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A Comparative Test of the ΛCDM and Rh = ct Cosmologies Based on Upcoming Redshift Drift Measurements

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arXiv 2024年

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

A measurement of the redshift drift constitutes a model-independent probe of fundamental cosmology. Several approaches are being considered to make the necessary observations, using (i) the Extremely Large Telescope (ELT), (ii) the Cosmic Accelerometer, and (iii) the differential redshift drift methodology. Our focus in this Letter is to assess how these upcoming measurements may be used to compare the predictions of ΛCDM with those of the alternative Friedmann-Lemaître-Robertson-Walker cosmology known as the Rh = ct universe, and several other models, including modified gravity scenarios. The ELT should be able to distinguish between Rh = ct and the other models at better than 3σ for z & 3.6 after 20 years of monitoring, while the Cosmic Accelerometer may be able to achieve the same result with sources at z & 2.6 after only 10 years. © 2024, CC BY.

关键词： Accelerometers

Strong Observational Support for the Rh = ct Timeline in the Early Universe

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arXiv 2024年

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

JWST’s recent discovery of well-formed galaxies and supermassive black holes only a few hundred Myr after the big bang seriously challenges the timeline predicted by ΛCDM. Now, the latest identification of polycyclic aromatic hydrocarbons (PAHs) at z = 6.71, together with these earlier inconsistencies, makes the time compression problem in this model quite overwhelming. We consider the timeline associated with the formation and growth of PAH grains based on current astrophysical models and argue that their appearance at z = 6.71 favors the structure formation history in Rh = ct rather than that of Planck-ΛCDM. We estimate the time at which they must have started growing in each case, and then trace their history through various critical events, such as the end of the ‘dark ages,’ the beginning of Pop III star formation, and the onset of reionization. Together, these three distinct discoveries by JWST, viz. high-z galaxies, high-z quasars and the surprisingly early appearance of PAHs, all paint a fully consistent picture in which the timeline in ΛCDM is overly compressed at z & 6, while strongly supporting the expansion history in the early Universe predicted by Rh = ct. © 2024, CC BY.

关键词： Equations of state

A comparison of the Rh = ct and ΛCDM cosmologies using the cosmic distance duality relation

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arXiv 2018年

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

The cosmic distance duality (CDD) relation (based on the Etherington reciprocity theorem) plays a crucial role in a wide assortment of cosmological measurements. Attempts at confirming it observationally have met with mixed results, though the general consensus appears to be that the data do support its existence in nature. A common limitation with past approaches has been their reliance on a specific cosmological model, or on measurements of the luminosity distance to Type Ia SNe, which introduces a dependence on the presumed cosmology in spite of beliefs to the contrary. Confirming that the CDD is actually realized in nature is crucial because its violation would require exotic new physics. In this paper, we study the CDD using the observed angular size of compact quasar cores and a Gaussian Process reconstruction of the HII galaxy Hubble diagram—without pre-assuming any particular background cosmology. In so doing, we confirm at a very high level of confidence that the angular-diameter and luminosity distances do indeed satisfy the CDD. We then demonstrate the potential power of this result by utilizing it in a comparative test of two competing cosmological models—the Rh = ct universe and ΛCDM—and show that Rh = ct is favoured by the CDD data with a likelihood ∼ 82.3% compared with ∼ 17.7% for the standard model. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Quantifying intragroup and intergroup connections in non-disjoint groups in social networks: A comprehensive analysis incorporating edges' and nodes' weights

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Information Sciences 2024年 670卷

作者： de Andrade, Ricardo Lopes Rêgo, Leandro Chaves Management Engineering Graduate Program Federal University of Pernambuco Brazil Statistics and Applied Math Department Universidade Federal do Ceará Brazil

In this paper, we propose generalizations of the EI index to quantify the distinction between intragroup and intergroup connections in social networks. These generalizations enable the analysis of interactions between non-disjoint groups, as large-scale disjoint groups are rarely found in many empirical networks. By expanding social network analysis, these measures facilitate the identification of actors with greater similarities or differences, generating previously untapped knowledge. Furthermore, we propose incorporating both edges' and nodes' weights in assessing the EI index. Intuitively, our approach classifies each network edge as internal or external, depending on the attribute groups that each node linked by the given edge belongs to. Since nodes can belong to more than one attribute group, three methods of classifying a network edge are proposed which depend on the number of shared groups by the pair of nodes. We evaluate the new measures in two distinct network contexts. The first context involves a co-authorship network, where researchers, acting as network actors, are categorized based on their respective areas of expertise in management engineering. The second network consists of trade relations among countries in the Americas, with countries grouped according to their participation in trade agreements. The analysis showed which area of management engineering is more independent by having more internal connections and made it possible to investigate the role of trade agreements in the actual trades made by countries. These proposals provide a more comprehensive and nuanced understanding of network dynamics, allowing for a more precise comprehension of interactions and patterns present in social systems. © 2024 Elsevier Inc.

