by jsendak | Feb 24, 2024 | GR & QC Articles
arXiv:2402.14038v1 Announce Type: new
Abstract: With regard to the coupling constant and the strong magnetic field of neutron stars, we have studied these stars in the 4D Einstein Gauss Bonnet (4D EGB) gravity model in order to grasp a better understanding of these objects. In this paper, we have shown that the neutron star properties are considerably affected by the coupling constant and magnetic field. We have found that as a consequence of the strong magnetic field and the coupling constant, the maximum mass and radius of a neutron star are increasing functions of the coupling constant, while Schwarzschild radius, compactness, surface gravitational redshift, and Kretschmann scalar are decreasing functions. Additionally, our study has shown that the physical properties of a magnetized neutron star are greatly influenced not only by the strong magnetic field, but also by the anisotropy. Moreover, we have shown that to obtain the hydrostatic equilibrium configuration of the magnetized material, both the local anisotropy effect and the anisotropy due to the magnetic field should be considered. Finally, we have found that in the anisotropic magnetized neutron stars, the maximum mass and radius do not always increase with increasing the internal magnetic field.
Understanding Neutron Stars in 4D Einstein Gauss Bonnet Gravity
In this study, we have delved into the properties of neutron stars by considering the coupling constant and the strong magnetic field in the 4D Einstein Gauss Bonnet (4D EGB) gravity model. By exploring these factors, we aim to gain a better understanding of the behavior and characteristics of these celestial objects.
Impact of Coupling Constant and Magnetic Field
Our findings reveal that the coupling constant and magnetic field significantly affect the properties of neutron stars. The maximum mass and radius of a neutron star are found to increase with the coupling constant. On the other hand, the Schwarzschild radius, compactness, surface gravitational redshift, and Kretschmann scalar decrease with increasing coupling constant.
Influence of Strong Magnetic Field and Anisotropy
Our study highlights that the physical properties of magnetized neutron stars are greatly influenced by both the strong magnetic field and anisotropy. It is important to consider both the local anisotropy effect and the anisotropy caused by the magnetic field to accurately determine the hydrostatic equilibrium configuration of the magnetized material within neutron stars.
Non-Linear Relationship Between Maximum Mass/Radius and Internal Magnetic Field
Contrary to expectations, our research demonstrates that in anisotropic magnetized neutron stars, the maximum mass and radius do not always increase with an increase in the internal magnetic field. This suggests a non-linear relationship between these factors, introducing complexity into our understanding of neutron star behavior.
Roadmap for Future Research
Building upon our findings, there are several potential challenges and opportunities to explore in future research on neutron stars:
- Further investigate the precise relationship between the coupling constant and neutron star properties, utilizing simulations and observational data for validation.
- Explore the impact of additional factors on neutron star behavior, such as rotation, temperature, and composition, to obtain a more comprehensive understanding of these celestial objects.
- Investigate the role of anisotropy and magnetic fields in other types of stars and compact objects, expanding our knowledge of their physical behavior.
- Collaborate with astronomers and astrophysicists to incorporate observational data into theoretical models, enabling more accurate predictions and explanations of neutron star properties.
In conclusion, our study sheds light on the intricate relationship between the coupling constant, strong magnetic field, anisotropy, and various properties of neutron stars. By delving deeper into this research field, we can continue to uncover new insights and enhance our understanding of these fascinating celestial objects.
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by jsendak | Feb 23, 2024 | GR & QC Articles
arXiv:2402.13360v1 Announce Type: new
Abstract: This study explores the behavior of compact stars within the framework of $f(R,L_m,T)$ gravity, focusing on the functional form $f(R,L_m,T) = R + alpha TL_m$. The modified Tolman-Oppenheimer-Volkoff (TOV) equations are derived and numerically solved for several values of the free parameter $alpha$ by considering both quark and hadronic matter — described by realistic equations of state (EoSs). Furthermore, the stellar structure equations are adapted for two different choices of the matter Lagrangian density (namely, $L_m= p$ and $L_m= -rho$), laying the groundwork for our numerical analysis. As expected, we recover the traditional TOV equations in General Relativity (GR) when $alpha rightarrow 0$. Remarkably, we found that the two choices for $L_m$ have appreciably different effects on the mass-radius diagrams. Results showcase the impact of $alpha$ on compact star properties, while final remarks summarize key findings and discuss implications, including compatibility with observational data from NGC 6397’s neutron star. Overall, this research enhances comprehension of $f(R,L_m,T)$ gravity’s effects on compact star internal structures, offering insights for future investigations.
