arXiv subjects

Rodger I. Thompson

Publications and source records attributed to Rodger I. Thompson.

At least 19 recordsLinked to original sources

arXiv2024

Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology

This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to {\Lambda}CDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of {\Lambda}CDM makes the exploration of the nature of such universes particularly relevant.

gr-qc↗

arXiv2023

Evolution of Cosmological Parameters and Fundamental Constants in a Flat Quintessence Cosmology: A Dynamical Alternative to ΛCDM

The primary purpose of this work is the provision of accurate, analytic, evolutionary templates for cosmological parameters and fundamental constants in a dynamical cosmology. A flat quintessence cosmology with a dark energy potential that has the mathematical form of the Higgs potential is the specific cosmology and potential addressed in this work. These templates, based on the physics of the cosmology and potential are intended to replace the parameterizations currently used to determine the likelihoods of dynamical cosmologies. Acknowledging that, unlike ΛCDM, the evolutions are dependent on both the specific cosmology and the dark energy potential the templates are referred to as Specific Cosmology and Potential, SCP, templates. The requirements set for the SCP templates are that they must be accurate, analytic functions of an observable such as the scale factor or redshift. This is achieved through the utilization of a modified beta function formalism that is based on a physically motivated dark energy potential to calculate the beta function. The methodology developed here is designed to be adaptable to other cosmologies and dark energy potentials. The SCP templates are essential tools in determining the relative likelihoods of a range of dynamical cosmologies and potentials. An ultimate purpose is the determination whether dark energy is dynamical or static in a quantitative manner. It is suggested that the SCP templates calculated in this work can serve as fiducial dynamical templates in the same manner as ΛCDM serves for static dark energy.

astro-ph.CO↗

arXiv2022

Dynamical templates for comparison to Lambda CDN: Static or dynamical dark energy?

This study forges new tools to discriminate between dynamical and static dark energy. It provides accurate evolutionary templates of dynamical cosmological parameters and fundamental constants as analytic functions of the scale factor. They are designed to replace the commonly used parameterizations in likelihood calculations with evolutionary templates based on the physics of specific dynamical cosmologies and dark energy potentials. Thus they are termed Cosmology and Potential Specific, CPS, templates. A suite of CPS templates are calculated for a flat quintessence cosmology with a dark energy potential of the same mathematical form as the Higgs potential. This Higgs inspired, HI, polynomial potential produces a rich set of evolutions unlike most monomial potentials. The study produces CPS templates that are analytic functions of the scale factor. It uses a recently developed beta function formalism that provides a differential function for the scalar in terms of the scale factor. This establishes a methodology for easily producing CPS templates for other dark energy potentials and cosmologies to determine the likelihoods of dynamical cosmologies relative to Lambda CDM. The study also examines the evolution of fundamental constants such as the proton to electron mass ratio and the fine structure constant involving an intersection between particle physics and cosmology. Appendix A displays an abridged suite of CPS templates for flat quintessence and the HI dark energy potential.

astro-ph.CO↗

arXiv2019

Testing bound dark energy with cosmological parameter and fundamental constant evolution

A new bound dark energy, BDE, cosmology has been proposed where the dark energy is the binding energy between light meson fields that condense a few tens of years after the big bang. It is reported that the correct dark energy density emerges using particle physics without fine tuning. This alone makes the BDE cosmology worthy of further investigation. This work looks at the late time BDE predictions of the evolution of cosmological parameters and the values of fundamental constants to determine whether the cosmology's predictions are consistent with observation. The work considers the time period between a scale factor of 0.1 and 1.0. A model BDE cosmology is considered with current day values of the cosmological parameters well within the observational limits. The calculations use three different values of the current day dark energy equation of state close to minus one. All three cases produce evolutions of the cosmological parameters and fundamental constants consistent with the observational constraints. Analytic relations between the BDE and cosmological parameters are developed to insure a consistent set of parameters.

astro-ph.CO↗

arXiv2018

Beta Function Quintessence Cosmological Parameters and Fundamental Constants II: Exponential and Logarithmic Dark Energy Potentials

