International Journal of Modern Physics B

The white noise calculus originated by T. Hida is presented as a powerful tool in investigating physical and social systems. Combined with Feynman's sum-over-all histories approach, we parameterize paths with memory of the past, and evaluate the corresponding probability density function. We discuss applications of this approach to problems in complex systems and biophysics. Examples in quantum mechanics with boundaries are also given where Markovian paths are considered.

In the present work, a perturbed virial expansion is applied to calculate fluid critical points. The paper contains two main parts. In the first part, we study the effect of a reference fluid on critical properties. In the second part, we use the square-well potential model and consider a temperature-dependent width of the attractive well to obtain the critical properties of several real fluids. It is found that: (i) The critical temperatures and pressures obtained using a temperature-dependent width of the attractive well have been improved with respect to experimental data except for some fluids. (ii) The best values for critical temperatures and pressures can be obtained using a temperature-dependent width of the attractive well as well as choosing a suitable reference fluid. (iii) Applying a temperature-dependent width of the attractive well is a simple method for obtaining better results.

This paper puts forward a novel image encryption algorithm that is based on permutation-diffusion architecture. In pixels' permutation stage, algorithm takes full advantage of the idea of magic cube's scrambling. There is only simple cyclic shift operation in each sub-block's permutation, but when the algorithm has disposed the current sub-block, the adjacent sub-blocks will be dealt with, too. In the cyclic shift of each row, stable points will help to decrease the correlation of adjacent pixels. To make encryption procedure uncertain, this paper brings in a parameter named delay-time that is generated by chaotic map. In the diffusion stage, by combining multiple operations and dynamic look-up table together, the proposed algorithm highly increases the uncertainty of the encryption procedure. At last, the experiment results of key space analysis, information entropy analysis, histogram analysis and etc. show that the encryption algorithm has well performance and it can be used in image encryption and transmission.

A unified method and theory for measuring anisotropic resistivity based on a single surface of a film with rapidly converging exact solutions is presented here for solutions appropriate to thin films (Type I solutions) and to thick samples (Type II solutions). Some of the exact solutions of the related simultaneous equation systems can be expressed in terms of elementary functions. The theory proposed here for measuring resistivity of anisotropic crystals is expected to be useful in many applications.

We develop a basic formulation of the spin (SU(2)) coherent state path integrals based not on the conventional highest or lowest weight vectors but on arbitrary fiducial vectors. The coherent states, being defined on a 3-sphere, are specified by a full set of Euler angles. They are generally considered as states without classical analogues. The overcompleteness relation holds for the states, by which we obtain the time evolution of general systems in terms of the path integral representation; the resultant Lagrangian in the action has a monopole-type term à la Balachandran et al. as well as some additional terms, both of which depend on fiducial vectors in a simple way. The process of the discrete path integrals to the continuous ones is clarified. Complex variable forms of the states and path integrals are also obtained. During the course of all steps, we emphasize the analogies and correspondences to the general canonical coherent states and path integrals that we proposed some time ago. In this paper we concentrate on the basic formulation. The physical applications as well as criteria in choosing fiducial vectors for real Lagrangians, in relation to fictitious monopoles and geometric phases, will be treated in subsequent papers separately.

The pseudogap (PG) excitation is analyzed as a natural event in multiband superconductivity. It corresponds to minimal quasiparticle excitation energy of an electron band not touched by the chemical potential. The critical points of the phase diagram are determined by vanishing conditions for normal state pseudogaps (NPG). For two bands (gapped or overlapping) these are positioned on edges of the superconducting dome. Theoretical background for a three-band system with two interband pairing channels is developed. There are three independent superconducting gaps (SCG). The PG is associated with the band component possessing a bare gap which can be quenched by doping. At low doping the PG and the SCG of another band component coexist. The critical point is not fixed in respect of the transition temperature (T_c) dome background. The depletion of the PG associated states is restored here. This effect can also be indirect by the participation of these states in determining the chemical potential position. At the critical point the PG looses its normal state contribution and continues as the SCG of the same band. Illustrative examples on the doping scale have been calculated.

An extended electronic cloud can acquire different Aharonov–Bohm (AB) phases in its parts when these parts experience different solenoidal fields. This is demonstrated by two models that describe an electron moving within a confining circular tube around a solenoidal vector potential and outside a magnetic field domain (just as in a usual AB set up): one in which the motion of the electron along the tube is restricted and moves adiabatically and another in which it extends freely and without restriction on its speed. When the electron cloud is split into two parts circling in opposite directions, we show that when the two parts of the electronic cloud rejoin, they do so with different phases. This set-up complements (and confirms the finding of) our previous work [Europhys. Lett.93, 20001 (2011)], in which the vector source was moving and the electron position was fixed.

The renormalized dynamics described by the equations of nonlinear fluctuating hydrodynamics (NFH) treated at one loop order gives rise to the basic model of the mode coupling theory (MCT). We investigate here by analyzing the density correlation function, a crucial prediction of ideal MCT, namely the validity of the multi step relaxation scenario. The equilibrium density correlation function is calculated here from the direct solutions of NFH equations for a hard sphere system. We make first detailed investigation for the robustness of the correlation functions obtained from the numerical solutions by varying the size of the grid. For an optimum choice of grid size we analyze the decay of the density correlation function to identify the multi-step relaxation process. Weak signatures of two step power law relaxation is seen with exponents which do not match predictions from the one loop MCT. For the final relaxation stretched exponential (KWW) behavior is seen and the relaxation time grows with increase of density. But apparent power law divergences indicate a critical packing fraction much higher than the corresponding MCT predictions for a hard sphere fluid.

