The adaptive voter model is a paradigmatic model in the study of opinion formation. Here we propose an extension for this model, in which conflicts are resolved by obtaining another opinion, and analytically study the time required for consensus to emerge. Our results shed light on the rich phenomenology of both the original and extended adaptive voter models, including a dynamical phase transition in the scaling behavior of the mean time to consensus.

Spontaneous symmetry breaking in quantum phase transitions leads to a system having degenerate ground states in its broken-symmetry phase. In order to detect all possible degenerate ground states for a broken-symmetry phase, we introduce a quantum fidelity defined as an overlap measurement between a system ground state and an arbitrary reference state. If a system has $N$-fold degenerate ground states in a broken-symmetry phase, the quantum fidelity is shown to have $N$ different values with respect to an arbitrarily chosen reference state. The quantum fidelity then exhibits an $N$-multiple bifurcation as an indicator of a quantum phase transition without knowing any detailed broken symmetry between a broken-symmetry phase and a symmetry phase as a system parameter crosses its critical value (i.e., a multiple bifurcation point). Each order parameter, characterizing a broken-symmetry phase from each degenerate ground state reveals an $N$-multiple bifurcation. Furthermore, it is shown that it is possible to specify how each order parameter calculated from degenerate ground states transforms under a subgroup of a symmetry group of the Hamiltonian. Examples are given through study of the quantum $q$-state Potts models with a transverse magnetic field by employing tensor network algorithms based on infinite-size lattices. For any $q$, a general relation between the local order parameters is found to clearly show the subgroup of the $Z_q$ symmetry group. In addition, we systematically discuss criticality in the $q$-state Potts model.

A variational approach based on Bogoliubov inequality for the free energy is employed in order to treat the quantum spin-1 anisotropic ferromagnetic Heisenberg model in the presence of a crystal field. Within the Bogoliubov scheme an improved pair approximation has been used. The temperature-dependent thermodynamic functions have been obtained and provide much better results than the previous simple mean-field scheme. In one dimension, which is still nonintegrable for quantum spin-1, we get the exact results in the classical limit, or near-exact results in the quantum case, for the free energy, magnetization, and quadrupole moment, as well for the transition temperature. In two and three dimensions the corresponding global phase diagrams have been obtained as a function of the parameters of the Hamiltonian. First-order transition lines, second-order transition lines, tricritical and tetracritical points, and critical endpoints have been located through the analysis of the minimum of the Helmholtz free energy and a Landau-like expansion in the approximated free energy. Only first-order quantum transitions have been found at zero temperature. Limiting cases, such as isotropic Heisenberg, Blume-Capel, and Ising models, have been analyzed and compared to previous results obtained from other analytical approaches as well as from Monte Carlo simulations.

We studied the distribution of glass transition temperature ($T_{\mathrm{g}}$) through neutron reflectivity in a poly(methyl methacrylate) (PMMA) thin film supported on a silicon substrate with a five-layered PMMA thin film consisting of deuterated-PMMA and hydrogenated-PMMA. The depth distribution of $T_{\mathrm{g}}$ was successfully observed in the PMMA thin film. Compared to the previously reported distribution of $T_{\mathrm{g}}$ in a polystyrene thin film, the presence of a long-range interfacial effect, supposedly caused by an interaction between PMMA and the substrate, is considered to be responsible for the differences in both the distribution of $T_{\mathrm{g}}$ and the thickness dependence of $T_{\mathrm{g}}$ in both polymers. Therefore, it is expected that the thickness dependence of $T_{\mathrm{g}}$ reported for single-layered polymer thin films can, in principle, be understood from the viewpoint of the difference in the depth distribution of $T_{\mathrm{g}}$.

