This paper explores the effectiveness of network attack when the attacker has imperfect information about the network. For Erdős-Rényi networks, we observe that dynamical importance and betweenness centrality-based attacks are surprisingly robust to the presence of a moderate amount of imperfect information and are more effective compared with simpler degree-based attacks even at moderate levels of network information error. In contrast, for scale-free networks the effectiveness of attack is much less degraded by a moderate level of information error. Furthermore, in the Erdős-Rényi case the effectiveness of network attack is much more degraded by missing links as compared with the same number of false links.

We study an opinion formation model by the means of a coevolving complex network where the vertices represent the individuals, characterized by their evolving opinions, and the edges represent the interactions among them. The network adapts to the spreading of opinions in two ways: not only connected agents interact and eventually change their thinking but an agent may also rewire one of its links to a neighborhood holding the same opinion as his. The dynamics, based on a global majority rule, depends on an external parameter that controls the plasticity of the network. We show how the information entropy associated to the distribution of group sizes allows us to locate the phase transition between a phase of full consensus and another, where different opinions coexist. We also determine the minimum size of the most informative sampling. At the transition the distribution of the sizes of groups holding the same opinion is scale free.

We investigate the dynamics of a kink in a damped parametrically driven nonlinear Klein-Gordon equation. We show by using a method of averaging that, in the high-frequency limit, the kink moves in an effective potential and is driven by an effective constant force. We demonstrate that the shape of the solitary wave can be controlled via the frequency and the eccentricity of the modulation. This is in accordance with the experimental results reported in a recent paper [Casic et al., Phys. Rev. Lett. 110, 168302 (2013)], where the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a time-dependent magnetic field has been studied.

The formation of dissipative structures is investigated in a planar semiconductor-gas-discharge device at room temperature. The width of the discharge gap is about 1 mm. The gap is filled with nitrogen at a pressure that corresponds to the discharge operation at the right branch of the Paschen curve. Wafers of semi-insulating GaAs that exhibit linear transport in the whole range of voltage and current studied are used as semiconductor electrodes. In addition to the earlier investigated Andronov-Hopf bifurcation, a different mode of self-organization of the device is observed, where the transport of charge proceeds through an ensemble of pulsating current filaments. The corresponding critical current for the present bifurcation does not depend on the polarity of the bias voltage, while the spatiotemporal dynamics of a pattern differs substantially for a change in the polarity. Pulsating filaments can form a spatially ordered pattern when the GaAs electrode is under the positive potential. We also observe self-organization modes, where pulsating filaments form an irregular spatiotemporal dynamics of a pattern. The data obtained are briefly discussed in the frame of corresponding theoretical results in the field.

We study self-excited oscillations (SEO) in an on-fiber optomechanical cavity. Synchronization is observed when the optical power that is injected into the cavity is periodically modulated. A theoretical analysis based on the Fokker-Planck equation evaluates the expected phase space distribution (PSD) of the self-oscillating mechanical resonator. A tomography technique is employed for extracting PSD from the measured reflected optical power. Time-resolved state tomography measurements are performed to study phase diffusion and phase locking of the SEO. The detuning region inside which synchronization occurs is experimentally determined and the results are compared with the theoretical prediction.

We present a phenomenological description of the hydrodynamics in terms of the Fokker-Planck (FP) equation for one-particle distribution function. Similar to the Boltzmann equation or the Bhatnager-Gross-Krook (BGK) model, this approach is thermodynamically consistent and has the $H$ theorem. In this model, transport coefficients as well as the equation of state can be provided independently. This approach can be used as an alternate to BGK-based methods as well as the direct simulation Monte Carlo method for the gaseous flows.

We reveal thermodynamic structure in population dynamics with phenotype switching. Mean fitness for a population of organisms is determined by a thermodynamic variational principle described by the large deviation of phenotype-switching dynamics. Owing to this variational principle, a response relation of the mean fitness with respect to changes of environments and phenotype-switching dynamics is represented as a thermodynamic differential form. Furthermore, we discuss the strength of the selection by using the difference between time-forward and time-backward (retrospective) processes.

