Article
Astronomy & Astrophysics
Anjan A. Sen, Shahnawaz A. Adil, Somasri Sen
Summary: This study explores the possibility of a negative cosmological constant in the Universe and finds that it is consistent with observational data.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. R. Cuzinatto, R. P. Gupta, R. F. L. Holanda, J. F. Jesus, S. H. Pereira
Summary: In this paper, the Co-varying Physical Couplings (CPC) framework is introduced, which assumes the gravitational quantities can be treated as space-time functions. By imposing specific constraints, the researchers deduce the functional forms of the couplings as functions of redshift, and demonstrate that this model can describe dark energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Fabrizio Renzi, Natalie B. Hogg, William Giare
Summary: The Etherington reciprocity theorem is used to build a consistency check and provides new results about cosmological models. Using late-time observational data, joint constraints on the Hubble parameter and epsilon are obtained and compared with other cosmological models. Additionally, a discrepancy between the validity of the DDR and the latest publicly available Cepheid-calibrated Type Ia supernova constraint on H-0 is identified.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. E. Eaves
Summary: The study explores the relationship between the speed of light and gravitational constant, using experimental data to determine the range of variation in the speed of light over time. It is noted that constraints on the speed of light variation are based on data from within the Solar system rather than cosmological observations. Additionally, a relationship between the speed of light and the fine-structure constant is identified as potentially offering tighter constraints.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
Alexandre Tkatchenko, Dmitry V. Fedorov
Summary: Quantum electrodynamic fields exhibit fluctuations in the form of particle-antiparticle dipoles, characterized by a nonvanishing polarizability density. In this study, a quantum scaling law is extended to describe the volumetric and radial polarizability density of a quantum field associated with electrons and positrons, and the Casimir self-interaction energy density (E over bar SIE) of the field is derived in terms of the fine-structure constant. The proposed model satisfies the cosmological equation of state w = -1 and the calculated E over bar SIE falls within the range of the recent measurements of the cosmological constant ? obtained by the Planck Mission and the Hubble Space Telescope.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Carlos Hernandez-Monteagudo, Jonas Chaves-Montero, Raul E. Angulo
Summary: The proposal introduces the use of angular fluctuations in the galaxy redshift field as a new way to extract cosmological information in the Universe. The new probe delta z((n) over cap) shows sensitivity to the density and peculiar velocity fields, as well as high correlation to the line-of-sight projected peculiar velocity field. It is concluded that delta z(<(n)over cap>) is a robust tomographic measure of the cosmic density and velocity fields that complements angular clustering in galaxy redshift surveys.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Timur Takhtaganov, Zarija Lukic, Juliane Mueller, Dmitriy Morozov
Summary: In this paper, a novel statistical framework utilizing multi-output Gaussian process emulators adaptively constructed using Bayesian optimization methods is proposed to maintain low emulation error in the region of the hypercube preferred by observational data. The approach allows for fewer simulations compared to traditional emulation methods and is more robust in reconstructing parameters and their Bayesian credible intervals, as demonstrated with a Ly alpha forest flux power spectrum.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
V Marra, T. Castro, D. Camarena, S. Borgani, A. Ragagnin
Summary: The study focuses on the evolution of large-scale structures in an inhomogeneous background using numerical cosmology. By conducting simulations, the researchers aim to gain a better understanding of the cosmic evolution and refine the standard model.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Physics, Multidisciplinary
Michele Arzano, Vittorio D'Esposito, Giulia Gubitosi
Summary: In this paper, the authors provide a rigorous derivation of quantum decoherence within a quantum spacetime model, showing that pure states can evolve into mixed states due to the effects of spacetime noncommutativity. This study sheds light on the fundamental properties of spacetime at the Planck scale, bridging quantum mechanics and general relativity, and holds significant importance in scientific research.
