Modified Gravity - Science topic

The existence of dark matter has long been extensively studied in the past few decades. In this study, we investigate the emission of neutrinos and photons from neutron stars (NSs) by employing the modified theory of gravity and the corresponding Tolman-Oppenheimer-Volkoff (TOV) system of equations. The extreme matter density and magnetic field ins...

This paper aims to explore the quasinormal modes (QNMs) and effective potential profiles of massless and rotating BTZ black holes within the frameworks of $f(\mathcal{R})$ and Ricci-Inverse ($\mathcal{RI}$) modified gravity theories, which, while producing similar space-time structures, exhibit variations due to distinct cosmological constants, $\L...

The kinematics of the ultra-diffuse galaxy (UDG) NGC1052-DF44 is primarily influenced by the presence of dark matter (DM). In this paper, we conduct a contrasting kinematic study of DF44 within the alternative modified gravity framework. In comparison to NFW DM, we test three alternative gravity models viz Milgromian dynamics (MOND), characterized...

Recent observations by the James Webb Space Telescope (JWST) have revealed the presence of bright and well-formed galaxies at high redshifts, challenging the predictions of the standard Lambda-Cold Dark Matter (LCDM) cosmological model. This paper explores the potential of Modified Gravity (MOG), specifically Scalar-Tensor-Vector Gravity (STVG), to...

The universe is evolving with deceleration and rotation Based on the above concepts and relationships, it seems better to work on cosmic models that have a deceleration evolution. Nowadays, many cosmologists are seriously working on understanding the future cosmic deceleration, considering dark energy and essence as different forms of cosmic drivin...

In this study, we investigate the impact of modified gravity (MG) on the merger rate of compact binaries within dark matter spikes surrounding supermassive black holes (SMBHs). Specifically, we calculate the binary merger rates involving primordial black holes (PBHs) and/or neutron stars (NSs) in Hu–Sawicki f(R) gravity and the normal branch of Dva...

In this work, we construct a new model of compact stars in the presence of anisotropic matter in the Rastall theory of gravity. For this, we considered the anisotropic matter content when formulating the Rastall field equations. Secondly, the Tolman–Oppenheimer–Volkoff (TOV) equation in the context of Rastall theory is formulated. We apply the Finc...

Hawking’s cosmology logically leads to an observed multiverse. This article argues it a superposition of at least three 3-dimensional universes in a 4-dimensional space, which each have two overlapping dimensions with the observed universe. For there is nothing outside it that could disturb the superposition, it could last forever. This explains wh...

Disc galaxies represent a promising laboratory for the study of gravitational physics, including alternatives to dark matter, owing to the possibility of coupling rotation curves' dynamical data with strong gravitational lensing observations. In particular, Euclid, DES and LSST are predicted to observe hundreds of thousands of gravitational lenses....

Hawking’s cosmology logically leads to an observed multiverse. This article argues it a superposition of at least three 3-dimensional universes in a 4-dimensional space, which each have two overlapping dimensions with the observed universe. For there is nothing outside it that could disturb the superposition, it could last forever. This explains wh...

This work presents a comprehensive study on the distribution of prime numbers through geometric and arithmetic methodologies, offering new insights into their behavior and verifying several conjectures, including Legendre’s, Oppermann’s, Brocard’s, and Andrica’s conjectures. By introducing tools such as the Parabolic Sieve of Primes with Offset (PS...

We propose an extension of General Relativity (GR) based on a space-time foliation by three-dimensional space-like hypersurfaces labeled by the Khronon scalar field τ. We show that this theory (i) leads to modified Newtonian dynamics (MOND) at galactic scales for stationary systems; (ii) recovers GR plus a cosmological constant in the strong field...

Numerical QUMOND-simulations of star clusters orbiting in a Galactic disk potential show that the leading tidal arm of open star clusters contains tendentially more members than the trailing arm. However, these type of simulations are performed by solving the field-equations of QUMOND and already become non-practical for star cluster masses at arou...

We present cosmological constraints on deviations from general relativity (GR) from the first-year of clustering observations from the Dark Energy Spectroscopic Instrument (DESI) in combination with other datasets. We first consider the $\mu(a,k)$-$\Sigma(a,k)$ modified gravity (MG) parametrization (as well as $\eta(a,k)$) in flat $\Lambda$CDM and...

Universe evolving with deceleration and rotation Based on the above concepts and relationships, it seems better to work on cosmological models that have decelerated evolution. Today, many cosmologists are seriously working on understanding the future cosmic deceleration, considering dark energy and matter as different forms of cosmic driving energy...

