Particle horizon

About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.

Long-wavelength gravitational waves and cosmic acceleration

Abstract: Multiple observations of distant type Ia supernovae show the deceleration parameter of the universe is negative. The standard cosmological model states expansion should be slowing down. A new theory is presented which explains cosmic acceleration only through the action of well-supported phenomena in the context of Einstein's general theory of relativity through the use of the Bianchi type IX homogeneous,closed cosmology. The evidence for acceleration is assessed and previously-unreported biases and insuffiencies in the evidence are revealed and discussed. The Einstein equations for the Bianchi type IX cosmology are solved to quadratic order in a matter-dominated universe. The first terms of a power-series solution are given for arbitrarily strong growing mode of gravitational waves in a matter-dominated Bianchi IX universe. The effect of these waves on the energy density of the universe is shown to becompatible with available data. The equations for redshift anisotropy in the Bianchi IX universe are solved to quadratic order. Reported anomalous structure in the cosmic microwave back-ground is considered in the light of these solutions. The Bianchi IX universe is shown to provide an explanation for these anomalies compatible with the CMB. In order to help typify a new class of standard sour es for determining cosmological parameters, a formula relating the time-dependent detection of light by a massive, compact binary such as a super-massive black hole binary is derived. This formula is applied to the system 3C66B and finds that in ideal circumstances, the best available observational techniques would detect a time-dependent omponent to the bending of light by the core of 3C66B. A solution for the Einstein equations in the Bianchi IX universe is found which explains cosmic acceleration while remaining compatible with the CMB and other cosmological parameters as reported by WMAP.

Causal horizons in a bouncing universe

Abstract: As our understanding of the past in a bouncing universe is limited, it becomes difficult to propose a cosmological model which can give some understanding of the causal structure of the bouncing universe. In this article we address the issue related to the particle horizon problem in the bouncing universe models. It is shown that in many models the particle horizon does not exist, and consequently the horizon problem is trivially solved. In some cases a bouncing universe can have a particle horizon and we specify the conditions for its existence. In the absence of a particle horizon the Hubble surface specifies the causal structure of a bouncing universe. We specify the complex relationship between the Hubble surface and the particle horizon when the particle horizon exists. The article also address the issue related to the event horizon in a bouncing universe. A toy example of a bouncing universe is first presented where we specify the conditions which dictate the presence of a particle horizon. Next we specify the causal structures of three widely used bouncing models. The first case is related to quintom matter bounce model, the second one is loop quantum cosmology based bounce model and lastly $f(R)$ gravity induced bounce model. We present a brief discussion on the horizon problem in bouncing cosmologies. We point out that the causal structure of the various bounce models fit our general theoretical predictions.

Black-hole formation in the new inflationary universe

Abstract: In the new inflationary universe the fluctuation of the Higgs scalar field in the supercooled expansion stage is the origin of the irregularities observed today. It is supposed that a sufficiently large fluctuation must have caused gravitational collapse. We present a numerical model for black-hole formation in the new inflationary universe.

Does Cosmological Scale Expansion Explain the Universe

Abstract: The idea of the creation of the world has been central in Western civilization since the earliest recorded history some 6000 years ago and it still prevails, supported by religious dogma. If the creation idea is wrong and the universe is eternal we might wonder why science has not yet revealed this fundamental truth. To understand why, we have to review how the Big Bang theory came to be the dominant cosmological paradigm in spite of many clear indications that the theory might be fundamentally flawed.