by jsendak | Feb 24, 2025 | GR & QC Articles
arXiv:2502.14927v1 Announce Type: new
Abstract: Our present contribution sets out to investigate how combined effects of Lorentz-symmetry violation (LSV) and Loop-Quantum-Gravity(LQG)-modified photon dispersion relations affect the threshold anomaly of cosmic photons. The point of departure is the post-Maxwellian version of Electromagnetism induced by LQG effects. We then consider the problem of gamma-ray attenuation by the Extragalactic Background Light (EBL) and the Cosmic Microwave Background Radiation (CMB) dominated by the Breit-Wheeler Effect. By following this path, we aim at the establishment of a new bridge between LSV and astrophysical phenomena in the framework of LQG.
Investigating the Combined Effects of Lorentz-Symmetry Violation and Loop-Quantum-Gravity on Cosmic Photon Threshold Anomaly
In this article, we explore the potential implications of Lorentz-symmetry violation (LSV) and Loop-Quantum-Gravity (LQG) modified photon dispersion relations on the threshold anomaly of cosmic photons. Our research starts with the post-Maxwellian version of Electromagnetism induced by LQG effects. We then delve into the problem of gamma-ray attenuation by the Extragalactic Background Light (EBL) and the Cosmic Microwave Background Radiation (CMB), focusing on the Breit-Wheeler Effect domination. Through this investigation, we aim to create a connection between LSV and astrophysical phenomena within the framework of LQG.
Future Roadmap: Challenges and Opportunities
1. Further Investigation of LSV and LQG Effects
One of the key challenges for future research is to gain a deeper understanding of the combined effects of Lorentz-symmetry violation and Loop-Quantum-Gravity on various physical phenomena. This requires rigorous theoretical studies and numerical simulations to explore the implications and constraints on LSV and LQG parameters. Collaborative efforts between physicists specializing in LSV and LQG can lead to significant advancements in this field.
2. Experimental Verification
In order to validate the theoretical predictions, experimental verification is required. Designing and conducting experiments that can probe the effects of LSV and LQG on photon dispersion relations and the Breit-Wheeler Effect is a promising avenue for future research. This would involve collaborations between astrophysicists and experimental physicists to design innovative experiments and analyze the resulting data.
3. Implications for Astrophysical Phenomena
The research presented in this article suggests a potential connection between LSV and astrophysical phenomena. Exploring the implications of LSV and LQG on various astrophysical processes, such as gamma-ray attenuation by the EBL and CMB, opens up new avenues for understanding the fundamental laws of physics in extreme cosmic environments. This can lead to novel insights into the behavior of high-energy photons and their interactions.
4. Theoretical and Practical Applications
The findings from this research can have broader implications beyond just theoretical physics. Understanding the fundamental aspects of LSV and LQG could potentially lead to the development of advanced technologies. For example, insights gained from studying the modification of photon dispersion relations could contribute to the improvement of high-energy photon detectors and communication systems.
5. Exploring New Frontiers
The investigation of LSV and LQG effects on cosmic photons is still a relatively unexplored territory. As more research is conducted and new theories and experiments emerge, there is an opportunity to push the boundaries of our understanding further. This field presents exciting prospects for both theoretical and experimental physicists to contribute to the development of a more comprehensive and accurate description of the fundamental nature of the universe.
Conclusion
By investigating the combined effects of Lorentz-symmetry violation and Loop-Quantum-Gravity on the threshold anomaly of cosmic photons, we aim to establish a new bridge between LSV and astrophysical phenomena within the framework of LQG. This roadmap highlights the challenges and opportunities that lie ahead in terms of further theoretical investigations, experimental verification, implications for astrophysics, technological applications, and pushing the boundaries of current knowledge. The exploration of LSV and LQG effects offers an exciting frontier for researchers to unravel the mysteries of the universe.
