Theory Of Gravity Research Articles

Existence of vacuum wormholes in Einsteinian cubic gravity

Wormhole solutions in gravitational theories typically require exotic matter. Here we present a wormhole solution to the field equations of Einsteinian Cubic Gravity — a phenomenological competitor to general relativity that includes terms cubic in the curvature — that has no matter, exotic or otherwise. These purely gravitational wormhole geometries are asymptotically AdS but contain a geometric deficit at infinity. The deficit, interpreted as a global monopole, plays an essential role in our construction. We find that our wormhole solution satisfies traversablility criteria. We also find, for different parameters, a range of possible wormhole solutions.

Theoretical Approaches to Solving the Shortest Vector Problem in NP-Hard Lattice-Based Cryptography with Post-SUSY Theories of Quantum Gravity in Polynomial Time by Orch-Or

The Shortest Vector Problem (SVP) is a cornerstone of lattice-based cryptography, underpinning the security of numerous cryptographic schemes like NTRU. Given its NP-hardness, efficient solutions to SVP have profound implications for both cryptography and computational complexity theory. This paper presents an innovative framework that integrates concepts from quantum gravity, non-commutative geometry, spectral theory, and post-supersymmetry (post-SUSY) particle physics to address SVP. By mapping high-dimensional lattice points to spinfoam networks and by means of Hamiltonian engineering, it is theoretically possible to devise new algorithms that leverage the interactions topologically protected Majorana fermionparticles have with the gravitational field through the spectral action principle to loop through these spinfoam networks where SVP vectors could then be encoded onto the spectrum of the corresponding Dirac-like dilation operators within the system. We establish a novel approach that leverages post-SUSY physics and theories of quantum gravity to achieve algorithmic speedups beyond those expected by conventional quantum computers. This interdisciplinary methodology not only proposes potential polynomial-time algorithms for SVP, but also bridges gaps between theoretical physics and cryptographic applications, providing further insights into the Riemann Hypothesis (RH) and the Hilbert-P ´olya Conjecture. Possible directions for experimental realization through biologically inspired hardware or biological tissues by orchestrated objective reduction (Orch-Or) theory are discussed.

Environmental gravitational decoherence with a higher derivative theory

We discuss the decoherence in a quantum system induced by interaction with gravitational degrees of freedom that are part of a higher derivative theory. The deformation of a mass distribution due to gravitational waves acquires naturally a mass quadrupole moment. This adds higher derivative dynamics of the quadrupole moment to the unitary evolution of the system, where the quadrupole moment oscillates with the gravitational frequencies following a higher derivative theory. The consequence of higher derivatives in the dynamics is that four canonical variables describe the system. This departure from the usual particle position and momentum operators gives an entirely different interpretation of the decoherence basis. This model focuses on the open dynamics of the quadrupole moment, rather than on individual particles. As such, a short example is given to utilize quadrupole measurements to probe gravitational decoherence and noise. We first derive a Langevin equation for a lower derivative model and show how higher derivatives naturally emerge on the boundary. A quantum master equation is derived for the emerging quadrupole moment, considering that the environment is a higher derivative theory of gravity. Published by the American Physical Society 2025

Dynamics of compact objects in higher-order curvature gravity using Finch–Skea spacetime

This paper explores anisotropic spherical structures within metric f(R) gravity, where R is the Ricci scalar, extending general relativity to include functions of R modified gravitational effects. We analyze compact stars using Finch–Skea solutions under the models; f(R)=R+αR2,f=R+αR2(1+γR),and f=R+αRe-Rγ-1. These models help us examine how gravity modifications affect the internal structure and behavior of neutrons and strange stars. We investigate material variables such as density, pressures, anisotropy, and forces (gravitational, hydrostatic, anisotropic) through graphical analysis. The physical viability of the stellar models is assessed by evaluating energy conditions (NEC, WEC, SEC, and DEC) and the equation of state (EoS) parameter. We also examine the role of anisotropy in stability and structure, comparing the results with general relativity to highlight the implications of f(R) gravity on compact stars. This study aims to enhance the understanding of how modified gravity theories could impact the properties of compact astrophysical objects.

