Workshop Schedule

Laura Bernard

Title: Analytical modelling of gravitational waves beyond general relativity

Abstract: The analytical modelling of gravitational waves in general relativity has been one of the key elements to allow the numerous detections by the LIGO-Virgo-KAGRA collaboration. Extending those results to alternative theories of gravity is crucial to test our gravitational paradigm at an unprecedented precision with next-generation detectors, such as the Einstein Telescope and the space-based interferometer LISA. In this talk, I will present the current status of analytical gravitational wave modelling in alternative theories of gravity, based on the multipolar post-Minkowskian and post-Newtonian formalism.

Break 17:00 - 17:15 

Saptaswa Ghosh

Title: Observables in Classical Gravitational Scattering from WQFT: a case study for Scalar-Tensor theory

Abstract: In this talk, we will briefly describe a technique useful for the computation of gravitational observable, impulse and waveform in a black hole scattering event, namely "Worldline Quantum Field theory." We then show how to apply this formalism for a theory beyond GR  involving additional scalar degrees of freedom, namely the Scalar-Tensor theory. We will show how the impulse and waveform get corrected due to the extra scalar degree of freedom upto 2PM. Furthermore, we will point out several intricacies when the mass of the scalar field is non-vanishing.

N. Emil J. Bjerrum-Bohr

Title: Studying Gravitational Interactions and Binary Black Hole Mergers with On-Shell Amplitude Methods

Abstract: Using on-shell scattering amplitudes has proven to be a valuable tool for calculating observables in general relativity and for studying the problem of binary black hole mergers. In this presentation, we will provide a comprehensive overview of the technology involved in this research and discuss the most recent advancements and current outlook.

Anna Heffernan

Title: Self-Force: Waveforms for EMRIs

Abstract: This talk will cover an overview of the self-force program and how it is the leading method for producing waveforms for Extreme Mass Ratio Inspirals, a key target for the upcoming space-based gravitational wave detector, LISA. The self-force tackles the two-body problem by means of a perturbation in the mass ratio; at zero order, the smaller body follows a test mass geodesic while at first order it deviates from this geodesic due to its mass, hence the so-called self-force. Particular emphasis will be giving on regularisation and how it is encompassed in the three main self-force techniques.

Break 17:00 - 17:15

Poulami Dutta Roy

Title: Parametrized tests of GR: Extension to 4PN order and PCA

Abstract: Parametrized tests of post-Newtonian (PN) theory have been very efficient in testing GR in the inspiral phase of compact binary dynamics. In this test, one introduces null-valued deformation coefficients at each PN order in the inspiral phase, and their consistency with zero is assessed using gravitational wave data. In the first half of the talk, we will discuss the recently computed 4PN and 4.5PN inspiral phase terms that carry information about new physical effects like the tail-of-memory, spin-quadrupolar tails and quartic-tail effects and the extension of single-parameter test of GR to these orders. We introduce four new deformation parameters at these PN orders and compute the bounds on them through the Fisher analysis for the current-generation detectors such as LIGO/Virgo, next-generation (XG) detectors such as Cosmic Explorer/Einstein Telescope and LISA. Gravitational waves from supermassive BHs observed in LISA provide the tightest projected constraints ranging from O($10^-4$ − $10^-2$) for the four different parameters. 

In the second segment, we focus on multi-parameter tests, i.e., simultaneous estimation of deformation parameters occurring at all PN orders and understand the associated problems due to their correlations. One possible resolution is shifting to a suitable basis obtained through Principal Component Analysis (PCA), which is the best-measured orthogonal linear combination of the original deformation parameters. We performed an extensive study of zero-noise GR and non-GR injections, that highlights the efficiency of PCA over the usual parametrized test in constraining GR deviations. Our study, therefore, highlights the advancements in parametrized tests to probe consistency with GR through current and future gravitational wave observations.

Alok Laddha

Title: Infra-red challenges in Classical and Quantum Gravitational Scattering 

Abstract: TBA