Measure synchronization (MS) in a two-species bosonic Josephson junction (BJJ) is studied based on semiclassical theory. Six different scenarios for MS, including two in the Josephson oscillation regime (the zero-phase mode) and four in the self-trapping regime (the $\pi$-phase mode), are clearly shown. Systematic investigations of the common features behind these different scenarios are performed. We show that the average energies of the two species merge at the MS transition point. The scaling of the power law near the MS transition is verified and the critical exponent is 1/2 for all of the different scenarios for MS. We also illustrate MS in a three-dimensional phase space; from this illustration, more detailed information on the dynamical process can be obtained. In particular, by analyzing the Poincaré sections with changing interspecies interactions, we find that the two-species BJJ exhibits separatrix crossing behavior at the MS transition point and such behavior depicts the general mechanism behind the different scenarios for the MS transitions. The new critical behavior found in a two-species BJJ is expected to be found in real systems of atomic Bose gases.

We report the experimental observation of the bacterial turbulence reduction in dense E. coli suspensions by increasing the coupling of passive particle additives (paramagnetic particles). Applying an external magnetic field induces magnetic dipoles for particles and causes the formation of vertical chain bundles, which are hard for bacterial flows to tilt and break. The larger effective drag coefficient of chains causes slow horizontal motion of chains, which in turn form obstacles to suppress bacterial flows through the strong correlation in coherent bacterial clusters and intercluster interaction. The interruption of the upward energy flow from individual self-propelling bacteria to the larger scale in the bacterial turbulence with multiscaled coherent flow by the chain bundle leads to more severe suppression in the low frequency (wave number) regimes of the power spectra.

We report measurements of dynamical tunneling rates of a Bose-Einstein condensate across a barrier in classical phase space. The atoms are initially prepared in quantum states that extend over a classically regular island region. We focus on the specific system of quantum accelerator modes of the kicked rotor in the presence of gravity. Our experimental data is supported by numerical simulations taking into account imperfections mainly from spontaneous emission. Furthermore, we predict experimentally accessible parameter ranges over which direct tunneling could be readily observed if spontaneous emission was further suppressed. Altogether, we provide a proof-of-principle for the experimental accessibility of dynamical tunneling rates in periodically driven systems.

Building on insights from the theory of integrable lattices, the integrability is claimed for nonlinear replica $\sigma$ models derived in the context of real symmetric random matrices. Specifically, the fermionic and the bosonic replica partition functions are proven to form a single (supersymmetric) Pfaff-KP hierarchy whose replica limit is shown to reproduce the celebrated nonperturbative formula for the density-density eigenvalue correlation function in the infinite-dimensional Gaussian orthogonal ensemble. Implications of the formalism outlined are briefly discussed.

Critical wetting transition for short-range forces in three dimensions ($d=3$) is reinvestigated by means of Monte Carlo simulation. Using an anisotropic finite size scaling approach, as well as approaches that do not rely on finite size scaling, we show that the critical wetting transition shows clear deviation from mean-field behavior. We estimate that the effective critical exponent ${\nu }_{\parallel }^{\mathrm{eff}}=1.76\pm 0.08$ for $J/kT=0.35$ and ${\nu }_{\parallel }^{\mathrm{eff}}=1.85\pm 0.07$ for $J/kT=0.25$. These values are in accord with predictions of Parry et al. [Phys. Rev. Lett. 100, 136105 (2008)]. We also point out that the anisotropic finite size scaling approach in $d=3$ requires additional modification in order to reach full consistency of simulational results.

We show both analytically and numerically that there is an infinite number of flat bands with different Chern numbers in a two-dimensional magnetic photonic crystal at nearly the same frequency determined by the condition that the effective magnetic permeability ${\mu }_{\text{eff}}\approx -1$. This opens the door to explore the physics involving higher order topological invariants in this system. The frequency of these states can be flexibly tuned by an external magnetic field.

