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A generalized van der waals model is considered to study the thermodynamic properties of pure fluids. Analytical solution of the equivalent cubic equation of state is presented and the critical properties in the general form are derived. The fluctuations of number of particles are calculated in the grand canonical ensemble by using three quantities (scaled variance ω (N) , skewness S σ , and kurtosis k σ 2 ). The critical behavior of these quantities is investigated in terms of the dimensionless particle number density and temperature for different models. It is found that the fluctuations have a singular behavior close to the critical point. [ABSTRACT FROM AUTHOR]

We argue that the elastic backbone (EB) (union of shortest paths) on a cylindrical system, studied by Sampaio Filho et al [2018 Phys. Rev. Lett. 120 175701], is in fact the backbone of two-dimensional directed percolation (DP). We simulate the EB on the same system as considered by these authors, and also study the DP backbone directly using an algorithm that allows backbones to be generated in a completely periodic manner. We find that both the EB in the bulk and the DP backbone have a fractal dimension of d b = d B,DP = 1.681 02(15) at the identical critical point p c,DP ≈ 0.705 485 22. We also measure the fractal dimension at the edge of the EB system and for the full DP clusters, and find d e = d DP = 1.840 54(4). We argue that those two fractal dimensions follow from the DP exponents as d B,DP = 2 âˆ' 2 β / ν ∥ = 1.681 072(12) and d DP = 2 âˆ' β / ν ∥ = 1.840 536(6). Our fractal dimensions differ from the value 1.750(3) found by Sampaio Filho et al. [ABSTRACT FROM AUTHOR]

The two-parameter van der Waals (vdW) equation of state is generalized, by adding another two parameters to the attractive term. General relations between thermodynamic functions of the generalized vdW equation and the hard sphere gas are derived. The cubic equation of the generalized vdW is solved and the critical points (Pc, Vc, Tc) are obtained for general k. The critical properties of the vdW real gas such as the isothermal compressibility KT, the isobaric expansion coefficient α and the isobaric heat capacity CP are calculated exactly. The temperature dependence of KT, α and CP is investigated close to the critical point on the critical isobar path Pr = 1(P = Pc). Numerical calculations for KT and CP are presented above and below Pr. [ABSTRACT FROM AUTHOR]

We propose a thermodynamic multi-state spin model in order to describe equilibrial behavior of a society. Our model is inspired by the Axelrod model used in social network studies. In the framework of the statistical mechanics language, we analyze phase transitions of our model, in which the spin interaction J is interpreted as a mutual communication among individuals forming a society. The thermal fluctuations introduce a noise T into the communication, which suppresses long-range correlations. Below a certain phase transition point T t , large-scale clusters of the individuals, who share a specific dominant property, are formed. The measure of the cluster sizes is an order parameter after spontaneous symmetry breaking. By means of the Corner transfer matrix renormalization group algorithm, we treat our model in the thermodynamic limit and classify the phase transitions with respect to inherent degrees of freedom. Each individual is chosen to possess two independent features f = 2 and each feature can assume one of q traits (e.g. interests). Hence, each individual is described by q 2 degrees of freedom. A single first-order phase transition is detected in our model if q > 2 , whereas two distinct continuous phase transitions are found if q = 2 only. Evaluating the free energy, order parameters, specific heat, and the entanglement von Neumann entropy, we classify the phase transitions T t ( q ) in detail. The permanent existence of the ordered phase (the large-scale cluster formation with a non-zero order parameter) is conjectured below a non-zero transition point T t ( q ) ≈ 0.5 in the asymptotic regime q → ∞ . [ABSTRACT FROM AUTHOR]

Abstract: In this work we study the critical behavior of the absorbing state phase transition exhibited by the contact process in a linear chain with power-law diluted long-range connections. Each pair of sites is connected with a probability that decays with the distance between the sites as . The model allows for a continuous tuning between a standard one-dimensional chain with only nearest neighbor couplings ( ) to a fully connected network ( ). We develop a finite-size scaling analysis to obtain the critical point and a set of dynamical and stationary critical exponents for distinct values of the decay exponent corresponding to finite average bond lengths and low average site connectivity. Data for the order parameter collapse over a universal curve when plotted after a proper rescaling of parameters. We show further that the critical exponents depend on in the regime of diverging bond-length fluctuations ( ). [Copyright &y& Elsevier]

Abstract: The overlap (inner product) between the ground-state eigenvectors with proximate interaction parameters, the so-called fidelity, plays a significant role in the quantum-information theory. In this paper, the critical behavior of the fidelity susceptibility is investigated for a two-dimensional transverse-field (quantum) Ising model by means of the numerical diagonalization method. In order to treat a variety of system sizes , we adopt the screw-boundary condition. Finite-size artifacts (scaling corrections) of the fidelity susceptibility appear to be suppressed, as compared to those of the Binder parameter. As a result, we estimate the fidelity susceptibility critical exponent as . [Copyright &y& Elsevier]