关键词： Commerce

A cosmological basis for E = mc2

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arXiv 2019年

作者： Melia, Fulvio Department of Physics Applied Math Program Department of Astronomy University of Arizona TucsonAZ85721 United States

The Universe has a gravitational horizon with a radius Rh = 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-Lemaître-Robertson-Walker spacetime, we see it retreating at proper speed c, giving rise to the eponymously named cosmological model Rh = ct. As of today, this cosmology has passed over 20 observational tests, often better than ΛCDM. The gravitational radius Rh 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 mc2. 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 Rh. 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. Copyright © 2019, The Authors. All rights reserved.

关键词： Relativity

The anomalous 21-cm absorption at high redshifts

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arXiv 2021年

作者： Melia, Fulvio Department of Physics Applied Math Program Department of Astronomy The University of Arizona TucsonAZ85721 United States

The EDGES collaboration has reported the detection of a global 21-cm signal with a plateau centered at 76 MHz (i.e., redshift 17.2), with an amplitude of 500+200−500 mK. This anomalous measurement does not comport with standard cosmology, which can only accommodate an amplitude . 230 mK. Nevertheless, the line profile’s redshift range (15 . z . 20) suggests a possible link to Pop III star formation and an implied evolution out of the ‘dark ages.’ Given this tension with the standard model, we here examine whether the observed 21-cm signal is instead consistent with the results of recent modeling based on the alternative Friedmann-Lemaître-Robertson-Walker cosmology known as the Rh = ct universe, showing that—in this model—the CMB radiation might have been rethermalized by dust ejected into the IGM by the first-generation stars at redshift z ∼ 16. We find that the requirements for this process to have occurred would have self-consistently established an equilibrium spin temperature Ts ≈ 3.4 K in the neutral hydrogen, via the irradiation of the IGM by deep penetrating X-rays emitted at the termination shocks of Pop III supernova remnants. Such a dust scenario has been strongly ruled out for the standard model, so the spin temperature (∼ 3.3 K) inferred from the 21-cm absorption feature appears to be much more consistent with the Rh = ct profile than that implied by ΛCDM, for which adiabatic cooling would have established a spin temperature Ts(z = 17.2) ∼ 6 K. © 2021, CC BY.

关键词： Cosmology

Classicalization of Quantum Fluctuations at the Planck Scale in the Rh=ct Universe

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Research Square

Research Square 2021年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona TucsonAZ85721 United States

The quantum to classical transition of fluctuations in the early universe is still not completely understood. Some headway has been made incorporating the effects of decoherence and the squeezing of states, though the methods and procedures continue to be challenged. But new developments in the analysis of the most recent Planck data suggest that the primordial power spectrum has a cutoff associated with the very first quantum fluctuation to have emerged into the semi-classical universe from the Planck domain at about the Planck time. In this paper, we examine the implications of this result on the question of classicalization, and demonstrate that the birth of quantum fluctuations at the Planck scale would have been a ‘process’ supplanting the need for a ‘measurement’ in quantum mechanics. Emerging with a single wavenumber, these fluctuations would have avoided the interference between different degrees of freedom in a superposed state. Moreover, the implied scalar-field potential had an equation-of-state consistent with the zero active mass condition in general relativity, allowing the quantum fluctuations to emerge in their ground state with a time-independent frequency. They were therefore effectively quantum harmonic oscillators with classical correlations in phase space from the very beginning. © 2021, CC BY.

关键词： Degrees of freedom (mechanics)

The cosmic timeline implied by the highest redshift quasars

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arXiv 2024年

作者： Melia, Fulvio Department of Physics The Applied Math Program Department of Astronomy The University of Arizona TucsonAZ85721 United States

The conventional picture of supermassive black-hole growth in the standard model had already been seriously challenged by the emergence of ∼ 109 M☉ quasars at z ∼ 7.5, conflicting with the predicted formation of structure in the early ΛCDM Universe. But the most recent JWST discovery of a ∼ 108 M☉ source at z ∼ 10.1 argues even more strongly against the possibility that these black holes were created in Pop II or III supernovae, followed by Eddington-limited accretion. Attempts at resolving this anomaly have largely focused on the formation of seeds via an exotic, direct collapse of primordial gas to an initial mass ∼ 105 M☉-a process that has never been seen anywhere in the cosmos. Our goal in this Letter is to demonstrate that the emergence of these black holes is instead fully consistent with standard astrophysics in the context of the alternative Friedmann-Lemaître-Robertson-Walker cosmology known as the Rh = ct universe. We show that, while the predicted evolution in the standard model is overly compressed, the creation, growth and appearance of such high-z quasars fall comfortably within the evolutionary history in this cosmology, thereby adding considerable observational support to the existing body of evidence favoring it over the standard scenario. © 2024, CC BY.

关键词： Black holes

A solution to the electroweak horizon problem in the Rh = ct universe

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arXiv 2018年

作者： Melia, Fulvio Department of Physics Applied Math Program and Department of Astronomy University of Arizona TucsonAZ85721 United States

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 ΛCDM 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 Rh = ct universe. Copyright © 2018, The Authors. All rights reserved.

关键词： Cosmology