We demonstrate a very general mathematical and physical expression of the rotation speed at the end of the galaxy (far from the vast majority of the galaxy’s baryonic mass) obtained from General Relativity without non-baryonic matter. We show the excellent agreement with measurements obtained for the Milky Way published in a recent article which co...

This paper argues that the universe possesses two scalar potentials similar to those proposed by E.T. Whittaker in which waveforms travel longitudinally. It is proposed that these scalar potentials form through black holes, creating normal transverse electromagnetic radiation as well as gravity. This opens up new avenues for understanding the unive...

We forecast constraints on minimal model-independent parametrisations of several Modified Gravity theories using mock Stage-IV cosmic shear data. We include nonlinear effects and screening, which ensures recovery of General Relativity on small scales. We introduce a power spectrum emulator to accelerate our analysis and evaluate the robustness of t...

A new model of gravity is presented here that is similar to MOND and Chameleon theory but uses an Entropic Gravity approach that is not based fundamentally on the First Law of Thermodynamics. Instead, the Second Law of Thermodynamics will be mainly used here as it was applied in Black Hole Physics via the Area Theorem and the Holographic Principle....

Milgrom's Modified Newtonian Dynamics (MOND) correction to Newtonian gravity is shown to be equivalent to a more fundamental transformation between a non-inertial local reference frame and the fixed background of the observable universe, complying with Mach's principle. Both Newton's gravitational constant and Milgrom's MOND acceleration parameter...

Milgrom’s Modified Newtonian Dynamics (MOND) correction to Newtonian gravity is shown to be equivalent to a more fundamental transformation between a non-inertial local reference frame and the fixed background of the observable universe, complying with Mach’s principle. Both Newton’s gravitational constant and Milgrom’s MOND acceleration parameter...

In the present contribution to the proceedings of MG17, the main aim is to elucidate the physically important effects of a special nonlinear gauge field with a square-root of the standard Maxwell Lagrangian in its action, interacting with a specific non-canonical modified $f(R)= R + R^2$ gravity formulated in terms of metric-independent spacetime v...

This study is about the consequences of fermionic q-deformation on Friedmann equations and its effects on cosmology within the framework of Verlinde’s entropic gravity proposal. We begin by examining the thermodynamic properties of q-deformed fermion gas model in two-dimensional space. We then extend our research to derive modified Friedmann equati...

It has recently been demonstrated (Giusti in Phys Rev D 101:124029, 2020, https://doi.org/10.1103/PhysRevD.101.124029 ) that characteristic traits of Milgrom’s modified Newtonian dynamics (MOND) can be replicated from an entirely distinct framework: a fractional variant of Newtonian mechanics. To further assess its validity, this proposal needs to...

We implement a test of MOND and Verlinde's Emergent Gravity using the galaxy cluster SMACS J0723-7327, which has been recently imaged using the eROSITA X-ray telescope as well as with JWST. We test MOND using two independent methods. The first method involves comparing the dynamical MOND mass and baryonic mass, while the second method entails a com...

The concept of ether, once dismissed in the wake of Einstein's theory of relativity, is experiencing a resurgence in modern physics, particularly in discussions surrounding alternative gravity theories. This paper explores the intriguing possibility that ether-like properties may provide valuable insights into the nature of gravity, spacetime, and...

In $f(T)$ gravity, the theory modifies the gravitational action by introducing a function of the torsion scalar $T$. This approach allows for a different treatment of gravity than general relativity, particularly in cosmological contexts. Dynamical system analysis is a powerful tool for exploring the stability and behavior of cosmological solutions...

The Standard Thrust Capacitor or STC uses relativistic MOND dark photons as rocket propellant to conserve momentum. We assume that the dark photon is massless and interacts with baryonic condensed matter only through gravitation. Momentum comes from one dark photon gravitationally backreacting one Planck mass of baryonic condensed matter in the STC...

We examine whether the radial acceleration relation (RAR) of dwarf galaxies can be explained by Verlinde's emergent gravity. This is the extension of arXiv:2206.11685v3, which examines the RAR of typical spiral galaxies, to less massive systems. To do this, we compile the line-of-sight velocity dispersion profiles of 30 dwarf galaxies in the Local...

