Model Selection based on the Angular-Diameter Distance to the Compact Structure in Radio Quasars

Of all the distance and temporal measures in cosmology, the angular-diameter distance, d_A(z), uniquely reaches a maximum value at some finite redshift z_max and then decreases to zero towards the big bang. This effect has been difficult to observe due to a lack of reliable, standard rulers, though refinements to the identification of the compact structure in radio quasars may have overcome this deficiency. In this Letter, we assemble a catalog of 140 such sources with 0 < z < 3 for model selection and the measurement of z_max. In flat LCDM, we find that Omega_m= 0.24^{+0.1}_{-0.09}, fully consistent with Planck, with z_max=1.69. Both of these values are associated with a d_A(z) indistinguishable from that predicted by the zero active mass condition, rho+3p=0, in terms of the total pressure p and total energy density rho of the cosmic fluid. An expansion driven by this constraint, known as the R_h=ct universe, has z_max=1.718, which differs from the measured value by less than ~1.6%. Indeed, the Bayes Information Criterion favours R_h=ct over flat LCDM with a likelihood of ~81% versus 19%, suggesting that the optimized parameters in Planck LCDM mimic the constraint p=-rho/3.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in EP

The AGN Hubble Diagram and Its Implications for Cosmology

We use a recently proposed luminosity distance measure for relatively nearby active galactic nuclei (AGNs) to test the predicted expansion of the Universe in the R_h=ct and LCDM cosmologies. This comparative study is particularly relevant to the question of whether or not the Universe underwent a transition from decelerated to accelerated expansion, which is believed to have occurred---on the basis of Type Ia SN studies---within the redshift range (0 < z < 1.3) that will eventually be sampled by these objects. We find that the AGN Hubble Diagram constructed from currently available sources does not support the existence of such a transition. While the scatter in the AGN data is still too large for any firm conclusions to be drawn, the results reported here nonetheless somewhat strengthen similar results of comparative analyses using other types of source. We show that the Akaike, Kullback, and Bayes Information Criteria all consistently yield a likelihood of ~84-96% that R_h=ct is closer to the "true" cosmology than LCDM is, though neither model adequately accounts for the data, suggesting an unnaccounted-for source of scatter.Comment: 9 pages, 3 figures. Accepted for publication in Astrophysics and Space Scienc

Degravitation and the Cascading DGP Model

We consider the 6D Cascading DGP model, a braneworld model which is a promising candidate to realize the phenomenon of the degravitation of vacuum energy. Focusing on a recently proposed thin limit description of the model, we study solutions where the induced metric on the codimension-2 brane is of the de Sitter form. While these solutions have already been recovered in the literature imposing by hand the bulk to be flat, we show that it is possible to derive them without making this assumption, by solving a suitably chosen subset of the bulk equations.Comment: 9 pages, 1 figure, PDFLatex, Special Issue Estate Quantistica Conference, published versio

On Recent Claims Concerning the R_h=ct Universe

The R_h=ct Universe is a Friedmann-Robertson-Walker (FRW) cosmology which, like LCDM, assumes the presence of dark energy in addition to (baryonic and non-luminous) matter and radiation. Unlike LCDM, however, it is also constrained by the equation of state (EOS) p=-rho/3, in terms of the total pressure p and energy density rho. One-on-one comparative tests between R_h=ct and LCDM have been carried out using over 14 different cosmological measurements and observations. In every case, the data have favoured R_h=ct over the standard model, with model selection tools yielding a likelihood ~90-95% that the former is correct, versus only ~5-10% for the latter. In other words, the standard model without the EOS p=-rho/3 does not appear to be the optimal description of nature. Yet in spite of these successes---or perhaps because of them---several concerns have been published recently regarding the fundamental basis of the theory itself. The latest paper on this subject even claims---quite remarkably---that R_h=ct is a vacuum solution, though quite evidently rho is not 0. Here, we address these concerns and demonstrate that all criticisms leveled thus far against R_h=ct, including the supposed vacuum condition, are unwarranted. They all appear to be based on incorrect assumptions or basic theoretical errors. Nevertheless, continued scrutiny such as this will be critical to establishing R_h=ct as the correct description of nature.Comment: 9 pages (0 figures). Accepted for publication in MNRA