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by jsendak | Feb 21, 2025 | GR & QC Articles
arXiv:2502.14025v1 Announce Type: new
Abstract: The Simulating eXtreme Spacetimes Collaboration’s code SpEC can now routinely simulate binary black hole mergers undergoing $sim25$ orbits, with the longest simulations undergoing nearly $sim180$ orbits. While this sounds impressive, the mismatch between the highest resolutions for this long simulation is $mathcal{O}(10^{-1})$. Meanwhile, the mismatch between resolutions for the more typical simulations tends to be $mathcal{O}(10^{-4})$, despite the resolutions being similar to the long simulations’. In this note, we explain why mismatch alone gives an incomplete picture of code — and waveform — quality, especially in the context of providing waveform templates for LISA and 3G detectors, which require templates with $mathcal{O}(10^{3}) – mathcal{O}(10^{5})$ orbits. We argue that to ready the GW community for the sensitivity of future detectors, numerical relativity groups must be aware of this caveat, and also run future simulations with at least three resolutions to properly assess waveform accuracy.
Future Roadmap for Readers: Challenges and Opportunities
Introduction
This article discusses the limitations of current simulations in accurately predicting gravitational wave (GW) waveforms, specifically in the context of providing waveform templates for future GW detectors like LISA and 3G detectors. It explains the importance of running simulations with higher resolutions and proposes a future roadmap for numerical relativity groups to enhance waveform accuracy.
Limitations of Current Simulations
The article highlights that while the current simulations using the code SpEC can simulate binary black hole mergers for a significant number of orbits (up to nearly 180 orbits), the resolution used in these simulations results in a significant mismatch compared to higher resolution simulations. The mismatch is on the order of $mathcal{O}(10^{-4})$ for typical simulations and $mathcal{O}(10^{-1})$ for longer simulations. This indicates that the quality of the code and waveform is not accurately represented by mismatch alone.
Importance of High-Resolution Simulations
The article emphasizes the need for waveform templates that accurately represent the behavior of GW signals for future detectors, which require templates with $mathcal{O}(10^{3}) – mathcal{O}(10^{5})$ orbits. To achieve this, numerical relativity groups must be aware of the limitations caused by mismatch and run simulations with at least three resolutions to properly assess waveform accuracy.
Roadmap for Enhancing Waveform Accuracy
- Awareness: Numerical relativity groups must be aware of the limitations of mismatch in assessing waveform accuracy. This requires understanding the incomplete picture provided by mismatch alone.
- Higher Resolutions: To improve waveform accuracy, future simulations should be conducted with higher resolutions. This will help reduce the mismatch between simulations and provide more reliable waveform templates for future detectors.
- Multi-Resolution Simulations: Simulations should be run with at least three resolutions to properly assess waveform accuracy. This will allow for a more comprehensive understanding of the code quality and waveform behavior.
Conclusion
The challenges and opportunities on the horizon involve improving the accuracy of GW waveform templates for future detectors. By addressing the limitations of mismatch and conducting simulations with higher resolutions, numerical relativity groups can provide more reliable waveform predictions. This roadmap will help prepare the GW community for the sensitivity of future detectors and enhance our understanding of extreme spacetimes.
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by jsendak | Feb 7, 2025 | GR & QC Articles
arXiv:2502.03483v1 Announce Type: new
Abstract: This thesis employs the dynamical systems approach to explore two cosmological models: an anisotropic dark energy scenario in a Bianchi-I background and the Generalized SU(2) Proca (GSU2P) theory in a flat FLRW background. In the first case, a numerical framework is developed to analyze the interaction between a scalar tachyon field and a vector field, identifying parameter regions that allow anisotropic accelerated attractors. The second case examines the viability of GSU2P as a driver of inflation and late-time acceleration. Our analysis reveals fundamental limitations, including the absence of stable attractors and smooth cosmological transitions, ultimately ruling out the model as a complete description of the Universe’s expansion. This work highlights the effectiveness of dynamical systems techniques in assessing alternative cosmological scenarios and underscores the need for refined theoretical frameworks aligned with observational constraints.
This thesis examines two cosmological models using the dynamical systems approach: an anisotropic dark energy scenario in a Bianchi-I background and the Generalized SU(2) Proca (GSU2P) theory in a flat FLRW background. The first case explores the interaction between a scalar tachyon field and a vector field, identifying parameter regions that allow anisotropic accelerated attractors. The second case investigates if GSU2P can drive inflation and late-time acceleration.
