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# Effective Field Theory and Gravitational Physics

Conference Date:
Lundi, Novembre 28, 2011 (All day) to Mercredi, Novembre 30, 2011 (All day)
Scientific Areas:
Cosmology

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This small three day workshop will focus on the applications of effective field theories to gravitational physics, with particular emphasis on gravitational wave production. These effective theories have been used to derive new results for calculating gravitational potentials and multipole moments for binary systems at third order in the post-Newtonian approximation, as well as thermodynamic properties of Kaluza-Klein black holes. It has also been recently utilized to calculate corrections to leading order radiation reaction forces in general relativity as well as classical electrodynamics. The power of the methodology is that it allows on to calculate systematically to arbitrarily high accuracy. Such higher order results will be used in generating gravitational wave templates to extract parameters such as masses and spins of binary constituents at LIGO and LISA. The purpose of the workshop will be to gather experts in the field to generate new applications (e.g., in cosmology) as well as to push present applications to higher orders.

Enrico Barausse, University of Maryland

Luc Blanchet, Institut d'Astrophysique de Paris

Aharon Brodutch, Macquarie University

Alessandra Buonanno, University of Maryland

Cliff Burgess, Perimeter Institute & McMaster University

Umberto Cannella, University of Maryland

Solomon Endlich, Columbia University

Stefano Foffa, University of Geneva

Laurent Freidel, Perimeter Institute

Chad Galley, California Institute of Technology

Walter Goldberger, Yale University

Michael Horbatsch, McMaster University

Barak Kol, Hebrew University

David Kubiznak, Perimeter Institute

Louis Leblond, Perimeter Institute

Luis Lehner, Perimeter Institute & University of Guelph

Michele Levi, Hebrew University

Mozhgan Mir, Ferdowsi University

Ryan Morrisey, University of Guelph

Robert Myers, Perimeter Institute

Alberto Nicolis, Columbia University

Riccardo Penco, Syracuse University

Eric Poisson, University of Guelph

Marcelo Ponce, University of Guelph

Rafael Porto, Institute for Advanced Study

Sohrab Rahvar, Sharif University of Technology

Andreas Ross, Carnegie Mellon University

Ira Rothstein, Carnegie Mellon University

Gerhard Schaefer, Friedrich-Schiller-Universität Jena

Erik Schnetter, Perimeter Institute

Leonardo Senatore, Stanford University

Misha Smolkin, Perimeter Institute

Riccardo Sturani, National Institute of Nuclear Physics

Daniel Terno, Perimeter Institute

Michele Vallisneri, California Institute of Technology

Ian Vega, University of Guelph

Dan Wohns, Perimeter Institute

Gang Xu, Cornell University

Peter Zimmerman, University of Guelph

Luc Blanchet, Institut d'Astrophysique de Paris

Post-Newtonian equations of motion and radiation (standard approach)

High-accuracy templates predicted by general relativity for the gravitational waves generated by inspiralling compact binaries (binary star systems composed of neutron stars and/or black holes) have been developed using a mixed multipolar and post-Newtonian (MPN) formalism. In this talk we shall review the foundations of this formalism and its main results, including the equations of motion and radiation from compact binaries up to 3.5PN order. We shall also present some recent work on the comparison between post-Newtonian approximations and black hole perturbations applied to compact binaries in the small mass ratio limit.

Alessandra Buonanno, University of Maryland

Modeling the Inspiral, Merger and Ringdown of Compact Binaries: Successes and Open Questions

Research at the interface between analytical and numerical relativity has deepened our understanding of the two-body problem in general relativity, revealing an intriguing simplicity to the merger process and indicating a universal merger signal over a large mass-ratio range. I will review those advances within the effective-one-body approach, which can incorporate the most accurate results from post-Newtonian theory and the gravitational self-force formalism, focusing my remarks on the most dynamic and non-linear phase of the evolution. I will discuss the implications of the advances in the search for gravitational waves from comparable, small and extreme mass-ratio compact binaries. I will also review recent results of modeling spin effects and matter within the same approach. Finally, I will discuss unresolved issues in the modeling of compact binaries' inspiral, merger and ringdown stages that would need to be addressed to extract the best science upon detection.

