by jsendak | Jan 3, 2024 | GR & QC Articles
We report unbiased AI measurements of the fine structure constant alpha in
two proximate absorption regions in the spectrum of the quasar HE0515-4414. The
data are high resolution, high signal to noise, and laser frequency comb
calibrated, obtained using the ESPRESSO spectrograph on the VLT. The high
quality of the data and proximity of the regions motivate a differential
comparison, exploring the possibility of spatial variations of fundamental
constants, as predicted in some theories. We show that if the magnesium
isotopic relative abundances are terrestrial, the fine structure constants in
these two systems differ at the 7-sigma level. A 3-sigma discrepancy between
the two measurements persists even for the extreme non-terrestrial case of 100%
^{24}Mg, if shared by both systems. However, if Mg isotopic abundances take
independent values in these two proximate systems, one terrestrial, the other
with no heavy isotopes, both can be reconciled with a terrestrial alpha, and
the discrepancy between the two measurements falls to 2-sigma. We discuss
varying constant and varying isotope interpretations and resolutions to this
conundrum for future high precision measurements.
We report unbiased AI measurements of the fine structure constant alpha in two proximate absorption regions in the spectrum of the quasar HE0515-4414. The data are high resolution, high signal to noise, and laser frequency comb calibrated, obtained using the ESPRESSO spectrograph on the VLT.
The high quality of the data and proximity of the regions motivate a differential comparison, exploring the possibility of spatial variations of fundamental constants, as predicted in some theories.
We show that if the magnesium isotopic relative abundances are terrestrial, the fine structure constants in these two systems differ at the 7-sigma level. A 3-sigma discrepancy between the two measurements persists even for the extreme non-terrestrial case of 100% ^{24}Mg, if shared by both systems. However, if Mg isotopic abundances take independent values in these two proximate systems, one terrestrial, the other with no heavy isotopes, both can be reconciled with a terrestrial alpha, and the discrepancy between the two measurements falls to 2-sigma.
Conclusion: The measurements of the fine structure constant alpha in two proximate absorption regions show a significant difference between the systems. The discrepancy can be reduced if magnesium isotopic abundances take independent values in each system. Future high precision measurements can explore varying constant and varying isotope interpretations and seek resolutions to this conundrum.
Roadmap for Future Research
- Further High Precision Measurements: Conduct additional AI measurements using high-resolution, high signal to noise data and laser frequency comb calibration to obtain precise measurements of the fine structure constant alpha in proximate absorption regions.
- Comparison of Different Systems: Compare multiple systems with varying magnesium isotopic abundances to determine if there is a consistent pattern and if the fine structure constants differ between these systems.
- Investigation of Varying Constant Theories: Explore theories that predict spatial variations of fundamental constants, such as the fine structure constant, and investigate whether the observed differences in alpha between the two systems can be explained by varying constant interpretations.
- Examine Varying Isotope Interpretations: Investigate whether the discrepancy in alpha measurements can be attributed to variations in magnesium isotopic abundances and analyze if the independent values of isotopes in proximate systems can reconcile the measurements with a terrestrial alpha.
- Develop Resolutions to the Conundrum: Seek resolutions to explain the observed differences in alpha measurements, considering both varying constant and varying isotope interpretations, and propose potential explanations for the findings.
Potential Challenges and Opportunities
Challenges:
- Data Quality: Ensuring high-resolution, high signal to noise data with accurate laser frequency comb calibration may be challenging, but is crucial for obtaining reliable measurements.
- Interpreting Discrepancies: Understanding the underlying causes of the observed differences in alpha measurements between proximate absorption regions and determining whether they are attributable to varying constants, isotope abundances, or other factors can pose challenges.
- Data Comparison: Comparing measurements from multiple systems and accounting for varying magnesium isotopic abundances require careful analysis and statistical techniques to draw meaningful conclusions.
Opportunities:
- Advancements in Technology: Continued advancements in AI, spectrograph technology, and calibration techniques can lead to even higher precision measurements of fundamental constants.
