. We have also implemented experimentally an efficient methodology for characterizing CPS, namely, the localized sets. Snapshots of the evolution of coupled systems and the sets as observed from the oscilloscope confirming CPS are shown experimentally. Numerical results from different approaches, namely, phase differences, localized sets, changes in the largest Lyapunov exponents, and the correlation of probability of recurrence $\left(C_{CPR}\right)$ corroborate the experimental observations.

We present the results of a numerical study of a model of the hydrodynamics of a sheared nematogenic fluid, taking into account the effects of order-parameter stresses on the velocity profile but allowing spatial variations only in the gradient direction. When parameter values are such that the stress from orientational distortions is comparable to the bare viscous stress, the system exhibits steady states with the characteristics of shear banding. In addition, nonlinearity in the coupling of extensional flow to orientation leads to the appearance of a new steady state in which the features of both spatiotemporal chaos and shear banding are present.

We employ a finite element framework, coupled to cohesive elements, to model material decohesion of a uniformly expanding ring. Our study focuses on the average fragment mass, the distribution of fragment masses, and the heaviest fragments. The computed fragment mass distributions are best captured by generalized gamma distributions, regardless of the model parameters. However, the distribution of the heaviest fragments depends on toughness, specimen size, and loading rate.

Many complex systems can be represented as networks, and separating a network into communities could simplify functional analysis considerably. Many approaches have recently been proposed to detect communities, but a method to determine whether the detected communities are significant is still lacking. In this paper, an index to evaluate the significance of communities in networks is proposed based on perturbation of the network. In contrast to previous approaches, the network is disturbed gradually, and the index is defined by integrating all of the similarities between the community structures before and after perturbation. Moreover, by taking the null model into account, the index eliminates scale effects. Thus, it can evaluate and compare the significance of communities in different networks. The method has been tested in many artificial and real-world networks. The results show that the index is in fact independent of the size of the network and the number of communities. With this approach, clear communities are found to always exist in social networks, but significant communities cannot be found in protein interactions and metabolic networks.

We propose a stochastic cellular-automaton model for two-lane traffic flow based on the misanthrope process in one dimension. The misanthrope process is a stochastic process allowing for an exact steady-state solution; hence, we have an exact flow-density diagram for two-lane traffic. In addition, we introduce two parameters that indicate, respectively, driver’s driving-lane preference and passing-lane priority. Due to the additional parameters, the model shows a deviation of the density ratio for driving-lane use and a biased lane efficiency in flow. Then, a mean-field approach explicitly describes the asymmetric flow by the hop rates, the driving-lane preference, and the passing-lane priority. Meanwhile, the simulation results are in good agreement with an observational data, and we thus estimate these parameters. We conclude that the proposed model successfully produces two-lane traffic flow particularly with the driving-lane preference and the passing-lane priority.

We study the synchronization properties of the Kuramoto model of coupled phase oscillators on a general network. Here we distinguish the ability of such a system to self-synchronize from the stability of this behavior. While self-synchronization is a consequence of genuine nonperturbative dynamics, the stability in dynamical systems is usually accessible by fluctuations about a fixed point, here taken to be the phase synchronized solution. We examine this problem in terms of modes of the graph Laplacian, by which the absolute Lyapunov stability of the phase synchronized fixed point is readily demonstrated. Departures from stability are seen to arise at the next order in fluctuations where, depending on a truncation in the number of time-dependent Laplacian modes, the dynamical equations can be reduced to forms resembling those for species population models, the logistic and the Lotka-Volterra equations. Methods from these systems are exploited to analytically derive new critical couplings signaling deviation from classical stability. We thereby analytically explain the existence of an intermediate regime of behavior between incoherence and synchronization, where system wide periodic behaviors are exhibited and stable, unstable, and hyperbolic fixed points can be identified. We discuss these results in light of numerical solutions of the equations of motion for various networks.

