by jsendak | Oct 13, 2025 | GR & QC Articles
arXiv:2510.08756v1 Announce Type: new
Abstract: Gravitational waves from compact binary inspirals offer a new opportunity to constrain the cosmological time dependence of gravitational coupling parameters, due to the high precision of the observations themselves as well as the significant cosmological redshifts at which such systems exist. We calculate theory-independent equations of motion for compact objects in a binary system, implementing a new approach to sensitivities, and subsequently determine the gravitational wave signal that one should expect to measure from their inspiral. Expressions for the wave phase and amplitude are derived in terms of post-Newtonian gravitational coupling parameters, radiative flux parameters, and compact body sensitivities. These results complement recent attempts to gain theory-independent constraints on the time-evolution of gravitational coupling parameters from cosmological probes, and represent a new opportunity to constrain modified gravity with gravitational wave data.
Conclusions
The study provides a new method to constrain the time dependence of gravitational coupling parameters using gravitational waves from compact binary inspirals. This offers a unique opportunity to explore modified gravity theories and gain insights into the evolution of the universe.
Future Roadmap
Challenges
- Obtaining high precision observations to accurately measure gravitational wave signals.
- Developing robust theoretical frameworks to interpret the data and extract meaningful constraints on gravitational coupling parameters.
- Accounting for cosmological redshift effects and their impact on the analysis of compact binary inspirals.
Opportunities
- Advancing our understanding of gravity and its role in shaping the cosmos through gravitational wave observations.
- Testing modified gravity theories and potentially discovering new insights into the fundamental laws of physics.
- Collaborating with cosmologists and astrophysicists to combine gravitational wave data with other cosmological probes for a more comprehensive study of the universe.
Overall, the future of using gravitational waves to constrain gravitational coupling parameters holds great promise for advancing our knowledge of the cosmos and unveiling the mysteries of gravity.
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by jsendak | Oct 10, 2025 | GR & QC Articles
arXiv:2510.07362v1 Announce Type: new
Abstract: Two distinct non-singular interior models that describe anisotropic spherical configurations are presented in this work. We develop the Einstein field equations and the associated mass function in accordance with a static spherical spacetime. We then discuss certain requirements that must be satisfied for compact models to be physically validated. Two distinct limitations are taken into account to solve the field equations, including different forms of the radial geometric component and anisotropy, which ultimately leads to a couple of relativistic models. In both cases, solving the differential equations result in the appearance of integration constants. By equating the Schwarzschild exterior metric and spherical interior line element on the interface, these constants are explicitly obtained. The disappearance of the radial pressure on the hypersurface is also used in this context. We further use estimated radii and masses of six different stars to graphically visualize the physical properties of new solutions. Both of our models are deduced to be well-aligned with all physical requirements, indicating the superiority of the presence of anisotropy in compact stellar interiors over the perfect isotropic fluid content.
Conclusions
The two non-singular interior models presented in this work offer a new perspective on anisotropic spherical configurations. By developing the Einstein field equations and mass functions for static spherical spacetimes, we have demonstrated the physical validity of these compact models. By considering different forms of radial geometric components and anisotropy, we have derived two relativistic models that satisfy all necessary requirements.
Furthermore, by equating the exterior and interior metrics at the interface, we have obtained explicit integration constants. The absence of radial pressure on the hypersurface has also been taken into account in our analysis. The physical properties of these models have been visualized through the estimation of radii and masses of various stars, demonstrating the applicability of our solutions.
Future Roadmap
- Continue to explore the implications of anisotropic configurations in stellar interiors.
- Investigate the potential effects of different forms of anisotropy on the structure and behavior of compact models.
- Conduct detailed comparisons with observational data to further validate the physical relevance of these solutions.
- Explore the possibility of extending these models to different types of celestial objects beyond stars.
Challenges
- Obtaining precise observational data for comparison with theoretical models.
- Understanding the implications of different forms of anisotropy on the overall stability and evolution of compact stellar interiors.
Opportunities
The development of non-singular models with anisotropic configurations opens up new avenues for understanding the complex dynamics of compact stellar objects. By incorporating these models into existing frameworks, we may gain valuable insights into the underlying physics governing the behavior of celestial bodies.
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by jsendak | Oct 9, 2025 | GR & QC Articles
arXiv:2510.06327v1 Announce Type: new
Abstract: We introduce a Bayesian null-stream method to constrain calibration errors in closed-geometry gravitational-wave (GW) detector networks. Unlike prior methods requiring electromagnetic counterparts or waveform models, this method uses sky-independent null streams to calibrate the detectors with any GW signals, independent of general relativity or waveform assumptions. We show a proof-of-concept study to demonstrate the feasibility of the method. We discuss prospects for next-generation detectors like Einstein Telescope, Cosmic Explorer, and LISA, where enhanced calibration accuracy will advance low-frequency GW science.