Modified gravity from Weyl connection and the f(R,A) extension

We use Weyl connection and Weyl geometry in order to construct novel modified gravitational theories. In the simplest case where one uses only the Weyl-connection Ricci scalar as a Lagrangian, the theory recovers general relativity. However, by upgrading the Weyl field to a dynamical field with a general potential and/or general couplings constructed from its trace, leads to new modified gravity theories, where the extra degrees of freedom arise from the Weyl field. Additionally, since the Weyl-connection Ricci scalar differs from the Levi–Civita Ricci scalar by terms up to first derivatives of the Weyl field, the resulting field equations for both the metric and the Weyl field are of second order, and thus the theory is free from Ostrogradsky ghosts. Finally, we construct the most general theory, namely the f(R~,A) gravity, which is also ghost free. Applying the above classes of theories at a cosmological framework we obtain an effective dark energy sector of geometrical origin. In the simplest class of theories we are able to obtain an effective cosmological constant, and thus we recover ΛCDM paradigm, nevertheless in more general cases we acquire a dynamical dark energy. These theories can reproduce the thermal history of the Universe, and the corresponding dark energy equation-of-state parameter presents a rich behavior.

Thermodynamical properties of a deformed Schwarzschild black hole via Dunkl generalization

In this paper, we construct a deformed Schwarzschild black hole from the de Sitter gauge theory of gravity within Dunkl generalization and we determine the metric coefficients versus Dunkl parameter and parity operators. Since the spacetime coordinates are not affected by the group transformations, only fields are allowed to change under the action of the symmetry group. A particular ansatz for the gauge fields is chosen and the components of the strength tensor are computed as well. Additionally, we analyze the modifications on the thermodynamic properties to a spherically symmetric black hole due to Dunkl parameters for even and odd parities. Finally, we verify a novel remark highlighted from heat capacity: the appearance of a phase transition when the odd parity is taken into account.

Extended near horizon symmetries of extremal BTZ black holes in 3D massive gravity

We study the asymptotic symmetries of near-horizon extremal BTZ black holes in higher derivative theories of gravity, such as New Massive Gravity and Topological Massive Gravity. By employing a particular boundary condition and the regularization prescription proposed earlier for the Einstein gravity, we demonstrate the existence of two centrally extended Virasoro algebras. The central charges evaluated within this framework are in agreement with their corresponding expressions evaluated at the spatial infinity. We also discuss the robustness of the regularization procedure by relating asymptotic and near- horizon geometries.

Post-newtonian tests of gravitational quantum field theory with spin and scaling gauge symmetry

A self-consistent gravitational quantum field theory, with gravitational force treated on the same footing as the other three fundamental interactions, was established recently. The gravidynamics predicted by such a theory could lead to important implications, and the comparisons with experimental results may provide us opportunities to test such new approach of gravity based on the framework of the quantum field theory of gauge interactions. In this work, we start with the effective field equation of the gravitational quantum field theory, and then solve the perturbative gravigauge field order by order up to the 1st post-Newtonian level under the assumption of a simplified energy–momentum tensor of perfect fluids. Having the constraints on the related post-Newtonian parameters from the most up-to-date observational data, the new bound on the combined coupling in the gravitational quantum field theory |γG(αG-αW/2)|≤(2.4±30)×10-6 is obtained. Under such bound, we found that the new gravitational quantum field theory successfully passed and found no conflict with the contemporary keynote Solar system experiments of gravity.