A Cosmological basis for E=mc^2

The Universe has a gravitational horizon with a radius R_h=c/H coincident with that of the Hubble sphere. This surface separates null geodesics approaching us from those receding, and as free-falling observers within the Friedmann-Lemaitre-Robertson-Walker spacetime, we see it retreating at proper speed c, giving rise to the eponymously named cosmological model R_h=ct. As of today, this cosmology has passed over 25 observational tests, often better than LCDM. The gravitational/Hubble radius R_h therefore appears to be highly relevant to cosmological theory, and in this paper we begin to explore its impact on fundamental physics. We calculate the binding energy of a mass m within the horizon and demonstrate that it is equal to mc^2. This energy is stored when the particle is at rest near the observer, transitioning to a purely kinetic form equal to the particle's escape energy when it approaches R_h. In other words, a particle's gravitational coupling to that portion of the Universe with which it is causally connected appears to be the origin of rest-mass energy.Comment: 5 pages. Accepted for publication in IJMP-

A Solution to the electroweak horizon problem in the R_h=ct universe

Particle physics suggests that the Universe may have undergone several phase transitions, including the well-known inflationary event associated with the separation of the strong and electroweak forces in grand unified theories. The accelerated cosmic expansion during this transition, at cosmic time t~10^{-36}-10^{-33} seconds, is often viewed as an explanation for the uniformity of the CMB temperature, T, which would otherwise have required inexplicable initial conditions. With the discovery of the Higgs particle, it is now quite likely that the Universe underwent another (electroweak) phase transition, at T=159.5 +/- 1.5 GeV---roughly ~10^{-11} seconds after the big bang. During this event, the fermions gained mass and the electric force separated from the weak force. There is currently no established explanation, however, for the apparent uniformity of the vacuum expectation value of the Higgs field which, like the uniformity in T, gives rise to its own horizon problem in standard LCDM cosmology. We show in this paper that a solution to the electroweak horizon problem may be found in the choice of cosmological model, and demonstrate that this issue does not exist in the alternative Friedmann-Robertson-Walker cosmology known as the R_h=ct universe.Comment: 6 pages, 2 figures. Accepted for publication in the European Physical Journal

Comparison of energy-wood and pulpwood thinning systems in young birch stands

In early thinnings, a profitable alternative to pulpwood could be to harvest whole trees as energy-wood. In theoretical analyses, we compared the extractible volumes of energy-wood and pulpwood, and their respective gross values in differently aged stands of early birch thinnings at varying intensities of removal. In a parallel field experiment, we compared the productivity at harvest of either pulpwood or energy-wood, and the profitability when the costs of harvesting and forwarding were included. The theoretical analyses showed that the proportion of the total tree biomass removed as pulpwood increased with increasing thinning intensity and stem size. The biomass volume was 1.5–1.7 times larger than the pulpwood volume for a 13.9 diameter at breast height stand and 2.0–3.5 times larger for a 10.4 diameter at breast height stand. In the field experiment, the harvested volume per hectare of energy-wood was almost twice as high as the harvest of pulpwood. The harvesting productivity (trees Productive harvesting Work Time-hour−1) was 205 in the energy-wood and 120 in the pulpwood treatment. The pulpwood treatment generated a net loss, whereas the energy-wood treatment generated a net income, the average difference being €595 ha−1. We conclude that in birch-dominated early thinning stands, at current market prices, harvesting energy-wood is more profitable than harvesting pulpwood

Angular Correlation of the CMB in the R_h=ct Universe

The emergence of several unexpected large-scale features in the cosmic microwave background (CMB) has pointed to possible new physics driving the origin of density fluctuations in the early Universe and their evolution into the large-scale structure we see today. In this paper, we focus our attention on the possible absence of angular correlation in the CMB anisotropies at angles larger than ~60 degrees, and consider whether this feature may be the signature of fluctuations expected in the R_h=ct Universe. We calculate the CMB angular correlation function for a fluctuation spectrum expected from growth in a Universe whose dynamics is constrained by the equation-of-state p=-rho/3, where p and rho are the total pressure and density, respectively. We find that, though the disparity between the predictions of LCDM and the WMAP sky may be due to cosmic variance, it may also be due to an absence of inflation. The classic horizon problem does not exist in the R_h=ct Universe, so a period of exponential growth was not necessary in this cosmology in order to account for the general uniformity of the CMB (save for the aforementioned tiny fluctuations of 1 part in 100,000 in the WMAP relic signal. We show that the R_h=ct Universe without inflation can account for the apparent absence in CMB angular correlation at angles > 60 degrees without invoking cosmic variance, providing additional motivation for pursuing this cosmology as a viable description of nature.Comment: Accepted for publication in Astronomy & Astrophysic