Conclusions
The Bayesian null-stream method presents a promising approach to constrain calibration errors in closed-geometry gravitational-wave detector networks. This method does not rely on electromagnetic counterparts or waveform models, making it versatile and independent of general relativity or waveform assumptions. The proof-of-concept study demonstrates the feasibility of this method, paving the way for enhanced calibration accuracy in next-generation detectors like the Einstein Telescope, Cosmic Explorer, and LISA. This advancement will significantly benefit low-frequency gravitational-wave science.
Future Roadmap
- Implementation: Researchers should focus on implementing the Bayesian null-stream method in existing gravitational-wave detector networks to assess its effectiveness in real-world scenarios.
- Validation: Conduct thorough validation tests to ensure the accuracy and reliability of the calibration constraints obtained through this method.
- Optimization: Explore ways to optimize the Bayesian null-stream method for improved efficiency and performance, especially in the context of next-generation detectors.
- Collaboration: Foster collaboration between research teams working on different aspects of gravitational-wave science to leverage collective expertise and resources.
- Evaluation: Regularly evaluate the impact of enhanced calibration accuracy on low-frequency gravitational-wave science to identify areas for further improvement.
Potential Challenges
- Integration of the Bayesian null-stream method into existing detector networks may pose technical challenges and require significant resources.
- Validation tests may uncover unforeseen limitations or constraints of the method that could necessitate adjustments or modifications.
- Optimizing the method for next-generation detectors like the Einstein Telescope, Cosmic Explorer, and LISA may require specialized expertise and advanced computational capabilities.
Potential Opportunities
- The Bayesian null-stream method opens up new possibilities for improving calibration accuracy in gravitational-wave detector networks, enhancing the overall scientific output in this field.
- Collaborative efforts to optimize and validate this method could lead to breakthroughs in low-frequency gravitational-wave science and attract additional research funding and support.
- The successful implementation of this method in next-generation detectors could establish a new standard for calibration techniques in the field of gravitational-wave astronomy.
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by jsendak | Oct 8, 2025 | GR & QC Articles
arXiv:2510.05166v1 Announce Type: new
Abstract: Extreme mass-ratio inspirals (EMRIs) are among the key targets for future space-based gravitational wave detectors. The gravitational waveforms emitted by EMRIs are highly sensitive to the orbital dynamics of the small compact object, which in turn are determined by the geometry of the underlying spacetime. In this paper, we explore the de- tectability of regular black holes with sub-Planckian curvature, which can be interpreted as regularized versions of the Schwarzschild black hole (RSBH). To do so, we begin by ana- lyzing the metric and geodesics, determining the effective potential, and investigating the marginally bound orbits and the innermost stable circular orbits for timelike particles. Our analysis reveals that orbital radius, angular momentum, and energy significantly depend on the model parameter {alpha} for both orbits. Our main aim is to focus on the influence of the model parameter on a specific kind of orbit, the periodic orbit, surrounding a supermassive RSBH. The findings show that, for a constant rational integer, {alpha} has a significant impact on the energy and angular momentum of the periodic orbit. Utilising the numerical kludge method, we further investigate the gravitational waveforms of the small celestial body over various periodic orbits. The waveforms display discrete zoom and spin phases within a complete orbital period, influenced by the RSBH parameter {alpha}. As the system evolves, the phase shift in the gravitational waveforms grows progressively more pronounced, with cumulative deviations amplifying over time. With the ongoing advancements in space- based gravitational wave detection systems, our results will aid in leveraging EMRIs to probe and characterize the RSBH properties.
Conclusions
The study shows that regular black holes with sub-Planckian curvature, as interpreted as regularized versions of Schwarzschild black holes, can have a significant impact on the orbital dynamics of small celestial objects. The model parameter α plays a crucial role in determining the energy, angular momentum, and gravitational waveforms of these objects. The findings suggest that EMRIs involving supermassive RSBHs can provide valuable insights into the properties of these unique black holes.
Roadmap for the Future
Challenges:
- Further refining the models and numerical methods to accurately simulate the behavior of EMRIs around regular black holes.
- Addressing computational constraints to handle the complexity of gravitational waveforms over various orbital periods.
- Validating theoretical predictions with observational data from space-based gravitational wave detectors.
Opportunities:
- Exploring new techniques to enhance the detectability of EMRIs and extract more information about regular black holes.
- Collaborating with the scientific community to analyze the implications of the study’s results on our understanding of astrophysical phenomena.
- Utilizing advancements in technology to improve the precision and resolution of gravitational wave measurements.
By overcoming these challenges and seizing the opportunities ahead, researchers can unlock the full potential of using extreme mass-ratio inspirals to study and characterize regularized black holes in depth.
