Article
Physics, Particles & Fields
Pawan Joshi, Sukanta Panda
Summary: A Hamiltonian for the nonlocal F(R) theory is constructed in this work, revealing the nature of the ghost degrees of freedom. Finally, conditions that lead to ghost-free theories are found.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
A. Costantini, E. Elizaide
Summary: This study extends the investigation of unimodular Einsteinian gravity in the context of F(R) gravities for constructing anisotropic evolution scenarios. By imposing the unimodular constraint, the metric can be redefined and the desired evolution equations can be obtained. The reconstruction method is demonstrated with characteristic examples.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Multidisciplinary
Roger Hurtado, Robel Arenas
Summary: A cosmologically viable hypergeometric model has been derived based on the requirements of asymptotic behavior towards Lambda CDM, the presence of an inflection point in the f (R) curve, and the viability conditions dictated by the phase space curves (m, r). The models were expressed in terms of a dimensionless variable and differential equations were formulated to establish the relationship between certain functions. The resulting solutions yielded specific types of models, but it was subsequently discovered that these differential equations correspond to a more general hypergeometric model.
Article
Astronomy & Astrophysics
A. Oliveros
Summary: In this study, a reparametrization method for a viable f(R) gravity model is proposed to represent it as a perturbation of the Lambda CDM model. The results show that the proposed model is practically indistinguishable from the Lambda CDM model at the background level and exhibits excellent agreement with the numerical solution. By appropriately choosing the model parameters, the obtained cosmological parameters are consistent with observations and the predictions of the Lambda CDM model. Additionally, the anomalous behavior at high redshifts is avoided by utilizing an approximate analytical solution.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Physics, Particles & Fields
Fateme Rajabi, Kourosh Nozari
Summary: This study investigates cosmological inflation and reheating in the context of unimodular f(R, T) gravity. The reheating temperature is calculated and the creation of massless particles in the universe is discussed.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
G. A. Carvalho, F. Rocha, H. O. Oliveira, R. V. Lobato
Summary: This study introduces a new approach in f(R, T) gravity theory to eliminate the influence of the trace of the energy-momentum tensor on field equations. By considering the trace as an unknown variable and relying on fundamental constants and inputs from the standard model, the limitations regarding energy-momentum tensor and Lagrangian definition are successfully overcome.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
Oktay Cebecioglu, Ahmet Saban, Salih Kibaroglu
Summary: Inspired by Maxwell symmetry, we have constructed the Maxwell extension of f(R) gravity. The semi-simple extension of Poincare symmetry allows for the introduction of a cosmological constant term in four-dimensional f(R) gravity. This symmetry also enables the presence of a non-vanishing torsion in the Maxwell f(R) theory.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
F. R. Klinkhamer
Summary: A new approach is proposed to cancel the cosmological constant by utilizing the determinant of the metric as a self-adjusting q-field. The allowed coordinate transformations are restricted to those with unit Jacobian due to the role played by the determinant of the metric in the physics. The study shows the natural cancellation of an initial cosmological constant if quantum-dissipative effects are taken into account.
Article
Astronomy & Astrophysics
J. G. Fernando Barbero, Bogar Diaz, Juan Margalef-Bentabol, Eduardo J. S. Villasenor
Summary: In this paper, we provide a detailed account of the Hamiltonian Gotay-Nester-Hinds (GNH) analysis of the parametrized unimodular extension of the Holst action. The main goal is to derive a simple Hamiltonian formulation for this model using the geometric picture furnished by the GNH method and explain the challenges in arriving at this formulation through other approaches. Additionally, we demonstrate how to utilize the field equations to anticipate the simple form of the constraints found in the paper.
Article
Physics, Multidisciplinary
M. Ilyas, Aftab Ahmad, Fawad Khan, M. Wasif
Summary: In this paper, the authors investigate the effects of perfect fluid models and extended f(R, G, T) gravity on the flat Friedmann-Lematre-Robertson-Walker metric. They focus on exploring finite-time future singularities in late-time cosmic accelerating phases using specific f(R, G, T) models. The authors also consider the most recent estimated values for various parameters to examine the viability and bounds of the models induced by different energy conditions.