I use an exact variational formulation of Mikheev and Fisher to study the critical Ising strip with a grain boundary and confining surfaces characterized by arbitrary and different surface magnetic fields. Energy density profiles that serve as order parameters of the system within the used method show strong nonmonotonous behavior in the vicinity of confining surfaces. I consider short-distance expansion of energy density profiles. New universal amplitudes associated with distant-wall corrections exhibit nontrivial crossover behaviors from positive to negative values as the field's variables are continuously varied. Casimir amplitudes calculated in a self-contained manner are characterized by complex manifolds which may comprise two disconnected positive wings separated by an area of negative values. I define and determine the generalized de Gennes-Fisher amplitude, which strongly suggests that a stress tensor is present within one of the distant-wall corrections. This is an unanticipated result given that a similar discovery for standard extraordinary (E) and ordinary (O) surface universality classes was based on the conformal invariance symmetry, which is broken under the present boundary conditions. A grain boundary essentially influences both energy density profiles and Casimir amplitudes, besides surface fields with a number of accompanying features that are examined in detail. We present closed analytic forms of energy density profiles for standard (N) and (O) BCs: ${\varepsilon }_{\text{NN}}(x,g),{\varepsilon }_{\text{OO}}(x,g),{\varepsilon }_{\text{NO}}(x,g)$ [(N) is the normal surface universality class, $g$ is the grain boundary's strength, $x$ is the relative distance $x:=z/L$ with $L$ as a film width], thus enabling us to deduce their important symmetry properties and to have a detailed insight into their general behaviors.

We consider a lossless one-dimensional nonlinear discrete bi-inductance electrical transmission line made of $N$ identical unit cells. When lattice effects are considered, we use the reductive perturbation method in the semidiscrete limit to show that the dynamics of modulated waves can be modeled by the classical nonlinear Schrödinger (CNLS) equation, which describes the modulational instability and the propagation of bright and dark solitons on a continuous-wave background. Our theoretical analysis based on the CNLS equation predicts either two or four frequency regions with different behavior concerning the modulational instability of a plane wave. With the help of the analytical solutions of the CNLS equation, we investigate analytically the effects of the linear capacitance $C_S$ on the dynamics of matter-wave solitons in the network. Our results reveal that the linear parameter $C_S$ can be used to manipulate the motion of bright, dark, and kink soliton in the network.

Attempts to extend the capillary-wave theory of fluid interfacial fluctuations to microscopic wavelengths, by introducing an effective wave-vector $\left(q\right)$ -dependent surface tension ${\sigma }_{\mathrm{eff}}\left(q\right)$, have encountered difficulties. There is no consensus as to even the shape of ${\sigma }_{\mathrm{eff}}\left(q\right)$. By analyzing a simple density functional model of the liquid-gas interface, we identify different schemes for separating microscopic observables into background and interfacial contributions. In order for the backgrounds of the density-density correlation function and local structure factor to have a consistent and physically meaningful interpretation in terms of weighted bulk gas and liquid contributions, the background of the total structure factor must be characterized by a microscopic $q$-dependent length $\zeta \left(q\right)$ not identified previously. The necessity of including the $q$ dependence of $\zeta \left(q\right)$ is illustrated explicitly in our model and has wider implications; i.e., in typical experimental and simulation studies, an indeterminacy in $\zeta \left(q\right)$ will always be present, reminiscent of the cutoff used in capillary-wave theory. This leads inevitably to a large uncertainty in the $q$ dependence of ${\sigma }_{\mathrm{eff}}\left(q\right)$.

It is demonstrated that a novel heating configuration applied to a large and cold magnetized plasma allows the study of avalanche phenomena under controlled conditions. Intermittent collapses of the plasma pressure profile, associated with unstable drift-Alfvén waves, exhibit a two-slope power-law spectrum with exponents near $-1$ at lower frequencies and in the range of $-2$ to $-4$ at higher frequencies. A detailed mapping of the spatiotemporal evolution of a single avalanche event is presented.

The conventional second-order path-integral Monte Carlo method is plagued with the sign problem in solving many-fermion systems. This is due to the large number of antisymmetric free-fermion propagators that are needed to extract the ground state wave function at large imaginary time. In this work we show that optimized fourth-order path-integral Monte Carlo methods, which use no more than five free-fermion propagators, can yield accurate quantum dot energies for up to 20 polarized electrons with the use of the Hamiltonian energy estimator.