- Exploring New Theories: The observed discrepancies present an opportunity to further investigate theories that propose spatial variations of fundamental constants and explore their implications.
- Collaborative Research: International collaborations and sharing of data and findings can enhance the understanding of spatial variations in fundamental constants and lead to potential resolutions.
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by jsendak | Jan 3, 2024 | GR & QC Articles
Electrostatic force actuation is a key component of the system of geodesic
reference test masses (TM) for the LISA orbiting gravitational wave observatory
and in particular for performance at low frequencies, below 1 mHz, where the
observatory sensitivity is limited by stray force noise. The system needs to
apply forces of order 10$^{-9}$ N while limiting fluctuations in the
measurement band to levels approaching 10$^{-15}$ N/Hz$^{1/2}$. We present here
the LISA actuation system design, based on audio-frequency voltage carrier
signals, and results of its in-flight performance test with the LISA Pathfinder
test mission. In LISA, TM force actuation is used to align the otherwise
free-falling TM to the spacecraft-mounted optical metrology system, without any
forcing along the critical gravitational wave-sensitive interferometry axes. In
LISA Pathfinder, on the other hand, the actuation was used also to stabilize
the TM along the critical $x$ axis joining the two TM, with the commanded
actuation force entering directly into the mission’s main differential
acceleration science observable. The mission allowed demonstration of the full
compatibility of the electrostatic actuation system with the LISA observatory
requirements, including dedicated measurement campaigns to amplify, isolate,
and quantify the two main force noise contributions from the actuation system,
from actuator gain noise and from low frequency “in band” voltage
fluctuations. These campaigns have shown actuation force noise to be a
relevant, but not dominant, noise source in LISA Pathfinder and have allowed
performance projections for the conditions expected in the LISA mission.
The conclusions drawn from this text are as follows:
- The electrostatic force actuation system is a key component of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory.
- In the LISA mission, TM force actuation is used to align the TM to the spacecraft-mounted optical metrology system, without forcing along the critical gravitational wave-sensitive interferometry axes.
- In the LISA Pathfinder mission, actuation was used to stabilize the TM along the critical $x$ axis and directly affected the mission’s main differential acceleration science observable.
- LISA Pathfinder demonstrated the compatibility of the electrostatic actuation system with LISA observatory requirements.
- Dedicated measurement campaigns were conducted during LISA Pathfinder to amplify, isolate, and quantify force noise contributions from the actuation system.
- Actuation force noise was found to be a relevant factor, but not the dominant noise source in LISA Pathfinder.
- Performance projections for the conditions expected in the LISA mission were made based on the findings during LISA Pathfinder.
Based on these conclusions, a future roadmap for readers can be outlined:
Future Roadmap
Challenges
- Reducing stray force noise in the LISA orbiting gravitational wave observatory, especially at low frequencies below 1 mHz.
- Improving actuator gain noise and minimizing low-frequency voltage fluctuations.
Opportunities
- Further optimizing the electrostatic actuation system for geodesic reference test masses in LISA.
- Exploring alternative actuation methods to potentially reduce force noise.
- Continuing dedicated measurement campaigns to better understand and quantify force noise contributions.
- Further aligning the TM to the spacecraft-mounted optical metrology system and improving stabilization along critical axes.
By addressing these challenges and exploring these opportunities, the performance of the electrostatic force actuation system can be optimized for the LISA orbiting gravitational wave observatory, ultimately improving its sensitivity and ability to detect gravitational waves.
