Particle horizon

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

Redshift: Expansion of Space or Inhomogeneities?

Abstract: Is it credible that light might experience a redshift if it travels through inhomogeneous space? It might seem unbelievable but the answer may be affirmative. The energy propagating in inhomogeneous universe exhibits a shift which could be attributed not only to the expansion of space but alternatively to fluctuations in material properties (inhomogeneities). When nothing is known about the kinematics of a system, both causes might contribute to the effect. This is because the Doppler effects, including redshift, are ordered depending on the measuring rod used in consecutive governing equations (the frames). There is a symmetry between a sufficiently large universe and a sufficiently small multiverse, and a parallel ordering of measuring rods. The observability of a sufficiently large universe or sufficiently small multiverses implies the existence of an observer neither too large nor too small. A humanoidal or non-humanoidal (e.g. insectoidal) being must be implemented, with an appropriate mental potential to stand as an observer, completing the existence of an observable universe. Complex scale and size entanglement has been shown to represent the common aspects of a measuring rod and invariantness in the frame of conservation laws and symmetry. A Doppler-like redshift effect in a motionless inhomogeneous universe is equivalent to a relativistic Doppler shift in a homogeneous Euclidean space, provided the conservation laws are preserved. Geophysical profiles of different physical properties taken by distant soundings bespeak multiverse’s fragmentation in geological time. Lunar and Martian layered sedimentary deposits are concerned as well.

Ultra-High Energy Cosmic Rays and Superheavy Particles in the Universe

Abstract: In this lecture we conjecture that the Ultra-High Energy Cosmic Rays (UHECR) with energies E>EGZK, where EGZK∼5⋅1019 eV is the Greisen-Zatsepin-Kuzmin cut-off energy of cosmic ray spectrum, may originate from decays of superheavy long-living X-particles populating the Universe thus providing a unique window into the very early epoch of the Universe, namely, that of preheating and reheating after inflation. These particles may constitute a considerable fraction of cold dark matter in the Universe. We argue that the unconventionally long lifetime of the superheavy particles, which should be in the range of 1010–1022 years, might require novel particle physics mechanisms of their decays, such as instantons. First of all I will describe a toy model illustrating the instanton scenario and then will describe the possible proper mechanism of creation of superheavy particles in the early Universe. It is my pleasure to emphasize that all I will talk about was done in collaboration with my friends V. A. Rubakov and...

Seeable universe and its accelerated expansion: an observational test

Abstract: From the equivalence principle, one gets the strength of the gravitational effect of a mass M on the metric at position r from it. It is proportional to the dimensionless parameter β 2=2GM/rc 2, which normally is ≪1. Here G is the gravitational constant, M the mass of the gravitating body, r the position of the metric from the gravitating body and c the speed of light. The seeable universe is the sphere, with center at the observer, having a size such that it shall contain all light emitted within it. For this to occur one can impose that the gravitational effect on the velocity of light at r is zero for the radial component, and non zero for the tangential one. Light is then trapped. The condition is given by the equality R g =2GM/c 2, where R g represents the radius of the seeable universe. It is the gravitational radius of the mass M. The result has been presented elsewhere as the condition for the universe to be treated as a black hole. According to present observations, for the case of our universe taken as flat (k=0), and the equation of state as p=−ρc 2, we prove here from the Einstein’s cosmological equations that the universe is expanding in an accelerated way as t 2, a constant acceleration as has been observed. This implies that the gravitational radius of the universe (at the event horizon) expands as t 2. Taking c as constant, observing the galaxies deep in space this means deep in time as ct, linear. Then, far away galaxies from the observer that we see today will disappear in time as they get out of the distance ct that is

The No-boundary probability for the universe starting at the top of the hill

Abstract: We use the Hartle-Hawking No-Boundary Proposal to make a comparison between the probabilities of the universe starting near, and at, the top of a hill in the effective potential. In the context of top-down cosmology, our calculation finds that the universe doesn't start at the top.

Detection of cmb anisotropy and spectral index constraints from cobe 3 year data

Abstract: By applying an exact pixel-space likelihood analysis on the 53 GHz and 90 GHz 3 year COBE DMR data, I find a 4σ detection of CMB anisotropies, and a spectral index of 0.95 ± 0.32, consistent with a flat or nearly flat primordial power spectrum. This provides the first glimpse of the seeds of later structure formation, together with the first direct test of one of the main predictions of inflation. Subject headings: cosmic microwave background — cosmology: observations — methods: statistical This century has seen a rapid development of the capabilities of telescopes, letting us probe the universe at ever greater depths. And since light travels to us at a finite speed, this increased reach in space translates into a reach in time as well, letting us see ever more deeply into the past. As we travel back in time, we see the universe growing more dense, and thus hotter. And since the structures we see in today’s universe must have grown by gravitational collapse, we expect that, traveling back in time, this collapse is undone, making the universe not only hot and dense, but also homogeneous. At last we reach a temperature where the hydrogen gas making up most of the universe becomes ionized and therefore starts scattering the light, letting us see no further. So as a backdrop for all the other objects we study in astronomy, there is a glowing, homogeneous wall of ionized gas, providing a snapshot of how the universe looked in its infancy. The radiation from this was first predicted by Gamov (1948), and observed by Penzias and Wilson (1965) as an isotropic excess of radiation in the microwave band, a discovery which earned them the Nobel prize. It was recently measured to be an almost perfect black-body(Smoot 1990), as expected from its thermal origins. It would, however, be problematic if this radiation were wholly isotropic; then there would be no seeds from which the structure of the current universe could grow. These anisotropies were first 2 detected by Smoot (1992) using the 1 year COBE dataset, but their statistical properties, expressed through the power spectrum, have only been investigated through approximate methods. It is critical to determine this power spectrum both because it sets the premises for later structure formation (though the parts of the power spectrum relevant for this remains out of reach), and because it appears as a product of inflation, letting us test the various inflationary scenarios and cosmological parameters.