This study examines the behavior of compact stars within the framework of $f(R,L_m,T)$ gravity, focusing specifically on the functional form $f(R,L_m,T) = R + alpha TL_m$. The modified Tolman-Oppenheimer-Volkoff (TOV) equations are derived and numerically solved for different values of the parameter $alpha$, considering both quark and hadronic matter with realistic equations of state. The stellar structure equations are adapted for two choices of the matter Lagrangian density, laying the foundation for the numerical analysis.
When $alpha$ approaches zero, the traditional TOV equations in General Relativity (GR) are recovered. However, it was discovered that the two choices for $L_m$ have significantly different effects on the mass-radius diagrams. This highlights the impact of $alpha$ on the properties of compact stars. The study concludes by summarizing the key findings and discussing their implications, including their compatibility with observational data from NGC 6397’s neutron star.
Overall, this research enhances our understanding of the effects of $f(R,L_m,T)$ gravity on the internal structures of compact stars. It provides insights that can contribute to future investigations in this field.
Roadmap for Future Investigations
To further explore the implications and potential applications of $f(R,L_m,T)$ gravity on compact stars, several avenues of research can be pursued:
1. Expansion to Other Functional Forms
While this study focuses on the specific functional form $f(R,L_m,T) = R + alpha TL_m$, there is potential for investigation into other functional forms. Different choices for $f(R,L_m,T)$ may yield interesting and diverse results, expanding our understanding of compact star behavior.
2. Exploration of Different Equations of State
Currently, the study considers realistic equations of state for both quark and hadronic matter. However, there is room for exploration of other equations of state. By incorporating different equations of state, we can gain a more comprehensive understanding of the behavior of compact stars under $f(R,L_m,T)$ gravity.
3. Inclusion of Additional Parameters
Expanding the analysis to include additional parameters beyond $alpha$ can provide a more nuanced understanding of the effects of $f(R,L_m,T)$ gravity on compact stars. By investigating how different parameters interact with each other and impact the properties of compact stars, we can uncover new insights into the behavior of these celestial objects.
4. Comparison with Observational Data
While this study discusses the compatibility of the findings with observational data from NGC 6397’s neutron star, it is important to expand this comparison to a wider range of observational data. By comparing the theoretical predictions with a larger dataset, we can validate the conclusions drawn and identify any discrepancies or areas for further investigation.
Challenges and Opportunities
Potential Challenges:
- Obtaining accurate and comprehensive observational data on compact stars for comparison with theoretical predictions can be challenging due to their extreme conditions and limited visibility.
- Numerically solving the modified TOV equations for various parameter values and choices of matter Lagrangian density may require significant computational resources and optimization.
- Exploring different functional forms and equations of state can lead to complex analyses, requiring careful interpretation and validation of results.
Potential Opportunities:
- The advancements in observational techniques and instruments provide opportunities for obtaining more precise data on compact stars, enabling more accurate validation of theoretical models.
- Ongoing advancements in computational power and numerical techniques allow for more efficient and faster solution of the modified TOV equations, facilitating the exploration of a broader parameter space.
- The diverse range of functional forms and equations of state available for investigation provides ample opportunities for uncovering novel insights into the behavior and properties of compact stars.
By addressing these challenges and capitalizing on the opportunities, future investigations into the effects of $f(R,L_m,T)$ gravity on compact star internal structures can continue to push the boundaries of our understanding and pave the way for further advancements in the field.
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by jsendak | Feb 22, 2024 | GR & QC Articles
arXiv:2402.12409v1 Announce Type: new
Abstract: The main objective of this paper is to investigate the impact of $f(mathcal{Q},mathcal{T})$ gravity on the geometry of anisotropic compact stellar objects, where $mathcal{Q}$ is non-metricity and $mathcal{T}$ is the trace of the energy-momentum tensor. In this perspective, we use the physically viable non-singular solutions to examine the configuration of static spherically symmetric structures. We consider a specific model of this theory to examine various physical quantities in the interior of the proposed compact stars. These quantities include fluid parameters, anisotropy, energy constraints, equation of state parameters, mass, compactness and redshift. The Tolman-Oppenheimer-Volkoff equation is used to examine the equilibrium state of stellar models, while the stability of the proposed compact stars is investigated through sound speed and adiabatic index methods. It is found that the proposed compact stars are viable and stable in the context of this theory.
