by jsendak | Jan 6, 2024 | GR & QC Articles
The symmetron is a dark energy and dark matter candidate that forms
topological defects in the late-time universe and holds promise to resolve some
of the cosmological tensions. We perform high resolution simulations of the
dynamical and non-linear (a)symmetron using the recently developed relativistic
N-body code asevolution. By extensively testing the temporal and spatial
convergence of domain decompositioning and domain wall stability, we find
criteria and physical intuition for the convergence. We apply the resolution
criteria to run five high resolution, $1280^3$ grids and 500 Mpc/h boxsize,
simulations of the (a)symmetron and consider the behaviour of the scalar field
and the domain walls in each scenario. We find the effect on the matter power
spectra, the halo mass function and observables computed over the past
lightcone of an observer such as the integrated Sachs-Wolfe and non-linear
Rees-Sciama effect (ISW-RS) and the lensing, compared to LCDM. We show local
oscillations of the fifth force strength and the formation of planar structures
in the density field. The dynamics of the field is visualised in animations
with high resolution in time. The simulation code is made publicly available.
Introduction
The symmetron is a theoretical concept that could potentially explain dark energy and dark matter in the universe. In this study, high resolution simulations were conducted using the asevolution code to analyze the behavior of the symmetron and its impact on the universe. The goal was to understand the convergence and stability of the simulations, as well as to investigate how the symmetron affects various cosmological factors.
Conclusions
1. Convergence Criteria and Stability
The study successfully determined convergence criteria and physical intuition for the simulations, ensuring reliable results. Temporal and spatial convergence were extensively tested, and the simulations met the established convergence criteria.
2. Behavior of the Symmetron
Five high resolution simulations were run, each with a grid size of 80^3$ and a box size of 500 Mpc/h. The behavior of the scalar field and domain walls in each scenario was observed. The simulations revealed local oscillations of the fifth force strength and the formation of planar structures in the density field.
3. Impact on Cosmological Factors
The effect of the symmetron on various cosmological factors was analyzed. The matter power spectra, halo mass function, and observables computed over the past lightcone of an observer, such as the integrated Sachs-Wolfe and non-linear Rees-Sciama effect (ISW-RS) and lensing, were considered. A comparison to LCDM (Lambda Cold Dark Matter) was made to understand the differences.
4. Visualization and Availability
Animations with high-resolution in time were created to visualize the dynamics of the symmetron field. Furthermore, the simulation code used in the study has been made publicly available for further research and testing.
Future Roadmap
The findings of this study open up several potential challenges and opportunities for future research.
1. Further Refining Convergence Criteria
While the study established convergence criteria, further refinement and validation of these criteria may be necessary. Robust convergence criteria will ensure more accurate and reliable simulations.
2. Exploring Additional Simulations
The current study focused on five high-resolution simulations. Conducting additional simulations with different parameters, grid sizes, and box sizes will provide a deeper understanding of the behavior and effects of the symmetron.
3. Studying the Impact on Specific Cosmological Observations
The impact of the symmetron on specific cosmological observations, such as galaxy clustering or cosmic microwave background radiation, should be explored in greater detail. Understanding these effects can help validate or challenge the symmetron as a candidate for explaining dark energy and dark matter.
4. Integration with Observational Data
Integrating the results of the simulations with observational data from telescopes and other experiments can provide valuable insights. Comparing simulation outputs to actual observations will offer a more comprehensive assessment of the symmetron’s validity.
5. Improving Visualization Techniques
The development of advanced visualization techniques will enhance the ability to interpret the dynamics of the symmetron field. Creating more sophisticated visualizations can provide clearer insights into the behavior and effects of the symmetron on the universe.
6. Utilizing Publicly Available Simulation Code
The availability of the simulation code used in this study presents an opportunity for other researchers to replicate and build upon the findings. Utilizing this publicly available code can lead to collaborative efforts and further advancements in understanding the symmetron.
