ICTS

Readings:
Kerr Black Holes Are Not Unique to General Relativity, by D. Psaltis https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.091101
Gravitational waves from the inspiral of a compact object into a massive, axisymmetric body with arbitrary multipole moments by F. Ryan  https://journals.aps.org/prd/abstract/10.1103/PhysRevD.52.5707
Towards a formalism for mapping the spacetimes of massive compact objects: Bumpy black holes and their orbits, by Collins & Hughes, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.69.124022
Systematic study of event horizons and pathologies of parametrically deformed Kerr spacetimes, by T. Johannsen, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.87.124017
Metric for rapidly spinning black holes suitable for strong-field tests of the no-hair theorem, by Johannsen & Psaltis, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.83.124015
Spacetime and orbits of bumpy black holes, by Vigeland & Hughes, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.81.024030
Regular black hole metric with three constants of motion, by T. Johannsen, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.88.044002

Readings:
Testing general relativity with the Event Horizon Telescope, by Psaltis, D., https://link.springer.com/article/10.1007/s10714-019-2611-5
Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole, by D. Psaltis and the EHT Collaboration, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.141104
First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric, EHT Collaboration, https://iopscience.iop.org/article/10.3847/2041-8213/ac6756/pdf

Readings:
The basics of gravitational wave theory, by Flanagan & Hughes, https://iopscience.iop.org/article/10.1088/1367-2630/7/1/204
Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays, by Yunes et al. https://arxiv.org/pdf/2408.05240
Tests of General Relativity with GW150914, LIGO Collaboration, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.221101
Tests of general relativity with the binary black hole signals from the LIGO-Virgo catalog GWTC-1, LIGO Collaboration, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.104036
Probing the black hole metric: Black hole shadows and binary black-hole inspirals, by Psaltis et al., https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.104036
New horizons for fundamental physics with LISA, https://link.springer.com/article/10.1007/s41114-022-00036-9

Readings:
Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole, GRAVITY collaboration, https://www.aanda.org/articles/aa/pdf/2020/04/aa37813-20.pdf
Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-periodic Variability, by Johannsen & Psaltis, https://iopscience.iop.org/article/10.1088/0004-637X/726/1/11/pdf
Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. IV. Relativistically Broadened Iron Lines, by Johannsen & Psaltis, https://iopscience.iop.org/article/10.1088/0004-637X/773/1/57/pdf
Testing Gravity with Black Hole X-Ray Data, by C. Bambi, https://arxiv.org/pdf/2210.05322

Gravitational wave signals from merging compact binary systems provide unique avenues for testing the general theory of relativity (GR) predictions in the strong-field, dynamic, and relativistic regimes. As the gravitational wave (GW) transient catalogue grows in number and source diversity, designing and implementing tests for these predictions in model-agnostic ways and for specific alternative theory predictions is mandatory. In this presentation, I will introduce the routinely employed model-agnostic tests of the nature of compact objects using the observed binary population and implications of such constraints to alternative models. Then, I will describe theory-specific tests of the nature of compact objects, focusing on spinning black holes in modified GR theories and discuss the possible constraints on such models from current and future GW observations.

Wave equation for integer spin fields
A second look at no-hair properties
Tidal properties of black holes
Dynamics: the QNMs of black holes
Resonant excitation of modes?
Wave phenomena for massive fields
Summary

Environmental effects I:
Accretion and drag in Newtonian approximation
Some relativistic results
Summary

The historic discovery of gravitational waves through direct detection by the LIGO observatories in the USA, in principle, opened up a new window to the cosmos.  In practice, however, the true launch of gravitational-wave astronomy will await a capable global array of LIGO like observatories, including the LIGO-India observatory recently flagged off by the Union cabinet of India. The talk presents the compelling science and leap-frog in technology possible with LIGO-India, its current status, and the challenges ahead.

Inspiral and spectroscopy in astrophysical setups
Summary