Bianchi Type Ⅲ String Cosmological Model with Bulk Viscosity

The Bianchi type Ⅲ cosmological model for a cloud string with bulk viscosity are presented. To obtain a determinate model, an equation of state ρ=kλ and a relation between metric potentials B = C^n are assumed. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy density is ζ∝ρ^1/2.     

Bianchi Type-Ⅲ String Cosmological Model With Bulk Viscosity and Magnetic Field

The Bianchi type-Ⅲ cosmological model for a cloud string in the presence of bulk viscosity and magnetic field are presented. To obtain the determinate model it is assumed that there is an equation of state ρ = kA and the scalar of expansion is proportional to the shear scalar θ ∝ σ, which leads to a relation between metric potentials B = mC^n. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start. In the absence of magnetic field, it reduces to the string model with bulk viscosity that was previously given in the literature.     

Locally Rotationally Symmetric Bianchi Type-ⅠString Cosmological Model with Bulk Viscosity

A locally rotationally symmetric (LRS) Bianchi type-I string cosmological model with bulk viscosity is investigated. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a power function of the energy density ζ= ζop^m and the scalar of expansion is proportional to the shear scalar θ σ or, which leadsto a relation between metric potentials R=AS^n, where R and S are only the functions of time. The physicaland geometrical aspects of the model are also discussed. The solution includes some results previously given inthe literature as special cases.     

Bianchi Type-I Cosmology with Cosmic String and Bulk Viscosity

Some locally rotationally symmetric Bianchi type=I cosmological solutions for a cloud string with bulk viscosity are presented. In the first case, an equation of state ρ = κλ and the relation between metric potentials R = AS^m are considered, and the solution represents shearing non-rotating model with the bulk viscosity ζ∝ρ^1/2, where ρ is the rest energy density of the cloud of strings with particles attached to them, λ is the tension density of the cloud of strings, ζ is the coefficient of the bulk viscosity, R and S are only the functions of time t, while A and κ are constant. In the second case, the constant coefficient of bulk viscosity is considered.     

Viscous Dark Energy Models with Variable G and Λ

We consider a cosmological model with bulk viscosity η and variable cosmological A ∝p^-α, alpha = const and gravitational G constants. The model exhibits many interesting cosmological features. Inflation proceeds du to the presence of bulk viscosity and dark energy without requiring the equation of state p =-p. During the inflationary era the energy density p does not remain constant, as in the de-Sitter type. Moreover, the cosmological and gravitational constants increase exponentially with time, whereas the energy density and viscosity decrease exponentially with time. The rate of mass creation during inflation is found to be very huge suggesting that all matter in the universe is created during inflation.     

Bianchi Type-Ⅲ String Cosmological Models with Time Dependent Bulk Viscosity

Bianchi type-Ⅲ string cosmological models with bulk viscous fluid for massive string are investigated. To obtain the determinate model of the universe, we assume that the coeffcient of bulk viscosity ξ is inversely proportional to the expansion θ in the model and expansion θ in the model is proportional to the shear g. This leads to B =lC^n, where l and n are constants. Behaviour of the model in the presence and absence of bulk viscosity is discussed. The physical implications of the models are also discussed in detail.     

Bianchi Type-V Bulk Viscous Barotropic Fluid Cosmological Model with Variable G and Λ

We investigate the Bianchi type-V bulk viscous barotropic fluid cosmological model with variable gravitational constant G and the cosmological constant A, assuming the condition on metric A/A=B/B=C/C=m/tn potential aswhere A, B, and C are functions of time t, while m and n are constants. To obtain the deterministic mo del, we also assume the relations P = p - 3η H, p = 7P, η = ηop^s, where p is the isotropic pressure, η the bulk viscosity,0≤r≤1 H the Hubble constant, ηo and s are constants. Various physical aspects of the model are discussed.The case of n = 1 is also discussed to compare the results with the actual universe.     

Structure and property of metal melt Ⅲ—Relationship between kinematic viscosity and size of atomic clusters

The method of crucible rotating oscillation damping was employed to measure the kinematic viscosity of aluminum melt,and the curve of viscosity v versus temperature T from 935 to 1383 K was obtained.Besides,based on the calculation model of the evolution behavior of atomic clusters in liquid structure,the curve of atomic clusters size d versus temperature was obtained,and the calculated results are in good agreement with the experimental values.By analyzing experimental data,it was found that both the viscosity and the size of atomic clusters of aluminum melt are monodrome functions of temperature,and the relation between v(T) and d(T) is a linear function,i.e.,v = v 0 + K·d(T).This relation indirectly verifies the calculation model of the structural information of metal melt,which is of great significance for studying the relation between melt microstructure and macro-physical properties.     