From spacetime thermodynamics to Weyl transverse gravity

There exist two consistent theories of self-interacting gravitons: general relativity and Weyl transverse gravity. The latter has the same classical solutions as general relativity but different local symmetries. We argue that Weyl transverse gravity also naturally arises from thermodynamic arguments. In particular, we show that thermodynamic equilibrium of local causal diamonds together with the strong equivalence principle encodes the gravitational dynamics of Weyl transverse gravity rather than general relativity. We obtain this result in a self-consistent way, verifying the validity of our initial assumptions, i.e., the proportionality between entropy and area and the different versions of the equivalence principle in Weyl transverse gravity. Furthermore, we extend the thermodynamic derivation of the equations of motion from Weyl transverse gravity to a class of modified theories of gravity with the same local symmetries. For this purpose, we employ the general expression for Wald entropy in such theories. Published by the American Physical Society 2025

Kaluza-Klein Universe with Wet Dark Fluid in f(R,T) Theory of Gravity

In this paper we have consider the Kaluza-Klein space-time in presence of wet dark fluid in f(R,T) theory of gravity. The general solution of the field equations have been obtained under the assumption of the assumption of constant deceleration parameter. The physical and geometrical aspect of the model is also discussed.

Quasinormal mode spectrum of rotating black holes in Einstein-Gauss-Bonnet-dilaton theory

Quasinormal modes are excited during the ringdown phase of black holes after merger. Determination of quasinormal modes of rapidly rotating black holes in alternative theories of gravity has remained a challenge for a long time. Here we discuss in detail our recently developed method to extract the quasinormal modes for rapidly rotating black holes in Einstein-Gauss-Bonnet-dilaton theory. We first obtain numerically the exact rapidly rotating background solutions, which also clarify their domain of existence. Then we solve the equations for the linear perturbations of the metric and the dilaton field by employing an appropriate set of boundary conditions and a spectral decomposition of the perturbation functions. The resulting spectrum agrees well with the known limits obtained for slow rotation and weak coupling, while it exhibits larger deviations for stronger coupling. Published by the American Physical Society 2025

LRS Bianchi-I universe model with domain wall in f(R, T) gravity

Abstract In this work, strange quark matter (SQM) and normal matter (NM) attached to domain wall (DW) matter distributions have been examined for locally rotationally symmetric (LRS) Bianchi-I space-time has been investigated. The model has been constructed in the framework of f(R, T) theory for f(R, T) = R + 2μT which is suggested as an alternative gravitation theory instead of Einstein's General Relativity Theory. Obtained modified field equations have been solved by using scale factors equation A = B m come from the proportion of expansion scalar θ to shear scalar ϖ 2. SQM and NM are added to DW with the help of equations of state (EoS) p m = 1 3 ( ρ m − 4 B c ) and p m = (γ − 1)ρ m . Pressure and energy densities of all matter distributions have been obtained depending on cosmic time t and their effects decrease by the time. It is found that DW matter behaves like stiff matter due to attaining DW pressure equal to DW energy density p DW = ρ DW . Also obtained values of scale factors and some kinematic quantities give an expanding universe for the model. Energy conditions and kinematic quantities of the model have been examined in the last section. In addition, General Relativity solutions of the model have been attained by assuming μ = 0 in f(R, T) = R + 2μT. All solutions have been concluded in detail.

Perfect fluid kantowski-sachs and bianchi type-III spacetimes and their concircular Symmetry in f(T) theory of gravity

Abstract The aim of this research is to classify Kantowski-Sachs (KS) and Bianchi type-III spacetimes through concircular vector fields in f(T) gravity theory. In order to achieve our goal we first obtained field equations for KS and Bianchi type-III spacetimes with perfect fluid as source in f(T) theory of gravity and then obtained the concircular symmetry equations. All these equations are solved simultaneously to obtain the vector field components. The whole process enabled us to obtain particular form of the metric functions and conformal factors. It has been found that perfect fluid KS and Bianchi type-III spacetimes allow concircular vector fields of 4-, 5-, 6-, 7- and 15-dimensions in f(T) gravity theory. The torsion scalar T, fluid pressure and energy density are all computed in each case. It has been shown that in all cases except one case pressure and density are constants. It has been observed that pressure and density are linked as p = − ρ in all the cases except two case, indicating that these spacetime metrics may represent a vacuum universe or a universe with dark energy. In one case p = ρ, means that the spacetime has an ordinary matter and in other case the pressure of the fluid and density are functions of the cosmic time t. By choosing particular values of the constants in this case, an equation of state p = − ρ can be achieved.