In this research we study cosmic-scale collective gravitational quantum phenomena in the framework of multistream quasiparticle model. The energy band structure of gravitational quasiparticles (GQs) reveal three distinct regimes of collapsing, stable and expansion of matter in gravitational quantum field. It is found that gravitational expansion is...

In Milgrom's modified Newtonian dynamics (MOND) framework, the dynamical mass of a galaxy is fully determined by its baryonic matter distribution. We fit the distribution of cold and hot gas halos, focusing on hot gas, around SDSS central galaxies using weak lensing signals from the DECaLS survey in MOND. The central galaxies are classified into tw...

We analyze consequences of trying to replace dark matter and dark energy with models of stochastic spacetime. In particular, we analyze the model put forth by ref. [1], in which it is claimed that “post-quantum classical gravity” (PQCG), a stochastic theory of gravity, leads to modified Newtonian dynamics (MOND) behavior on galactic scales that rep...

In a recent paper: “On the time dependency of a0” the authors claim that they have tested “one of the predictions of the Scale Invariant Vacuum (SIV) theory on MOND” by studying the dependence of the Modified Newtonian Dynamics (MOND) accelera- tion at two data sets, low-z (3.2 × 10−4 ≤ z ≤ 3.2 × 10−2) and high-z (0.5 ≤ z ≤ 2.5). They claim “both s...

Observation of the distribution of the velocity of galactic rotation curves differed from their expected centripetal form and lead to the notion of Dark Matter or modifications to Newtonian and General Relativity, such as MOND, TeVeS and the like and even Quantised Inertia. We aim to show that General Relativity with Dark Energy/the Cosmological Co...

In a recent paper: ``On the time dependency of $a_0$" the authors claim that they have tested ``one of the predictions of the Scale Invariant Vacuum (SIV) theory on MOND" by studying the dependence of the Modified Newtonian Dynamics (MOND) acceleration at two data sets, low-$z$ ($3.2\times10^{-4}\le z\le 3.2\times10^{-2}$) and high-$z$ ($0.5\le z\l...

Low-acceleration gravitational anomaly is investigated with a new method of exploiting the normalized velocity profile v ˜ ≡ v p / v c of wide binary stars as a function of the normalized sky-projected radius s / r M , where v p is the sky-projected relative velocity between the pair, v c is the Newtonian circular velocity at the sky-projected sepa...

The baryonic mass–velocity relation provides an important test of different galaxy dynamics models such as Lambda–cold dark matter (ΛCDM) and alternatives like Modified Newtonian Dynamics (MOND). Novel nonlinear density wave theory with a soliton solution gives an opportunity to test whether the derived rotational velocity expression is able to sup...

A modified gravity model of Starobinsky inflation and primordial black hole production is proposed in good (within 1σ) agreement with current measurements of the cosmic microwave background radiation. The model is an extension of the singularity-free Appleby–Battye–Starobinsky model by the R4 term with different values of the parameters whose fine-...

In this manuscript, we have continued the work of Herrera et al. (Gen. Relativ. Gravit. 44, 1143, 2012) to investigate the instability of non-static spheres supported by anisotropic matter configuration in the background of D-dimensional Einstein gravity. For this purpose, we assume that our relativistic sphere undergoes adiabatic evolution with a...

Current cosmological observations allow for deviations from the standard growth of large-scale structures in the universe. These deviations could indicate modifications to General Relativity on cosmological scales or suggest the dynamical nature of dark energy. It is important to characterize these departures in a model-independent manner to unders...

One key piece of evidence for dark matter is the flat rotation curve problem: the disagreement between measured galactic rotation curves and their luminous mass. A novel solution to this problem is presented here. A model of relativistic frame effects on Doppler shifts due to the slightly curved frames of an emitting galaxy and the Milky Way is der...

This work investigates the impact of different Modified Gravity (MG) models on the large-scale structures (LSS) properties in relation to the cosmic web (CW), using N-body simulations of f(R) and nDGP models. We analyse the impact of the MG effect on the density field through density distribution and clustering statistics, and assess its influence...

In this study, we investigate the impact of modified gravity on the merger rate of compact binaries within dark-matter spikes surrounding super-massive black holes (SMBHs). Specifically, we calculate binary merger rates involving primordial black holes (PBHs) and/or neutron stars (NSs) in Hu-Sawicki $f(R)$ gravity and the normal branch of Dvali-Gab...

The hypothesis of low entropy in the initial state of the universe usually explains the observed entropy increase is in only one time direction: the thermodynamic arrow of time. The Hamiltonian formalism is commonly used in the context of general relativity. The set of Lagrange multipliers are introduced in the formalism, and they are corresponding...