Article
Astronomy & Astrophysics
Luis Rey Diaz-Barron, M. Sabido
Summary: In this work, we investigate the modifications to the Friedmann equations arising from ungravity, with particular focus on the modified entropy-area relation. By using the first law of thermodynamics and the new entropy-area relationship, we derive modified Friedmann equations and discover an effective cosmological constant in the late-time regime. This simple model thus offers an ungravity explanation for the cosmological constant Λ.
Article
Physics, Particles & Fields
Vipin Kumar Sharma, Bal Krishna Yadav, Murli Manohar Verma
Summary: We study the galactic scale dynamics through gravitational lensing phenomenon in power-law f(R) gravity theory and utilise the single effective point potential to analyze galaxy rotation curve observations and their lensing profiles. The calculations show consistency with the generalised pseudo-isothermal galaxy halo model.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Mathematical
Nisha Godani, Gauranga C. Samanta
Summary: In this paper, Morris Thorne wormholes in the context of f(R) gravity are investigated. The shape function is defined, and the equation of state and f(R) function are derived. The wormhole solutions are obtained and energy conditions are examined. The f(R) model is found to be consistent with local gravity tests and stability of cosmological perturbations and late-time de Sitter point. Furthermore, the cosmological evolution is explored using the Friedman-Robertson-Walker (FRW) metric in f(R) gravity.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Physics, Particles & Fields
Vipin Kumar Sharma, Murli Manohar Verma
Summary: We explore the shifted f (R) model with delta as a distinguishing physical parameter for the study of constraints at local scales. This model seems to provide a unique f (R) at local scales and is suitable for the alternative explanation of dark matter-like effects.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Rodrigo Calderon, Benjamin L'Huillier, David Polarski, Arman Shafieloo, Alexei A. Starobinsky
Summary: Based on a formalism introduced in previous work, the phenomenological function Geff(z) describing deviations from general relativity (GR) is reconstructed in a model-independent manner. Two different toy models are used to forecast growth-rate measurements from a stage-IV survey to reconstruct the shape of Geff. The impact of massive neutrinos on the reconstructions of Geff is assessed assuming the expansion history is known and only the neutrino mass varies.
Article
Astronomy & Astrophysics
Jose A. R. Cembranos, Alvaro de la Cruz-Dombriz, Viviana Gammaldi, Miguel Mendez-Isla
PHYSICS OF THE DARK UNIVERSE
(2020)
Article
Physics, Particles & Fields
Alba Quelle, Antonio L. Maroto
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Physics, Particles & Fields
Shambel Sahlu, Joseph Ntahompagaze, Amare Abebe, Alvaro de la Cruz-Dombriz, David F. Mota
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Astronomy & Astrophysics
J. A. R. Cembranos, A. L. Maroto, H. Villarrubia-Rojo
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
Miguel Aparicio Resco, Antonio L. Maroto
Summary: FARO is a new public Python code that computes the Fisher matrix for galaxy survey observables, allowing for tomographic and model-independent analysis, and forecasting the sensitivity of future galaxy surveys like DESI, Euclid, J-PAS and LSST.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
S. Bonoli, A. Marin-Franch, J. Varela, H. Vazquez Ramio, L. R. Abramo, A. J. Cenarro, R. A. Dupke, J. M. Vilchez, D. Cristobal-Hornillos, R. M. Gonzalez Delgado, C. Hernandez-Monteagudo, C. Lopez-Sanjuan, D. J. Muniesa, T. Civera, A. Ederoclite, A. Hernan-Caballero, V Marra, P. O. Baqui, A. Cortesi, E. S. Cypriano, S. Daflon, A. L. de Amorim, L. A. Diaz-Garcia, J. M. Diego, G. Martinez-Solaeche, E. Perez, V. M. Placco, F. Prada, C. Queiroz, J. Alcaniz, A. Alvarez-Candal, J. Cepa, A. L. Maroto, F. Roig, B. B. Siffert, K. Taylor, N. Benitez, M. Moles, L. Sodre Jr, S. Carneiro, C. Mendes de Oliveira, E. Abdalla, R. E. Angulo, M. Aparicio