260 research outputs found

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

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    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

    A Cosmological basis for E=mc^2

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    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

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    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

    Angular Correlation of the CMB in the R_h=ct Universe

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    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

    Physical Basis for the Symmetries in the Friedmann-Robertson-Walker Metric

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    Modern cosmological theory is based on the Friedmann--Robertson--Walker (FRW) metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein's equations owes its elegant and highly practical formulation to the cosmological principle and Weyl's postulate, upon which it is founded. However, there is physics behind such symmetries, and not all of it has yet been recognized. In this paper, we derive the FRW metric coefficients from the general form of the spherically symmetric line element and demonstrate that, because the co-moving frame also happens to be in free fall, the symmetries in FRW are valid only for a medium with zero active mass. In other words, the spacetime of a perfect fluid in cosmology may be correctly written as FRW only when its equation of state is rho+3p=0, in terms of the total pressure p and total energy density rho. There is now compelling observational support for this conclusion, including the Alcock--Paczynski test, which shows that only an FRW cosmology with zero active mass is consistent with the latest model-independent baryon acoustic oscillation data.Comment: 7 Pages. Final published versio
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