Tree- and one-loop-level double copy for the (anti)self-dual sectors of Yang-Mills and gravity theories

By employing the perturbiner method, we study the tree- and one-loop-level amplitudes in (anti)self-dual Yang-Mills, focusing on color-kinematics duality and double copy features; they arise naturally even in the fully off-shell case. In particular, we calculate the respective the Kawai-Lewellen-Tye relations for tree-level Berends-Giele currents and color-kinematics master numerators at one loop, both cases for any number of external particles. Published by the American Physical Society 2025

Testing screened scalar-tensor theories of gravity with atomic clocks

Testing screened scalar-tensor theories of gravity with atomic clocks

Five Dimensional Bianchi Type-V Cosmological Model in Presence of Barotropic Equation of State With Bulk Viscous String in Modified Theory of Gravity

In this paper, we analysed five dimensional Bianchi Type-cosmological model with Bulk Viscous String in Modified theory of gravity. We assume that the expansion scalar is proportional to the shear scalar and hybrid scale factor is used to solve the field equations in modified theory of gravity. The barotropic equation of state is used to obtained pressure as well as energy density. Some physical aspects are also discussed in details.

Adaptive reinforcement learning of spatial interaction based on taxi trajectory data

A novel approach for analysing spatial interaction characteristics and land use using taxi trajectory data and urban geographic data is introduced. An adaptive reinforcement learning model, based on non-linear theory, is proposed to improve the accuracy and adaptability of spatial interaction predictions. By dividing an urban area into smaller units, a spatial interaction matrix is constructed that captures push–pull force characteristics and distance features between origins and destinations. The innovative aspect of the model lies in its ability to integrate multiple weak spatial interaction learners to form a strong learner, thus significantly outperforming traditional models based on gravity theory in terms of prediction performance (higher R2, lower mean absolute error and lower root mean squared error). The findings of this work reveal the importance of adjacent flows in predicting spatial interaction patterns and show that travel distance in public transportation is the most significant factor in describing the difficulty of completing spatial interactions. The push force from origins was found to have the highest relative importance, followed by the pull force from destinations and adjacent flows. The results of this study provide valuable insights for traffic and urban planning.

A cosmological holographic reconstruction of f(Q) theory

This paper explores a cosmological reconstruction scheme in the background of [Formula: see text] gravity theory from a Holographic perspective. The basic motivation for this work is that the reconstruction is performed from a holographic origin, which has its roots in the black hole thermodynamics and quantum gravity. Dark energy models inspired by holographic prescription are used to reconstruct the [Formula: see text] gravity models. Two such models, namely, the Granda–Oliveros holographic dark energy model and its generalization, the Chen-Jing model, are considered for the study. Different scale factors are used and a thorough reconstruction scheme is set up using the dark energy models. The observationally constrained values of the free model parameters have been used to form the reconstructed models. Finally, a thorough investigation of the energy conditions has been performed to check the cosmological viability of the reconstructed [Formula: see text] models. As an outcome, we get some very promising and cosmologically viable [Formula: see text] models that present some interesting properties and demand further investigation. Finally, a method is discussed how the constructed [Formula: see text] models can be reconciled with a generalized holographic dark energy.

IS PHILOSOPHY NEEDED TO SOLUTION THE PROBLEMSOF MODERN PHYSICS? (RESPONDING TO STEPHEN HAWKING)

