Scalar dark energy models mimicking Λ\LambdaCDM with arbitrary future evolution

Dark energy models with various scenarios of evolution are considered from the viewpoint of the formalism for the equation of state. It is shown that these models are compatible with current astronomical data. Some of the models presented here evolve arbitrarily close to $\Lambda$CDM up to the present, but diverge in the future into a number of different possible asymptotic states, including asymptotic de-Sitter (pseudo-rip) evolution, little rips with disintegration of bound structures, and various forms of finite-time future singularities. Therefore it is impossible from observational data to determine whether the universe will end in a future singularity or not. We demonstrate that the models under consideration are stable for a long period of time (billions of years) before entering a Little Rip/Pseudo-Rip induced dissolution of bound structures or before entering a soft finite-time future singularity. Finally, the physical consequences of Little Rip, Type II, III and Big Crush singularities are briefly compared.Comment: 15 pages, 1 figure, version to appear in Physics Letters

Domain wall brane in squared curvature gravity

We suggest a thick braneworld model in the squared curvature gravity theory. Despite the appearance of higher order derivatives, the localization of gravity and various bulk matter fields is shown to be possible. The existence of the normalizable gravitational zero mode indicates that our four-dimensional gravity is reproduced. In order to localize the chiral fermions on the brane, two types of coupling between the fermions and the brane forming scalar is introduced. The first coupling leads us to a Schr\"odinger equation with a volcano potential, and the other a P\"oschl-Teller potential. In both cases, the zero mode exists only for the left-hand fermions. Several massive KK states of the fermions can be trapped on the brane, either as resonant states or as bound states.Comment: 18 pages, 5 figures and 1 table, references added, improved version to be published in JHE

Reconstruction of the equation of state for the cyclic universes in homogeneous and isotropic cosmology

We study the cosmological evolutions of the equation of state (EoS) for the universe in the homogeneous and isotropic Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) space-time. In particular, we reconstruct the cyclic universes by using the Weierstrass and Jacobian elliptic functions. It is explicitly illustrated that in several models the universe always stays in the non-phantom (quintessence) phase, whereas there also exist models in which the crossing of the phantom divide can be realized in the reconstructed cyclic universes.Comment: 29 pages, 8 figures, version accepted for publication in Central European Journal of Physic

Screening of cosmological constant for De Sitter Universe in non-local gravity, phantom-divide crossing and finite-time future singularities

We investigate de Sitter solutions in non-local gravity as well as in non-local gravity with Lagrange constraint multiplier. We examine a condition to avoid a ghost and discuss a screening scenario for a cosmological constant in de Sitter solutions. Furthermore, we explicitly demonstrate that three types of the finite-time future singularities can occur in non-local gravity and explore their properties. In addition, we evaluate the effective equation of state for the universe and show that the late-time accelerating universe may be effectively the quintessence, cosmological constant or phantom-like phases. In particular, it is found that there is a case in which a crossing of the phantom divide from the non-phantom (quintessence) phase to the phantom one can be realized when a finite-time future singularity occurs. Moreover, it is demonstrated that the addition of an $R^2$ term can cure the finite-time future singularities in non-local gravity. It is also suggested that in the framework of non-local gravity, adding an $R^2$ term leads to possible unification of the early-time inflation with the late-time cosmic acceleration.Comment: 42 pages, no figure, version accepted for publication in General Relativity and Gravitatio

Randall-Sundrum limit of f(R) brane-world models

By setting some special boundary conditions in the variational principle we obtain junction conditions for the five-dimensional $f(R)$ gravity which in the Einstein limit $f(R)\rightarrow R$ transform into the standard Randall-Sundrum junction conditions. We apply these junction conditions to a particular model of a Friedmann universe on the brane and show explicitly that the limit gives the standard Randall-Sundrum model Friedmann equation.Comment: 6 pages, no figures, REVTEX4, minor change

The influence of structural short-range order on the phase diagrams of diluted FCC magnet with arbitrary spin and modified RKKY interaction

A diluted FCC magnet with modified long-range RKKY interaction and arbitrary Ising spin S is considered within two-sublattice model. In the molecular field approximation the Gibbs free-energy is derived, from which all magnetic thermodynamic properties can be self-consistently obtained. In particular, the phase diagrams are studied for different magnetic ion and free-charge concentration, the atomic short-range-order (Warren-Cowley) parameter being taken into account.Comment: 12 pages, 6 figures, revtex4 fil

Non-Keynesian Effects of Fiscal Consolidations in Central Europe in the Years 2000-2013

Last two decades were a period of significant discussion concerning determinants of effectiveness of fiscal policy. After some cases of expansionary episodes of fiscal consolidations in eighties of XX century, an intensive international research on the possibility of non-Keynesian effects of fiscal contractions in highly developed countries has started. The aim of the article is to analyze the possibility of obtaining non-Keynesian effects of fiscal consolidations in post-transformation countries of Central Europe. An important aim of macroeconomic policy in the analyzed economies is to benefit the advantages of convergence process. Thus, the empirical analysis is made within conditional β-convergence framework. The verification of hypothesis of β-convergence enables to identify the long term tendency of output per capita, in the same time it enables to identify non-Keynesian effects of fiscal prudence and to assess their role in the process of reducing GDP gap between the analyzed economies. Then the potential transmission channels for non-Keynesian effects of fiscal policy were analyzed. In the research the data from Eurostat and European Commission for the years 2000-2013 was used. The paper provides arguments in favor of the existence of non-Keynesian effects of fiscal consolidations in Central Europe that support the process of conditional convergence

f(R) theories

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in Relativity, Published version, Comments are welcom

A Philosophically Plausible Formal Interpretation of Intuitionistic Logic

This study addresses the mediating role of settlement patterns in the relationship between urbanization and start-up activity. Places do not operate in a vacuum and to understand the effect of 'own' density on start-up patterns, we need to account for the urban spillovers or borrowed size that they may experience from other places nearby. The results can explain the empirical ambiguity in the relationship between urbanization and start-up patterns: the relationship between urbanization and start-up rates becomes more similar between countries when controlling for country-specific settlement patterns by including a spatially lagged urbanization variable and variables measuring the distance to urban centers. Accounting for the relative location of places and relevant sorting effects, we find that 'own' density has a consistently negative effect on start-up activity. Yet, access to other places has a generally positive effect. This implies that nearby regions profit from the advantages offered by urban environments without having to deal with the costs involved