Particle horizon

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

The Origin of the Universe as Revealed Through the Polarization of the Cosmic Microwave Background

Abstract: Modern cosmology has sharpened questions posed for millennia about the origin of our cosmic habitat. The age-old questions have been transformed into two pressing issues primed for attack in the coming decade: • How did the Universe begin? The current cosmological paradigm successfully explains how the majestic structure observed in the Universe today grew out of small ripples in the density of matter. What is the physical origin of the primordial seeds which are ultimately responsible for the existence of galaxies, stars, planets, and people in the Universe? It is natural to expect (and many theories predict) that whatever produced the density ripples also produced gravity waves – undulations in the fabric of space-time which travel at the speed of light. Does the Universe contain a spectrum of primordial gravity waves produced by the same mechanism which produced the ripples in the density? • What physical laws govern the Universe at the highest energies? All explanations for the seeds of structure rely on physics at energies far beyond those probed by, e.g., CERN’s Large Hadron Collider. Experiments probing these seeds therefore may provide information about new particles, forces, or perhaps even extra dimensions of space that are visible only at the highest energies. The clearest window onto these questions is the pattern of polarization in the Cosmic Microwave Background (CMB), which is uniquely sensitive to primordial gravity waves. A detection of the special pattern produced by gravity waves would be not only an unprecedented discovery, but also a direct probe of physics at the earliest observable instants of our Universe. Experiments which map CMB polarization over the coming decade will lead us on our first steps towards answering these age-old questions.

A simple all-time model for the birth, big bang, and death of the universe

Abstract: We model the standard ΛCDM model of the universe by the spatially flat FLRW line element dsΛCDM2 = −c2dt2 + 8πGρm,0 Λc22/3 sinh 1 23Λct4/3dσ Euclid2 which we extend for all time t ∈ (−∞,∞). Although there is a cosmological singularity at the big bang t = 0, since the spatial part of the metric collapses to zero, nevertheless, this line element is defined for all time t ∈ (−∞,∞), is C∞ for all t≠0, is C1 differentiable at t = 0, and is non-degenerate and solves Friedmann’s equation for all t≠0. Thus, we can use this extended line element to model the universe from its past-asymptotic initial state dS4− at t = −∞, through the big bang at t = 0, and onward to its future-asymptotic final state dS4+ at t = ∞. Since in this model the universe existed before the big bang, we conclude that (1) the universe was not created de novo at the big bang and (2) cosmological singularities such as black holes or the big bang itself need not be an end to spacetime. Our model shows that the universe was asymptotically created de novo out of nothing at t = −∞ from an unstable vacuum negative half de Sitter dsdS4−2 initial state and then dies asymptotically at t = ∞ as the stable positive half de Sitter dsdS4+2 final state. Since the de Sitter states are vacuum matter states, our model shows that the universe was created from nothing at t = −∞ and dies at t = ∞ to nothing.

The Static Universe Hypothesis: Theoretical Basis and Observational Tests of the Hypothesis

Abstract: From the axiom of the unrestricted repeatability of all experiments, Bondi and Gold argued that the universe is in a stable, self-perpetuating equilibrium state. This concept generalizes the usual cosmological principle to the perfect cosmological principle in which the universe looks the same from any location at any time. Consequently, I hypothesize that the universe is static and in an equilibrium state (non-evolving). New physics is proposed based on the concept that the universe is a pure wave system. Based on the new physics and assuming a static universe, processes are derived for the Hubble redshift and the cosmic background radiation field. Then, following the scientific method, I test deductions of the static universe hypothesis using precise observational data primarily from the Hubble Space Telescope. Applying four different global tests of the space-time metric, I find that the observational data consistently fits the static universe model. The observational data also show that the average absolute magnitudes and physical radii of first-rank elliptical galaxies have not changed over the last 5 to 15 billion years. Because the static universe hypothesis is a logical deduction from the perfect cosmological principle and the hypothesis is confirmed by the observational data, I conclude that the universe is static and in an equilibrium state.