Article
Astronomy & Astrophysics
Saptaswa Ghosh, Arpan Bhattacharyya
Summary: This study investigates the equatorial deflection angle of light rays in KerrNewman black-bounce spacetime and derives a closed-form formula for this deflection angle in terms of elliptic integrals. The results show that the deflection angle increases with the decrease of charge and regularization parameter, while the effect of the regularization parameter on the ring size is negligible.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Surajit Kalita, Shruti Bhatporia, Amanda Weltman
Summary: In recent decades, numerous modifications to general relativity have been proposed to address cosmological and astrophysical issues. While many modified gravity models have been ruled out, some theories remain viable albeit with parameters constrained by observations. Fast Radio Bursts have proven to be powerful tools for constraining cosmology and fundamental physics. This study examines the implications of a generic modified gravity theory on gravitational lensing using Fast Radio Bursts, and utilizes observations to constrain the fraction of dark matter composed of primordial black holes. Additionally, it demonstrates that modified gravity produces a screening effect on gravitational lensing akin to the presence of plasma acting as a scattering screen.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Lingyi Hu, Alan Heavens, David Bacon
Summary: In this study, the effect of the cosmological constant A on the gravitational bending of light was revisited by numerical integration of the geodesic equations. The research found that the bending of light is virtually unaffected by the cosmological constant, as it is already accounted for in the standard lensing equations. The only small modifications arise when the bending is restricted to a finite region covered by the hole. Therefore, it is concluded that there is no need for modification of the standard cosmological lensing equations in the presence of a cosmological constant.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Nisha Godani, Gauranga C. Samanta
Summary: The paper explores the modification of general relativity and the presence of extra matter for traversable wormhole solutions, particularly in the background of f(R, T) gravity influenced by scalar field and electric charge. It examines the energy conditions with both the scalar field and electric charge, compares the results, and studies the existence of photon spheres due to strong gravitational lensing, along with the formation of relativistic images.
Article
Astronomy & Astrophysics
Sankarshana Srinivasan, Daniel B. Thomas, Francesco Pace, Richard Battye
Summary: This study conducts model-independent modified gravity N-body simulations on all cosmological scales, finding that the ReACT framework provides the most consistent performance for both matter power spectrum and weak-lensing observables fitting. This approach paves the way for a full model-independent test of modified gravity using data from upcoming surveys like Euclid and the Vera Rubin Telescope.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Giulio Scelfo, Maria Berti, Alessandra Silvestri, Matteo Viel
Summary: In a General Relativistic framework, the response of Gravitational Waves (GW) and Electromagnetic (EM) waves to matter perturbations is expected to be the same. This study explores the cross-correlation of resolved GW events and EM signals to investigate alternative theories of gravity. The findings show that considering weak lensing, angular clustering, and their cross term as observable probes can provide valuable information on the behavior of these two observables, potentially revealing non-General Relativistic signatures.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Xiaoge Xu, Tingyuan Jiang, Junji Jia
Summary: This study examines the trajectory deflection and gravitational-electromagnetic dual lensing of charged signals in general charged static and spherically symmetric spacetimes. The electromagnetic corrections affect the apparent angles, magnifications, and time delay of the images, with the sign and relative size of the corrections determined by the mass, charge, signal particle charge, and energy. The results have implications for the deflection and lensing of charged particles in various charged spacetimes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
G. Vernardos
Summary: We present a self-consistent and versatile forward modelling software package for time-varying strongly lensed systems. It addresses the missing time dimension in existing approaches and demonstrates the importance of observation cadence and combining information from different wavelengths in correctly measuring time delays.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Janquart, M. Wright, S. Goyal, J. C. L. Chan, A. Ganguly, A. Garron, D. Keitel, A. K. Y. Li, A. Liu, R. K. L. Lo, A. Mishra, A. More, H. Phurailatpam, P. Prasia, P. Ajith, S. Biscoveanu, P. Cremonese, J. R. Cudell, J. M. Ezquiaga, J. Garcia-Bellido, O. A. Hannuksela, K. Haris, I. Harry, M. Hendry, S. Husa, S. Kapadia, T. G. F. Li, I. Magana Hernandez, S. Mukherjee, E. Seo, C. Van den Broeck, J. Veitch
Summary: This paper presents follow-up analyses to assess the significance of candidate lensed signals, even if high significance is not found. These analyses provide insight into potential avenues for dealing with high-significance candidates in future observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ashish Kumar Meena, Anuj Mishra, Anupreeta More, Sukanta Bose, Jasjeet Singh Bagla