In this paper, for the first time, we consider theoretically all the potential orientations of dipoles for second harmonic generation (SHG) under crystallized type I collagen fiber. With high numerical aperture (NA = 14), the effect of dipole orientation angle Φ on the SHG intensity, on the maximum SHG emergence angles (θ_max, φ_max) and the action of these dipole sources on the ratio of forward to backward (F/B) SHG have been studied under different cases of fibrils diameter d₁ and the QPM order (m, l) in the crystallized collagen fiber, and it is found that the influential patterns of the same Φ on SHG at different fibrils diameter d₁ and the QPM order (m, l) are different. The dipoles arrangement is related to the characteristic changes in biological tissue so that our work may provide a helpful theoretical tool for pathological status detecting.

The electronic properties of EuS are studied by band structure calculation based on the density functional theory within LDA, LDA + U and fully relativistic schemes. When the Coulomb potential is added to the Eu 4f orbitals, the degeneracy between the different f orbitals is lifted and they are split into lower Hubbard bands and upper Hubbard bands. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f_7/2 and the 4f_5/2 multiplet. EuS has high magnetic moments around 6.9 μ_B/f.u and its magnetic properties are determined by the occupancy of the strongly localized 4f electronic states near the Fermi level.

Using the first-principles plane wave pseudopotential method, the structural and electronic properties of intermetallic compound SrLiSb have been studied within generalized gradient approximation in the frame of density functional theory. The calculations of lattice parameters are in well agreement with the available experimental data. The geometry optimization results indicated the compressibility of SrLiSb is anisotropic under high pressure. The energy band structure and density of states of SrLiSb were also calculated, indicating that SrLiSb has an electronic phase transition from direct-gap semiconductor to indirect-gap semiconductor at approximate 8 GPa.

In this paper, the transport properties of the band-to-band-tunneling carbon nanotube field-effect transistors (BTBT-CNTFETs) under uniaxial strain are studied, with the nonequilibrium Green's function (NEGF) formalism. The effects of the uniaxial strain on the electrical properties, such as the ON current (I_ON), OFF current (I_OFF), I_ON/I_OFF ratio, subthreshold swing and intrinsic delay are evaluated. It was observed that the uniaxial strain has strong effects on the transport properties of these transistors. The results show that appropriate uniaxial strain, although degrades the ON current and the intrinsic delay, it also decreases the power consumption of the BTBT-CNTFETs and as a result can be used for low-power applications.

We investigate the ground state phase diagram of the two dimensional Extended Hubbard Model (EHM) with more than Nearest-Neighbor (NN) interactions for finite size system at low concentration. This EHM is solved analytically for finite square lattice at one-eighth filling. All eigenvalues and eigenvectors are given as a function of the on-site repulsion energy U and the off-site interaction energy V_ij. The behavior of the ground state energy exhibits the emergence of phase diagram. The obtained results clearly underline that interactions exceeding NN distances in range can significantly influence the emergence of the ground state conductor–insulator transition.

The magnetic and transport properties of lightly Ce doped, Y_1-xCe_xSr₂Ru_0.9Cu_2.1 O_7.9(x = 0.05 and 0.1) samples have been studied and their results are compared with the pristine rutheno-cuprate, YSr₂Ru_0.9Cu_2.1O_7.9. The electron doping due to Ce⁴⁺ for Y³⁺ ion impacts on the physical properties of the present system. The tetragonal stabilized samples exhibit magneto superconducting properties under zero field cooled condition (H = 10 Oe) and the diamagnetic onset transition, T_d shift slightly towards higher temperature with the increase of "x". Weak antiferromagnetic like hysteresis curves are seen for these samples at 2 K in the magnetic field strength up to ±10 kOe and the magnetization moment, M(μ_B/Ru) decreases with increase of "x". While the magnetic property of the present system is due to canted Ru moments, the superconducting signal originates from CuO₂ plane. Through electrical resistivity measurements we observe that none of the samples exhibit bulk superconductivity down to 2 K. However the x = 0.05 sample reveals lowest resistivity in the entire temperature range than x = 0 and 0.1 samples. The isothermal magnetoresistance, MR(H) measured at different temperatures vary with tuning of "x". While x = 0.1 doped sample shows lower -MR(~ 8%), the pristine sample exhibits maximum -MR(45%) at 2 K under ±90 kOe field condition.

Transparent films of PMMA (poly methyl methacrylate), PVAc (polyvinyl acetate) and their blends, have been prepared by using a solution-casting technique. The dielectric properties and the electrical conductivity are reported. The frequency and temperature dependence of the dielectric constant, ε′ and tan δ, have been investigated for the studied samples in the frequency range from 1 kHz to 5 MHz and over a range of temperature from 303–413 K. In addition, AC conductivity values were calculated from the dielectric data and the conduction mechanism is discussed. The frequency-dependent conductivity behavior at different temperatures provides a qualitative description of the conduction mechanism. Also, differential scanning calorimetry (DSC) scans have been measured for the studied samples.

Upon the importance of the preservation of nonclassical properties, in this paper we investigate the effect of temporal stability on the stability of nonclassicality features of two classes of generalized coherent states that are temporal stable and nontemporal stable. We use the Gazeau–Klauder coherent states as the temporal stable states and nonlinear coherent states as the nontemporal stable states. Among the nonclassical criteria, we pay attention to first and second-order squeezing, Mandel parameter, second-order correlation function, Wigner and Hussimi functions. In addition, the auto-correlation function of states are obtained and the quantum feature of the observed revival and collapse phenomena of the two considered classes of states are compared.