The article considers the ideological and methodological issues of solving the problems of development of scientific knowledge in physics. The authors do not claim to solve specific problems of science, but seek to reveal the role of philosophical generalization in scientific search and solution of problems of creation of the general theory of the Universe. It is noted that S. Hawking managed to present the modern physical picture of the world in an accessible and popular form. The authors believe that the main problem identified by him in modern physics is the problem of incompatibility of two main concepts describing the modern physical picture of the world. These concepts are the theory of relativity and quantum mechanics. The authors share S. Hawking’s point of view that scientific search should lead to the synthesis of these theories in a broader quantum theory of gravity. At the same time, the authors object to two provisions of S. Hawking’s work. The first is the assertion that the creation of a unified quantum theory of gravity is still a very long time coming, the second is the assertion that philosophy can give nothing to modern physical science. The position on the impossibility of creating a new comprehensive physical theory in the near future contradicts what S. Hawking himself says about the state of modern physics. He claims that physicists already know what features this theory should have. In this regard, using the system of inequalities of A.S. Panarin, according to which theoretical knowledge should develop at an accelerated pace in relation to applied knowledge, the authors come to the conclusion that philosophical knowledge sets the area of the possible, and, consequently, the area and vector of scientific research for special sciences. Knowledge of the parameters that a new scientific theory must meet narrows the area of scientific research, leads to saving intellectual efforts and, ultimately, accelerates the creation of a unified physical theory that can describe all phenomena of the world. Moreover, formal logic itself allows us to limit the possible solutions to this issue. The authors approach the solution of the problem of the importance of philosophical knowledge for physics from the position of science research put forward by T. Kuhn. This allows them to substantiate their position on the importance of philosophical knowledge for the development of science. T. Kuhn distinguishes two stages in the development of science. Normal science is a stage at which the development of science goes “in breadth” within the framework of an existing paradigm, scientists solve “standard problems” that do not require a revision of the fundamental laws of science. Scientific revolution is a period of scientific development during which one paradigm is replaced by another paradigm, scientists’ ideas about the fundamental laws of the world’s existence change. It is at the stage of scientific revolution that the role of philosophical generalization increases, since the revision of the fundamental laws of the universe requires going beyond a narrow discipline, abandoning established “templates” of thinking. The authors agree with S. Hawking’s opinion that philosophers do not know modern physics, and this does not allow them to outline the area of scientific research for physicists. This is due to the fact that the volume of modern knowledge has increased so much that in order to be at the forefront of science, a scientist is forced to work in a highly specialized field. Narrow specialization does not allow a scientist to make broad philosophical generalizations. But S. Hawking himself notes that scientific knowledge is gradually spreading. Today, most people have heard of the theory of relativity and quantum mechanics, and there are hundreds of people who at least superficially know what these theories are about. Thus, the dissemination of scientific knowledge raises the level of society, including philosophers, to an understanding of modern science. On the other hand, there is a need for a broader philosophical training of mathematicians and physicists who will be capable of philosophical generalization, which will allow going beyond the existing paradigms of science and creating a quantum theory of gravity.

PySCo: A fast particle-mesh N-body code for modified gravity simulations in Python

We present a fast and user-friendly Python library designed to run cosmological N-body simulations across various cosmological models, such as ΛCDM (Λ with cold dark matter) and w_0w_aCDM, and alternative theories of gravity, including f(R), MOND (modified newtonian dynamics) and time-dependent gravitational constant parameterisations. employs particle-mesh solvers, using multigrid or fast Fourier transform (FFT) methods in their different variations. Additionally can be easily integrated as an external library, providing utilities for particle and mesh computations. The library offers key features, including an initial condition generator based on up to third-order Lagrangian perturbation theory (LPT), power spectrum estimation, and computes the background and growth of density perturbations. In this paper, we detail architecture and algorithms and conduct extensive comparisons with other codes and numerical methods. Our analysis shows that, with sufficient small-scale resolution, the power spectrum at redshift z = 0 remains independent of the initial redshift at the 0.1% level for ini ≥ 125, 30, and 10 when using first, second, and third-order LPT, respectively. Moreover, we demonstrate that acceleration (or force) calculations should employ a configuration-space finite-difference stencil for central derivatives with at least five points, as three-point derivatives result in significant power suppression at small scales. Although the seven-point Laplacian method used in multigrid also leads to power suppression on small scales, this effect can largely be mitigated when computing ratios. In terms of performance only requires approximately one CPU hour to complete a Newtonian simulation with $512^3$ particles (and an equal number of cells) on a laptop. Due to its speed and ease of use is ideal for rapidly generating vast ensemble of simulations and exploring parameter spaces, allowing variations in gravity theories, dark energy models, and numerical approaches. This versatility makes a valuable tool for producing emulators, covariance matrices, or training datasets for machine learning.