This paper uses the beta function formalism to extend the analysis of quintessence cosmological parameters to the logarithmic and exponential dark energy potentials. The previous paper (Thompson 2018) demonstrated the formalism using power and inverse power potentials. The essentially identical evolution of the Hubble parameter for all of the quintessence cases and LambdaCDM is attributed to the flatness of the quintessence dark energy potentials in the dark energy dominated era. The Hubble parameter is therefore incapable of discriminating between static and dynamic dark energy. Unlike the other three potentials considered in the two papers the logarithmic dark energy potential requires a numerical integration in the formula for the superpotential rather than being an analytic function. The dark energy equation of state and the fundamental constants continue to be good discriminators between static and dynamical dark energy. A new analysis of quintessence with all four of the potentials relative the swampland conjectures indicates that the conjecture on the change in the scalar field is satisfied but that the conjecture on the change of the potential is not.

astro-ph.CO↗

arXiv2018

Beta Function Quintessence Cosmological Parameters and Fundamental Constants I: Power and Inverse Power Law Dark Energy Potentials

This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar $ϕ$ with respect to the natural log of the scale factor $a$, $β(ϕ)=\frac{d ϕ}{d \ln(a)}$. Once the beta function is specified, modulo a boundary condition, the evolution of the scalar $ϕ$ as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated "beta potential" is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are that are not calculable using only the model action. As an example this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that $Λ$CDM is part of the family of quintessence cosmology power law potentials with a power of zero.

astro-ph.CO↗

arXiv2017

The Relation Between Fundamental Constants and Particle Physics Parameters

The observed constraints on the variability of the proton to electron mass ratio $μ$ and the fine structure constant $α$ are used to establish constraints on the variability of the Quantum Chromodynamic Scale and a combination of the Higgs Vacuum Expectation Value and the Yukawa couplings. Further model dependent assumptions provide constraints on the Higgs VEV and the Yukawa couplings separately. A primary conclusion is that limits on the variability of dimensionless fundamental constants such as $μ$ and $α$ provide important constraints on the parameter space of new physics and cosmologies.

astro-ph.CO↗

arXiv2017

Fundamental Constant Observational Bounds on the Variability of the QCD Scale

Many physical theories beyond the Standard Model predict time variations of basic physics parameters. Direct measurement of the time variations of these parameters is very difficult or impossible to achieve. By contrast, measurements of fundamental constants are relatively easy to achieve, both in the laboratory and by astronomical spectra of atoms and molecules in the early universe. In this work measurements of the proton to electron mass ratio $μ$ and the fine structure constant $α$ are combined to place mildly model dependent limits on the fractional variation of the Quantum Chromodynamic Scale and the sum of the fractional variations of the Higgs Vacuum Expectation Value and the Yukawa couplings on time scales of more than half the age of the universe. The addition of another model parameter allows the fractional variation of the Higgs VEV and the Yukawa couplings to be computed separately. Limits on their variation are found at the level of less than $5 \times 10^{-5}$ over the past seven gigayears. A model dependent relation between the expected fractional variation of $α$ relative to $μ$ tightens the limits to $10^{-7}$ over the same time span. Limits on the present day rate of change of the constants and parameters are then calculated using slow roll quintessence. A primary result of this work is that studies of the dimensionless fundamental constants such as $α$ and $μ$, whose values depend on the values of the physics parameters, are excellent monitors of the limits on the time variation of these parameters.

