Chaplygin inflation on the brane

In this paper, we study two different models of dark energy based on Chaplygin gas equation of state. The first model is the variable modified Chaplygin gas while the second one is the extended Chaplygin gas. Both models are considered in the framework of higher order $f(R)$ modified gravity. We also consider the case of time varying gravitational constant $G$ and $\Lambda$ for both models. We investigate some cosmological parameters such as the Hubble, the deceleration and the equation of state parameters. Then we showed that the model that we considered, extended Chaplygin gas with time-dependent $G$ and $\Lambda$, is consistent with the observational data. Finally we conclude with the discussion of cosmological perturbations of our model.

We investigate an interacting two-fluid model in a spatially flat Friedmann–Lemaître–Robertson–Walker (FLRW) Universe, when the energy transfer between these two dark components is produced by a factorizable nonlinear sign-changeable interaction depending linearly on the energy density and quadratically on the deceleration parameter. We solve the source equation and obtain the effective energy densities of the dark sector and their components. We show that the effective equation of state of the dark sector includes some of the several kinds of Chaplygin gas equations of state as well as a generalization of the polytropic equation of state. We use Bayesian statistics methods to constrain free parameters in the models during the most recent evolution considering supernovae type Ia and measurements of the Hubble expansion rate. The resulting constraints provide new information on sign-changeable interactions, its equivalences and compatibility with previous models and novel late time universe dynamics.

We review the essential features of the Chaplygin gas cosmological models and provide some examples of appearance of the Chaplygin gas equation of state in modern physics. A possible theoretical basis for the Chaplygin gas in cosmology is discussed. The relation with scalar field and tachyon cosmological models is also considered.

We review the essential features of the Chaplygin gas cosmological models and provide some examples of appearance of the Chaplygin gas equation of state in modern physics. A possible theoretical basis for the Chaplygin gas in cosmology is discussed. The relation with scalar field and tachyon cosmological models is also considered.

Semi-hyperbolic patches of solutions to the two-dimensional nonlinear wave system for Chaplygin gases

We investigate models of interacting dark matter and dark energy for the\nuniverse in a spatially flat Friedmann-Robertson-Walker (FRW) space-time. We\nfind the "source equation" for the total energy density and determine the\nenergy density of each dark component. We introduce an effective one-fluid\ndescription to evidence that interacting and unified models are related with\neach other, analyze the effective model and obtain the attractor solutions. We\nstudy linear and nonlinear interactions, the former comprises a linear\ncombination of the dark matter and dark energy densities, their first\nderivatives, the total energy density, its first and second derivatives and a\nfunction of the scale factor. The latter is a possible generalization of the\nlinear interaction consisting of an aggregate of the above linear combination\nand a significant nonlinear term built with a rational function of the dark\nmatter and dark energy densities homogeneous of degree one. We solve the\nevolution equations of the dark components for both interactions and examine\nexhaustively several examples. There exist cases where the effective one-fluid\ndescription produces different alternatives to the $\\La$CDM model and cases\nwhere the problem of coincidence is alleviated. In addition, we find that some\nnonlinear interactions yield an effective one-fluid model with a Chaplygin gas\nequation of state, whereas others generate cosmological models with de Sitter\nand power-law expansions. We show that a generic nonlinear interaction induces\nan effective equation of state which depends on the scale factor in the same\nway that the variable modified Chaplygin gas model, giving rise to the "relaxed\nChaplygin gas model".\n

Given a finite sequence x1, x2, .. . , x, the essential problem in lossless data compression is to process the symbols in some order and assign a conditional probability distribution for the current symbol based on the previously processed symbols [44]. For example, if we are to process x1, x2, .. . , x in a sequenal manner [53] then we need to estimate the distributions p(x+iIxi, x2, . . . , xe), 1 < j < fl The number of bits needed to optimally encode the sequence x1, . . , x, is then given by —log flp(x+iIx,...,x). Coding techniques that can encode the sequence at rates close to the optimal are known [43]. Hence, higher the probabilities assigned in the above product, the lesser the number of bits that are needed to encode the sequence. A model, in this context is then simply a scheme for assigning conditional probability distributions [53]. Clearly, it is the model that determines the rate at which we can encode the sequence. Hence the critical task in lossless data compression is finding good models for the data under consideration. Finding good models for a given data set is a difficult problem. In lossless compression applications some structure is usually imposed on the data in the form offinile-state models, Markov-models, tree-models, finiie-con1ex models etc to make the problem mathematically and/or computationally tractable. Algorithms are then designed that encode the given data, in an optimal or sub-optimal manner. Algorithms that 'learn' the parameters of the model that best describes the data and achieve rates that are asymptotically optimal are known as oplimal universal coding schemes. Such schemes have been applied very successfully in text or string compression applications. Unfortunately, universal coding schemes and other standard modelling techniques do not work well in practice when applied to gray-scale image data.

