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We investigate cosmology with complex scalar field. It is shown that such models can describe two stages of inflation and the oscillatory regime. Thus we don't need both quintessence and $\Lambda$-term. It is enough to have single complex…

High Energy Physics - Theory · Physics 2007-05-23 A. V. Yurov

We present a rich class of exact solutions which contains radiation-dominated and matter-dominated models for the early and late universe. They include a variable cosmological ``constant'' which is derived from a higher dimension and…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Hongya Liu , Paul S. Wesson

It is generally argued that the present cosmological observations support the accelerating models of the universe, as driven by the cosmological constant or `dark energy'. We argue here that an alternative model of the universe is possible…

Astrophysics · Physics 2009-11-07 J. V. Narlikar , R. G. Vishwakarma , G. Burbidge

We discuss a cosmological model where the universe shrinks rather than expands during the radiation and matter dominated periods. Instead, the Planck mass and all particle masses grow exponentially, with the size of atoms shrinking…

Cosmology and Nongalactic Astrophysics · Physics 2013-11-13 C. Wetterich

This article reviews recent developments in the study of universes with a positive cosmological constant in string theory.

High Energy Physics - Theory · Physics 2009-11-10 Vijay Balasubramanian

The universe is viewed as a dust gas filling a sphere and floating in infinite empty space. Einstein's gravitational equations are applied to this case together with appropriate boundary values. The equations are solved for initial…

General Relativity and Quantum Cosmology · Physics 2015-12-01 Ingo Müller , Wolf Weiss

We consider an Einstein-Dirac-Maxwell system with two charged massless spinors coupled with an electromagnetic field, and construct a family of exact solutions to the system. The solution spacetime is an anisotropic generalization of the…

High Energy Physics - Theory · Physics 2024-10-08 Fumihiro Ueno , Satsuki Matsuno

An exact inhomogeneous solution of Einstein's field equations is shown to be able to inflate in a non-uniform way in the early universe and explain anomalies in the WMAP power spectrum data. It is also possible for the model to explain the…

Astrophysics · Physics 2007-06-13 J. W. Moffat

We investigate whether an accelerating universe can be realized as an asymptotic late-time solution of FLRW-cosmology with multi-field multi-exponential potentials. Late-time cosmological solutions exhibit a universal behavior which enables…

High Energy Physics - Theory · Physics 2023-09-25 Gary Shiu , Flavio Tonioni , Hung V. Tran

The spacetime structure of the spatially uniformly expanding universe is described in terms of a kind of global space and global time instead of the space and time we usually recognize. The global space at some instant is a space in which…

Astrophysics · Physics 2022-08-31 Yoshio Kubo

In many cases a scalar field can lead to accelerated expansion in cosmological models. This paper contains mathematical results on this subject particularly on type I Bianchi space-time. In this paper, global existence to the coupled…

Analysis of PDEs · Mathematics 2017-03-07 Alexis Nangue

The possibility of an emergent universe solution to Einstein's field equations allowing for an irreversible creation of matter at the expense of the gravitational field is shown. With the universe being chosen as spatially flat FRW…

General Relativity and Quantum Cosmology · Physics 2016-09-27 Sunandan Gangopadhyay , Anirban Saha , S. Mukherjee

The fractal cosmological model which accounts for observable fractal properties of the Universe's large-scale structure is constructed. In this framework these properties are consequences of the rotary symmetry of charged scalar meson…

Cosmology and Nongalactic Astrophysics · Physics 2012-12-03 I. K. Rozgacheva , A. A. Agapov

Special theory of relativity has been formulated in a vacuum momentum-energy representation which is equivalent to Einstein special relativity and predicts just the same results as it. Although in this sense such a formulation would be at…

General Relativity and Quantum Cosmology · Physics 2007-05-23 P. F. Gonzalez-Diaz

It is argued that when the dimension of space is a constant integer the full set of Einstein's field equations has more information than the spatial components of Einstein's equation plus the energy conservation law. Applying the former…

General Relativity and Quantum Cosmology · Physics 2015-06-25 J. A. S. Lima , M. Mohazzab

A new model of nonlinear electrodynamics with a dimensional parameter $\beta$ coupled to gravity is considered. We show that an accelerated expansion of the universe takes place if the nonlinear electromagnetic field is the source of the…

General Relativity and Quantum Cosmology · Physics 2016-01-26 S. I. Kruglov

A generalized quintessence model is presented which corresponds to a richer vacuum structure that, besides a time-dependent, slowly varying scalar field, contains a varying cosmological term. From first principles we determine a number of…

Astrophysics · Physics 2009-10-31 Pedro F. Gonzalez-Diaz

The cosmological Friedmann equation for the universe filled with a scalar field is reduced to a system of two equations of the first order, one of which is an equation with separable variables. For the second equation the exact solutions…

General Relativity and Quantum Cosmology · Physics 2015-12-31 E. A. Kuryanovich

We show that scalar field fluctuations alone can drive cosmic acceleration, provided the universe is spatially closed and the Compton wavelength of the field exceeds the radius of curvature. This mechanism may open new perspectives on…

General Relativity and Quantum Cosmology · Physics 2026-02-12 Daniel Jiménez-Aguilar

The detection of magnetic fields at high redshifts, and in empty intergalactic space, support the idea that cosmic magnetism has a primordial origin. Assuming that Maxwellian electromagnetism and general relativity hold, and without…

General Relativity and Quantum Cosmology · Physics 2015-06-11 J. D. Barrow , C. G. Tsagas , K. Yamamoto