Summary: With the increase in the number of observed gravitational wave signals, it has become possible to detect strongly lensed gravitational waves by galaxies. The presence of microlenses in lens galaxies introduces frequency-dependent modulations in the strongly lensed gravitational wave signal within the LIGO frequency range. This study investigates the fraction of strong lens systems affected by microlensing using realistic mock observations and concludes that microlensing effects are more sensitive to the macro-magnification than the underlying microlens density.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Mark H. Y. Cheung, Joseph Gais, Otto A. Hannuksela, Tjonnie G. F. Li
Summary: The study reveals that gravitational waves can be microlensed by stars, leading to observable irregular waveforms but also introducing systematic errors. Numerical simulations show that diffraction effects introduced by microlensing are significant in the LIGO frequency band, significantly suppressing the magnification by stellar lenses.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Simon M. C. Yeung, Mark H. Y. Cheung, Eungwang Seo, Joseph A. J. Gais, Otto A. Hannuksela, Tjonnie G. F. Li
Summary: Gravitational lensing describes the bending of light and gravitational waves due to the gravitational potential of massive objects. Strong lensing can create multiple images with different characteristics, and microlensing can further affect the amplification and mismatch of these images. This study focuses on the microlensing effect on type-II images and explores the possibility of detecting and analyzing these microlensed signals through Bayesian parameter estimation. The results confirm previous findings and emphasize the necessity for more realistic microlensing templates.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Anuj Mishra, Ashish Kumar Meena, Anupreeta More, Sukanta Bose, Jasjeet Singh Bagla
Summary: In this study, the wave effects of microlensing in gravitational wave signals were extensively investigated, revealing that the impact of microlensing becomes increasingly significant with higher macro-magnification values. It was found that microlensing cannot be neglected when inferring source parameters for macro-magnifications greater than or equal to 15, and for extremely high macro-magnifications exceeding 100, there is a risk of missed detection of lensed signals.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Xikai Shan, Chengliang Wei, Bin Hu
Summary: This study focuses on the magnification effect and selection effect of gravitational waves, finding that the average magnification remains unbiased for observed luminosity distances up to 3 Gpc. However, beyond this distance, estimation bias becomes significant, highlighting the importance of considering lensing effects in distance estimation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Elham Nazari
Summary: In this study, the motion of light in the weak-field limit of energy-momentum-squared gravity (EMSG) is derived, and the effects of EMSG theory on Solar System tests and microlensing are investigated. The results show that the EMSG theory passes the Solar System tests and has a small impact on the lensed images.
Article
Astronomy & Astrophysics
Dongdong Zhang, Jia-Rui Li, Jiaqi Yang, Yufei Zhang, Yi-Fu Cai, Wenjuan Fang, Chang Feng
Summary: We use the Ali Cosmic Microwave Background Polarization Telescope (AliCPT) to forecast the constraints on neutrino physics parameters using the Cosmic Microwave Background (CMB) temperature, E-mode polarization, and lensing spectra. Our numerical simulations show that AliCPT can achieve a precision of sigma(N (eff)) = 0.56 and M (nu) < 1.10 eV (95% CL.) for the first year of observation, based on TT, TE, EE, and CMB lensing power spectra. We also investigate how instrumental parameters such as noise level, FWHM, and sky coverage affect these constraints on neutrino parameters.
ASTROPHYSICAL JOURNAL
(2023)
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
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
Astronomy & Astrophysics
Lei-Hua Liu, Mian Zhu, Wentao Luo, Yi-Fu Cai, Yi Wang
Summary: We systematically investigate the microlensing effect of a charged spherically symmetric wormhole, where the light source is remote from the throat. The numerical result shows that the range of total magnification is from 105 to 10-2 depending on various metrics. Our theoretical investigation could shed new light on exploring the wormhole with the microlensing effect.
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
Yu-Min Hu, Yaqi Zhao, Xin Ren, Bo Wang, Emmanuel N. Saridakis, Yi-Fu Cai
Summary: This study investigates the scalar perturbations and possible strong coupling issues of f(T) gravity using the effective field theory (EFT) approach. The generalized EFT framework of modified teleparallel gravity is revisited and applied to examine both linear and second-order perturbations in f(T) theory. The results suggest that there is no new scalar mode present in f(T) gravity, indicating a strong coupling problem. However, an estimation of the strong coupling scale based on the ratio of cubic to quadratic Lagrangians shows that the strong coupling problem can be avoided for certain modes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ali Dehghani, Behnam Pourhassan, Soodeh Zarepour, Emmanuel N. Saridakis
Summary: This study investigates the thermodynamic schemes of charged BTZ-like black holes in arbitrary dimensions. Two possible thermodynamic schemes are identified with different outcomes. In the traditional scheme, the charged black holes violate the reverse isoperimetric inequality and have a fundamental thermodynamic instability. In the second scheme, the black holes are thermodynamically stable and can explain the van der Waals critical phenomenon.
PHYSICS OF THE DARK UNIVERSE
(2023)