Static magnetization for single crystals of NdPbMnO has been studied around the ferromagnetic-to-paramagnetic transition temperature T. The results of measurements carried out in the critical range |( T− T)/ T|≤0.1 are reported. The critical exponents β and γ for the thermal behavior of magnetization and susceptibility have been obtained both from the modified Arrott plots and the Kouvel-Fisher method. The exponent δ, independently obtained from the critical isotherm, was found to satisfy the Widom scaling relation δ= γ/ β+1. The values of exponents are consistent with those expected for isotropic magnets belonging to the Heisenberg universality class with short-range exchange in three dimensions. The maximum magnetic entropy change is found at around T. We found a universal scaling behavior in the relative change of magnetic entropy (Δ S). The rescaled curves of the magnetic entropy change for different applied fields are observed to collapse onto a single curve, which validates the second order nature of the phase transition in NdPbMnO. [ABSTRACT FROM AUTHOR]

For a system near a quantum critical point (QCP), above its lower critical dimension d, there is in general a critical line of second-order phase transitions that separates the broken symmetry phase at finite temperatures from the disordered phase. The phase transitions along this line are governed by thermal critical exponents that are different from those associated with the quantum critical point. We point out that, if the effective dimension of the QCP, d = d + z ( d is the Euclidean dimension of the system and z the dynamic quantum critical exponent) is above its upper critical dimension $d_{_{C}}$ there is an intermingle of classical (thermal) and quantum critical fluctuations near the QCP. This is due to the breakdown of the generalized scaling relation ψ = νz between the shift exponent ψ of the critical line and the crossover exponent νz, for $d+z>d_{_{C}}$ by a dangerous irrelevant interaction. This phenomenon has clear experimental consequences, like the suppression of the amplitude of classical critical fluctuations near the line of finite temperature phase transitions as the critical temperature is reduced approaching the QCP. [ABSTRACT FROM AUTHOR]

Abstract: We have extended the mean field calculations of Zandi et al. (2007) and have obtained an approximate mathematical expression for the Casimir scaling function , which if extrapolated to the domain , becomes surprisingly similar to that obtained experimentally by Ganshin et al. (2006). The extrapolated can be regarded as a proposed fitting function, that appears to agree better with the experiments in , than the exact mean field results of Zandi et al. (2007) . [Copyright &y& Elsevier]

Abstract: The criticality of the -dimensional transverse-field Ising model is investigated with the numerical diagonalization method. The scaling behavior is improved by tuning the coupling-constant parameters; the spin model allows us to incorporate a variety of interactions such as the single-ion anisotropy and the biquadratic interactions. Simulating the clusters with spins, we estimate the critical indices as and . [Copyright &y& Elsevier]

Abstract: We present a modified susceptible–infected–susceptible (SIS) model on complex networks, small-world and scale-free, to study epidemic spreading with the effect of time delay which is introduced to the infected phase. Considering topologies of the networks, both uniform and degree-dependent delays are studied during the contagion process. It is found that the existence of delay will enhance both outbreaks and prevalence of infectious diseases in the networks. [Copyright &y& Elsevier]

We investigate the critical features of coupling parameters in the synchronization of the ensemble of identical neural networks with small-world connectivity. An exponential decay form is observed in the extreme case of global coupling among subsystems and full connection in each networks: there exists a maximum and a minimum of the critical coupling intensity for synchronization in this spatially extended system. For partial coupling, we present the primary result about the critical coupling fraction for various linked degree of subnetworks. [ABSTRACT FROM AUTHOR]

Abstract: The density (ρ) and the refractive index (n) in each phase of the critical binary fluid mixture “isobutyric acid–water” (I–W) with added (K+, Cl−) ions at various concentrations, were measured in the vicinity and far from the critical temperature. The obtained data were used to test the Lorentz–Lorenz (L–L) relation in this electrolyte system. The density and refractive index coexistence curve data were analyzed to determine the critical exponent β. The results show that the density (ρ) and refractive index (n) constitute good order parameters as valid as the volume fraction (ϕ). Furthermore, the critical exponent β obtained for the pure mixture is in good agreement with theoretical predictions. The shift of the transition phase''s area depends on the ion concentration. The Lorentz–Lorenz (L–L) is verified for all systems (I–W) and (I–W)+(K+, Cl−) ions. The relative deviation of the (L–L) relation is generally in the order of 7%, as well for the case of the pure system without ions, and in the presence of the ions with weak concentration. [Copyright &y& Elsevier]

Abstract: The equivalence between Tsallis thermodynamics and Hill''s nanothermodynamics is established. The correct thermodynamic forces in Tsallis thermodynamics are pointed out. Through this connection we also find a general expression for the entropic index q which we illustrate with two physical examples, allowing in both cases to relate q to the underlying dynamics of the Hamiltonian systems. [Copyright &y& Elsevier]