If modified gravity holds, but the weak lensing analysis is done in the standard way, we find that dark matter halos have peculiar shapes that do not follow the standard Navarro-Frenk-White profiles and which are fully predictable from the distribution of baryons. In this work, we study in detail the distribution of the apparent DM around point mas...

Some gas-rich ``ultra-diffuse'' galaxies (UDGs), which are extreme examples of low surface brightness (LSB) dwarf galaxies, have been reported to lack dark matter and to be offset from the baryonic Tully-Fisher relation (BTFR). If confirmed, these UDGs would represent a serious challenge for both Lambda CDM galaxy-formation models and Milgromian dy...

If modified gravity holds, but the weak lensing analysis is done in the standard way, one finds that dark matter halos have peculiar shapes, not following the standard Navarro-Frenk-White profiles, and are fully predictable from the distribution of baryons. Here we study in detail the distribution of the apparent dark matter around point masses, wh...

We consider a dynamic scenario for characterizing the late Universe evolution, aiming to mitigate the Hubble tension. Specifically, we consider a metric f(R) gravity in the Jordan frame which is implemented to the dynamics of a flat isotropic Universe. This cosmological model incorporates a matter creation process, due to the time variation of the...

Over the last couple of years, the appearance of the third data release from the {\it Gaia} satellite has triggered various wide binary low acceleration gravity tests. Wide binaries with typical total masses $\approx 1.0 - 1.6 M_{\odot}$ and separations above a few thousand au probe the low acceleration $a \lesssim a_{0}$ regime, where at galactic...

Although the existence of dark matter has been widely acknowledged in the cosmology community, it is as yet unknown in nature, despite decades of research, which questions its very existence. This never-ending search for dark matter leads to consider alternatives. Since increasing the enclosed mass is the only way to explain the flat appearance of...

Ultra-diffuse galaxies (UDGs) in the Coma cluster have velocity dispersion profiles that are in full agreement with the predictions of modified Newtonian dynamics (MOND) in isolation. However, the external field effect (EFE) from the cluster seriously undermines this agreement. It has been suggested that this could be related to the fact that UDGs...

Dynamical friction works very differently for Newtonian gravity with dark matter and in modified Newtonian dynamics (MOND). While the absence of dark matter considerably reduces the friction in major galaxy mergers, analytic calculations indicate the opposite for very small perturbations, such as globular clusters (GCs) sinking in dwarf galaxies. H...

We investigate static cylindrical solutions within an extended theory of modified gravity. By incorporating various coupling functions through a straightforward boost symmetry approach, we establish the equations of motion in a self-consistent manner and subsequently determine the linear scalar field profile. Utilizing analytical methods, we solve...

Observation of the distribution of the velocity of galactic rotation curves differed from their expected centripetal form and lead to the notion of Dark Matter or modifications to Newtonian and General Relativity, such as MOND, TeVeS and the like and even Quantised Inertia. We aim to show that General Relativity with Dark Energy/the Cosmological Co...

We revisit slow rotating black hole (BH) solutions in Chern-Simons modified gravity (CSMG) by considering perturbative solution about Schwarzschild BH. In particular, the case when nondynamical CSMG with noncanonical CS scalar is considered. We provide a new solution different from the previously obtained one \cite{Konno:2007ze} which we refer to a...

The purpose of this article is twofold. First, by means of Padmanabhan's proposal on the emergence nature of gravity, we recover the ΛCDM model and the effect of the dark matter in the context of cosmology. Toward this goal, we use the key idea of Padmanabhan that states cosmic space emerges as the cosmic time progresses and links the emergence of...

With the release of Gaia DR3, we extend the comparison between dynamical models for the Milky Way rotation curve initiated in the previous work. Utilising astrometric and spectro-photometric data for 719143 young disc stars within $|z|<1$ kpc and up to $R \simeq 19$ kpc, we investigate the accuracy of MOND and $\Lambda$CDM frameworks in addition to...

In this paper, our objective is to explore a time-machine space-time formulated in general relativity, as introduced by Li (Phys. Rev. D {\bf 59}, 084016 (1999)), within the context of modified gravity theories. We consider Ricci-inverse gravity of all Classes of models, {\it i.e.}, (i) Class-{\bf I}: $f(\mathcal{R}, \mathcal{A})=(\mathcal{R}+\beta...