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by jsendak | Oct 7, 2025 | GR & QC Articles
arXiv:2510.03444v1 Announce Type: new
Abstract: New time-dependent metric tensors with spherical symmetry satisfying the Einstein-Maxwell equations in space-times with FLRW asymptotic behaviour are derived here for the first time. These geometries describe dynamical charged non-rotating black holes hosted by the perfect fluid of the asymptotic FLRW space-times. Their gravitational sources are the stress-energy tensors formed by a contribution of the perfect fluid and an electromagnetic one due to the Coulomb field produced by the time-dependent black-hole charge in the asymptotic FLRW background. The dynamics of these models is determined by the dynamical mass, which may be an arbitrary function of time, and two arbitrary real-valued parameters. The first one simulates the effect of a cosmological constant as in our $kappa$-models we proposed recently [I. I. Cotaescu, Eur. Phys. J. C (2024) 84:819]. The second parameter relates surprisingly the dynamical black hole charge to the cubic root of the mass function. The role of these parameters is investigated analyzing simple examples of dynamical charged black holes in the matter-dominated universe.
Conclusions
The study presented in this article introduces new time-dependent metric tensors with spherical symmetry that satisfy the Einstein-Maxwell equations in space-times with FLRW asymptotic behavior. These derived geometries describe dynamical charged non-rotating black holes within the perfect fluid of the asymptotic FLRW space-times. The gravitational sources for these black holes come from both the perfect fluid and an electromagnetic contribution due to the Coulomb field generated by the time-dependent black-hole charge in the background.
The dynamics of these models are determined by the dynamical mass, which can vary with time, as well as two arbitrary real-valued parameters. These parameters play a crucial role in simulating the effect of a cosmological constant and establishing a relationship between the dynamical black hole charge and the mass function.
Future Roadmap
- Further investigation into the implications of the two arbitrary parameters on the dynamics of dynamical charged black holes.
- Exploration of more complex examples and scenarios involving these new time-dependent metric tensors with spherical symmetry.
- Validation of these models through observational data and comparison with existing theoretical predictions.
- Collaboration with researchers in the field to expand the scope of this study and potentially uncover new insights into the nature of black holes in FLRW space-times.
Potential Challenges and Opportunities
Challenges
- Complexity of the models may pose challenges in practical applications and numerical simulations.
- Verification of these theoretical constructs through empirical observations could be difficult due to the nature of black holes and their interactions with their surrounding environments.
Opportunities
- Advancements in computational techniques and simulations can help in exploring the dynamics of these new geometries in more detail.
- Collaborative efforts with observational astronomers and astrophysicists could lead to groundbreaking discoveries regarding the nature of black holes in FLRW space-times.
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by jsendak | Oct 6, 2025 | GR & QC Articles
arXiv:2510.02321v1 Announce Type: new
Abstract: This article is a status report on the Anholonomic Frame and Connection Deformation Method, AFCDM, for constructing generic off-diagonal exact and parametric solutions in general relativity, GR, relativistic geometric flows, and modified gravity theories, MGTs. Such models can be generalized to nonassociative and noncommutative star products on phase spaces and modelled equivalently as nonassociative Finsler-Lagrange-Hamilton geometries. Our approach involves a nonholonomic geometric reformulation of classical models of gravitational and matter fields described by Lagrange and Hamilton densities on relativistic phase spaces. Using nonholonomic dyadic variables, the Einstein equations in GR and MGTs can be formulated as systems of nonlinear partial differential equations(PDEs), which can be decoupled and integrated in some general off-diagonal forms. In this approach, the Lagrange and Hamilton dynamics and related models of classical and quantum evolution are equivalently described in terms of generalized Finsler-like or canonical metrics and (nonlinear) connection structures on deformed phase spaces defined by solutions of modified Einstein equations. New classes of exact and parametric solutions in (nonassociative) MGTs are formulated in terms of generating and integration functions and generating effective/ matter sources. The physical interpretation of respective classes of solutions depends on the type of (non) linear symmetries, prescribed boundary/ asymptotic conditions, or posed Cauchy problems.
Conclusions
The Anholonomic Frame and Connection Deformation Method, AFCDM, provides a powerful tool for constructing exact and parametric solutions in general relativity, relativistic geometric flows, and modified gravity theories. By reformulating classical models in terms of nonholonomic dyadic variables, this approach allows for the decoupling and integration of systems of nonlinear PDEs in general off-diagonal forms.
Roadmap
- Explore nonassociative and noncommutative star products on phase spaces for further generalization of models.
- Investigate the equivalence of models as nonassociative Finsler-Lagrange-Hamilton geometries for deeper insight.
- Study the implications of the nonholonomic geometric reformulation on Lagrange and Hamilton dynamics.
- Develop methods for integrating generating functions and effective matter sources into new classes of solutions.
Potential Challenges
- Complexity in solving systems of nonlinear PDEs may present computational challenges.
- Interpreting the physical significance of solutions requires a deep understanding of (non) linear symmetries.
Opportunities on the Horizon
- Exploration of new classes of exact and parametric solutions could lead to breakthroughs in cosmology and gravitational physics.
- The development of Finsler-like metrics and connection structures opens up avenues for novel approaches to classical and quantum evolution.
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