Article
Physics, Multidisciplinary
Nihat Sadik Deger, Marc Geiller, Jan Rosseel, Henning Samtleben
Summary: The minimal massive gravity model in three dimensions propagates a single massive spin-2 mode around an anti-de Sitter vacuum, allowing for vacua with positive central charges and a bulk graviton of positive energy. Surprisingly, all vacua complying with bulk and boundary unitarity appear to break supersymmetry spontaneously in the supersymmetric extension of the model.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
M. Mousavi, K. Atazadeh
Summary: The study examines future cosmological singularities in the context of massive gravity and minimal massive bigravity theory. It identifies sudden and big brake singularities in different cosmological models, noting that the sudden singularity can be eliminated when model parameters approach zero.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
G. Fanizza, G. Marozzi, M. Medeiros, G. Schiaffino
Summary: Inspired by the fully non-linear Geodesic Light-Cone (GLC) gauge, a new cosmological perturbation theory is built and the connection with standard cosmological perturbation theory is explored through gauge transformations related to a new set of perturbations. In addition, various definitions for gauge invariant combinations are utilized, with emphasis on the relationships with linearized GLC gauge perturbations. The GLC gauge is shown to offer advantages in terms of providing simple expressions for light-like observables and matching the proper time of a free-falling observer.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Mahmoud Hashim, Waleed El Hanafy, Alexey Golovnev, Amr A. El-Zant
Summary: The study investigates the cosmological viability of an infrared corrected teleparallel gravity model assuming a spatially flat universe. It shows that despite being physically different, the model is equivalent to ΛCDM in terms of phenomenology and statistics, while being more adept at accurately fitting observational constraints and reducing the H-0 tension without worsening the S-8 tension. This calls for a full examination of the empirical viability of the theory at the linear perturbation level.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Anamaria Hell
Summary: This study compares the massive Kalb-Ramond and Proca fields with a quartic self-interaction, and shows that they have the same strong coupling scale. However, the different modes in these theories behave differently beyond the strong coupling scale, indicating a potential contradiction with claims in the literature about their duality.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Particles & Fields
J. W. Moffat, V. T. Toth
Summary: This study investigates the contributions of the Friedmann-Lemaitre-Robertson-Walker metric in standard cosmology to the first-order approximation of the gravitational field in Moffat's theory of modified gravity (MOG). It also considers the contributions resulting from the fact that the MOG theory does not satisfy the shell theorem or Birkhoff's theorem, leading to the external field effect (EFE). The study shows that these effects have small contributions to the radial acceleration law, which are orders of magnitude smaller than the radial acceleration in spiral galaxies.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Holger Gies, Dimitrios Gkiatas, Luca Zambelli
Summary: In this paper, we combine a construction of BRST-invariant, nonlinear massive gauge fixing with the background field formalism. The resulting functional preserves the background-field invariance and BRST invariance of the quantum field. We verify the theory by computing the one-loop effective action and the beta function of the gauge coupling. We also study off-shell one-loop contributions and the application of the decoupling solution.
Article
Astronomy & Astrophysics
G. Parimbelli, C. Carbone, J. Bel, B. Bose, M. Calabrese, E. Carella, M. Zennaro
Summary: This article provides an accurate comparison of different methodologies for modeling the nonlinear matter power spectra in the presence of massive neutrinos and dynamical dark energy. The results show that HMcode and ReACT perform better than HALOFIT, while EuclidEmulator2 agrees remarkably well with the simulated spectra in some scenarios. This study highlights the importance of selecting appropriate methods when modeling complex cosmological scenarios.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Miguel A. Garcia-Aspeitia, A. Hernandez-Almada, Juan Magana, V Motta
Summary: This passage presents an exhaustive analysis of unimodular gravity as a potential solution to the cosmological constant problem and current universe acceleration. By estimating the CC-like value and a new parameter z(ini), the analysis gets numbers close to the reionization epoch. Joint analysis of various observational data shows consistent results with estimations from Planck and Supernovae measurements.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Hao-Jui Kuan, Jasbir Singh, Daniela D. Doneva, Stoytcho S. Yazadjiev, Kostas D. Kokkotas
Summary: Recent research has shown the existence of scalarized neutron star solutions in a class of tensor-multiscalar theories of gravity with a nontrivial target space metric, where the scalar charge is zero and the structure of the solutions is very complex. Up to three solutions can exist for a single neutron star, and stability changes occur at the maximum mass models.
Article
Multidisciplinary Sciences
Mohsen Fathi, Jose R. Villanueva, Norman Cruz
Summary: In this paper, a rotating de Rham-Gabadadze-Tolley black hole with a positive cosmological constant under massive gravity is presented using a modified Newman-Janis algorithm. Stable orbits of constant radii were observed, leading to a numerical study of the solutions to a nonic equation governing the radii of planar orbits. The stability of orbits near the event horizon and the solutions to the angular equations of motion were also investigated, followed by a simulation of spherical particle orbits around the black hole.