The main objective of this paper is to investigate the impact of $f(mathcal{Q},mathcal{T})$ gravity on the geometry of anisotropic compact stellar objects. The authors focus on using physically viable non-singular solutions to study the configuration of static spherically symmetric structures. Specifically, they consider a specific model of $f(mathcal{Q},mathcal{T})$ gravity and examine various physical quantities in the interior of the compact stars.
The paper discusses the implications of $f(mathcal{Q},mathcal{T})$ gravity on fluid parameters, anisotropy, energy constraints, equation of state parameters, mass, compactness, and redshift of the proposed compact stars. The authors utilize the Tolman-Oppenheimer-Volkoff equation to analyze the equilibrium state of stellar models and investigate the stability of the proposed compact stars using sound speed and adiabatic index methods.
Future Roadmap
Potential Challenges:
- Theoretical Complexity: Further research may be required to fully understand the intricacies and complexities of $f(mathcal{Q},mathcal{T})$ gravity and its impact on compact stellar objects.
- Experimental Verification: Experimental tests or observations are necessary to validate the predictions and conclusions of this study.
- Generalizability: The authors focus on a specific model of $f(mathcal{Q},mathcal{T})$ gravity. Future studies could explore the generalizability of their findings by considering different models within this framework.
Potential Opportunities:
- Understanding Compact Stellar Objects: This study provides insights into the geometry and physical quantities of anisotropic compact stellar objects, which could contribute to our understanding of these astrophysical entities.
- Exploring Modified Gravity Theories: $f(mathcal{Q},mathcal{T})$ gravity is a modified theory of gravity. Further investigations into this theory may shed light on the nature of gravity itself and its implications in various astrophysical contexts.
- Advancing Stellar Structure Theory: The analysis of equilibrium states and stability of compact stars in the context of $f(mathcal{Q},mathcal{T})$ gravity can enhance our knowledge of stellar structure and the fundamental forces governing star formation and evolution.
In conclusion, this paper investigates the impact of $f(mathcal{Q},mathcal{T})$ gravity on anisotropic compact stellar objects and provides valuable insights into their geometry and physical quantities. While further research and experimental verification are needed, this study opens up opportunities for understanding compact stellar objects, exploring modified gravity theories, and advancing our knowledge of stellar structure.
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by jsendak | Feb 21, 2024 | GR & QC Articles
arXiv:2402.10916v1 Announce Type: new
Abstract: In this analysis, we study the dynamics of quantum oscillator fields within the context of a position-dependent mass (PDM) system situated in an Einstein-Maxwell space-time, incorporating a non-zero cosmological constant. The magnetic field is aligned along the symmetry axis direction. To analyze PDM quantum oscillator fields, we introduce a modification to the Klein-Gordon equation by substituting the four-momentum vector $p_{mu} to Big(p_{mu}+i,eta,X_{mu}+i,mathcal{F}_{mu}Big)$ into the Klein-Gordon equation, where the four-vector is defibed by $X_{mu}=(0, r, 0, 0)$, $mathcal{F}_{mu}=(0, mathcal{F}_r, 0, 0)$ with $mathcal{F}_r=frac{f'(r)}{4,f(r)}$, and $eta$ is the mass oscillator frequency. The radial wave equation for the relativistic modified Klein-Gordon equation is derived and subsequently solved for two distinct cases: (i) $f(r)=e^{frac{1}{2},alpha,r^2}$, and (ii) $f(r)=r^{beta}$, where $alpha geq 0, beta geq 0$. The resultant energy levels and wave functions for quantum oscillator fields are demonstrated to be influenced by both the cosmological constant and the geometrical topology parameter which breaks the degeneracy of the energy spectrum. Furthermore, we observed noteworthy modifications in the energy levels and wave functions when compared to the results derived in the flat space background.
