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Galaxies represent the visible fabric of the Universe and there has been considerable progress recently in both observational and theoretical studies. The underlying goal is to understand the present-day diversity of galaxy forms, masses…

Astrophysics · Physics 2007-05-23 Richard Ellis

Quantum gravity may remove classical space-time singularities and thus reveal what a universe at and before the big bang could be like. In loop quantum cosmology, an exactly solvable model is available which allows one to address precise…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald

The model of the homogenous and isotropic universe is considered in which the coordinate system of reference is not defined by the matter but is a priori specified. The scale factor of the universe changes following the linear law. The…

Astrophysics · Physics 2007-05-23 D. L. Khokhlov

We present a novel test of the cosmological principle: the idea that, on sufficiently large scales, the universe should appear homogeneous and isotropic to observers comoving with the Hubble flow. This is a fundamental assumption in modern…

Cosmology and Nongalactic Astrophysics · Physics 2023-05-19 Oliver T. Oayda , Geraint F. Lewis

We present here a general relativistic mechanism for accelerated cosmic expansion and the Hubble's constant. It is shown that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one…

Cosmology and Nongalactic Astrophysics · Physics 2019-03-20 Babur M. Mirza

We investigate a $(n+1)$-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors. One obtain a positive effective cosmological constant $\Omega_{eff}\sim10^{-124}$ (in Planck unit)…

General Relativity and Quantum Cosmology · Physics 2020-12-02 Guang-Zhen Kang , De-Sheng Zhang , Long Du , Dan Shan , Hong-Shi Zong

A Universe with finite age also has a finite causal scale. Larger scales can not affect our local measurements or modeling, but far away locations could have different cosmological parameters. The size of our causal Universe depends on the…

General Physics · Physics 2020-04-17 Enrique Gaztanaga

We study cosmological solutions for the very early universe beginning at the Planck scale for a universe containing radiation, curvature and, as a simplification of a possible scalar field potential, a cosmological constant term. The…

General Relativity and Quantum Cosmology · Physics 2010-01-30 E. Galindo-Dellavalle , G. German , A. de la Macorra

We study the evolution of the universe in the presence of inflaton, matter, radiation, and holographic dark energy. The time evolution of the scale factor is obtained by solving the Friedmann equation of the universe with a good…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Hyeong-Chan Kim , Jae-Weon Lee , Jungjai Lee

The Kepler problem is considered in a space with the Friedmann--Lemaitre--Robertson--Walker metrics of the expanding universe. The covariant differential of the Friedmann coordinates (X=a(t)x) is considered as a possible mechanism of the…

Astrophysics · Physics 2009-11-07 A. Gusev , P. Flin , V. Pervushin , S. Vinitsky , A. Zorin

We characterize good clocks, which are naturally subject to fluctuations, in statistical terms. We also obtain the master equation that governs the evolution of quantum systems according to these clocks and find its general solution. This…

Quantum Physics · Physics 2009-10-31 Inigo L. Egusquiza , Luis J. Garay , Jose M. Raya

We investigate the origin and evolution of primordial electric and magnetic fields in the early universe, when the expansion is governed by a cosmological constant $\Lambda_0$. Using the gravitoelectromagnetic inflationary formalism with…

General Relativity and Quantum Cosmology · Physics 2009-04-06 Federico Agustin Membiela , Mauricio Bellini

A new universal constant of expansion has been discovered with amazing predictive power once its density-time relations have been deciphered. The new constant is kappa, the product of the gravitational constant, and the average total…

Astrophysics · Physics 2007-05-23 Charles B. Leffert

We propose that primordial black hole (PBH) binary systems can lead to standard timers in tracking the evolution of the Universe. Through gravitational waves from monochromatic PBH binaries, the probability distribution on major axis and…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-26 Qianhang Ding

Emergent scenario of cosmic evolution is a topic of great interest in recent cosmology, especially because it describes a non-singular origin of the Universe unlike the Big-Bang models. This types of cosmic evolution pattern have already…

General Relativity and Quantum Cosmology · Physics 2023-09-01 Subhayan Maity , Sujayita Bakra

Many of the fundamental physical constants in Physics, as a discipline, are measured to exquisite levels of precision. The fundamental constants that define Cosmology, however, are largely determined via a handful of independent techniques…

Recently, a novel idea about our expanding Universe was proposed by T. Padmanabhan [arXiv:1206.4916]. He suggested that the expansion of our Universe can be thought of as the emergence of space as cosmic time progresses. The emergence is…

High Energy Physics - Theory · Physics 2012-11-13 Ke Yang , Yu-Xiao Liu , Yong-Qiang Wang

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

Edwin Hubble is often credited with discovering the expanding Universe based on spectra taken by him. This statement is incorrect and we feel that it is the responsibility of those who are aware of the historical facts to set the record…

History and Philosophy of Physics · Physics 2011-08-31 M. J. Way , Harry Nussbaumer

Georges Lemaitre was a remarkable contributor to the advancement of cosmology in the heady years following two great revolutions in theoretical physics in the last century: general relativity and quantum mechanics. In the present century,…

History and Philosophy of Physics · Physics 2020-07-21 Simon A. Mitton