astro-ph.CO↗

arXiv2016

Fundamental Constants as Monitors of the Universe

Astronomical observations have a unique ability to determine the laws of physics at distant times in the universe. They, therefore, have particular relevance in answering the basic question as to whether the laws of physics are invariant with time. The dimesionless fundamental constants, such as the proton to electron mass ratio and the fine structure constant are key elements in the investigation. If they vary with time then the answer is clearly that the laws of physics are not invariant with time and significant new physics must be developed to describe the universe. Limits on their variance, on the other hand, constrains the parameter space available to new physics that requires a variation with time of basic physical law. There are now observational constraints on the time variation of the proton to electron mass ratio mu at the 1.E-7 level. Constraints on the variation of the fine structure constant alpha are less rigorous, 1E-5, but are imposed at higher redshift. The implications of these limits on new cosmologies that require rolling scalar fields has already had its first investigations. Here we address the implications on basic particle physics. The proton to electron mass ratio is obviously dependent on the particle physics parameters that set the mass of the proton and the electron. To first order the ratio is dependent on a combination of the Quantum Chromodynamic scale, the Yukawa couplings, and the Higgs Vacuum Expectation Value. Here that relationship is quantitative defined for the first time. When coupled with previous determinations of the relation of the fine structure constant to the same parameters two constraints exist on the fractional variation of these parameters with time. A third independent constraint involving only the three parameters could set the stage for constraints on their individual fractional variation.

astro-ph.CO↗

arXiv2013

Confronting Cosmology and New Physics with Fundamental Constants

The values of the fundamental constants such as $μ= m_P/m_e$, the proton to electron mass ratio and $α$, the fine structure constant, are sensitive to the product $\sqrt{ζ_x^2(w+1)}$ where $ζ_x$ is a coupling constant between a rolling scalar field responsible for the acceleration of the expansion of the universe and the electromagnetic field with x standing for either $μ$ or $α$. The dark energy equation of state $w$ can assume values different than $-1$ in cosmologies where the acceleration of the expansion is due to a scalar field. In this case the value of both $μ$ and $α$ changes with time. The values of the fundamental constants, therefore, monitor the equation of state and are a valuable tool for determining $w$ as a function of redshift. In fact the rolling of the fundamental constants is one of the few definitive discriminators between acceleration due to a cosmological constant and acceleration due to a quintessence rolling scalar field. $w$ is often given in parameterized form for comparison with observations. In this manuscript the predicted evolution of $μ$, is calculated for a range of parameterized equation of state models and compared to the observational constraints on $Δμ/ μ$. We find that the current limits on $Δμ/ μ$ place significant constraints on linear equation of state models and on thawing models where $w$ deviates from $-1$ at late times. They also constrain non-dynamical models that have a constant $w$ not equal to $-1$. These constraints are an important compliment to geometric tests of $w$ in that geometric tests are sensitive to the evolution of the universe before the epoch of observation while fundamental constants are sensitive to the evolution of the universe after the observational epoch. Abstract truncated.

astro-ph.CO↗

arXiv2013

A new substantive proton to electron mass ratio constraint on rolling scalar field cosmologies

New PKS1830-211 radio frequency observations of methanol at a redshift of 0.88582 have established the most stringent limits on changes in the proton to electron mass ratio mu to date. The observations place the limit of (delta mu)/mu </= (0.0 +/- 1.0) x 10^{-7} which is approximately a factor of four lower than the previous lowest limit at a redshift of 0.6742. This stringent limit at a look back time of roughly half the age of the universe has profound implications for rolling scalar field cosmologies and the new physics that they require. Many of these cosmologies invoke a scalar field phi that is also coupled to the electromagnetic field causing the values of the fundamental constants, mu and the fine structure constant alpha to roll with time. If the lowest expected value of the coupling to mu, zeta_{mu}$ is invoked the new limit requires a limit on the dark energy equation of state parameter w such that w+1 </= 0.001 at a redshift of 0.88582. This eliminates almost all of the expected parameter space for such cosmologies and new physics that have a coupling to the electromagnetic field. In these cases the limit requires that w must be extremely close to -1 for the last half of the age of the universe or that the coupling of the rolling scalar field to mu and the electromagnetic field be significantly below or at the limit of its expected range. The new observations solidify the role of fundamental constants in providing probes of the possible cosmologies and new physics to explain the acceleration of the expansion of the universe.

astro-ph.CO↗

arXiv2012

Constraining cosmologies with fundamental constants I. Quintessence and K-Essence