Analysis of Quantum Oscillator Fields with Position-Dependent Mass
In this analysis, we examine the dynamics of quantum oscillator fields within the context of a position-dependent mass (PDM) system situated in an Einstein-Maxwell space-time, incorporating a non-zero cosmological constant. The magnetic field is aligned along the symmetry axis direction.
To analyze PDM quantum oscillator fields, we introduce a modification to the Klein-Gordon equation by substituting the four-momentum vector pμ → (pμ + iηXμ+ i𝓕μ) into the Klein-Gordon equation. Here, the four-vector is defined by Xμ = (0, r, 0, 0), 𝓕μ = (0, 𝓕r, 0, 0) with 𝓕r=f'(r) / (4f(r)), and η is the mass oscillator frequency.
Derivation and Solutions
The radial wave equation for the relativistic modified Klein-Gordon equation is derived and subsequently solved for two distinct cases:
- f(r) = e(1/2)αr²
- f(r) = rβ
In case (i), where f(r) = e(1/2)αr², and in case (ii), where f(r) = rβ, with α ≥ 0 and β ≥ 0, we obtain the resultant energy levels and wave functions for the quantum oscillator fields.
Influence of Cosmological Constant and Geometrical Topology Parameter
The energy levels and wave functions for quantum oscillator fields are demonstrated to be influenced by both the cosmological constant and the geometrical topology parameter, which breaks the degeneracy of the energy spectrum. Notably, there are modifications observed in the energy levels and wave functions when compared to the results derived in a flat space background.
Future Roadmap
Looking ahead, there are several potential challenges and opportunities on the horizon regarding the analysis of quantum oscillator fields with position-dependent mass:
- Further investigation: More extensive research is needed to explore different forms of position-dependent mass functions and their effects on quantum oscillator fields. This could involve considering more complex mass distributions or non-linear mass dependence.
- Experimental verification: Conducting experiments or simulations to validate the theoretical predictions and properties of quantum oscillator fields with position-dependent mass would provide valuable insights and potential applications in various fields, such as quantum computing or high-energy physics.
- Generalization of findings: Extending the analysis to higher-dimensional space-times or incorporating additional physical factors, such as magnetic fields, gravitational waves, or other forces, could enhance our understanding of the behavior of quantum oscillator fields with position-dependent mass in more complex scenarios.
- Applications: Exploring the potential practical applications of this analysis, such as in quantum technologies or novel materials with tailored physical properties, could lead to groundbreaking advancements in various fields.
- Interdisciplinary collaborations: Collaborations between physicists, mathematicians, and other scientists from different disciplines could foster new approaches and perspectives in studying quantum oscillator fields with position-dependent mass, leading to innovative breakthroughs.
Overall, the study of quantum oscillator fields with position-dependent mass presents an intriguing avenue for research and opens up new possibilities for understanding and manipulating quantum systems in diverse contexts.
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by jsendak | Feb 20, 2024 | GR & QC Articles
arXiv:2402.10249v1 Announce Type: new
Abstract: Linear superposition of gravitational fields is shown to be possible for a large class of spacetimes, in some specific coordinates. Explicit examples are presented.
Future Roadmap: Linear Superposition of Gravitational Fields
Future Roadmap: Linear Superposition of Gravitational Fields
Introduction
The article explores the possibility of linear superposition of gravitational fields in certain spacetimes and specific coordinates. It presents explicit examples to showcase this phenomenon.
Conclusion
The study demonstrates that for a large class of spacetimes, linear superposition of gravitational fields can occur. This implies that the combined effect of multiple gravitational fields can be accurately calculated in these specific coordinates.
Roadmap for Readers
In order to further understand and explore the concept of linear superposition of gravitational fields, readers can consider the following roadmap:
- Understand the Basics: Familiarize yourself with the fundamental principles and equations of general relativity, including the concept of gravitational fields and their interactions.
- Review Example Cases: Study the explicit examples presented in the article to gain a practical understanding of how linear superposition manifests in specific spacetimes and coordinates.
- Explore Applicability: Investigate the extent to which linear superposition applies to different classes of spacetimes and coordinates. Assess whether it can be generalized beyond the specific cases shown in the examples.