Bianchi Type III Bulk Viscous Barotropic Fluid Cosmological Models with Variable G and Λ

Bianchi type-Ⅲ bulk viscous barotropic fluid cosmological model with variables G and A is investigated. To obtain the realistic model, we assume the conditions between the metric potentials A, B, C as A/A = B/B = m1/t^N and C/C = m2/t^n, P = p - 3ηH, η =ηop^s, p=γρ, 0 ≤ γ ≤ 1, where p is isotropic pressure,η the coefficient of bulk viscosity, η0 and S the constants, H the Hubble constant, m1 = 2m2 where m1 〉 0, m2 〉 O. The solutions obtained lead to inflationary phase and the results obtained match with the observations. The case n = 1 for S = 1 is also discussed, relating the results with the observations.     

Transport coefficients of a massive pion gas

We review our main results concerning the transport coefficients of a light meson gas,in particular we focus on the case of a massive pion gas.Leading order results according to the chiral power-counting are presented for the DC electrical conductivity,thermal conductivity,shear viscosity,and bulk viscosity.We also comment on the possible correlation between the bulk viscosity and the trace anomaly in QCD,as well as the relation between unitarity and a minimum of the quotient η/s near the phase transition.     

Friedmann Cosmology with a Generalized Equation of State and Bulk Viscosity

The universe content is considered as a non-perfect fluid with bulk viscosity and is described by a more general equation of state (endowed some deviation from the conventionally assuned cosmic perfect fluid model).We assume the bulk viscosity is a linear combination of two termsone is constant,and the other is proportional to the scalar expansion θ = 3a/a.The equation of state is described as p = (γ - 1)p p0,where p0 is a parameter.In this framework we demonstrate that this model can be used to explain the dark energy dominated universe,and different proper choices of the parameters may lead to three kinds of fates of the cosmological evolutionno future singularity,big rip,or Type-Ⅲ singularity as presented in [S.Nojiri,S.D.Odintsov,and S.Tsujikawa,Phys.Rev.D 71 (2005) 063004].     

Transport coefficients of a massive pion gas

We review our main results concerning the transport coefficients of a light meson gas,in particular we focus on the case of a massive pion gas.Leading order results according to the chiral power-counting are presented for the DC electrical conductivity,thermal conductivity,shear viscosity,and bulk viscosity.We also comment on the possible correlation between the bulk viscosity and the trace anomaly in QCD,as well as the relation between unitarity and a minimum of the quotient η/s near the phase transition.     

Bulk Modulus and Electronic Band Structure of ZnGa2Xa （X=S,Se）： a First-Principles Study

First-principles local density functional calculations are presented for the compounds ZnGa2X4 （X = S, Se）. We investigate the bulk moduli and electronic band structures in a defect chalcopyrite structure. The lattice constants and internal parameters are optimized. The electronic structures are analysed with the help of total and partial density of states. The relation between the cohesive energy and the unit cell volume is obtained by fully relaxed structures. We derive the bulk modulus of ZnGa2Xa by fitting the Birch-Murnaghan＇s equation of state. The extended Cohen＇s empirical formula agrees well with our ab initio results.     

Scalar glueball in a soft-wall model of AdS/QCD

The scalar glueball is investigated in a soft-wall model of AdS/QCD.Constraints of the mass of the scalar glueball are given through an analysis of a relation between the bulk mass and the anomalous dimension.The mass of the ground scalar glueball is located at 0.96_(-0.07)~(+0.04)GeVmGl.36_(-0.10)~(+0.05)GeV.In terms of a background dilaton fieldΦ(z)=cz~2,the two-point correlation function for the scalar gluon operator is obtained.The two-point correlation function at△=4 gives a different behavior compared with the one in QCD.     

Entropy description of a cooperation-competition system

Understanding the cooperation-competition dynamics is a long-standing challenge in studying complex systems.Inspired by the idea of Shannon entropy,we define competition information entropy and propose an entropy evolution model.The analytic results of the model of the relation between competition gain distribution parameters and entropy,as well as the relation between entropy and time are compared with empirical results obtained in 14 real world systems.They are found to be in good agreement with each other.     