Resco, A. Balaguera-Antolinez, F. J. Ballesteros, D. Brito-Silva, T. Broadhurst, E. R. Carrasco, T. Castro, R. Cid Fernandes, P. Coelho, R. B. de Melo, L. Doubrawa, A. Fernandez-Soto, F. Ferrari, A. Finoguenov, R. Garcia-Benito, J. Iglesias-Paramo, Y. Jimenez-Teja, F. S. Kitaura, J. Laur, P. A. A. Lopes, G. Lucatelli, V. J. Martinez, M. Maturi, M. Quartin, C. Pigozzo, J. E. Rodriguez-Martin, V Salzano, A. Tamm, E. Tempel, K. Umetsu, L. Valdivielso, R. von Marttens, A. Zitrin, M. C. Diaz-Martin, G. Lopez-Alegre, A. Lopez-Sainz, A. Yanes-Diaz, F. Rueda-Teruel, S. Rueda-Teruel, J. Abril Ibanez, J. L. Anton Bravo, R. Bello Ferrer, S. Bielsa, J. M. Casino, J. Castillo, S. Chueca, L. Cuesta, J. Garzaran Calderaro, R. Iglesias-Marzoa, C. Iniguez, J. L. Lamadrid Gutierrez, F. Lopez-Martinez, D. Lozano-Perez, N. Maicas Sacristan, E. L. Molina-Ibanez, A. Moreno-Signes, S. Rodriguez Llano, M. Royo Navarro, V Tilve Rua, U. Andrade, E. J. Alfaro, S. Akras, P. Arnalte-Mur, B. Ascaso, C. E. Barbosa, J. Beltran Jimenez, M. Benetti, C. A. P. Bengaly, A. Bernui, J. J. Blanco-Pillado, M. Borges Fernandes, J. N. Bregman, G. Bruzual, G. Calderone, J. M. Carvano, L. Casarini, A. L. Chies-Santos, G. Coutinho de Carvalho, P. Dimauro, S. Duarte Puertas, D. Figueruelo, J. Gonzalez-Serrano, M. A. Guerrero, S. Gurung-Lopez, D. Herranz, M. Huertas-Company, J. A. Irwin, D. Izquierdo-Villalba, A. Kanaan, C. Kehrig, C. C. Kirkpatrick, J. Lim, A. R. Lopes, R. Lopes de Oliveira, A. Marcos-Caballero, D. Martinez-Delgado, E. Martinez-Gonzalez, G. Martinez-Somonte, N. Oliveira, A. A. Orsi, R. A. Overzier, M. Penna-Lima, R. R. R. Reis, D. Spinoso, S. Tsujikawa, P. Vielva, A. Z. Vitorelli, J. Q. Xia, H. B. Yuan, A. Arroyo-Polonio, M. L. L. Dantas, C. A. Galarza, D. R. Goncalves, R. S. Goncalves, J. E. Gonzalez, A. H. Gonzalez, N. Greisel, R. G. Landim, D. Lazzaro, G. Magris, R. Monteiro-Oliveira, C. B. Pereira, M. J. Reboucas, J. M. Rodriguez-Espinosa, S. Santos da Costa, E. Telles
Summary: The J-PAS survey will scan thousands of square degrees in the northern sky using a unique set of 56 filters, with miniJPAS already demonstrating the scientific potential through a survey in the AEGIS field.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
David Figueruelo, Miguel Aparicio Resco, Florencia A. Teppa Pannia, Jose Beltran Jimenez, Dario Bettoni, Antonio L. Maroto, L. Raul Abramo, Jailson Alcaniz, Narciso Benitez, Silvia Bonoli, Saulo Carneiro, Javier Cenarro, David Cristobal-Hornillos, Renato A. Dupke, Alessandro Ederoclite, Carlos Lopez-Sanjuan, Antonio Marin-Franch, Valerio Marra, Claudia Mendes de Oliveira, Mariano Moles, Laerte Sodre, Keith Taylor, Jesus Varela, Hector Vazquez Ramio
Summary: The study examines a cosmological model with coupling between dark matter and dark energy, and finds through fitting and forecasting that a coupling is more suitable than an uncoupled scenario in cosmology, primarily driven by cluster counts.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Alfredo D. Miravet, Antonio L. Maroto
Summary: We explore the use of conformal vector models in cosmology, and find that gravitational waves are suppressed at large scales. Additionally, we observe anisotropies in the tensor power spectrum, despite the isotropy of the cosmological background metric. The presence of background vector fields also leads to net polarization of gravitational waves and potential linear to circular polarization conversion.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Antonio L. Maroto, Alfredo D. Miravet
Summary: In this study, we find that the gravitational leptogenesis mechanism can occur without requiring new axial couplings in the inflaton sector. We demonstrate that the spacetime metric itself breaks parity symmetry in the perturbed Robertson-Walker background after inflation, generating a nonvanishing Pontryagin density that leads to matter-antimatter asymmetry. We analyze the asymmetry produced in different inflationary and reheating scenarios and find that it can be locally comparable to observations in some cases, although the size of the matter-antimatter regions is usually much smaller than the present Hubble radius.