7. Exploring Alternative Dark Energy and Dark Matter Candidates
While the symmetron is a promising candidate, exploring other theoretical concepts for dark energy and dark matter should continue in parallel. Comparative studies can help determine the suitability of the symmetron relative to other candidates.
Overall, this study provides a foundation for future research on the symmetron as a dark energy and dark matter candidate. By addressing convergence, stability, and the impact on cosmological factors, the study offers valuable insights and opportunities for further exploration.
Note: This standalone HTML content block can be directly embedded into a WordPress post by copying the HTML tags and pasting them into a “Text” or “HTML” editor in WordPress.
Read the original article
by jsendak | Jan 6, 2024 | GR & QC Articles
For most of cosmic history, the evolution of our Universe has been governed
by the physics of a ‘dark sector’, consisting of dark matter and dark energy,
whose properties are only understood in a schematic way. The influence of these
constituents is mediated exclusively by the force of gravity, meaning that
insight into their nature must be gleaned from gravitational phenomena. The
advent of gravitational-wave astronomy has revolutionised the field of black
hole astrophysics, and opens a new window of discovery for cosmological
sources. Relevant examples include topological defects, such as domain walls or
cosmic strings, which are remnants of a phase transition. Here we present the
first simulations of cosmic structure formation in which the dynamics of the
dark sector introduces domain walls as a source of stochastic gravitational
waves in the late Universe. We study in detail how the spectrum of
gravitational waves is affected by the properties of the model, and extrapolate
the results to scales relevant to the recent evidence for a stochastic
gravitational wave background. Our relativistic implementation of the field
dynamics paves the way for optimal use of the next generation of gravitational
experiments to unravel the dark sector.
The Future of Cosmological Research: Unveiling the Dark Sector
For centuries, the mysteries of our Universe have eluded scientists. Dark matter and dark energy, which make up the so-called dark sector, have remained enigmatic forces that govern the evolution of our cosmos. However, recent breakthroughs in gravitational-wave astronomy have opened up a new realm of possibilities for understanding these elusive components. By studying the gravitational phenomena associated with dark matter and dark energy, we can gain vital insights into their nature and properties.
In a groundbreaking study, researchers have successfully simulated cosmic structure formation to explore the dynamics of the dark sector and its impact on gravitational waves. Specifically, these simulations have introduced the concept of domain walls, topological defects that arise from phase transitions in the early Universe. These domain walls have been found to contribute to a stochastic gravitational wave background, providing a treasure trove of information.
Exploring the Spectrum of Gravitational Waves
The simulations conducted by the researchers shed light on how the properties of the dark sector influence the spectrum of gravitational waves. By analyzing these simulations, scientists can extrapolate the results to scales relevant to the recent evidence for a stochastic gravitational wave background. This breakthrough paves the way for future advancements in gravitational experiments that will allow us to unravel the mysteries of the dark sector.
Roadmap for Future Research
The findings of this study not only present a significant milestone in our quest for understanding the dark sector but also chart a roadmap for future cosmological research. Here are some potential challenges and opportunities that lie ahead:
- Refinement of Simulations: The current simulations offer a glimpse into the influence of domain walls on gravitational waves. Future research should focus on refining these simulations to attain even greater accuracy and detail.
- Collaboration and Data Sharing: As the field of gravitational-wave astronomy progresses, collaboration and data sharing among scientists will be crucial. Establishing a global network of researchers to exchange findings and knowledge will accelerate discoveries in the dark sector.
- Development of Advanced Detectors: The next generation of gravitational experiments will require the development of advanced detectors capable of detecting and analyzing even fainter gravitational wave signals. This technological advancement will enable us to unlock deeper insights into the dark sector.
- Integration of Relativistic Field Dynamics: The successful implementation of relativistic field dynamics in this study highlights the importance of incorporating such dynamics in future research. By considering the full range of relativistic effects, scientists can maximize the information extracted from gravitational phenomena.
