Topics on Strong Gravity: Modern View on Theories and Experiments

Description

For more than a century, our understanding of gravitational physics was based on Albert Einstein's theory of General Relativity, which fundamentally changed our understanding of the Universe, its origin, and its evolutionary process. General Relativity accurately describes a large number of phenomena on very different scales. As such, it has been very well tested and its remarkable predictions are compatible with most experimental and observational data. However, the observational and experimental results compatible with General Relativity fall in its vast majority under the weak gravitational field regime. In recent years, discrepancies between the data and the corresponding predictions of General Relativity have been observed and have generated intense research activity. One of the most critical aspects of General Relativity is the presence of singularities in extreme physical situations. These discrepancies indicate that either the parameters of the theory must be modified in the regime of strong field gravity/high energy and large space-time curvature, or the theory itself should be modified. In this book, we focus our attention on extended alternative gravity theories and the best astrophysical laboratories to probe the strong field regime: black holes, pulsars, and neutron stars. Preface Introduction Contents List of Figures List of Tables 1. Spacetime Singularities in General Relativity 1.1. General Relativity 1.2. Einstein Equations of General Relativity 1.3. Singularities at the Beginning of the Universe 1.4. Standard Cosmological Model 1.5. Friedmann Equations References 2. Astrophysical Constraints on Strong Modified Gravity 2.1. General Relativity in the Strong Field Domain: Problems and Challenges 2.2. Modified Gravity: Different Approaches 2.3. Neutron Stars in Modified Gravity 2.3.1. 2.4. Black Holes in Modified Gravity 2.5. Accretion Disks 2.6. Effects on Jets 2.7. Gravitational Waves 2.8. Singularities and Beyond Acknowledgments References 3. The Pseudo-Complex General Relativity: Theory and Observational Predictions 3.1. Introduction 3.2. The Pseudo-Complex General Relativity 3.3. Observational Consequences 3.4. Gravitational Waves 3.5. Conclusions Acknowledgment References 4. Dense Baryonic Matter in the Cores of Neutron Stars 4.1. Introduction 4.2. Neutron Star Equation of State and Structure 4.2.1. 4.2.2. 4.2.3. 4.3. Constraining the Equation of State 4.4. Hyperons in Neutron Star Matter 4.5. Summary and Conclusions Acknowledgments References 5. Probing the Spacetime Around a Black Hole with X-Ray Variability 5.1. Introduction: The Promise of X-Ray Binaries 5.2. Spectral Approaches 5.2.1. 5.2.2. 5.3. Fast Time Variability 5.4. Observations 5.4.1. 5.4.2. 5.5. Models 5.5.1. 5.5.2. 5.5.3. 5.6. Where We Stand 5.7. Conclusions References 6. Supermassive Black Holes in the Early Universe 6.1. Introduction 6.2. Spherical Accretion and the Eddington Limit 6.3. Intermittent Growth of Black Holes 6.4. The Early Formation of SMBHs 6.5. Conclusions References 7. Astrophysical Aspects of General Relativistic Mass Twin Stars 7.1. Introduction 7.2. Self-Consistent Set of Field Equations for Stationary Rotating and Tidally Deformed Stars 7.3. Tidal Deformability of Compact Stars 7.4. Models for the EoS with a Strong Phase Transition 7.5. Results 7.6. Implications for the Phenomenology of Compact Stars 7.7. Summary and Conclusions Acknowledgments References Index