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by jsendak | Jan 2, 2024 | GR & QC Articles
We investigate the tachyonic instability of Kerr-Newman (KN) black hole with
a rotation parameter $a$ in the Einstein-Chern-Simons-scalar theory coupled
with a quadratic massive scalar field. This instability analysis corresponds to
exploring the onset of spontaneous scalarization for KN black holes. First, we
find no $a$-bound for $alpha<0$ case by considering (1+1)-dimensional
analytical method. A direct numerical method is adopted to explore
(2+1)-dimensional time evolution of a massive scalar perturbation with positive
and negative $alpha$ to obtain threshold curves numerically. We obtain
threshold curves $alpha_{rm th}(a)$ of tachyonic instability for positive
$alpha$ without any $a$-bounds. We expect to find the same threshold curves
$alpha_{rm th}(a)$ of tachyonic instability for negative $alpha$ without any
$a$-bound because its linearized scalar theory is invariant under the
transformation of $alphato -alpha $ and $thetato -theta$. In addition, it
is found that the scalar mass term suppresses tachyonic instability of KN black
holes.
According to the article, the authors investigate the tachyonic instability of Kerr-Newman (KN) black holes with a rotation parameter a in the Einstein-Chern-Simons-scalar theory coupled with a quadratic massive scalar field. The purpose of this analysis is to explore the onset of spontaneous scalarization for KN black holes. The following conclusions can be drawn:
1. No a-bound for α<0 case
The authors use a (1+1)-dimensional analytical method and find that there is no bound on the rotation parameter a for the case where α is negative.
2. Numerical exploration of (2+1)-dimensional time evolution
The authors adopt a direct numerical method to explore the time evolution of a massive scalar perturbation with positive and negative α in a (2+1)-dimensional setup. They obtain threshold curves numerically, indicating the values of α that lead to tachyonic instability. They find that there are no a-bounds for positive α.
3. Invariance under transformation of α and θ
The authors expect that the same threshold curves of tachyonic instability (αth(a)) for negative α can be obtained without any a-bound. This is because the linearized scalar theory is invariant under the transformation of α→-α and θ→-θ.
4. Suppression of tachyonic instability by scalar mass term
The authors observe that the presence of a scalar mass term suppresses the tachyonic instability of KN black holes.
Roadmap:
- Further exploration of the tachyonic instability and onset of spontaneous scalarization for KN black holes
- Investigation of the behavior of tachyonic instability with negative α, expected to be similar to the positive α case
- Confirmation of the absence of a-bound for negative α
- Study of the effects of varying the rotation parameter a on tachyonic instability
- Analyze the impact of the scalar mass term on the stability and properties of KN black holes
- Potential applications of the findings in astrophysics and gravitational wave research
Challenges and opportunities:
- Obtaining more precise numerical results to confirm the absence of a-bound for negative α
- Exploring the physical implications and consequences of tachyonic instability and spontaneous scalarization for KN black holes
- Potential for developing new theoretical frameworks or models to explain the observed phenomena
- Possibility of testing the predictions and conclusions through observational data and experiments
Note: The information provided in this article is based on the conclusions drawn by the authors. Further research and peer review may be necessary to validate and expand upon these findings.
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by jsendak | Jan 2, 2024 | GR & QC Articles
We generalize Integration-By-Parts (IBP) and differential equations methods
to de Sitter amplitudes related to inflation. While massive amplitudes in de
Sitter spacetime are usually regarded as highly intricate, we find they have
remarkably hidden concise structures from the perspective of IBP. We find the
irrelevance of IBP relations to propagator-types. This also leads to the
factorization of the IBP relations of each vertex integral family corresponding
to $mathrm{d} tau_i$ integration. Furthermore, with a smart construction of
master integrals, the universal formulas for iterative reduction and
$mathrm{d} log$-form differential equations of arbitrary vertex integral
family are presented and proved. These formulas dominate all tree-level de
Sitter amplitude and play a kernel role at the loop-level as well.
Conclusions
The generalization of Integration-By-Parts (IBP) and differential equations methods to de Sitter amplitudes related to inflation has revealed the existence of hidden concise structures in massive amplitudes in de Sitter spacetime. These structures are not dependent on the type of propagator being used. Additionally, the IBP relations of each vertex integral family can be factorized with respect to integration over $mathrm{d} tau_i$. Moreover, the development of smart constructions of master integrals has led to the discovery of universal formulas for iterative reduction and $mathrm{d} log$-form differential equations for arbitrary vertex integral families.