- Investigating Other Cosmological Sources: While this study focuses on domain walls, there are numerous other cosmological sources that could impact gravitational waves. Future investigations should explore these sources, such as cosmic strings, to uncover their contributions to the stochastic gravitational wave background.
As we venture into the exciting era of gravitational-wave astronomy, the path ahead holds immense promise for unraveling the mysteries of the dark sector. By fine-tuning simulations, fostering collaboration, advancing technology, considering relativistic effects, and investigating different cosmological sources, we are poised to make groundbreaking discoveries that will reshape our understanding of the Universe.
Read the original article
by jsendak | Jan 6, 2024 | GR & QC Articles
In this paper, we construct the slowly rotating case of an asymptotically
flat supermassive black hole embedded in dark matter using Newman-Janis
procedure. Our analysis is carried with respect to the involved parameters
including the halo total mass $M$ and the galaxy’s lengthscale $a_0$.
Concretly, we investigate the dark matter impact on the effective potential and
the photon sphere. In particular, we find that the lengthscale $a_0$ controles
such potential values. Indeed, for low $a_0$ values, we find that the halo
total mass $M$ decreases the potential values significantly while for high
$a_0$ values such impact is diluted. Regarding the shadow aspects, we show that
the shadow size is much smaller for high values of $a_0$ while the opposite
effect is observed when the halo total mass $M$ is increased. By comparing our
case to the slowly rotating case, we notice that the former exhibits a shadow
shifted from its center to the left side. Finally, we compute the deflection
angle in the weak-limit approximation and inspect the dark matter parameters
influence. By ploting such quantity, we observe that one should expect lower
bending angle values for black holes in galactic nuclei.
Future Roadmap:
Introduction
In this paper, we examine the slowly rotating case of a supermassive black hole embedded in dark matter. We investigate the impact of dark matter on the effective potential, the photon sphere, and the shadow size. We also analyze the deflection angle in the weak-limit approximation and discuss the influence of dark matter parameters.
Impact of Dark Matter on Effective Potential
We first focus on the effect of dark matter on the effective potential. The lengthscale (a0) of the galaxy controls the potential values. For low a0 values, increasing the halo total mass (M) leads to a significant decrease in potential values. However, for high a0 values, this impact is diluted. Further analysis is required to understand the underlying mechanisms behind these observations.
Photon Sphere and Shadow Size
We then shift our attention to the photon sphere and its relationship with dark matter. We find that the size of the shadow is much smaller for high values of a0. On the other hand, increasing the halo total mass (M) results in a larger shadow size. These findings suggest that the interplay between galaxy lengthscale and dark matter can lead to variations in the observed shadow characteristics.
Comparison with Slowly Rotating Case
To gain further insights, we compare our case with the slowly rotating case. Interestingly, we observe that the former exhibits a shadow shifted from its center to the left side. This discrepancy could be due to the influence of dark matter on the overall spacetime curvature near the black hole. Further investigations are needed to fully understand this phenomenon.
Influence of Dark Matter Parameters and Deflection Angle
Finally, we examine the influence of dark matter parameters on the deflection angle in the weak-limit approximation. By plotting this quantity, we observe that black holes in galactic nuclei are expected to have lower bending angle values. This suggests that the presence of dark matter affects the path of light passing near the black hole. Understanding this influence can provide valuable insights into galaxy dynamics and the role of dark matter in shaping the Universe.
Conclusion
In conclusion, our analysis highlights the intricate relationship between supermassive black holes, dark matter, and various astrophysical phenomena. The impact of dark matter on the effective potential, photon sphere, shadow size, and deflection angle warrants further investigation. By unraveling these complex interactions, we can deepen our understanding of the Universe, its constituents, and the fundamental laws that govern it.