Dynamical friction works very differently for Newtonian gravity with dark matter and in modified Newtonian dynamics (MOND). While the absence of dark matter considerably reduces the friction in major galaxy mergers, analytic calculations indicate the opposite for very small perturbations, such as globular clusters (GCs) sinking in dwarf galaxies. H...

The chameleon screening mechanism has been constrained many a time using dynamic and kinematic galaxy cluster observables. Current constraints are, however, insensitive to different mass components within galaxy clusters and have been mainly focused on a single mass density profile, the Navarro-Frenk-While mass density model. In this work, we exten...

Recently a low acceleration gravitational anomaly was reported for wide binaries, that is a system of two binary stars which are separated by more than five kilo astronomical units (kau). The increase in gravitational force was reported to be about 1.37 greater than Newtonian gravity. At the same time binaries which are not wide that is of separati...

Ultra-diffuse galaxies (UDGs) in the Coma cluster have velocity dispersion profiles that are in full agreement with the predictions of Modified Newtonian Dynamics (MOND) in isolation. However, the external field effect (EFE) from the cluster seriously deteriorates this agreement. It has been suggested that this could be related to the fact that UDG...

MOND assumes that Newtonian dynamics is not accurate. Therefore, it needs modification. AuND assumes that Newtonian dynamics is accurate but not complete. For more than 300 years, Newtonian dynamics has remained an incomplete mathematical model. The shortcomings of the incomplete Newtonian dynamics have given reason to consider the classical model...

Aims. We explore the dynamical friction on a test mass in gravitational systems in the quasi-linear formulation of modified Newtonian dynamics (QuMOND). Methods. Exploiting the quasi-linearity of QuMOND, we derived a simple expression for the dynamical friction in akin to its Newtonian counterpart in the standard Chandrasekhar derivation. Moreover,...

Context. The stellar halo of the Milky Way is built up at least in part from debris from past mergers. The stars from these merger events define substructures in phase space, for example in the form of streams, which are groups of stars that move on similar trajectories. The nearby Helmi streams discovered more than two decades ago are a well-known...

Galaxies in the early universe appear to have grown too big too fast, assembling into massive, monolithic objects more rapidly than anticipated in the hierarchical $\Lambda$CDM structure formation paradigm. The available data are consistent with there being a population of massive galaxies that form early ($z \gtrsim 10$) and follow an approximatel...

A low acceleration gravitational anomaly was reported for wide binaries: two binary stars which are separated by more than five kilo astronomical units (kau). The increase in gravitational force was reported to be about $1.37$ greater than Newtonian gravity. At the same time binaries separated less than one kau were shown to obey standard Newtonian...

Testing gravity and the concordance model of cosmology, $\Lambda$CDM, at large scales is a key goal of this decade's largest galaxy surveys. Here we present a comparative study of dark matter power spectrum predictions from different numerical codes in the context of three popular theories of gravity that induce scale-independent modifications to t...

The stellar halo of the Milky Way is built up, at least in part, from debris from past mergers. Stars from such merger events define substructures in phase-space, for example in the form of streams, which are groups of stars moving on similar trajectories. The nearby Helmi streams discovered more than two decades ago are a well-known example. Using...

This paper argues that the universe possesses two scalar potentials similar to those proposed by E.T. Whittaker in which waveforms travel longitudinally. It is proposed that these scalar potentials form through black holes, creating normal transverse electromagnetic radiation as well as gravity. This opens up new avenues for understanding the unive...

Baryon Acoustic Oscillations (BAOs) are crucial in cosmological analysis, providing a standard ruler, as well as constraints on dark energy. In General Relativity models, the BAO Linear Point - the midpoint between the dip and the peak in the correlation function - has been shown to be rather robust to evolution and redshift space distortions. We s...

It is postulated that the energy density of the (quantum) vacuum acts firstly as dark energy and secondly as a part of dark matter. Assisted by electric fields arising from a small charge mismatch in the cosmic plasma, it can condense on mass concentrations. No longer participating in the cosmic expansion, this constitutes “electro-aether-energy” (...

Modified Newtonian dynamics (MOND), which postulates a breakdown of Newton's laws of gravity/dynamics below some critical acceleration threshold, can explain many otherwise puzzling observational phenomena on galactic scales. MOND competes with the hypothesis of dark matter, which successfully explains the cosmic microwave background and large-scal...