The susceptible-infected-susceptible (SIS) model is one of the simplest memoryless systems for describing information or epidemic spreading phenomena with competing creation and spontaneous annihilation reactions. The effect of quenched disorder on the dynamical behavior has recently been compared to quenched mean-field (QMF) approximations in scale-free networks. QMF can take into account topological heterogeneity and clustering effects of the activity in the steady state by spectral decomposition analysis of the adjacency matrix. Therefore, it can provide predictions on possible rare-region effects, thus on the occurrence of slow dynamics. I compare QMF results of SIS with simulations on various large dimensional graphs. In particular, I show that for Erdős-Rényi graphs this method predicts correctly the occurrence of rare-region effects. It also provides a good estimate for the epidemic threshold in case of percolating graphs. Griffiths Phases emerge if the graph is fragmented or if we apply a strong, exponentially suppressing weighting scheme on the edges. The latter model describes the connection time distributions in the face-to-face experiments. In case of a generalized Barabási-Albert type of network with aging connections, strong rare-region effects and numerical evidence for Griffiths Phase dynamics are shown. The dynamical simulation results agree well with the predictions of the spectral analysis applied for the weighted adjacency matrices.

The clustering behavior of a compartmentalized monodisperse granular gas with the addition of one heavy intruding particle is investigated experimentally. Depending on the number of particles, the presence of a heavy intruder leads to three population states: a homogeneous state, an expelled clustering state, and a fully clustering state. These states are found to be consistent with the clustering of a purely monodisperse granular gas in an asymmetric compartmentalized structure. We obtain an exact relation between the size of an intruder and the elevation of the compartment bottom. This relation quantifies the particle-expelling ability of a heavy intruder, and suggests that the one-intruder system is a type of asymmetric system with an intruder-size-related asymmetrical index $\xi$. Under the framework of the flux model, a $\xi$-associated $\Xi$ function is proposed to quantitatively reproduce the experimental results.

We study stress relaxation in hand folded aluminum foils subjected to the uniaxial compression force $F\left(\lambda \right)$. We found that once the compression ratio is fixed ($\lambda =\mathrm{const}$) the compression force decreases in time as $F\propto F_{0}P\left(t\right)$, where $P\left(t\right)$ is the survival probability time distribution belonging to the domain of attraction of max-stable distribution of the Fréchet type. This finding provides a general physical picture of energy dissipation in the crumpling network of a crushed elastoplastic foil. The difference between energy dissipation statistics in crushed viscoelastic papers and elastoplastic foils is outlined. Specifically, we argue that the dissipation of elastic energy in crushed aluminum foils is ruled by a multiplicative Poisson process governed by the maximum waiting time distribution. The mapping of this process into the problem of transient random walk on a fractal crumpling network is suggested.

We show that the experimental data for the action of ultrasonic waves on homeotropically aligned nematic-liquid-crystal cells reported by Kapustina, in Akust. Zh. 54, 900 (2008) [Acoust. Phys. 54, 778 (2008)] can be explained in the framework of the director-density coupling theory in the regime of low acoustic intensity. This result therefore provides support for the hypothesis that the interaction between sound and nematic liquid crystals is dominated by an elastic energy.

We use coarse grained molecular dynamics simulations to investigate diffusion properties of sheared lipid membranes with embedded transmembrane proteins. In membranes without proteins, we find normal in-plane diffusion of lipids in all flow conditions. Protein embedded membranes behave quite differently: by imposing a simple shear flow and sliding the monolayers of the membrane over each other, the motion of protein clusters becomes strongly superdiffusive in the shear direction. In such a circumstance, the subdiffusion regime is predominant perpendicular to the flow. We show that superdiffusion is a result of accelerated chaotic motions of protein-lipid complexes within the membrane voids, which are generated by hydrophobic mismatch or the transport of lipids by proteins.

In this work we analyze the evolution of voluntary vaccination in networked populations by entangling the spreading dynamics of an influenza-like disease with an evolutionary framework taking place at the end of each influenza season so that individuals take or do not take the vaccine upon their previous experience. Our framework thus puts in competition two well-known dynamical properties of scale-free networks: the fast propagation of diseases and the promotion of cooperative behaviors. Our results show that when vaccine is perfect, scale-free networks enhance the vaccination behavior with respect to random graphs with homogeneous connectivity patterns. However, when imperfection appears we find a crossover effect so that the number of infected (vaccinated) individuals increases (decreases) with respect to homogeneous networks, thus showing the competition between the aforementioned properties of scale-free graphs.

