Particle horizon

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

Age of the Universe, Average Deceleration Parameter and Possible Implications for the End of Cosmology

Abstract: A new expression to the total age of the Universe is derived in terms of the average deceleration parameter. This kinematic result holds regardless of the curvature of the universe as well as of the underlying gravity theory. It remains valid even in the context of brane-world motivated cosmologies. Since the present age parameter of the Universe is accurately adjusted to $H_0t_0 = 1$, it is shown that the time averaged value of the deceleration parameter is zero. This also means that the cosmic age today is exactly the one predicted by a relativistic flat cosmological model filled by K-matter, a fluid satisfying the equation of state $p = -{1/3}\rho$. By assuming the validity of this relation (in an average long time meaning), it is argued that the decelerating stages of the expansion must exactly be compensated by the accelerated phases, as if the observed Universe coasts forever. If this is true, the present accelerating stage must be followed by a subsequent decelerating phase as predicted by some recent scalar field and brane-world motivated cosmologies.

Graviton production as a measure of gravitational entropy in an isotropic universe

Abstract: The number of gravitons produced within the particle horizon of an isotropic universe describes the capacity of the gravitational field to create matter and is associated with the gravitational entropy. A geometrical expression for gravitational entropy in an isotropic universe is justified in this approach.

The Hubble Constant is a Measure of the Increase in the Energy of the Universe

Abstract: We postulate the universe to be the three dimensional surface volume of an expanding, hollow, four dimensional hypersphere, called the hyperverse. Using current measurements, we find that a hyperverse, whose surface volume matches the volume of the observable universe, has a radius of 27.7 billion light years, giving a radial expansion rate of twice the speed of light, and a circumferential expansion rate that matches the Hubble constant. We show that the Hubble constant is a measure of the increase in the energy of the universe, implying the hyperverse surface, our universe, is composed of energy. The 2c radial expansion both sets the speed limit in the universe, and is the basis of time. The hypersphere model provides a positively curved, and closed universe, and its 2c radial expansion rate, and circumferential expansion rate matching the Hubble expansion, give strong support that the universe is the 3D surface volume of an expanding 4D hypersphere.

Particle creation, inflation, and cosmic isotropy.

Abstract: Within the framework of homogeneous models of the Universe, inflation provides the simplest explanation for the present cosmic isotropy, and a Bianchi type-IX (mixmaster) model is the least prejudiced guess we can make about the state of the Universe before the inflationary phase. However, a mixmaster model would not inflate unless either shear or the radiation energy density are large enough. Particle creation enhances the radiation energy density and therefore enlarges the set of inflating initial conditions for the Universe.