- Consider Implications: Analyze the potential implications of linear superposition of gravitational fields. How can this concept enhance our understanding of gravity? What are the implications for practical applications, such as space exploration or cosmology?
- Engage in Further Research: If interested, delve deeper into related research papers and studies that expand upon the concept of linear superposition in different contexts. Stay updated with the latest developments in the field.
Challenges and Opportunities
While the concept of linear superposition of gravitational fields opens up new possibilities for understanding and calculating gravitational interactions, there are several challenges and opportunities on the horizon:
- Coordination Complexity: Implementing linear superposition in practical scenarios may require complex coordinate transformations and calculations, making it challenging to apply in certain contexts.
- Validation and Verification: Further experimental validation and verification are crucial to ensure the accuracy and reliability of the results obtained from linear superposition calculations.
- Extending to General Cases: The applicability of linear superposition to a wider range of spacetimes and coordinate systems needs to be investigated. It is important to determine the limitations and boundaries of this concept beyond the specific cases presented.
- Expanding Practical Applications: Exploring real-world applications of linear superposition, such as improving space mission trajectories or refining cosmological models, can lead to exciting opportunities for advancements in various fields.
In summary, while linear superposition of gravitational fields has been shown to be possible for a large class of spacetimes, there are challenges to overcome as this concept is further explored. Nevertheless, it presents promising opportunities for advancing our understanding of gravity and its applications.
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by jsendak | Feb 17, 2024 | GR & QC Articles
arXiv:2402.09435v1 Announce Type: new
Abstract: Black bounces are spacetimes that can be interpreted as either black holes or wormholes depending on specific parameters. In this study, we examine the Simpson-Visser and Bardeen-type solutions as black bounces and investigate the gravitational wave in the background of these solutions. We then explore the displacement and velocity memory effects by analyzing the deviation of two neighboring geodesics and their derivatives influenced by the magnetic charge parameter a. This investigation aims to trace the magnetic charge in the gravitational memory effect. Additionally, we consider another family of traversable wormhole solutions obtained from non-exotic matter sources to trace the electric charge Qe in the gravitational memory effect, which can be determined from the far field asymptotic. This project is significant not only for detecting the presence of compact objects like wormholes through gravitational memory effects but also for observing the charge Qe, which provides a concrete realization of Wheeler’s concept of “electric charge without charge.”
Investigating Black Bounces and Gravitational Waves
In this study, we delve into the fascinating concept of black bounces – spacetimes that can be interpreted as both black holes and wormholes depending on certain parameters. Specifically, we examine two types of solutions known as the Simpson-Visser and Bardeen-type solutions, treating them as black bounces. Our goal is to understand the behavior of gravitational waves in the background of these solutions.
Analyzing Displacement and Velocity Memory Effects
To gain deeper insights, we focus on the displacement and velocity memory effects by studying the deviation between two neighboring geodesics and their derivatives, which are influenced by the magnetic charge parameter known as a. By tracing the magnetic charge, we aim to uncover its role in the gravitational memory effect.
Non-Exotic Traversable Wormholes and Electric Charge
In addition to investigating black bounces, we also explore another family of traversable wormhole solutions obtained from non-exotic matter sources. Here, our aim is to trace the electric charge Qe in the gravitational memory effect, which can be determined from the far field asymptotic.
Future Roadmap: Challenges and Opportunities
- Challenges: The investigation of black bounces and their gravitational wave behavior presents some challenges. Understanding the complex dynamics of spacetime, particularly when it can be interpreted as both a black hole and a wormhole, requires advanced mathematical techniques and in-depth analysis.
- Opportunities: Despite the challenges, our research offers exciting opportunities. By studying displacement and velocity memory effects, we may gain valuable insights into the characteristics and nature of black bounces. Additionally, tracing the magnetic charge and electric charge in the gravitational memory effect can potentially lead to the detection and observation of compact objects like wormholes and Wheeler’s concept of “electric charge without charge.”
Conclusion
This project holds significant scientific importance. Through our investigation of black bounces, gravitational waves, and memory effects, we aim to contribute to our understanding of the fundamental nature of spacetime. Furthermore, the potential detection of wormholes and observation of electric charge without charge would mark major milestones in astrophysics and shape our understanding of the universe.
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