arXiv subjects

Michael L. Smith

Publications and source records attributed to Michael L. Smith.

5 recordsLinked to original sources

arXiv2021

Re-evaluation of $Ω_k$ of the normalised Friedmann-Lema\^ıtre-Robertson-Walker model: Implications for Hubble constant determinations

The description of spacetime is an fundamental problem of cosmology. We explain why the current assignments of spacetime geometries for $Ω_k$ of the Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) model are probably incorrect and suggest more useful descriptions. We show that $Ω_k$ represents not only curvature but the influence of matter density on the extent of spacetime between massive objects. Recent analyses of supernovae type Ia (SNe Ia) and HII/GEHR data with the FLRW model present the best fits with a small value for $Ω_m$ and a large $Ω_k$. These results are consistent with our Universe exhibiting sparse matter density and quasi-Euclidean geometry and the small $Ω_m$ value agrees with Big Bang nucleosynthesis calculations. We suggest the geometry of our current Universe is better described by a value for $Ω_k\approx$1 rather than 0. As an example we extend the FLRW model towards the Big Bang and discover a simple explanation of how matter creation developed into the currently geometrically flat Universe with sparse, homogeneous, isotropic matter and energy distributions. Assigning $Ω_k\approx1$ to describe quasi-Euclidean spacetime geometry is also useful for estimating $H_0$ and should help resolve the tension surrounding current estimates by different investigators.

physics.gen-ph↗

arXiv2018

Adiabatic expansion of polytropic universe with varying cosmological constant: Models tested with observational data

We use two large collections of observational data of supernovae type Ia (SNe Ia) to investigate the polytropic Universe including the situation with a varying cosmological constant; details of our new derivations are presented. We examine the fitness of our new models of a polytropic Universe with two sets of SNe Ia data to test if these are better descriptions than the current standard model of cosmology. Beginning with the established relationships for polytropic matter we derive new equations describing the influence of polytropic matter on the expanding Universe including the situation with a varying cosmological constant. When the models derived here are tested with large sets of supernovae type I a data we find a significant influence of polytropic matter on the state of our expanding Universe. We find that one of our models with a varying Λ describes the SNe Ia data significantly better than the, ΛCDM, standard model.

gr-qc↗

arXiv2015

Elliptical Solutions to the Standard Cosmology Model with Realistic Values of Matter Density

We have examined a solution to the FRW model of the Einstein and de Sitter Universe, often termed the standard model of cosmology, using wide values for the normalized cosmological constant Omega_L and spacetime curvature Omega_k with proposed values of normalized matter density. These solutions were evaluated using a combination of the third type of elliptical equations and were found to display critical points for redshift z, between 1 and 3, when Omega_L is positive. These critical points occur at values for normalized cosmological constant higher than those currently thought important, though we find this solution interesting because the Omega_L term may increase in dominance as the Universe evolves bringing this discontinuity into importance. We also find positive Omega_L tends towards attractive at values of z which are commonly observed for distant galaxies.

gr-qc↗

arXiv2014

The Cosmological Constant Constrained with Union2.1 Supernovae Type Ia Data. Derivation and evaluation of several FRW and Carmeli models presenting underwhelming support for the standard model

We derive several, detailed relationships in terms of the Friedmann, Robertson, Walker (FRW) generalization which describe the Universe during both the radiation and matter dominated epochs. We explicitly provide for the influence of radiation, rather than burying this term within the matter term. Several models allow the cosmological constant (CC) to vary with universe expansion in differing manners. We evaluate these and other popular models including the $Λ$CDM({standard model}), quintessence as presented by Vishwakarma, Equation of State (EoS) and the Carmeli model with data from the 580 Union2.1 supernovae type Ia collection, using several minimization routines and find models built about the CC, the $Λ$CDM models, fare no better than those without.

astro-ph.CO↗

arXiv2006

Distribution of Matter from Singularity with Spherical Symmetry Using Fick Diffusion

A model is presented allowing calculation of energy and matter distribution in the Universe after expansion from singularity without introduction of expansion energy. Beginning with Fick's law of diffusion, we solve the Bessel function for spherical systems during expansion, presuming isotropic matter distribution in the Hubble flow. This function can be substituted with the Associated Legendre differential equation and when solved we discover useful parameters for those of energy and matter densities, diffusion and temperature. Though we can follow the decline of matter density over spacetime, we cannot suggest a precise value at singularity. This model may be useful though, as a starting point for modeling star formation rates, SFR, galaxy formation horizon lengths and regions devoid of matter where tracing the matter density decline over time is important.

astro-ph↗