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1
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Reconstruction of the equation of state for the cyclic universes in homogeneous and isotropic cosmology

100%
Bamba K., Yesmakhanova K., Yerzhanov K., Myrzakulov R.
Open Physics
|
2013
|
vol. 11
|
issue 4
397-411
EN
We study the cosmological evolutions of the equation of state (EoS) for the universe in the homogeneous and isotropic Friedmann-Lemaître-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.
2
Content available remote

New results in the use of a “reverse engineering” method in cosmologies with scalar field

80%
Vulcanov D.
Open Physics
|
2008
|
vol. 6
|
issue 1
84-96
EN
The method of “reverse engineering” for designing potentials in cosmologies with “quintessence” scalar field is systematically used for several types of cosmologies (through the time behavior of the scale factor). The general recipe is introduced and then applied when matter other than the scalar field is present, and for tachyonic scalar fields. The possibility of using this method for prescribing initial data in numerical simulations in cosmology is investigated.
3
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Light refraction in the Swiss-cheese model

80%
Csapó A., Bene G.
Open Physics
|
2012
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vol. 10
|
issue 4
821-835
EN
We investigate light propagation in the Swiss-cheese model. On both sides of Swiss-cheese sphere surfaces, observers resting in the flat Friedmann-Robertson-Walker (FRW) space and the Schwarzschild space respectively, see the same light ray enclosing different angles with the normal. We examine light refraction at each crossing of the boundary surfaces, showing that the angle of refraction is larger than the angle of incidence for both directions of the light.
4
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On the origin of space

80%
Herrmann R.
Open Physics
|
2013
|
vol. 11
|
issue 10
1212-1220
EN
Within the framework of fractional calculus with variable order the evolution of space in the adiabatic limit is investigated. Based on the Caputo definition of a fractional derivative using the fractional quantum harmonic oscillator a model is presented, which describes space generation as a dynamic process, where the dimension d of space evolves smoothly with time in the range 0 ≤ d(t) ≤ 3, where the lower and upper boundaries of dimension are derived from first principles. It is demonstrated, that a minimum threshold for the space dimension is necessary to establish an interaction with external probe particles. A possible application in cosmology is suggested.
5
Content available remote

Neutrinos from the Early Universe and physics beyond standard models

70%
Kirilova D.
Open Physics
|
2015
|
vol. 13
|
issue 1
EN
Neutrino oscillations present the only robust example of experimentally detected physics beyond the standard model. This review discusses the established and several hypothetical beyond standard models neutrino characteristics and their cosmological effects and constraints. Particularly, the contemporary cosmological constraints on the number of neutrino families, neutrino mass differences and mixing, lepton asymmetry in the neutrino sector, neutrino masses, light sterile neutrino are briefly reviewed.
6
Content available remote

Sources of inertia in an expanding universe

70%
Prytz K.
Open Physics
|
2015
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vol. 13
|
issue 1
EN
In a cosmological perspective, gravitational induction is explored as a source to mechanical inertia in line with Mach’s principle. Within the standard model of cosmos, considering the expansion of the universe and the necessity of retarded interactions, it is found that the assumed dynamics may account for a significant part of an object’s inertia.
7
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Phase space analysis of interacting dark energy in f(T) cosmology

70%
Jamil M., Yesmakhanova K., Momeni D., Myrzakulov R.
Open Physics
|
2012
|
vol. 10
|
issue 5
1065-1071
EN
In this paper, we examine the interacting dark energy model in f(T) cosmology. We assume dark energy as a perfect fluid and choose a specific cosmologically viable form f(T) = β√T. We show that there is one attractor solution to the dynamical equation of f(T) Friedmann equations. Further we investigate the stability in phase space for a general f(T) model with two interacting fluids. By studying the local stability near the critical points, we show that the critical points lie on the sheet u* = (c − 1)v* in the phase space, spanned by coordinates (u, v, Ω, T). From this critical sheet, we conclude that the coupling between the dark energy and matter c ∈ (−2, 0).
8
Content available remote

Cosmological sigma model with non-minimal coupling to the target space

70%
Shchigolev V.
Open Physics
|
2014
|
vol. 12
|
issue 1
32-41
EN
A homogeneous and isotropic Universe in the framework of a nonlinear sigma model with non-minimal coupling to the target space is considered. Preliminary investigation of a two-component model of this sort is conducted. Some solutions for this model are given. Perspectives and directions of development of such a sort of models are discussed.
9
Content available remote

Einstein equation at singularities

70%
Stoica O.-C.
Open Physics
|
2014
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vol. 12
|
issue 2
123-131
EN
Einstein’s equation is rewritten in an equivalent form, which remains valid at the singularities in some major cases. These cases include the Schwarzschild singularity, the Friedmann-Lemaître-Robertson-Walker Big Bang singularity, isotropic singularities, and a class of warped product singularities. This equation is constructed in terms of the Ricci part of the Riemann curvature (as the Kulkarni-Nomizu product between Einstein’s equation and the metric tensor).
10
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Content available

Pochodzenie materii meteorytowej

70%
Kozłowski S.
Acta Societatis Metheoriticae Polonorum
|
2023
|
vol. 14
100-113
EN
In this article, I briefly review the history of the elements in the Universe, starting from cosmic inflation and ending at the creation of elements and minerals that we find in meteorites.
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