Article
Astronomy & Astrophysics
Antonio De Felice, Shinji Mukohyama, Masroor C. Pookkillath
Summary: The Minimal theory of Massive Gravity (MTMG) includes two tensor modes in the gravity sector with non-zero mass, showing self-accelerating and normal branches with constraints on the graviton mass for the latter branch giving an upper bound at 95%CL as mu(0) < 8.4 x 10(-34) eV.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Takashi Hiramatsu, Tsutomu Kobayashi
Summary: This article presents a cosmological test of modified gravity with two tensorial degrees of freedom and no extra propagating scalar mode. The gravity theory considered in this study allows for a cosmological model that is indistinguishable from the ACDM model at the level of the background evolution. The model has a single modified-gravity parameter /3, whose effect can be observed in linear perturbations, although no extra scalar mode is propagating. By using a modified Boltzmann code to incorporate the present model, the constraints -0.047 < beta < -0.028 at 68% confidence are derived from Planck CMB data. As our modified gravity model is hardly constrained by Solar System tests and gravitational-wave propagation, our result offers the first observational test on the model.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Qiuyue Liang, Mark Trodden
Summary: The study explores the potential of pulsar timing arrays in detecting stochastic gravitational wave backgrounds in massive gravity theories. They compute the overlap reduction function analogous to the Hellings-Downs curve for massive gravity, providing a starting point for future numerical studies.
Article
Astronomy & Astrophysics
F. F. Faria
Summary: This paper examines the cosmological solutions of the massive conformal gravity field equations in the presence of matter fields, showing that the solution with negative curvature aligns well with the late universe.
MODERN PHYSICS LETTERS A
(2021)
Article
Physics, Particles & Fields
Emmanuel N. Saridakis, Weiqiang Yang, Supriya Pan, Fotios K. Anagnostopoulos, Spyros Basilakos
Summary: Soft cosmology extends the standard cosmology by allowing for different equation-of-state parameters for dark matter and dark energy at different scales. Data analysis suggests that soft cosmology is favored by observational constraints.
Article
Astronomy & Astrophysics
Maria Mylova, Jackson Levi Said, Emmanuel N. Saridakis
Summary: This paper constructs the effective field theory (EFT) of the teleparallel equivalent of general relativity (TEGR). The EFT contains more terms compared to the EFT of general relativity (GR) and possesses minor but non-zero differences. However, these differences are suppressed by a heavy mass scale ? and may not be measurable in future experiments and observations.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Shreya Banerjee, Sayantani Bera, David F. Mota
Summary: The Lambda-Cold Dark Matter model is currently the most accurate model for explaining cosmological observations, but there are still issues at galactic scales. Various models of dark matter, such as superfluid dark matter, Bose-Einstein Condensate (BEC) dark matter, and fuzzy dark matter, have been proposed to address these shortcomings. This study investigates these models using the constraint on gravitational wave propagation speed from the detection of the binary neutron star GW170817 by the LIGO-Virgo detector network. The findings suggest that the fuzzy dark matter model is the most feasible scenario to be tested in the near future, especially with detection frequencies < 10-9 Hz.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Theodoros Papanikolaou, Andreas Lymperis, Smaragda Lola, Emmanuel N. Saridakis
Summary: Primordial black holes (PBHs) can be formed through non-canonical inflation, and can provide observational evidence of the early Universe. Constraints on the non-canonical exponents are extracted by requiring significant PBH production. Asteroid-mass PBHs can explain the dark matter, and solar-mass PBHs within the LIGO-VIRGO detection band can be produced. The collapse of enhanced cosmological perturbations that form PBHs can also generate a detectable stochastic gravitational wave (GW) background.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
G. G. L. Nashed, Emmanuel N. Saridakis
Summary: In this study, new classes of anisotropic solutions are extracted within the framework of mimetic gravity. By applying the Tolman-Finch-Skea metric and a specific anisotropy unrelated to it, and smoothly matching the interior solution to the exterior Schwarzschild solution, the authors investigate various properties of these solutions. The results show positive energy density, decreasing pressures towards the center of the star, repulsive anisotropic force, and monotonically increasing equation-of-state parameters. The stability of the solutions is also examined, and it is found that the stars in all cases are stable.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Chemistry, Multidisciplinary
Shreya Banerjee, Sunil K. Gupta, Erode N. Prabhakaran
Summary: The presence of sinusoidal synchronicity between rotational motion along C-alpha-C ' sigma bond and the concomitant pyramidalization of C ' in amides is demonstrated for the first time in solution. It has been found that synchronicity is perturbed when tau-rotation is 'locked' with interactions, resulting in a strain on the amide bond and a decrease in energy barrier for the amide bond cis/trans isomerism by approximately 1.68 kcal/mol.