A novel method of summation for power series is developed. The method is based on the self-similar approximation theory. The trick employed is in transforming, first, a series expansion into a product expansion and in applying the self-similar renormalization to the latter rather to the former. This results in self-similar factor approximants extrapolating the sought functions from the region of asymptotically small variables to their whole domains. The method of constructing crossover formulas, interpolating between small and large values of variables is also analysed. The techniques are illustrated on different series which are typical of problems in statistical mechanics, condensed-matter physics, and, generally, in many-body theory. [Copyright &y& Elsevier]

We study weakly dissipative two-parameter generalized standard maps with a view to understanding the effect of dissipation on the recurrences of periodic orbits of the Hamiltonian maps. We obtain fractal diagrams and understand recurring periodic attractors as due to paird of saddle-node bifurcations. These bifurcations occur in place of each of the stability exchanges and form gaps in the fractal diagram where the periodic attractor does not exist. [ABSTRACT FROM AUTHOR]

The unmixing transition of both symmetrical polymer blends AB ( i.e. chain lengths N = N = N) and asymmetrical ones ( N / N =2,3) is studied by large-scale Monte Carlo simulations of the bond fluctuation model. Combination of semi-grand-canonical simulation techniques, «histogram reweighting» and finitesize scaling allows an accurate location of the coexistence curve in the critical region. The variation of the critical temperature with chain length ( N) is studied and compared to theoretical predictions. For the symmetrical case, use of chain lengths up to N=512 allows a rough estimation of crossover scaling functions for the crossover from Ising to mean-field exponents. The order-disorder transitions in melts of both symmetric (composition f= N /( N + N )=1/2) and asymmetric ( f=3/4) block copolymers is studied for very short chains (16≤ N≤60). The interplay between structure and chain configuration is emphasized. Qualitative evidence for «dumbell formation» of chains and vacancy enrichment in A-B-interfaces and near hard walls is presented. [ABSTRACT FROM AUTHOR]

By means of a well-developed method in self-organized criticality, we can obtain the lower bound for the percolation threshold ( p ) of the corresponding site percolation problem. In some special cases, we have proved that such lower bounds are indeed the percolation thresholds. We can reproduce some well-known percolation thresholds of various lattices including the Cayley trees and Kock curves in this framework. [ABSTRACT FROM AUTHOR]

Electromagnetic wave propagation in an inhomogeneous medium is discussed in the context of light propagation in a fluid near its critical point, stratified under gravity. The system exhibits birefringence, where the transverse electric ( te) and the transverse magnetic ( tm) waves travel with different phase-velocities, depending upon the density-gradients with height set up in the system. The possibility of experimentally detecting the predicted phenomenon is also discussed. [ABSTRACT FROM AUTHOR]

Purpose: This study showed to what extent ASIR improves CT-image and to what extent it degrades it., Methods: In our study we used GE HD750 CT-scanner, Siemens Sensation CT-scanner, Catphan, PTW-pin-ion- chamber, CTDI-phantom. We measured the CT-dose using the PTW-pinion-chamber and CTDI-phantom. Image-quality and noise were evaluated using catphan and GE water phantom., Results: Image noise reduce as higher levels of ASIR are applied. A phantom scan showed that 50%ASIR with 50% lower-dose (10.8mGy) achieved the same image noise of standard FBP image with full dose 21.7mGy (noise∼5). To confirm that the two same-noise images retain same image-quality, two scans were compared; one with full dose 260mAs(21.7mGy) and the other one with 50% lower dose 130mAs(10.8mGy). The results showed that ASIR failed to retain the same quality. For high contrast resolution, 50%ASIR reduced the resolution of patterns = 71p/cm, however it improved the detectability of patterns = 61p/cm. ASIR has degraded the CNR of the low-contrast-objects of = 5HU (CNR of 1.4 at 260mAs STND to CNR of 1.08 at 130mAs ASIR), however it improved the CNR of the low-contrast-objects of = 10HU (CNR of 2.35 at 260mAs STND to CNR of 2.63 at 130mAs ASIR). ASIR degraded the edges and killed some of the small objects. This shows that ASIR has a critical point of improve/degrade. Also, ASIR can improve images for the same dose, but with high levels of ASIR (e.g. 100%ASIR), cause disapear of small low contrast objects (e.g. 2mm)., Conclusions: People think that ASIR only improves image and reduces patient dose. Our study showed that ASIR has some drawbacks. There is a threshold before wich ASIR is positive and after which ASIR is negative. Recently only GE provide ASIR in the market but our study showed that other CTs such as Siemens can do similar performance like ASIR., (© 2012 American Association of Physicists in Medicine.)