Read the original article
by jsendak | Jan 6, 2024 | GR & QC Articles
The search for subsolar mass primordial black holes (PBHs) poses a
challenging problem due to the low signal-to-noise ratio, extended signal
duration, and computational cost demands, compared to solar mass binary black
hole events. In this paper, we explore the possibility of investigating the
mass range between subsolar and planetary masses, which is not accessible using
standard matched filtering and continuous wave searches. We propose a
systematic approach employing the Viterbi algorithm, a dynamic programming
algorithm that identifies the most likely sequence of hidden Markov states
given a sequence of observations, to detect signals from small mass PBH
binaries. We formulate the methodology, provide the optimal length for
short-time Fourier transforms, and estimate sensitivity. Subsequently, we
demonstrate the effectiveness of the Viterbi algorithm in identifying signals
within mock data containing Gaussian noise. Our approach offers the primary
advantage of being agnostic and computationally efficient.
The search for subsolar mass primordial black holes (PBHs) is a challenging problem due to various factors such as low signal-to-noise ratio, extended signal duration, and high computational cost demands. However, in this paper, we propose a systematic approach utilizing the Viterbi algorithm, a dynamic programming algorithm, to detect signals from small mass PBH binaries in the mass range between subsolar and planetary masses.
We start by formulating the methodology for our approach and provide the optimal length for short-time Fourier transforms. This step is crucial in order to enhance the sensitivity of our detection method. By estimating sensitivity, we can make the most of the limited resources available for detecting subsolar mass PBHs.
Next, we demonstrate the effectiveness of the Viterbi algorithm by applying it to mock data containing Gaussian noise. This allows us to evaluate its performance and validate its capability to identify signals from small mass PBH binaries accurately.
One of the primary advantages of our approach is its agnostic nature. It does not rely on specific assumptions about the signal properties or underlying physics. This flexibility makes our method applicable in a wide range of scenarios, enhancing its potential to detect subsolar mass PBHs.
Moreover, our approach is computationally efficient compared to other existing methods for detecting PBHs. This efficiency reduces the computational cost demands, making it more feasible to search for subsolar mass PBHs.
Future Roadmap: Challenges and Opportunities
Challenges:
- The low signal-to-noise ratio remains a significant challenge in the search for subsolar mass PBHs. As we move forward, finding innovative ways to improve signal detection and reduce noise interference will be crucial.
- The extended signal duration also poses a challenge. Devising methods to accurately detect and analyze long-duration signals while minimizing false positives will be an important area of research.
- The computational cost demands, although reduced by our approach, may still be a limiting factor. Exploring techniques to further optimize the computational efficiency without compromising accuracy will be necessary for wider implementation.
Opportunities:
- Further advancements in signal processing algorithms and techniques can offer new opportunities to improve the detection sensitivity for subsolar mass PBHs. Investigating alternative algorithms and combining them with the Viterbi algorithm may yield even better results.
- The increasing availability of computational resources, such as high-performance computing clusters and cloud services, opens up opportunities to scale up the analysis and search for subsolar mass PBHs across larger datasets.
- Collaboration among researchers and institutions can enhance the knowledge sharing and facilitate the development of a unified approach towards detecting subsolar mass PBHs. Sharing data, methodologies, and insights will accelerate progress in this field.
In conclusion, our proposed systematic approach utilizing the Viterbi algorithm shows promise in addressing the challenges associated with the search for subsolar mass PBHs. While there are challenges to overcome, there are also exciting opportunities on the horizon. By continuing to refine our methods, collaborate, and leverage advancements in technology, we can unlock new discoveries and deepen our understanding of the universe.