COMMUNICATIONS PHYSICS
(2023)
Article
Astronomy & Astrophysics
Hassan Firouzjahi, Alireza Talebian
Summary: We considered a model of single field inflation containing an intermediate phase of ultra slow-roll and calculated the induced gravitational waves from the enhanced curvature perturbations during this period. The model can accommodate the current observations but has non-trivial predictions for higher frequency ranges that can be tested in future observations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Wilmar Cardona, M. A. Sabogal
Summary: Interesting discrepancies in cosmological parameters challenge the success of the ACDM model. The Hubble constant and matter clustering strength derived from various measurements are higher/lower than those inferred from the Cosmic Microwave Background (CMB) in the context of ACDM. In this study, we propose a Dark Energy (DE) model with an evolving equation of state and constant sound speed squared to address these discrepancies. By considering the impact of DE sound speed on gravitational potential evolution, we find good agreement between our results and low redshift probes, but tension with BBN constraints in the case of baryon energy density.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
M. Berti, M. Spinelli, B. S. Haridasu, M. Viel, A. Silvestri
Summary: In this study, we explore constraints on dark energy and modified gravity using forecasted 21cm intensity mapping measurements. We find that adding the power spectrum of the 21cm signal to the latest CMB data significantly tightens the constraints on certain parameters. We also demonstrate the importance of tomography in improving the constraining power on theories beyond the standard ΛCDM model.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
F. G. Alvarenga, L. A. M. Diniz, S. V. B. Goncalves, G. A. Monerat, E. V. Correa Silva
Summary: In this study, a classical cosmological model based on a modified theory of gravitation is presented. The ADM formalism is used to incorporate the Einstein-Aether theory, which couples a timelike vector field to the metric, and the Schutz formalism is introduced to describe the material content of the Universe as a perfect baryonic fluid. The Wheeler-DeWitt quantization scheme is then applied to obtain the wave function of the Universe. The study explores the many-worlds interpretation and the de Broglie-Bohm interpretation of quantum mechanics, showing the possibility of avoiding a singularity at the beginning of the Universe.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Shek Yeung, King Lau, M-C Chu
Summary: This study investigates the impact of a finite relic neutrino degeneracy on the CMB angular power spectra and its correlations with other cosmological parameters. The results suggest that the relic neutrino degeneracy is a significant physical parameter for cosmological analyses, potentially loosening constraints on inflation models and slightly alleviating tensions in measurements.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Carlos Hernandez-Monteagudo, Jonas Chaves-Montero, Raul E. Angulo, Giovanni Arico
Summary: Fluctuations in sky maps of galaxy redshifts, known as angular redshift fluctuations (ARF), provide precise information about the growth rate of structures and the nature of gravity in the Universe. Utilizing the BOSS LOWZ+CMASS DR12 galaxy samples, we obtained 7% accurate constraints on H/H(0)f sigma(8)(z) and found the gravity index gamma to be 0.44, within 2 sigma of the prediction of General Relativity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Fulvio Melia
Summary: This passage discusses the evidence for a Big Bang origin of the universe and the mystery surrounding its cause. It explores the refinement of the range of possible initial conditions based on current physical theories, focusing on the spatial flatness of the universe and its implications. The passage also raises questions about the quantum beginning and the existence of fluctuations with nonzero energy.
ASTRONOMISCHE NACHRICHTEN
(2022)
Article
Astronomy & Astrophysics
M-A Sanchis-Lozano, F. Melia, M. Lopez-Corredoira, N. Sanchis-Gual
Summary: Recent research has found that there is a maximum correlation angle in the two-point angular temperature correlations of cosmic microwave background (CMB) radiation, which contradicts the prediction of standard cosmology. The angular power spectrum of the CMB also shows a dominance of odd-over-even parity multipoles. This paper examines the relationship between these features and their impact on the theoretical fit to the Planck 2018 data. The results suggest that considering both the maximum correlation angle and the parity imbalance is crucial for optimizing the fit.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Education, Scientific Disciplines
Fulvio Melia
Summary: The future observation of real-time cosmic expansion is an exciting research that can reveal the properties of the universe and answer the question of whether the cosmic expansion is accelerating. It has significant impacts on cosmology and the standard model of particle physics.
EUROPEAN JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Fulvio Melia
Summary: This paper significantly advances the discussion by using the Local Flatness Theorem in general relativity to prove the dependence of gtt in FLRW on the expansion dynamics. It argues that gtt cannot be arbitrarily chosen without ensuring its consistency with the energy-momentum tensor.
MODERN PHYSICS LETTERS A
(2022)
Article
Physics, Multidisciplinary
Fulvio Melia
Summary: This paper discusses the existence of a "preferred" frame of reference in the universe and explains how it is consistent with Einstein's theory of relativity.
