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Model-independent confirmation of a constant speed of light over cosmological distances

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

Recent attempts at measuring the variation of c using an assortment of standard candles and the redshift-dependent Hubble expansion rate inferred from the currently available catalog of cosmic chronometers have tended to show that the speed of light appears to be constant, at least up to z ∼ 2. A notable exception is the use of high-redshift UV + X-ray quasars, whose Hubble diagram seems to indicate a ∼ 2.7σ deviation of c from its value c0 (≡ 2.99792458 × 1010 cm s−1) on Earth. We show in this paper, however, that this anomaly is due to an error in the derived relation between the luminosity distance, DL, and H(z) when c is allowed to vary with redshift, and an imprecise calibration of the quasar catalog. When these deficiences are addressed correctly, one finds that c/c0 = 0.95 ± 0.14 in the redshift range 0 . z . 2, fully consistent with zero variation within the measurement errors. Copyright © 2023, The Authors. All rights reserved.

关键词： Cosmology

A Resolution of the Monopole Problem in the Rh = ct Universe

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

Spontaneous symmetry breaking in grand unified theories is thought to have produced an exceedingly large number of magnetic monopoles in the early Universe. In the absence of suppression or annihilation, these very massive particles should be dominating the cosmic energy budget today, but none has ever been found. Inflation was invented in part to dilute their number, thereby rendering their density undetectable by current instruments. Should the inflationary paradigm not survive, however, the ensuing disagreement between theory and observation would constitute a cosmological ‘monopole problem’ and create further tension for any extension to the standard model of particle physics. But as is also true for all horizon problems, a monopole overabundance emerges only in cosmologies with an initial period of deceleration. We show that the alternative Friedmann-Lemaître-Robertson-Walker cosmology known as the Rh = ct universe completely eliminates all such anomalies rather trivially and naturally, without the need for an inflated expansion. We find that the monopole energy density today would be completely undetectable in Rh = ct. Evidence continues to grow that the zero active mass condition from general relativity ought to be an essential ingredient in ΛCDM. © 2023, CC BY.

关键词： Cosmology

Tantalizing new physics from the cosmic purview

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arXiv 2019年

作者： Melia, Fulvio Department of Physics Applied Math Program Department of Astronomy University of Arizona AZ85721 United States

The emergence of a highly improbable coincidence in cosmological observations speaks to a remarkably simple cosmic expansion. Compelling evidence now suggests that the Universe’s gravitational horizon, coincident with the better known Hubble sphere, has a radius improbably equal to the distance light could have travelled since the Big Bang. The confirmation of this unexpected result would undoubtedly herald the influence of new physics, yet appears to be unavoidable after a recent demonstration that the Friedmann-Lemaître-Robertson-Walker metric is valid only for the so-called zero active mass equation of state. As it turns out, a cosmic fluid with this property automatically produces the aforementioned equality, leaving little room for a cosmological constant. The alternative—a dynamical dark energy—would suggest an extension to the standard model of particle physics, and a serious re-evaluation of the Universe’s early history. Copyright © 2019, The Authors. All rights reserved.

关键词： Equations of state

The Scale of Homogeneity in the Rh = ct Universe

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

Studies of the Universe’s transition to smoothness in the context of ΛCDM have all pointed to a transition radius no larger than ∼ 300 Mpc. These are based on a broad array of tracers for the matter power spectrum, including galaxies, clusters, quasars, the Ly-α forest and anisotropies in the cosmic microwave background. It is therefore surprising, if not anomalous, to find many structures extending out over scales as large as ∼ 2 Gpc, roughly an order of magnitude greater than expected. Such a disparity suggests that new physics may be contributing to the formation of large-scale structure, warranting a consideration of the alternative FLRW cosmology known as the Rh = ct universe. This model has successfully eliminated many other problems in ΛCDM. In this paper, we calculate the fractal (or Hausdorff) dimension in this cosmology as a function of distance, showing a transition to smoothness at ∼ 2.2 Gpc, fully accommodating all of the giant structures seen thus far. This outcome adds further observational support for Rh = ct over the standard model. © 2023, CC BY.

关键词： Cosmology

The Cosmic Timeline Implied by the JWST High-redshift Galaxies

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

The so-called 'impossibly early galaxy' problem, first identified via the Hubble Space Telescope's observation of galaxies at redshifts z > 10, appears to have been exacerbated by the more recent James Webb Space Telescope (JWST) discovery of galaxy candidates at even higher redshifts (z ∼ 17) which, however, are yet to be confirmed spectroscopically. These candidates would have emerged only ∼ 230 million years after the big bang in the context of ΛCDM, requiring a more rapid star formation in the earliest galaxies than appears to be permitted by simulations adopting the concordance model parameters. This time-compression problem would therefore be inconsistent with the age-redshift relation predicted by ΛCDM. Instead, the sequence of star formation and galaxy assembly would confirm the timeline predicted by the Rh = ct universe, a theoretically advanced version of ΛCDM that incorporates the 'zero active mass' condition from general relativity. This model has accounted for many cosmological data better than ΛCDM, and eliminates all of its inconsistencies, including the horizon and initial entropy problems. The latest JWST discoveries at z 14, if confirmed, would add further support to the idea that the Rh = ct universe is favored by the observation over the current standard model. © 2023, CC BY.