Equation of physical adsorption on a homogeneous surface based on a two-dimensional analog of the Beattie-Bridgeman equation of a real gas state

Inflationary models and their claim to solve many of the outstanding problems in cosmology have been the subject of a great deal of debate over the last few years. A major sticking point has been the lack of both good observational and theoretical arguments to single out one particular model out of the many that solve these problems. Here we examine the degree of restrictiveness on the dynamical relationship between the cosmological scale factor and the inflation driving self-interaction potential of a minimally coupled scalar field, imposed by the condition that the scalar field is required to be real during a classical regime (the reality condition). We systematically look at the effects of this constraint on many of the inflationary models found in the literature within the FLRW framework, and also look at what happens when physically motivated perturbations such as shear and bulk viscosity are introduced. We find that in many cases, either the models are totally excluded or the reality condition gives rise to constraints on the scale factor and on the various parameters of the model.

In this paper we construct charged thin-shell wormholes in (2+1)-dimensions applying the cut-and -paste technique implemented by Visser, from a BTZ black hole which was discovered by Banados, Teitelboim and Zanelli, and the surface stress are determined using the Darmois-Israel formalism at the wormhole throat. We analyzed the stability of the shell considering phantom-energy or generalised Chaplygin gas equation of state for the exotic matter at the throat. We also discussed the linearized stability of charged thin-shell wormholes around the static solution.

We have presented FRW cosmological model in the framework of Brans-Dicke theory. This paper deals with a new proposed form of deceleration parameter and cosmological constant Λ. The effect of bulk viscosity is also studied in the presence of modified Chaplygin gas equation of state (p=Aρ-B/ρn). Furthermore, we have discussed the physical behaviours of the models.

In this paper we develop a probabilistic microscale compartmental model and use it to study macroscale properties of axonal transport, the process by which intracellular cargo is moved in the axons of neurons. By directly modeling the smallest scale interactions, we can use recent microscopic experimental observations to infer all the parameters of the model. Then, using techniques from probability theory, we compute asymptotic limits of the stochastic behavior of individual motor-cargo complexes, while also characterizing both equilibrium and nonequilibrium ensemble behavior. We use these results in order to investigate three important biological questions: (1) How homogeneous are axons at stochastic equilibrium? (2) How quickly can axons return to stochastic equilibrium after large local perturbations? (3) How is our understanding of delivery time to a depleted target region changed by taking the whole cell point of view?

A model previously developed for the equation of state of pure fluids consisting of hard convex body molecules is extended to mixtures. The parameters of the model can be determined from the geometrical characteristics of the molecules which form the mixture. The equation of state is in excellent agreement with simulation data for mixtures of hard spheres with hard spherocylinders.

Energy density functionals (EDFs) have been used extensively with great success to calculate properties of nuclei and to predict the equation of state of dense nuclear matter. Besides non-relativistic EDFs, mostly of the Skyrme or Gogny type, relativistic EDFs of different types are in widespread use. In these latter approaches, the effective in-medium interaction is described by an exchange of mesons between nucleons. In most cases, only minimal meson-nucleon couplings are considered. The effects of additional tensor couplings were rarely investigated. In this work, a new relativistic EDF with tensor couplings and density dependent minimal meson-nucleon couplings will be presented. The parameters of the model are determined using a carefully selected set of experimental data with realistic uncertainties that are determined self-consistently. Predictions for various nuclear observables, the nuclear matter equation of state, and properties of neutron stars are discussed.

Plenitude of models incorporating a dynamical dark energy equation of state are proposed and the scalar-tensor gravity is certainly one possible candidate. In this paper we examine whether a cosmological rip scenarios are possible in the scalar-tensor gravity by parametrizing the equation of state of dark energy Wde(z) in an appropriate way. The parameters of the model are constrained by the observational data of type Ia supernovas collected to Union 2.1 compilation.