We report that infinite and semi-infinite lattices with spatially inhomogeneous self-defocusing (SDF) onsite nonlinearity, whose strength increases rapidly enough toward the lattice periphery, support stable unstaggered (UnST) discrete bright solitons, which do not exist in lattices with the spatially uniform SDF nonlinearity. The UnST solitons coexist with stable staggered (ST) localized modes, which are always possible under the defocusing onsite nonlinearity. The results are obtained in a numerical form and also by means of variational approximation (VA). In the semi-infinite (truncated) system, some solutions for the UnST surface solitons are produced in an exact form. On the contrary to surface discrete solitons in uniform truncated lattices, the threshold value of the norm vanishes for the UnST solitons in the present system. Stability regions for the novel UnST solitons are identified. The same results imply the existence of ST discrete solitons in lattices with the spatially growing self-focusing nonlinearity, where such solitons cannot exist either if the nonlinearity is homogeneous. In addition, a lattice with the uniform onsite SDF nonlinearity and exponentially decaying intersite coupling is introduced and briefly considered. Via a similar mechanism, it may also support UnST discrete solitons. The results may be realized in arrayed optical waveguides and collisionally inhomogeneous Bose-Einstein condensates trapped in deep optical lattices. A generalization for a two-dimensional system is briefly considered.

We study the dispersion of light particles floating on a flat shear-free surface of an open channel in which the flow is turbulent. This configuration mimics the motion of buoyant matter (e.g., phytoplankton, pollutants, or nutrients) in water bodies when surface waves and ripples are smooth or absent. We perform direct numerical simulation of turbulence coupled with Lagrangian particle tracking, considering different values of the shear Reynolds number (${\mathrm{Re}}_{\tau }=171$ and 509) and of the Stokes number ($0.06<\mathrm{St}<1$ in viscous units). Results show that particle buoyancy induces clusters that evolve towards a long-term fractal distribution in a time much longer than the Lagrangian integral fluid time scale, indicating that such clusters overlive the surface turbulent structures which produced them. We quantify cluster dynamics, crucial when modeling dispersion in free-surface flow turbulence, via the time evolution of the cluster correlation dimension.

We analyze a linear perturbation scheme for a two-dimensional background plasma, which is rotating at a differential frequency and is embedded in a poloidal magnetic field. The main two assumptions of the present study, which in turn are related, are (i) that the plasma profile is axially symmetric, both in the background and in the perturbation approximation, where the azimuthal magnetic field is requested to vanish identically, and (ii) that the angular frequency depends on the magnetic surface function only, still holds in the nonstationary regime, which, in the steady background equilibrium, is ensured by the validity of the corotation theorem [V. C. A. Ferraro, Mon. Not. R. Astron. Soc. 97, 458 (1937)]. Indeed, such a restriction of the model is rather natural and it implies that the azimuthal component of the linear plasma shift is reabsorbed in the expression for the nonstationary electric field (in principle, at any order of approximation) and can no longer provide a nonzero azimuthal component of the magnetic tension field. As a result, the magnetorotational instability is suppressed and the magnetic field has the effect to stabilize the plasma configuration with respect to the pure hydrodynamical case.

We study the thermodynamic notion of quantum projective measurements, using a framework for the fluctuation theorem of nonequilibrium work. The energy change induced by measurements satisfies the Jarzynski equality, leading us to the interpretation that the quantum projective measurements perform nonequilibrium work on the measured system. The work average exhibits intriguing limiting behaviors due to the heat-up effect caused by repeated measurements and the quantum Zeno effect caused by measurements of an infinite frequency. If the measured system relaxes back to its initial equilibrium state, the work is completely dissipated in the form of heat into a reservoir. The corresponding entropy increase in the reservoir is shown to be not less than the von Neumann entropy change generated during the course of the measurements, proving Landauer's principle.