Dynamic renormalization-group (RG) methods were originally used by Forster, Nelson, and Stephen (FNS) to study the large-scale behavior of randomly stirred incompressible fluids governed by the Navier-Stokes equations. Similar calculations using a variety of methods have been performed but have led to a discrepancy in results. In this paper, we carefully reexamine in $d$ dimensions the approaches used to calculate the renormalized viscosity increment and, by including an additional constraint which is neglected in many procedures, conclude that the original result of FNS is correct. By explicitly using step functions to control the domain of integration, we calculate a nonzero correction caused by boundary terms which cannot be ignored. We then go on to analyze how the noise renormalization, which is absent in many approaches, contributes an $\mathcal{O}\left(k^2\right)$ correction to the force autocorrelation and show conditions for this to be taken as a renormalization of the noise coefficient. Following this, we discuss the applicability of this RG procedure to the calculation of the inertial range properties of fluid turbulence.

Three-dimensional double-diffusive Marangoni convection in a cubic cavity is studied in the present paper. Both the temperature and solute concentration gradients are applied horizontally. Direct numerical simulations are carried out for surface-tension Reynolds number $10\le \text{Re}\le 500$, surface-tension ratio $-2\le R_{\sigma }\le 1$, and Lewis number $1<\text{Le}\le 200$. Symmetry-breaking pitchfork bifurcation is observed, which does not exist in the pure thermocapillary case, and the flow field is essentially three dimensional. The evolution of the flow structure, as well as the dependence of the heat and mass transfer rates on the different parameters, is investigated systematically. The simulations are performed until the temporal chaotic flow regime is reached and an atypical bifurcation sequence is identified. Namely, as the thermal forcing of the system increases, the flow can undergo a reverse transition from a temporal chaotic to a steady state. Multiple solution branches exist in some parameter ranges, and these are depicted in terms of the heat and mass transfer rates. Corresponding two-dimensional simulations are also performed to clearly illustrate the deviations from the three-dimensional model. The onset of oscillatory flow from the quiescent equilibrium state is also considered. The present work intends to initiate the study of double-diffusive Marangoni convection in three-dimensional confined cavities with horizontal temperature and concentration gradients.

By using a recently proposed numerical method, the fractional diffusion equation with memory in a finite domain is solved for different asymmetry parameters and fractional orders. Some scaling laws are revisited in this condition, such as growth rate in a distance from pulse perturbation, the time when the perturbative peak reaches the other points, and advectionlike behavior as a result of asymmetry and memory. Conditions for negativity and instability of solutions are shown. Also up-hill transport and its time-space region are studied.

We study the designing principles of the simplest colloidal propeller, an architecture built from four identical spheres that can couple translation with rotation to produce controlled drift motion. By considering superparamagnetic beads, we show that the simultaneous action of a magnetic field and a shear flow leads to the migration of the cluster in the vorticity direction. We investigate the dependence of the migration velocity on the geometrical parameters of the cluster and find that significant cluster separation can be achieved under the typical operation conditions of microfluidic devices.

The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.

Tumor angiogenesis is a landmark of solid tumor development, but it is also directly relevant to chemotherapy. Indeed, the density and quality of neovessels may influence the effectiveness of therapies based on blood-born agents. In this paper, first we define a deterministic model of antiproliferative chemotherapy in which the drug efficacy is a unimodal function of vessel density, and then we show that under constant continuous infusion therapy the tumor-vessel system may be multistable. However, the actual drug concentration profiles are affected by bounded even if possibly large fluctuations. Through numerical simulations, we show that the tumor volume may undergo transitions to the higher equilibrium value induced by the bounded noise. In case of periodically delivered boli-based chemotherapy, we model the fluctuations due to time variability of both the drug clearance rate and the distribution volume, as well as those due to irregularities in drug delivery. We observed noise-induced transitions also in case of periodic delivering. By applying a time dense scheduling with constant average delivered drug (metronomic scheduling), we observed an easier suppression of the transitions. Finally, we propose to interpret the above phenomena as an unexpected non-genetic kind of resistance to chemotherapy.