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School of Physical and Chemical Sciences
  1. School of Physical and Chemical Sciences
  2. Collaborative Research Centres
  3. Gravitational Wave Initiative
  4. Perturbative Approaches

Perturbative Approaches

Exploiting Post-Minkowskian, Post-Newtonian, Self-Force and Effective Field Theory techniques to study gravitational binaries and waveforms. 

In the study of gravitational binaries it is very natural to use rather different approaches to describe the problems in different regimes. The Post-Newtonian approach has traditionally provided concrete results that can be directly used to describe the inspiral phase of the mergers of similar mass compact objects, but it can be also applied to the hyperbolic motions at low velocities. The Post-Minkowskian approach starts from the scattering case keeping the relative velocity generic and has allowed researchers to use techniques developed in a particle physics context (in particular Feynman integrals, unitarity properties of amplitudes, the double copy and more) to find new results about gravitational binaries. These results can be useful in the study of binaries with large eccentricity and with very different masses. This regime is very well-suited for another approach, known as the gravitational Self-Force, which is developing a systematic perturbation theory around the known single black hole solutions.

Comparison of different Perturbative Techniques (from 1805.10385)

Various techniques have been developed for analysing a binary system, which efficiently capture different ranges of separation and mass ratios. 

[Credit: L. Barack and A. Pound, Fig 11 of 1805.10385]

Comparing and complementing these different approaches has proved to be very inspiring in the last few years providing a better overall understanding of gravitational binaries and their waveform and has yielded several new explicit results. The effective field theory language provides a general framework to connect the different avenues to this rich problem.

 

Key questions

  • Use all perturbative approaches to inform Effective-One-Body models to generate realistic waveforms and compare with data from Numerical Relativity
  • Explore binaries and their waveforms in extreme situations: ultra-relativistic limit in the scattering case, extreme mass ratio inspirals, etc.
  • Investigate models beyond GR both for phenomenological purposes and also for conceptual motivations (as in the case of supergravity)
  • Provide accurate predictions for spinning (Kerr) black holes
  • Describe systematically dissipative effects in the inspiral phase for bound systems and in the scattering case

 

Relevant Members

GWI members working on scattering amplitudes and other perturbative approaches include:

  • Andreas Brandhuber
  • Graham Brown

  • Alessandro Georgoudis

  • Lidia Joana Gomes Da Silva

  • Josh Gowdy

  • Carlo Heissenberg

  • Charalampos Markakis

  • Pablo Matasan

  • Scott Melville

  • Ricardo Monteiro

  • Paolo Pichini

  • Rodolfo Russo

  • Gabriele Travaglini

  • David Waisman Andrade

(See Our Members for contact links)

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