Friedmann Cosmology with Bulk Viscosity： A Concrete Model for Dark Energy

The universe content is considered as a non-perfect fluid with bulk viscosity and can be described by a general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. An explicitly bulk viscosity dark energy model is proposed to confront consistently with the current observational data sets by statistical analysis and is shown consistent with （not deviated away much from） the concordant A Cold Dark Matter （CDM） model by comparing the decelerating parameter. Also we compare our relatively simple viscosity dark energy model with a more complicated one by contrast with the concordant ACDM model and find our model improves for the viscosity dark energy model building. Finally we discuss the perspectives of dark energy probes for the coming years with observations.     

Bulk viscosity for interacting strange quark matter and r-mode instability windows for strange stars

We investigate the bulk viscosity of strange quark matter in the framework of the equivparticle model,where analytical formulae are obtained for certain temperature ranges,which can be readily applied to those with various quark mass scalings.In the case of adopting a quark mass scaling with both linear confinement and perturbative interactions,the obtained bulk viscosity increases by 1-2 orders of magnitude compared with those in bag model scenarios.Such an enhancement is mainly due to the large quark equivalent masses adopted in the equivparticle model,which are essentially attributed to the strong interquark interactions and are related to the dynamical chiral symmetry breaki ng.Due to the high bulk viscosity,the predicted damping time of oscillatio ns for a can on ical 1.4 M⊙ strange star is less than one millisecond,which is shorter than previous findings.Consequently,the obtained r-mode instability window for the canonical strange stars well accommodates the observational frequencies and temperatures for pulsars in low-mass X-ray binaries(LMXBs).     

The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

The dynamic viscosity of Al-Yb and Al-Ni-Yb superheated melts was measured using a torsional oscillation viscometer. The results show that the temperature dependence of viscosity fits the Arrhenius law well and the fitting factors are calculated. The amorphous ribbons of these alloys were produced by the melt spinning technique and the thermal properties were characterized by using a differential scanning calorimetry (DSC). E (the activation energy for viscous flow), which reflects the change rate of viscosity, has a good negative relation with the GFA in both Al-Yb and Al-Ni-Yb systems. However, there is no direct relation between liquidus viscosity (ηL) and GFA. The superheated fragility M can predict GFA in Al-Yb or Al-Ni-Yb alloy system.     

Pion transverse-momentum spectrum,elliptic flow,and Hanbury-Brown-Twiss interferometry in a viscous granular source model

We examine the evolution of quark-gluon plasma(QGP) droplets with viscous hydrodynamics and analyze the pion transverse-momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss(HBT) interferometry in a granular source model consisting of viscous QGP droplets. The shear viscosity of the QGP droplet speeds up and slows down the droplet evolution in the central and peripheral regions of the droplet, respectively. The effect of the bulk viscosity on the evolution is negligible. Although there are viscous effects on the droplet evolution, the pion momentum spectrum and elliptic flow change little for granular sources with and without viscosity. On the other hand,the influence of viscosity on HBT radius Rout is considerable. It makes Rout decrease in the granular source model.We determine the model parameters of granular sources using the experimental data of pion transverse-momentum spectrum, elliptic flow, and HBT radii together, and investigate the effects of viscosity on the model parameters. The results indicate that the granular source model may reproduce the experimental data of pion transverse-momentum spectrum, elliptic flow, and HBT radii in heavy-ion collisions of Au-Au at√s_(NN)=200 GeV and Pb-Pb at√s_(NN) =2.76 Te V in different centrality intervals. The viscosity of the droplet leads to an increase in the initial droplet radius and a decrease of the source shell parameter in the granular source model.     

Determination of bulk viscosity of liquid water via pulse duration measurements in stimulated Brillouin scattering

We present a method by which to determine the bulk viscosity of water from pulse duration measurements of stimulated Brillouin scattering （SBS）. Beginning from a common model of Brillouin scattering, the bulk viscosity is shown to play an important role in Brillouin linewidth determination. Pulse durations of SBS back-reflected optical pulses are measured over the temperature range of 5-40℃. SBS linewidths are de- termined via Fourier transformation of the time-domain results, and the bulk viscosity of water is measured and derived from the obtained values. Our results show that the proposed method for measurement of pulse durations is an effective approach for determining bulk viscosity. The method can be easily extended to determine bulk viscosities of other Newtonian liquids.