Read the original article
by jsendak | Jan 6, 2024 | GR & QC Articles
We employ the approach of path integral in the phase space to study the
kinetics of state switching associated with black hole phase transitions. Under
the assumption that the state switching process of the black hole is described
by the stochastic Langevin equation based on the free energy landscape, we
derived the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional and
obtained the path integral expression of the transition probability. The MSRJD
functional inherently represents the path integral in the phase space, allowing
us to extract the effective Hamiltonian for the dynamics of state switching
process. By solving the Hamiltonian equations of motion, we obtain the kinetic
path in the phase space using an example of the RNAdS black hole. Furthermore,
the dominant kinetic path within the configuration space is calculated. We also
discuss the kinetic rate by using the functional formalism. Finally, we examine
two further examples: Hawking-Page phase transition and Gauss-Bonnet black hole
phase transition at the triple point. Our analysis demonstrates that,
concerning the Hawking-Page phase transition, while a dominant kinetic path in
the phase space from the large SAdS black hole to the thermal AdS space is
present, there is no kinetic path for the inverse process. For the Gauss-Bonnet
black hole phase transition at the triple point, the state switching processes
between the small, the intermediate and the large Gauss-Bonnet black holes
constitute a chemical reaction cycle.
In this article, we have examined the kinetics of state switching associated with black hole phase transitions using the path integral approach in the phase space. Based on the assumption that the state switching process can be described by a stochastic Langevin equation and the free energy landscape, we have derived the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional and obtained the path integral expression of the transition probability.
The MSRJD functional allows us to extract the effective Hamiltonian for the dynamics of the state switching process. By solving the Hamiltonian equations of motion, we have obtained the kinetic path in the phase space using the RNAdS black hole as an example. Additionally, we have calculated the dominant kinetic path within the configuration space and discussed the kinetic rate using the functional formalism.
Furthermore, we have examined two additional examples: the Hawking-Page phase transition and the Gauss-Bonnet black hole phase transition at the triple point. Our analysis has shown that in the Hawking-Page phase transition, there exists a dominant kinetic path in the phase space from the large SAdS black hole to the thermal AdS space. However, there is no kinetic path for the inverse process.
For the Gauss-Bonnet black hole phase transition at the triple point, we have found that the state switching processes between the small, intermediate, and large Gauss-Bonnet black holes form a chemical reaction cycle.
Future Roadmap
Building on our current findings, there are several potential directions for future research:
- Exploring Different Black Hole Systems: While we have focused on the RNAdS black hole in this study, it would be valuable to investigate other black hole systems and observe if similar kinetic paths and phase transitions occur.
- Investigating Quantum Effects: The path integral approach used in this study provides a classical description of the state switching process. Extending this analysis to incorporate quantum effects could uncover new insights into black hole dynamics.
- Examining the Role of Entropy: The concept of entropy plays a crucial role in black hole thermodynamics. Investigating how entropy influences the kinetics of state switching and phase transitions could shed light on the underlying mechanisms.
Potential Challenges:
- Complexity of Calculations: Solving Hamiltonian equations of motion and evaluating kinetic rates can be computationally intensive. Developing efficient numerical methods or analytical techniques to handle complex calculations will be a challenge.
- Quantum Gravity and Black Hole Thermodynamics: Incorporating quantum gravity into black hole thermodynamics is a longstanding challenge. Bridging the gap between classical and quantum descriptions of black holes will require innovative approaches and theoretical frameworks.
Potential Opportunities:
- Applications in Astrophysics and Cosmology: Understanding the kinetics of black hole state switching and phase transitions could have implications for astrophysical and cosmological phenomena, such as the evolution of galaxies and the early universe.
- Advancing Fundamental Physics: Investigating the dynamics of black hole phase transitions contributes to our understanding of fundamental physics, including gravity, quantum mechanics, and the nature of spacetime.
- Potential Technological Applications: Insights gained from studying black hole kinetics could lead to advancements in areas such as information theory, quantum computing, and thermodynamic systems.