Article
Astronomy & Astrophysics
Maria Petronikolou, Emmanuel N. Saridakis
Summary: In this study, we investigate scalar-tensor and bi-scalar-tensor modified theories of gravity that can alleviate the H-0 tension. We show that by choosing particular models with specific features, such as a shift-symmetric friction term or phantom behavior of the effective dark-energy equation-of-state parameter, the tension can be alleviated. These theories provide known mechanisms for alleviating the H0 tension.
Article
Astronomy & Astrophysics
Shreya Banerjee, Maria Petronikolou, Emmanuel N. Saridakis
Summary: We investigate the cosmological applications of gravitational scalar-tensor theories and analyze them in the context of the H0 tension. Two specific models are explored, showing negligible effects at high redshifts but an increasing deviation as time passes. At low redshifts, the Hubble parameter takes on higher values in a controlled manner. This behavior is attributed to the phantom nature of the effective dark-energy equation-of-state parameter, providing a possible solution to the H0 tension. Comparison with cosmic chronometer data demonstrates full agreement within 1σ confidence level.
Article
Astronomy & Astrophysics
Petros Asimakis, Spyros Basilakos, Andreas Lymperis, Maria Petronikolou, Emmanuel N. Saridakis
Summary: This study constructs new classes of modified theories that couple the matter sector with the Einstein tensor, specifically considering direct couplings to the energy-momentum tensor and its trace derivatives. The general field equations, without higher-order derivatives, are derived and applied in a cosmological framework, resulting in Friedmann equations with additional terms that give rise to an effective dark energy sector. The study shows successful description of the thermal history of the universe at the background level, with matter and dark energy epochs, and the dark energy equation-of-state parameter can approach -1 as time progresses. Comparison with cosmic chronometer data demonstrates a very good agreement. Detailed investigations of scalar and tensor perturbations validate the predicted behavior of the matter overdensity.
Article
Chemistry, Multidisciplinary
Mita Dutta, Shreya Banerjee, Mahitosh Mandal, Manish Bhattacharjee
Summary: A self-healable metallohydrogel of Mn(ii) has been successfully prepared using a low molecular weight gelator, Na2HL. It has been characterized by various techniques and encapsulated with drugs IND and GEM. The GEM-loaded metallogel showed enhanced delivery and cytotoxicity against breast cancer cells, while the MOG_IND exhibited improved anti-inflammatory response compared to the drug alone.
Article
Astronomy & Astrophysics
Wompherdeiki Khyllep, Jibitesh Dutta, Emmanuel N. Saridakis, Kuralay Yesmakhanova
Summary: Motivated by the success of f(Q) gravity in fitting observational data, we analyze the behavior of two studied f(Q) models, power-law and exponential, through dynamical system analysis. We find that both models have a matter-dominated saddle point followed by a stable dark-energy-dominated accelerated universe. The models fit observational data well and can be considered as promising alternatives to the ACDM concordance model.
Article
Physics, Particles & Fields
Sebastian Bahamonde, Konstantinos F. Dialektopoulos, Manuel Hohmann, Jackson Levi Said, Christian Pfeifer, Emmanuel N. Saridakis
Summary: This study focuses on the cosmological perturbation theory in f(T) gravity, which is a simple extension of the teleparallel equivalent of general relativity. The authors examine the possibility of a non-flat FLRW background solution and perform perturbations for different spatial geometries. They determine the behavior of the perturbative modes in this non-flat FLRW setting for arbitrary f(T) models and identify propagating modes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Fotios K. Anagnostopoulos, Viktor Gakis, Emmanuel N. Saridakis, Spyros Basilakos
Summary: The f(Q) theories of modified gravity, based on non-metricity as the fundamental geometric quantity, have shown great effectiveness in describing the late-time Universe. By using Big Bang Nucleosynthesis (BBN) formalism and observations, constraints on various classes of f(Q) models are obtained. The deviations on the freeze-out temperature caused by f(Q) terms are calculated and constraints on the model parameters are imposed by applying the observational bound on |delta Tf/Tf|. It is found that f(Q) gravity can pass the BBN constraints, distinguishing itself from many other gravitational modifications that fail to do so.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Theodoros Papanikolaou, Charalampos Tzerefos, Spyros Basilakos, Emmanuel N. Saridakis
Summary: Research shows that the fluctuations of primordial black holes can be used as a novel tool to test general relativity and constrain possible modified gravity deviations in the framework of f(T) gravity. By investigating three viable mono-parametric models, we find that the deviations from general relativity in terms of the gravitational-wave source and propagation are negligible within the observationally allowed range of f(T) model parameters. Therefore, we conclude that realistic and viable f(T) theories can safely pass the primordial black hole constraints, providing additional support for them.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Bikash R. Dinda, Md. Wali Hossain, Anjan A. Sen
Summary: This study investigates the detectability of deviation in interacting and non-interacting cubic Galileon models from the similar CDM model through the 21-cm power spectrum. The results show that interferometric observations, such as the upcoming SKA1-mid, can detect the deviations depending on the parameter values.
JOURNAL OF ASTROPHYSICS AND ASTRONOMY
(2023)