Roadmap for Readers: Challenges and Opportunities
1. Understanding the Hidden Concise Structures
Readers should strive to gain a comprehensive understanding of the hidden concise structures found within massive amplitudes in de Sitter spacetime. This exploration presents an opportunity to further investigate the underlying principles behind these structures and their significance in the context of de Sitter amplitudes related to inflation.
2. Investigating the Irrelevance of IBP Relations to Propagator-Types
Exploring the irrelevance of IBP relations to propagator-types opens up avenues for studying the fundamental properties of de Sitter amplitudes and their behavior under different types of interactions. Readers should delve into the implications of this discovery and its potential implications in other areas of physics.
3. Factorization of IBP Relations and $mathrm{d} tau_i$ Integration
The factorization of IBP relations with respect to $mathrm{d} tau_i$ integration offers an opportunity to investigate the underlying mathematical properties and connections between different vertex integral families. Readers should explore the consequences of this factorization and its implications for the computation of de Sitter amplitudes.
4. Universal Formulas for Iterative Reduction and $mathrm{d} log$-Form Differential Equations
The discovery of universal formulas for iterative reduction and $mathrm{d} log$-form differential equations provides a powerful tool for analyzing and computing arbitrary vertex integral families. Readers should focus on understanding the applications of these formulas and their potential impact on the study of de Sitter amplitudes at both tree-level and loop-level.
5. Role of Universal Formulas in Tree-Level and Loop-Level Amplitudes
Investigating the role played by the universal formulas in tree-level and loop-level de Sitter amplitudes is crucial for understanding their significance and potential applications in cosmology and quantum field theory. Readers should explore the implications and limitations of these formulas in various physical scenarios.
6. Future Developments and Applications
As research in de Sitter amplitudes related to inflation progresses, there will be opportunities to develop new techniques and apply existing methods to address open questions in the field. Readers should stay updated with these advancements and contribute to further developments in this area of research.
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by jsendak | Jan 2, 2024 | GR & QC Articles
In this work, we generalize the spacetime induced by a rotating cosmic
string, taking into account anisotropic effects due the breaking of the Lorentz
violation. In particular, we explore the energy levels of a massive spinless
particle that is covariantly coupled to a uniform magnetic field aligned with
the string. Subsequently, we introduce a scalar potential featuring both a
Coulomb-type and a linear confining term and comprehensively solve the
Klein-Gordon equations for each configuration. Finally, by imposing rigid-wall
boundary conditions, we determine the Landau levels when the linear defect
itself possesses magnetization. Notably, our analysis reveals the occurrence of
Landau quantization even in the absence of gauge fields, provided the string
possesses spin. Finally, the thermodynamic properties are computed as well in
these scenarios.
Generalizing the Spacetime Induced by a Rotating Cosmic String
In this work, we aim to generalize the spacetime induced by a rotating cosmic string and consider the anisotropic effects due to the breaking of the Lorentz violation. Specifically, we investigate the energy levels of a massive spinless particle that is covariantly coupled to a uniform magnetic field aligned with the string.
Introducing a Scalar Potential
In addition to studying the energy levels, we introduce a scalar potential that includes both a Coulomb-type and a linear confining term. By solving the Klein-Gordon equations for each configuration, we can fully understand the behavior of the system under these potential conditions.
Determining Landau Levels with Magnetized Linear Defects
By imposing rigid-wall boundary conditions, we can determine the Landau levels in cases where the linear defect itself possesses magnetization. Interestingly, our analysis reveals that Landau quantization can occur even in the absence of gauge fields, as long as the string possesses spin.
Computing Thermodynamic Properties
Finally, we compute the thermodynamic properties of the system under these scenarios. Understanding the thermodynamic behavior is crucial for practical applications and further theoretical developments.
Roadmap: Challenges and Opportunities
- Challenge: Exploring anisotropic effects and breaking of Lorentz violation can be complex and require advanced mathematical techniques.
