Article
Astronomy & Astrophysics
Eleonora Di Valentino, Alessandro Melchiorri, Olga Mena, Supriya Pan, Weiqiang Yang
Summary: Recent measurements by the Planck satellite suggest a preference for a closed universe, but this conflicts with low redshift observables such as Type Ia supernovae luminosity distances. Interacting dark energy models could help reconcile these discrepancies in a closed Universe, indicating potential for a different coupling and curvature above 99% confidence level. This highlights the significance of broader cosmological data analyses and the possibility of better agreement between theory and observations by relaxing flatness and vacuum energy assumptions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jens Chluba
Summary: The observed excess radio background has puzzled scientists for over a decade. A recent new physics solution involves the decay of dark matter into dark photons which then convert into standard photons in the reionization era. This simple power-law model fits the current data closely, although additional work is needed to address challenges and improve the model.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Weiqiang Yang, Eleonora Di Valentino, Supriya Pan, Yabo Wu, Jianbo Lu
Summary: This article compares various dynamical dark energy models using different observational data and discusses the alleviation of H-0 tension. Bayesian evidence analysis shows that all models perform better than Lambda CDM scenario, with the CPL model being the best in fitting the data and solving H-0 tension. However, the tension reappears when considering the baryon acoustic oscillations data, not supporting the dynamical dark energy solution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Eleonora Di Valentino, Nils A. Nilsson, Mu-In Park
Summary: This study proposes a renormalizable, higher derivative, Lorentz-violating quantum gravity model without ghost problems known as Hoava gravity. Furthermore, a Hoava gravity-based dark energy (HDE) model is proposed by identifying the additional contributions from Lorentz-violating terms as an effective energy-momentum tensor in Einstein equation. The results show a preference for non-flat universes in the cosmic microwave background, baryon acoustic oscillation, and supernova Ia data tests, aligning with the cosmic concordance model.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Eleonora Di Valentino
Summary: The study combines multiple measurements of the Hubble constant, resulting in an optimistic estimate of H-0 = 72.94 +/- 0.75 km s(-1) Mpc(-1), significantly different from the ACDM model. The research also highlights various new phenomena that emerge in different dark energy cosmological models, such as phantom dark energy and coupling between dark matter and dark energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Sergei F. Shandarin
Summary: The study examines the density distribution of dark matter at caustic surfaces and the corresponding geometrical features, as well as the methods and challenges in identifying caustics in numerical simulations. The halo boundary is found to be asymmetrical, but a convex hull is a good approximation. Analyses of kinetic and potential energies, as well as examination of the two-dimensional phase space, confirm that the halo is gravitationally bound. The discovery of non-ellipsoidal oval shapes in a sample of halos from large simulations shows promise for further detailed analysis on higher resolution simulations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
L. Gelo, C. J. A. P. Martins, N. Quevedo, A. M. M. Vieira
Summary: The redshift dependence of the cosmic microwave background temperature has important implications for fundamental cosmology, and its constraining power is comparable to other background cosmology probes.
Article
Astronomy & Astrophysics
Nanoom Lee, Yacine Ali-Haimoud
Summary: This study introduces a new formalism to compute the impact of small-scale baryon perturbations on free-electron abundance and applies it to probe cosmic microwave background anisotropies. Analysis on four different combinations of fluctuation modes shows that Planck data is consistent with the absence of small-scale isocurvature perturbations.
Article
Astronomy & Astrophysics
E. Camphuis, K. Benabed, S. Galli, E. Hivon, M. Lilley
Summary: This study focuses on the analytical calculation of covariance matrices for estimating cosmological parameters, particularly in the observation of CMB using small footprints. A new approximation method is introduced to improve the accuracy in predicting wide bandpowers, achieving over four times the precision compared to current approaches. The results are not only applicable to CMB observations but also to other cosmological probes requiring the calculation of pseudo-power spectrum covariance matrices.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jiten Dhandha, Jens Chluba
Summary: The excess radio background observed at similar to 0.1-10GHz has sparked scientific debate in recent years. A recent hypothesis suggests that the soft photon emission from accreting primordial black holes could explain this signal. However, our study shows that the expected ultraviolet photon emission from these accreting black holes would fully ionize the universe at z > 6, thereby diminishing the 21-cm absorption signature at z similar to 20 and conflicting with the current limits of cosmic microwave background anisotropy and average spectral distortion.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jozef Bucko, Sambit K. Giri, Aurel Schneider
Summary: From observations at low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or very long-lived, but the possibility of a small fraction or all of the DM decaying with a significantly longer half-life time than the age of the Universe is not ruled out. In this study, the researchers investigated models in which a fraction or all DM decays into radiation, focusing on the long-lived regime. They used data from the Kilo-Degree Survey (KiDS) for weak-lensing analysis and CMB data from Planck. The results showed that the constraints on DM decay are more stringent from CMB data than from weak-lensing data.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Tirthankar Roy Choudhury, Suvodip Mukherjee, Sourabh Paul
Summary: By comparing predictions of a physical seminumerical model with CMB data, constraints on allowed reionization histories were studied, leading to the determination of tight constraints on parameters such as reionization duration and halo mass. Analysis showed implications for future CMB surveys and 21 cm studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Markus R. Mosbech, Celine Boehm, Yvonne Y. Y. Wong
Summary: Similar to warm dark matter, many interacting dark matter models predict a suppression of the matter power spectrum due to collisional damping. 21cm line intensity mapping can probe this suppression and set strong limits on dark matter-neutrino scattering. However, precise measurements of the matter power spectrum at high redshifts are needed to distinguish between warm dark matter and interacting scenarios.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Eleonora Di Valentino, Olga Mena
Summary: This paper analyzes the constraints and potential hints obtained for models involving an interaction between the dark matter and dark energy sectors using simulated Planck data. The simulations suggest a potential fake detection for a non-zero interaction among the dark matter and dark energy fluids when dealing with current cosmic microwave background (CMB) Planck measurements alone. Future CMB observations, particularly cosmic variance limited polarization experiments, may provide more reliable cosmological constraints and break existing parameter degeneracies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
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)