However, the analysis reveals fundamental limitations in both models. In the anisotropic dark energy scenario, stable attractors and smooth cosmological transitions are found to be absent, ruling out this model as a complete description of the Universe’s expansion. Similarly, GSU2P is also deemed inadequate in providing a complete understanding of cosmological phenomena.
Despite these limitations, this work demonstrates the effectiveness of dynamical systems techniques in assessing alternative cosmological scenarios. This research highlights the importance of refined theoretical frameworks that are aligned with observational constraints to further our understanding of the Universe’s expansion.
Future Roadmap
While the current models explored in this thesis may not provide a complete description of the Universe’s expansion, there are several opportunities for future research and development in the field. These include:
- Refining existing models: There is still scope for refining the anisotropic dark energy scenario and the GSU2P theory to overcome their limitations and potentially align them with observational constraints.
- Exploring other cosmological models: The dynamical systems approach can be applied to investigate other cosmological models and scenarios. By analyzing their attractors and transitions, we can gain valuable insights into the behavior of these models and their viability as complete descriptions of the Universe’s expansion.
- Integrating observational data: Future research should focus on incorporating observational data from cosmological surveys and experiments to further constrain and validate theoretical frameworks. This integration will enable a more comprehensive understanding of the Universe’s expansion.
- Developing new theoretical frameworks: Building on the insights gained from dynamical systems techniques, there is a need for the development of new theoretical frameworks that can better explain the observed cosmological phenomena. These frameworks should be able to account for the absence of stable attractors and smooth transitions found in the current models.
It is important for researchers to collaborate and share their findings to collectively advance our understanding of cosmology. By embracing the challenges and opportunities of refining and developing theoretical frameworks, we can strive towards a comprehensive and accurate description of the Universe’s expansion.
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by jsendak | Jan 24, 2025 | GR & QC Articles
arXiv:2501.13176v1 Announce Type: new
Abstract: We consider the self-force acting on a pointlike (electromagnetic or conformal-scalar) charge held fixed on a spacetime with a spherically-symmetric mass distribution of constant density (the Schwarzschild star). We calculate the self-force with two complementary regularization methods, direct and difference regularization, and we find agreement. The Schwarzschild star is shown to be conformal to a three-sphere geometry; we use this conformal symmetry to obtain closed-form expressions for mode solutions. The new results for the self-force come in three forms: series expansions for the self-force in the far field; an approximation that captures the divergence in the self-force near the star’s boundary; and as numerical data presented in a selection of plots. We conclude with a discussion of the logarithmic divergence in the self-force in the approach to the star’s surface.
Future Roadmap: Challenges and Opportunities
Introduction
The article investigates the self-force acting on a pointlike charge fixed on a spacetime with a spherically-symmetric mass distribution of constant density, known as the Schwarzschild star. The self-force is calculated using two regularization methods, direct and difference regularization, with agreement found between them. The article also discusses the conformal symmetry of the Schwarzschild star and its implications for obtaining closed-form expressions for mode solutions. The self-force is presented in three different forms: series expansions in the far field, an approximation for the divergence near the star’s boundary, and numerical data presented in plots.
Roadmap
To fully understand the conclusions of the article and explore potential future directions, readers should consider the following roadmap:
- Understanding the Self-Force: Dive deeper into the concept of the self-force and its significance in the context of a pointlike charge held fixed on a Schwarzschild star. Gain a clear understanding of the self-force calculations performed using direct and difference regularization methods.
- Exploring Conformal Symmetry: Explore the conformal symmetry of the Schwarzschild star and its implications for obtaining closed-form expressions for mode solutions. Understand how this symmetry contributes to the understanding of the self-force acting on the charge.
- Series Expansions in the Far Field: Examine the series expansions for the self-force in the far field. Analyze the implications of these expansions and their usefulness in practical applications. Consider potential challenges in extending these series expansions to more complex mass distributions.
- Approximation for Divergence Near the Star’s Boundary: Study the approximation presented to capture the divergence in the self-force near the star’s boundary. Evaluate the accuracy of the approximation and potential limitations in real-world scenarios.
- Numerical Data and Plots: Analyze the numerical data presented in a selection of plots. Identify patterns, trends, and potential correlations between the self-force and various parameters. Consider the limitations and challenges in extrapolating these numerical results to other scenarios.