Many cosmological models invoke rolling scalar fields to account for the observed acceleration of the expansion of the universe. These theories generally include a potential V(phi) which is a function of the scalar field phi. Although V(phi) can be represented by a very diverse set of functions, recent work has shown the under some conditions, such as the slow roll conditions, the equation of state parameter w is either independent of the form of V(phi) or is part of family of solutions with only a few parameters. In realistic models of this type the scalar field couples to other sectors of the model leading to possibly observable changes in the fundamental constants such as the fine structure constant alpha and the proton to electron mass ratio mu. This paper explores the limits this puts on the validity of various cosmologies that invoke rolling scalar fields. We find that the limit on the variation of mu puts significant constraints on the product of a cosmological parameter w+1 times a new physics parameter zeta_mu^2, the coupling constant between mu and the rolling scalar field. Even when the cosmologies are restricted to very slow roll conditions either the value of zeta_mu must be at the lower end of or less than its expected values or the value of w+1 must be restricted to values vanishingly close to 0. This implies that either the rolling scalar field is very weakly coupled with the electromagnetic field, small zeta_mu, very weakly coupled with gravity, w+1 ~ 0 or both. These results stress that adherence to the measured invariance in mu is a very significant test of the validity of any proposed cosmology and any new physics it requires. The limits on the variation of mu also produces a significant tension with the reported changes in the value of alpha.

astro-ph.CO↗

arXiv2012

Constraints on quintessence and new physics from fundamental constant

Changes in the values of the fundamental constants mu, the proton to electron mass ratio, and alpha, the fine structure constant due to rolling scalar fields have been discussed both in the context of cosmology and in new physics such as Super Symmetry (SUSY) models. This article examines the changes in these fundamental constants in a particular example of such fields, freezing and thawing slow roll quintessence. Constraints are placed on the product of a cosmological quantity, w, the equation of state parameter, and the square of the coupling constants for mu and alpha with the field, zeta_x, x = mu,alpha, using the existing observational limits on the values of Delta x/x. Various examples of slow rolling quintessence models are used to further quantify the constraints. Some of the examples appear to be rejected by the existing data which strongly suggests that conformation to the values of the fundamental constants in the early universe is a standard test that should be applied to any cosmological model or suggested new physics.

astro-ph.CO↗

arXiv2009

An Observational Determination of the Proton to Electron Mass Ratio in the Early Universe

In an effort to resolve the discrepancy between two measurements of the fundamental constant mu, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in the earlier studies. Our analysis of the molecular hydrogen absorption lines in archival VLT/UVES spectra of the damped Lyman alpha systems in the QSOs Q0347-383 and Q0405-443 yields a combined measurement of a (Delta mu)/mu value of (-7 +/- 8) x 10^{-6}, consistent with no change in the value of mu over a time span of 11.5 gigayears. Here we define (Delta mu) as (mu_z - mu_0) where mu_z is the value of mu at a redshift of z and mu_0 is the present day value. Our null result is consistent with the recent measurements of King et al. 2009, (Delta mu)/u = (2.6 +/- 3.0) x 10^{-6}, and inconsistent with the positive detection of a change in mu by Reinhold et al. 2006. Both of the previous studies and this study are based on the same data but with differing analysis methods. Improvements in the wavelength calibration over the UVES pipeline calibration is a key element in both of the null results. This leads to the conclusion that the fundamental constant mu is unchanged to an accuracy of 10^{-5} over the last 80% of the age of the universe, well into the matter dominated epoch. This limit provides constraints on models of dark energy that invoke rolling scalar fields and also limits the parameter space of Super Symmetric or string theory models of physics. New instruments, both planned and under construction, will provide opportunities to greatly improve the accuracy of these measurements.

astro-ph.CO↗

arXiv2008

Alternative Data Reduction Procedures for UVES: Wavelength Calibration and Spectrum Addition