Article
Astronomy & Astrophysics
Rafael L. Delgado, Antonio Dobado, Domenec Espriu
Summary: Some effective field theories exhibit dynamical resonances that can mitigate their bad behavior at high energies when properly included. The preferred method to unveil such resonances is the unitarization of the partial wave amplitudes. In this study, we interpret the Einstein-Hilbert theory as part of effective Lagrangians and implement the inverse amplitude method to unitarize the one-loop level graviton-graviton scattering in pure gravity, considering the careful treatment of infrared divergences and the introduction of infrared regulators to fulfill perturbative unitarity.
Article
Astronomy & Astrophysics
Bruno J. Barros, Alvaro de la Cruz-Dombriz, Francisco S. N. Lobo
Summary: In this study, novel analytical solutions for static and spherically symmetric wormhole geometries threaded by an anisotropic distribution of matter conformally coupled to a scalar ghost field are presented. The dynamics of the scalar field and matter throughout the wormhole, as well as the role played by the nonminimal coupling, are explored. Furthermore, coupled ghosts in the presence of a scalar potential are considered, and the traversability conditions within such geometrical scheme are analyzed.
Article
Astronomy & Astrophysics
Adrian Casado-Turrion, Alvaro de la Cruz-dombriz, Antonio Dobado
Summary: This article provides a systematic overview of f(R) models allowing for constant-curvature solutions and the constant-curvature solutions themselves. It concludes that most f(R) models suffer from several shortcomings and exhibit unphysical properties.
Article
Astronomy & Astrophysics
Adrian Casado-Turrion, Antonio Dobado, Alvaro de la Cruz-Dombriz
Summary: This study investigates gravitational collapse in the context of f(R) theories of gravity. By generalizing the Oppenheimer-Snyder model to fit within metric f(R) gravity, novel exterior solutions are found, and it is verified that certain vacuum metrics cannot represent spacetime outside a collapsing dust star in metric f(R) gravity. Additionally, it is discovered that the Oppenheimer-Snyder model is incompatible with the junction conditions of the Palatini formulation of f(R) gravity.
Article
Astronomy & Astrophysics
Alfredo D. Miravet, Antonio L. Maroto
Summary: The study shows that ultralight vector field dark matter can induce an anisotropic suppression of gravitational wave amplitude, especially for primordial gravity waves. Future cosmic microwave background B-mode polarization detectors may be able to detect this effect.
Review
Astronomy & Astrophysics
A. Weltman, P. Bull, S. Camera, K. Kelley, H. Padmanabhan, J. Pritchard, A. Raccanelli, S. Riemer-Sorensen, L. Shao, S. Andrianomena, E. Athanassoula, D. Bacon, R. Barkana, G. Bertone, C. Boehm, C. Bonvin, A. Bosma, M. Brueggen, C. Burigana, F. Calore, J. A. R. Cembranos, C. Clarkson, R. M. T. Connors, A. de la Cruz-Dombriz, P. K. S. Dunsby, J. Fonseca, N. Fornengo, D. Gaggero, I Harrison, J. Larena, Y-Z Ma, R. Maartens, M. Mendez-Isla, S. D. Mohanty, S. Murray, D. Parkinson, A. Pourtsidou, P. J. Quinn, M. Regis, P. Saha, M. Sahlen, M. Sakellariadou, J. Silk, T. Trombetti, F. Vazza, T. Venumadhav, F. Vidotto, F. Villaescusa-Navarro, Y. Wang, C. Weniger, L. Wolz, F. Zhang, B. M. Gaensler
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA
(2020)