Article
Astronomy & Astrophysics
Jun-Jie Wei, Fulvio Melia
Summary: We analyzed the ages of 114 old astrophysical objects in the redshift range 0 to 8 to investigate the Hubble tension. By assuming a flat ACDM model and setting a Gaussian prior on Omega(m), we obtained an upper limit on the Hubble constant H-0. The inferred upper limit strongly depends on the prior for Omega(m), suggesting a possible explanation for the tension between early-time and local measurements of H-0. We also found that the R-h = ct universe model fits the data well, while the Einstein-de Sitter model fails the cosmic-age test. Additionally, we estimated the spatial curvature of the universe using the ages of 61 galaxies and the luminosity distances of 1048 Type Ia supernovae, finding marginal consistency with spatial flatness.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
F. Melia, M. Lopez-Corredoira
Summary: This paper compares the standard model (Lambda CDM) with R-h = ct universe model using data from the Sloan Digital Sky Survey IV. The study employs baryon acoustic oscillation (BAO) peak measurements and a volume-averaged distance probe to assess the models. The results suggest that R-h = ct is favored by the AP effect, while Planck-Lambda CDM is favored by the distance probe. A joint analysis using both probes produces inconclusive outcomes.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Astronomy & Astrophysics
Fulvio Melia, Jun-Jie Wei, Xue-Feng Wu
Summary: The sample of time-delay gravitational lenses for studying the geometry of the Universe is growing with the completion of dedicated campaigns. Comparisons of two competing models show that the R-h = ct universe is favored by the current sample with a likelihood of about 84% over the standard model. As ongoing surveys uncover more lens systems in the next few years, the accuracy of the comparison will greatly improve.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Fulvio Melia
Summary: The evidence for a Universe expanding at a constant rate has been accumulating for over a decade. Recent studies have further strengthened this inference by examining the Friedmann-Lemaitre-Robertson-Walker metric in relation to Einstein's principle of equivalence. This paper demonstrates and confirms the result by directly testing the self-consistency of four well-known FLRW cosmologies, showing that only the constantly expanding models are consistent with the principle of equivalence.
ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES
(2023)
Article
Astronomy & Astrophysics
Fulvio Melia
Summary: The impossibly early galaxy problem, identified by the Hubble Space Telescope and exacerbated by JWST's recent discoveries, suggests a faster rate of star formation than predicted by simulations. The R-h = ct universe, which incorporates the zero active mass condition from general relativity, provides a better explanation for cosmological data and eliminates the inconsistencies in the current standard model. The latest JWST discoveries, if confirmed, would further support the R-h = ct universe.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Multidisciplinary
Fulvio Melia
Summary: The energy conditions in general relativity are introduced to establish powerful theorems without being restricted to specific stress-energy tensors. However, they have become controversial as they seem to be violated by certain scenarios like inflation and late-time acceleration. This paper argues that the 'numen' scalar field, derived from the zero active mass condition in general relativity, satisfies all energy conditions in the early Universe. This unique feature makes it more successful in explaining the observed properties of the cosmic microwave background compared to inflation.
ANNALEN DER PHYSIK
(2023)
Article
Astronomy & Astrophysics
F. Melia
Summary: In standard inflationary cosmology, scalar and tensor perturbations in the cosmic microwave background (CMB) can indicate whether the primordial fluctuations were generated during inflation or from other quantum fluctuations. This study compares the scalar and tensor modes produced in both scenarios and suggests that upcoming observations of the B-mode polarization of the CMB can potentially distinguish between them. The non-detection of B-mode polarization would not rule out inflation completely, as purely classical gravity could result in unmeasurably weak gravitational waves.
ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
F. Melia
Summary: The recent release of the final survey on Lyman-alpha baryonic acoustic oscillation measurements provides significant data for studying cosmic geometry. The results rule out the Milne universe and the Einstein-de Sitter universe, and raise doubts about the standard model. The evidence supports the zero active mass condition from general relativity as an essential ingredient in Lambda CDM.
Article
Chemistry, Physical
Fulvio Melia
Summary: This paper discusses the origin and conservation of momentum, particularly for particles with mass and those without mass. The study shows that momentum can be uniformly defined for all particles, regardless of their mass, and there is no different origin based on mass.
ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES
(2023)
Article
Astronomy & Astrophysics
Fulvio Melia
Summary: Spontaneous symmetry breaking in grand unified theories is believed to have generated a large number of magnetic monopoles in the early Universe. However, none of these massive particles has ever been found, possibly because inflation diluted their number. If the inflationary paradigm is invalid, it would create a cosmological 'monopole problem' and pose a challenge to the standard model of particle physics. In the Rh = ct universe, all such anomalies are eliminated naturally, and the monopole energy density would be undetectable.
PHYSICS OF THE DARK UNIVERSE
(2023)