The fundamental question of the behavior of the dielectric constant near the critical point is addressed using Ar as the probe system. The neighborhood of the liquid-vapor critical point of Ar is accessed by classical Monte Carlo simulation and then explicit quantum mechanics calculations are performed to study the behavior of the dielectric constant. The theoretical critical temperature is determined by calculating the position of the discontinuity of the specific heat and is found to be at $T_{\mathrm{c}}^{\mathrm{Theor}}=148.7\mathrm{K}$, only 2 K below the experimental value. The large fluctuations and the inhomogeneity of the density that characterize the critical point rapidly disappear and are not seen at $T=T_{\mathrm{c}}^{\mathrm{Theor}}+2\mathrm{K}$. The structure of Ar obtained by the radial distribution function is found to be in very good agreement with experiment both in the liquid phase and 2 K above the critical temperature. The behavior of the dielectric constant is then analyzed after calculating the static dipole polarizability and using a many-body Clausius-Mossotti equation. The dielectric constant shows a density-independent behavior around the critical density, 2 K above the critical temperature. At this point, the calculated value of the dielectric constant is $1.173\pm 0.005$ in excellent agreement with the experimental value of 1.179.

When driven out of equilibrium by a temperature gradient, fluids respond by developing a nontrivial, inhomogeneous structure according to the governing macroscopic laws. Here we show that such structure obeys strikingly simple scaling laws arbitrarily far from equilibrium, provided that both macroscopic local equilibrium and Fourier's law hold. Extensive simulations of hard disk fluids confirm the scaling laws even under strong temperature gradients, implying that Fourier's law remains valid in this highly nonlinear regime, with putative corrections absorbed into a nonlinear conductivity functional. In addition, our results show that the scaling laws are robust in the presence of strong finite-size effects, hinting at a subtle bulk-boundary decoupling mechanism which enforces the macroscopic laws on the bulk of the finite-sized fluid. This allows one to measure the marginal anomaly of the heat conductivity predicted for hard disks.

Self-propulsion allows living systems to display self-organization and unusual phase behavior. Unlike passive systems in thermal equilibrium, active matter systems are not constrained by conventional thermodynamic laws. A question arises, however, as to what extent, if any, can concepts from classical thermodynamics be applied to nonequilibrium systems like active matter. Here we use the new swim pressure perspective to develop a simple theory for predicting phase separation in active matter. Using purely mechanical arguments we generate a phase diagram with a spinodal and critical point, and define a nonequilibrium chemical potential to interpret the “binodal.” We provide a generalization of thermodynamic concepts like the free energy and temperature for nonequilibrium active systems. Our theory agrees with existing simulation data both qualitatively and quantitatively and may provide a framework for understanding and predicting the behavior of nonequilibrium active systems.

We establish a rigorous connection between fundamental resource theories at the quantum scale. Correlations and entanglement constitute indispensable resources for numerous quantum information tasks. However, their establishment comes at the cost of energy, the resource of thermodynamics, and is limited by the initial entropy. Here, the optimal conversion of energy into correlations is investigated. Assuming the presence of a thermal bath, we establish general bounds for arbitrary systems and construct a protocol saturating them. The amount of correlations, quantified by the mutual information, can increase at most linearly with the available energy, and we determine where the linear regime breaks down. We further consider the generation of genuine quantum correlations, focusing on the fundamental constituents of our universe: fermions and bosons. For fermionic modes, we find the optimal entangling protocol. For bosonic modes, we show that while Gaussian operations can be outperformed in creating entanglement, their performance is optimal for high energies.

Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorizes the output state. Moreover, the change in entropy is also positive for the same majorization condition. This makes a strong connection between the two operational laws of thermodynamics.

Trajectory-pattern formation of a self-propelled oil droplet floating on the surface of a surfactant solution in a circular dish is studied both experimentally and by simulation. The Marangoni effect induced by the dissolution of oil in the solution drives the droplet's motion. The trajectories spontaneously organize into several patterns including circular, knot-forming, back-and-forth, and irregular ones. They are either global patterns, whose center corresponds to the dish center, or other local patterns. Our simple model consisting of three forces, the driving force, the viscous resistance, and the repulsion from the boundary, successfully reproduces the global trajectory patterns including the power spectrum of the droplet speed.

Isometric deformations in thin elastic films easily form ridges to connect large flat regions or facets. Depending on the forces applied or the boundary conditions imposed, these ridges can be isometric, with no stretching or “stretching ridges” when bending and stretching are required to relax the elastic energy. Here we study a simple configuration to observe the transition between an isometric ridge to the well-known stretching ridge observed in crumpled films, and obtain the parameters that determine the ridge type. Specifically, we show that the transversal size of a stretching ridge acts as a cutoff length scale: a ridge is isometric if its width is greater than this characteristic length.