- Discussion of Logarithmic Divergence: Engage in the discussion regarding the logarithmic divergence in the self-force as the charge approaches the star’s surface. Understand the implications of this divergence and potential future research directions to mitigate or utilize its effects.
Conclusion
The article provides an in-depth analysis of the self-force acting on a pointlike charge held fixed on a Schwarzschild star. It offers various insights into the calculations, conformal symmetry, series expansions, approximations, and numerical data related to the self-force. Readers can further explore the topics outlined in the roadmap to gain a deeper understanding of the conclusions and potentially uncover future challenges and opportunities in this area of study.
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by jsendak | Jan 14, 2025 | GR & QC Articles
arXiv:2501.06315v1 Announce Type: new
Abstract: The orbiting LISA instrument is designed to detect gravitational waves in the millihertz band, produced by sources including galactic binaries and extreme mass ratio inspirals, among others. The detector consists of three spacecraft, each carrying a pair of free-falling test masses. A technology-demonstration mission, LISA Pathfinder, was launched in 2015, and observed several sudden changes in test mass acceleration, referred to as “glitches.” Similar glitches in the full LISA mission have the potential to contaminate the Time-Delay Interferometry outputs that are the detector’s primary data product. In this paper, we describe an optimization technique using maximum likelihood estimation for detecting and removing glitches with a known waveform.
Future Roadmap: Challenges and Opportunities
1. Challenges
- Contamination of Time-Delay Interferometry Outputs: Glitches observed in test mass acceleration during the LISA mission have the potential to contaminate the primary data product of the detector, the Time-Delay Interferometry outputs. This contamination can lead to inaccurate gravitational wave detection and analysis.
- Identification and Removing Glitches: The optimization technique using maximum likelihood estimation described in the paper aims to detect and remove glitches with a known waveform. However, accurately identifying and removing glitches can be challenging, especially if the glitches have unknown or unpredictable waveforms.
- Improving Detector Sensitivity: Another challenge for the LISA mission is to improve the detector’s sensitivity to gravitational waves in the millihertz band. Enhancements in technology and instrumentation will be crucial to achieving this goal.
2. Opportunities
- Advancement in Technology: The glitches observed during the LISA Pathfinder mission provide valuable insights into the behavior of the test masses and potential sources of contamination. Further research and technological advancements can help in developing robust techniques to identify and remove glitches effectively.
- Collaborative Efforts: Collaboration among scientists, engineers, and researchers from various disciplines will play a vital role in overcoming the challenges associated with glitch detection and removal. Sharing knowledge, expertise, and resources can result in significant breakthroughs.
- Data Analysis Techniques: Developing advanced data analysis techniques, such as machine learning algorithms and artificial intelligence, can help in automated glitch detection and removal, making the process more efficient and accurate.
3. Future Roadmap
- Continue research and development efforts to improve the detector sensitivity of LISA instrument in detecting gravitational waves.
- Investigate and analyze the glitches observed during the LISA Pathfinder mission to gain a better understanding of their characteristics and potential sources.
- Develop and refine optimization techniques, such as maximum likelihood estimation, to enhance the detection and removal of glitches with known waveforms.
- Explore and invest in innovative technologies and instrumentation that can improve glitch detection, identification, and removal.
- Encourage collaboration among scientists, engineers, and researchers to share knowledge and expertise in developing effective glitch detection and removal techniques.
- Investigate the feasibility of utilizing advanced data analysis techniques, such as machine learning algorithms and artificial intelligence, for automated glitch detection and removal.
- Continuously test and validate glitch detection and removal techniques using simulated and real data from the LISA instrument.
- Ensure regular updates and improvements to the LISA instrument based on the research findings and technological advancements.
Conclusion
The detection and removal of glitches in the LISA instrument’s data is crucial for accurate gravitational wave detection and analysis. While challenges such as contamination of outputs and identifying unknown waveforms exist, there are opportunities for improvement through advancements in technology, collaborative efforts, and data analysis techniques. Following the outlined future roadmap will contribute to overcoming these challenges and ensuring the success of the LISA mission.
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