This work presents a novel approach to address the longstanding challenge posed by the rotation curves of galaxies and the associated missing mass problem. Utilizing the four-dimensional modified gravity framework of Einstein-Gauss-Bonnet (EGB), we develop a new model that integrates the concept of dark matter featuring negative mass due to the Gau...

i ) morphology, remains somewhat uncertain. We present unmatched ultra-deep optical imaging of AGC 114905 reaching surface brightness limits $ r,lim 32$ mag/arcsec$^2$ ($3 10 arcsec times 10 arcsec) obtained with the 10.4 m Gran Telescopio Canarias. With the new imaging, we characterise the galaxy's optical morphology, surface brightness, colours,...

In this work, we consider the emergent origin of gravity in the framework of Hamilton–Randers theory, a theoretical framework for emergent quantum mechanics. After presenting the essential ingredients of the theory, a derivation of the weak equivalence principle from the first principles of the theory follows. Then it is shown that the Newtonian mo...

We investigates the effect of accretion of cosmic fluid on the evolution of Primordial Black Holes (PBHs) within the framework of Modified gravity theories. We consider a general form of the Hubble parameter, reflecting a general class of modified gravity theories and bouncing models. We then study the effect of such modified dynamics on PBH in the...

In a recent paper by Ambr\'osio et al. [arXiv:2405.14799], it was shown that the gravitational force law of the Modified Newtonian Dynamics (MOND) phenomenology can be derived within the framework of entropic gravity and the holographic principle by assuming an entropy function other than the conventional Boltzmann-Gibbs entropy. In particular, the...

Weak Field General Relativity and in fact any physical theory applicable to an arbitrary inertial observer must be symmetrical under the Lorentz group. Equations which are invariant under the Lorentz transformation do not allow "action at a distance" solutions of the Newtonian gravity type, but rather require retarded solutions. Galaxies and even m...

Newtonian dynamics was based on the assumption of instantaneous propagation of interaction. Roamer’s studies showed that the velocity of interaction cannot exceed the velocity of light in free space. (c=3x108 mps). Lorentz’ electron theory and electrodynamics take this fact into account. It is possible to rectify the defects of Newtonian theory by...

Gravitational alternatives to dark matter require additional fields or assumptions beyond general relativity while continuing to agree with tight solar system constraints. Modified Newtonian Dynamics (MOND), for example, predicts the Tully–Fisher relation for galaxies more accurately than dark matter models while limiting to Newtonian gravity in th...

I learned about a very interesting finding Kyu-Hyun Chae related to the dynamics of binaries of widely separated stars. The dynamics seems to violate Newtonian gravitation for low accelerations, which naturally emerge at large separations and the violations are roughly consistent with the MOND hypothesis. This raises the question whether the TGD ba...

This is a summary of the main results within the Scale-Invariant Vacuum (SIV) paradigm based on Weyl integrable geometry. We also review the mathematical framework and utilize alternative derivations of the key equations based on the reparametrization invariance as well. The main results discussed are related to the early universe; that is, applica...

We examine the potential of Kaniadakis entropy to describe black hole entropy, proposing a modified version accounting for black hole thermodynamics. Additionally, we discuss the Modified Newtonian Dynamics (MOND) theory, a modification of Newton's second law aimed at explaining galaxy rotation curves without resorting to dark matter. Furthermore,...

It has recently been demonstrated [A. Giusti, Phys. Rev. D 101, 124029 (2020)] that characteristic traits of Milgrom's modified Newtonian dynamics (MOND) can be replicated from an entirely distinct framework: a fractional variant of Newtonian mechanics. To further assess its validity, this proposal needs to be tested in relevant astrophysical scena...

General relativity (GR) is the most successful theory of gravity, with great observational support at local scales. However, to keep GR valid at over cosmic scales, some phenomena (such as the flat galaxy rotation curves and the cosmic acceleration) require the assumption of exotic dark matter. The radial acceleration relation (RAR) indicates a tig...

A bouncing Universe avoids the big-bang singularity. Using the time-like and null Raychaudhhuri equations, we explore whether the bounce near the big-bang, within a broad spectrum of modified theories of gravity, allows for cosmologically relevant power-law solutions under reasonable physical conditions. Our study shows that certain modified theori...

In this work, we investigate the merger rate of primordial black hole–neutron star (PBH-NS) binaries in two widely studied modified gravity (MG) models: Hu–Sawicki f(R) gravity and the normal branch of Dvali–Gabadadze–Porrati gravity. In our analysis, we take into account the effects of MG on the halo properties, including halo mass function, halo...