This paper addresses alternative procedures to the ESO supplied pipeline procedures for the reduction of UVES spectra of two quasar spectra to determine the value of the fundamental constant mu = Mp/Me at early times in the universe. The procedures utilize intermediate product images and spectra produced by the pipeline with alternative wavelength calibration and spectrum addition methods. Spectroscopic studies that require extreme wavelength precision need customized wavelength calibration procedures beyond that usually supplied by the standard data reduction pipelines. An example of such studies is the measurement of the values of the fundamental constants at early times in the universe. This article describes a wavelength calibration procedure for the UV-Visual Echelle Spectrometer on the Very Large Telescope, however, it can be extended to other spectrometers as well. The procedure described here provides relative wavelength precision of better than 3E-7 for the long-slit Thorium-Argon calibration lamp exposures. The gain in precision over the pipeline wavelength calibration is almost entirely due to a more exclusive selection of Th/Ar calibration lines.

astro-ph↗

arXiv2008

Super Star Clusters in SBS0335-052E

As one of the lowest metallicity star forming galaxies, with a nucleus of several super star clusters, SBS0335-052E is the subject of substantial current study. We present new insights on this galaxy based on new and archival high spatial resolution NICMOS and ACS images. We provide new measurements and limits on the size of several of the SSCs. The images have sufficient resolution to divide the star formation into compact regions and newly discovered extended regions, indicating a bi-modal form of star formation. The star formation regions are dated via the equivalent width of the Pa alpha emission and we find that two of the extended regions of star formation are less than 10 million years old. Our previous finding that stellar winds confine the photo-ionizing flux to small regions around individual stars is consistent with the new observations. This may allow planet formation in what would traditionally be considered a harsh environment and has implications for the number of planets around globular cluster stars. In addition the images pinpoint the regions of H2 emission as located in, but not at the center of the two star forming super star clusters, S1 and S2.

astro-ph↗

arXiv2008

NICMOS Measurements of the Near Infrared Background

This paper addresses the nature of the near infrared background. We investigate whether there is an excess background at 1.4 microns, what is the source of the near infrared background and whether that background after the subtraction of all known sources contains the signature of high redshift objects (Z > 10). Based on NICMOS observations in the Hubble Ultra Deep Field and the Northern Hubble Deep Field we find that there is no excess in the background at 1.4 microns and that the claimed excess is due to inaccurate models of the zodiacal background. We find that the near infrared background is now spatially resolved and is dominated by galaxies in the redshift range between 0.5 and 1.5. We find no signature than can be attributed to high redshift sources after subtraction of all known sources either in the residual background or in the fluctuations of the residual background. We show that the color of the fluctuations from both NICMOS and Spitzer observations are consistent with low redshift objects and inconsistent with objects at redshifts greater than 10. It is most likely that the residual fluctuation power after source subtraction is due to the outer regions of low redshift galaxies that are below the source detection limit and therefore not removed during the source subtraction.

astro-ph↗

arXiv2007

Evidence for a Z < 8 Origin of the Source Subtracted Near Infrared Background

This letter extends our previous fluctuation analysis of the near infrared background at 1.6 microns to the 1.1 micron (F110W) image of the Hubble Ultra Deep field. When all detectable sources are removed the ratio of fluctuation power in the two images is consistent with the ratio expected for faint, z<8, sources, and is inconsistent with the expected ratio for galaxies with z>8. We also use numerically redshifted model galaxy spectral energy distributions for 50 and 10 million year old galaxies to predict the expected fluctuation power at 3.6 microns and 4.5 microns to compare with recent Spitzer observations. The predicted fluctuation power for galaxies at z = 0-12 matches the observed Spitzer fluctuation power while the predicted power for z>13 galaxies is much higher than the observed values. As was found in the 1.6 micron (F160W) analysis the fluctuation power in the source subtracted F110W image is two orders of magnitude below the power in the image with all sources present. This leads to the conclusion that the 0.8--1.8 micron near infrared background is due to resolved galaxies in the redshift range z<8, with the majority of power in the redshift range of 0.5--1.5.

astro-ph↗