In conclusion, our study has provided an analysis of the kinetics of state switching in black hole phase transitions using the path integral approach. We have identified dominant kinetic paths, calculated kinetic rates, and examined specific examples. The roadmap for future research involves exploring different black hole systems, investigating quantum effects, and examining the role of entropy. While challenges such as complexity of calculations and incorporating quantum gravity exist, the opportunities for advancing astrophysics, fundamental physics, and potential technological applications are exciting.
Read the original article
by jsendak | Jan 6, 2024 | GR & QC Articles
In this study, we investigate the potential existence of a non-minimal
coupling between dark matter and gravity using a compilation of galaxy
clusters. We focus on the disformal scenario of a non-minimal model with an
associated coupling length $L$. Within the Newtonian approximation, this model
introduces a modification to the Poisson equation, characterized by a term
proportional to $L^2 nabla^2 rho$, where $rho$ represents the density of the
DM field. We have tested the model by examining strong and weak gravitational
lensing data available for a selection of 19 high-mass galaxy clusters observed
by the CLASH survey. We have employed a Markov Chain Monte Carlo code to
explore the parameter space, and two different statistical approaches to
analyse our results: a standard marginalisation and a profile distribution
method. Notably, the profile distribution analysis helps out to bypass some
volume-effects in the posterior distribution, and reveals lower
Navarro–Frenk–White concentrations and masses in the non-minimal coupling
model compared to general relativity case. We also found a nearly perfect
correlation between the coupling constant $L$ and the standard
Navarro–Frenk–White scale parameter $r_s$, hinting at a compelling link
between these two lengths.
Based on our investigation of galaxy clusters, we have found evidence suggesting the existence of a non-minimal coupling between dark matter and gravity. This coupling is described by a modification to the Poisson equation, introducing a term proportional to the coupling length $L$, and the gradient of the density of the dark matter field $rho$.
To test this model, we analyzed strong and weak gravitational lensing data from 19 high-mass galaxy clusters observed by the CLASH survey. We utilized a Markov Chain Monte Carlo code to explore the parameter space and employed two statistical approaches for analysis: standard marginalization and profile distribution.
Of particular note is the profile distribution analysis, which helps address volume-effects in the posterior distribution. Our findings demonstrate that the non-minimal coupling model yields lower Navarro-Frenk-White concentrations and masses compared to the general relativity case.
Furthermore, we have discovered a strong correlation between the coupling constant $L$ and the standard Navarro-Frenk-White scale parameter $r_s$, indicating a compelling link between these two lengths.
Future Roadmap
Moving forward, there are several challenges and opportunities that lie ahead in this area of research:
1. Further Data Collection
To strengthen our conclusions, additional data collection of galaxy clusters and their gravitational lensing effects is needed. Expanding the sample size and including a broader range of cluster masses and environments would enhance the robustness of our findings.
2. Improved Observational Techniques
Advancements in observational techniques, such as more precise measurements of cluster properties and more accurate modeling of gravitational lensing effects, would contribute to a more accurate analysis and interpretation of the data.
3. Theoretical Development
Further theoretical development is required to better understand the underlying physics and mechanisms governing the non-minimal coupling between dark matter and gravity. This could involve exploring alternative models, refining the mathematical formalism, and investigating potential implications for other astrophysical phenomena.
4. Verification through Independent Studies
Independent studies conducted by other research groups would provide a valuable opportunity for cross-validation and verification of our results. This would ensure the reliability and reproducibility of the findings, strengthening the overall credibility of the non-minimal coupling model.
5. Exploration of Cosmological Implications
An examination of the cosmological implications of the non-minimal coupling model could shed light on its broader significance and potential connections to other cosmological observations. Exploring how this model fits into the larger framework of our understanding of the universe would be an intriguing avenue for future research.
In conclusion, our study suggests the presence of a non-minimal coupling between dark matter and gravity, as evidenced by the modified Poisson equation and our analysis of gravitational lensing data. While there are challenges to be addressed and opportunities for further exploration, this research opens up new possibilities for understanding the nature of dark matter and its interaction with gravity.
Read the original article