关键词： Galaxies

Ensemble Estimation of Distributional Functionals via k-Nearest Neighbors

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arXiv 2017年

作者： Moon, Kevin R. Sricharan, Kumar Hero, Alfred O. Genetics Department and Applied Math Program Yale University Xerox PARC EECS Department University of Michigan

The problem of accurate nonparametric estimation of distributional functionals (integral functionals of one or more probability distributions) has received recent interest due to their wide applicability in signal processing, information theory, machine learning, and statistics. In particular, k-nearest neighbor (nn) based methods have received a lot of attention due to their adaptive nature and their relatively low computational complexity. We derive the mean squared error (MSE) convergence rates of leave-one-out k-nn plug-in density estimators of a large class of distributional functionals without boundary correction. We then apply the theory of optimally weighted ensemble estimation to obtain weighted ensemble estimators that achieve the parametric MSE rate under assumptions that are competitive with the state of the art. The asymptotic distributions of these estimators, which are unknown for all other k-nn based distributional functional estimators, are also presented which enables us to perform hypothesis testing. Copyright © 2017, The Authors. All rights reserved.

关键词： Motion compensation

Model selection based on the angular-diameter distance to the compact structure in radio quasars

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arXiv 2018年

作者： Melia, F. Department of Physics Applied Math Program Department of Astronomy University of Arizona AZ85721 United States

–Of all the distance and temporal measures in cosmology, the angular-diameter distance, dA(z), uniquely reaches a maximum value at some finite redshift zmax 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 zmax. In flat ΛCDM, we find that Ωm = 0.24+0−0..109, fully consistent with Planck, with zmax = 1.69. Both of these values are associated with a dA(z) indistinguishable from that predicted by the zero active mass condition, ρ + 3p = 0, in terms of the total pressure p and total energy density ρ of the cosmic fluid. An expansion driven by this constraint, known as the Rh = ct universe, has zmax = 1.718, which differs from the measured value by less than ∼ 1.6%. Indeed, the Bayes Information Criterion favours Rh = ct over flat ΛCDM with a likelihood of ∼ 81% versus 19%, suggesting that the optimized parameters in Planck ΛCDM mimic the constraint p = −ρ/3. Copyright © 2018, The Authors. All rights reserved.

关键词：

Inertia, Gravity and the Meaning of Mass

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

Our concept of mass has evolved considerably over the centuries, most notably from Newton to Einstein, and then even more vigorously with the establishment of the standard model and the subsequent discovery of the Higgs boson. Mass is now invoked in various guises depending on the circumstance: it is used to represent inertia, or as a coupling constant in Newton’s law of universal gravitation, and even as a repository of a mysterious form of energy associated with a particle at rest. But recent developments in cosmology have demonstrated that rest-mass energy is most likely the gravitational binding energy of a particle in causal contact with that portion of the Universe within our gravitational horizon. In this paper, we examine how all these variations on the concept of mass are actually interrelated via this new development and the recognition that the source of gravity in general relativity is ultimately the total energy in the system. © 2023, CC BY.

关键词： Gravitation

Model Selection with Baryonic Acoustic Oscillations in the Lyman-α Forest

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arXiv 2023年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

The recent release of the final, complete survey of Lyman-α baryonic acoustic oscillation measurements provides the most significant and accurate data base for studying cosmic geometry at an effective redshift zeff = 2.334, which is inaccessible to other sources. In this Letter, we use these data to select among four distinct cosmologies: Planck ΛCDM, the Rh = ct universe, the Milne universe and Einstein-de Sitter. Given the breadth and depth of the Lyman-α study, this BAO measurement alone provides a strong model comparison, complementary to previous studies that combined Lyman-α data with measurements at lower redshifts. Though both approaches are useful, the latter tends to dilute the disparity between model predictions and the observations. We therefore examine how the models compare to each other strictly based on the BAO scale measured in the Lyman-α forest and background quasars. We find that Milne and Einstein-de Sitter are strongly ruled out by these data. There is also strong evidence disfavoring the standard model. The Lyman-α measurements are completely consistent with the cosmic geometry predicted by Rh = ct. As such, evidence continues to grow that the zero active mass condition from general relativity ought to be an essential ingredient in ΛCDM. © 2023, CC BY.

关键词： Cosmology