- Opportunity: Understanding the energy levels of particles coupled to cosmic strings can have implications for particle physics and cosmology.
- Challenge: Solving the Klein-Gordon equations for different potential configurations can be computationally intensive.
- Opportunity: The insights gained from solving these equations can contribute to our understanding of quantum phenomena and the behavior of particles in unique spacetime structures.
- Challenge: Imposing rigid-wall boundary conditions can introduce additional complications in the calculations.
- Opportunity: Studying Landau quantization in the absence of gauge fields opens up new possibilities for experimental verification and theoretical investigations.
- Challenge: Computing thermodynamic properties requires considering the statistical behavior of particles in the system.
- Opportunity: Understanding the thermodynamic properties can provide insights into the behavior of cosmic strings and their potential impact on the universe.
Conclusion
This work brings new insights into the behavior of particles coupled to cosmic strings, taking into account anisotropic effects and the breaking of Lorentz violation. By studying the energy levels, solving the Klein-Gordon equations, determining Landau levels in the presence of magnetized linear defects, and computing thermodynamic properties, we have deepened our understanding of these complex systems. Challenges such as mathematical complexity, computational intensity, and imposing boundary conditions present opportunities for further research, experimentation, and theoretical advancements. The findings of this study have implications for both particle physics and cosmology.
“The only way of discovering the limits of the possible is to venture a little way past them into the impossible.” – Arthur C. Clarke
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by jsendak | Jan 2, 2024 | GR & QC Articles
Disformal transformations of Friedmann-Lema^itre-Robertson-Walker and
Bianchi geometries are analyzed in the context of scalar-tensor gravity. Novel
aspects discussed are the $3+1$ splitting, the effective fluid equivalent of
the gravitational scalar, Bianchi models, stealth solutions and de Sitter
solutions with non-constant scalar field (which are signatures of scalar-tensor
gravity). Both pure disformal transformations and more general ones are
discussed.
Conclusions
In this article, we have examined the implications of disformal transformations in the context of scalar-tensor gravity. We have analyzed their effects on Friedmann-Lema^itre-Robertson-Walker and Bianchi geometries. The novel aspects discussed include the +1$ splitting, the effective fluid equivalent of the gravitational scalar, and the existence of stealth solutions and de Sitter solutions with non-constant scalar field, which are unique to scalar-tensor gravity.
We have also explored both pure disformal transformations and more general ones, highlighting their significance in understanding the dynamics of the universe. These transformations provide a new perspective on the connection between geometry and gravity, shedding light on potential modifications to the standard models of cosmology.
Future Roadmap
Potential Challenges:
- Experimental Validation: One of the key challenges in further studying disformal transformations in scalar-tensor gravity is experimental validation. It is crucial to design experiments or observations that can test and confirm the predictions made by these theoretical analyses.
- Theoretical Refinements: Exploring more complex and realistic scenarios, such as incorporating matter fields and other interactions, will require further theoretical refinements. Developing appropriate mathematical frameworks to account for these complexities is a challenge that researchers will need to tackle.
- Data Analysis: As more observational data becomes available, it will be important to develop sophisticated data analysis techniques to extract meaningful insights from the observed signatures of scalar-tensor gravity and disformal transformations.
Potential Opportunities:
- Cosmological Consequences: Further investigation of disformal transformations in scalar-tensor gravity may uncover new cosmological consequences and provide a deeper understanding of the evolution and structure of the universe.
- Modified Gravity Theories: The insights gained from studying disformal transformations may contribute to the development of modified gravity theories, which can offer alternative explanations for observed phenomena and potentially resolve long-standing problems in cosmology.
- Interdisciplinary Collaborations: Exploring the implications of disformal transformations requires expertise from multiple disciplines, including theoretical physics, cosmology, and mathematics. This presents an opportunity for interdisciplinary collaborations and the exchange of ideas between researchers with different backgrounds.
References
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