Chad Galley, California Institute of Technology

The mechanics of open systems and applications in effective field theory

Recent years have seen the paradigm of effective field theory (EFT) successfully applied to an increasing number of classical systems that range from the gravitational inspiral of compact binaries to hydrodynamics. Many of these systems exhibit dissipation in one form or another, such as radiation reaction or viscous fluid flow, that naturally results from the system being open. This "openness" can manifest as energy leaving the dynamical variables of interest via radiation or heat transfer, for example. As the EFT approach typically utilizes the action, and hence Hamilton's Principle of Extremal Action, it is crucial to determine how generally and consistently to accommodate dissipative effects in a variational principle. In this talk, I discuss why Hamilton's Principle fails to incorporate dissipation. I then provide a reformulation that has been used successfully to confirm well-established results as well as to provide new predictions regarding dissipative systems. I show specific examples drawn from EFT applications. Finally, I show how this reformulation of Hamilton's Principle turns out to correspond to the classical limit of quantum theories based on the so-called "in-in" or "closed-time-path" approaches.

Stefano Foffa, University of Geneva

Riccardo Sturani, National Institute of Nuclear Physics

Conservative binary dynamics at 3PN order and beyond via effective field theory methods

The Effective Field Theory (EFT) approach can be employed to perform high PN order calculations of the Hamiltonian of a binary system.  We show how we reproduced the 3PN dynamics by means of an algorithm implemented in Mathematica and our progress towards the computation of the 4PN Hamiltonian.  We also show the EFT computation of the tail term affecting the conservative dynamics at 4PN order, first derived using traditional methods by Blanchet and Damour.

Barak Kol, Hebrew University

Perturbative Classical Field Theory

Alberto Nicolis, Columbia University

Effective field theories for hydrodynamical systems

will review EFT techniques that have been developed recently for dealing with the infrared dynamics of ordinary fluids and of superfluids. Gravity does not play an essential role in the construction (though it can be added straightforwardly to the system), yet certain applications resemble very closely the EFT approach to gravity wave emission by binary systems. I will describe in some detail one such application, as well as a possible application to cosmology.

Rafael Porto, Institute for Advanced Study

Dissipative effects during inflation: An EFT approach

Using an approach originally developed to study gravitational wave absorption in black hole binary systems, we generalize the EFT of single clock inflation to include dissipative effects. We restrict ourselves to situations where the degrees of freedom responsible for dissipation do no contribute to the density perturbations at late time, and moreover they are predominately sensitive to the field whose fluctuations control the end of inflation. The dynamics of the perturbations is then modified by the appearance of `friction' and noise terms, and assuming certain locality properties we show that there is a regime, characterized by a large friction coefficient \gamma >> H, in which the power spectrum is dominated by the noise and it is significantly modified with respect to the Bunch-Davies result. Furthermore, the non-linear realization of the symmetries implies non-gaussianties which are enhanced with respect to single clock models without dissipation by a factor of \gamma/H, and whose shape functions can in principle be distinguished from those obtained in the Bunch-Davies vacuum. We also discuss the matching of the EFT with a few key examples such as trapped and warm inflation.

Andreas Ross, Carnegie Mellon University

This talk will review the description of gravitational radiation in the effective field theory framework NRGR and report some recent results obtained in the radiation sector. In the matching to the radiation theory one needs to perform a multipole expansion which we present to all order. Furthermore, we will show how non-linear radiative corrections (such as tail effects) are handled in the EFT, how different kinds of divergences arise and how the renormalization group can be used to resum logarithmic terms in the PN expansion of the energy flux. Finally, we present results for the spin components of the multipole moments which are sufficient to compute the phase to 3PN including all spin effects and the waveform to 2.5PN.

Ira Rothstein, Carnegie Mellon University

World Line Effective Theories and 2-D Partition Functions on the Plane with Compact Boundaries

In this talk I will describe how to  calculate the exact partition function for free bosons on the plane with lacunae using world line effective field theory. It will be shown that the partition function for a plane with two spherical holes can be  calculated by matching exactly for the infinite set of Wilson coefficients and then performing the ensuing Gaussian integration. This same  partition function  can also be calculated using conformal field theory technique and the equality of the two results will be shown. I will   demonstrate that there is an exact correspondence between the Wilson coefficients (susceptabilities) in the effective field theory and the weights of the individual excitations of the closed string coherent state on the boundary.  The partition function for the case of three holes, where CFT techniques necessitate a closed form for the map from the corresponding closed string pants diagram,  is still calculable within the EFT.  I will also show how  conformal mappings can be used within the matching  procedure to calculate the partition function for elliptically shaped boundaries.  Finally I will show that the Wilson coefficients for the case of quartic and higher order kernels, where standard CFT techniques are no longer applicable, can also be completely determined.

Gerhard Schaefer, Friedrich-Schiller-Universitat Jena

Recent Developments in Generalized ADM Formalism for the Dynamics of Compact Binaries with Spin

Based on tetrad-generalized canonical formalism by Arnowitt, Deser, and Misner most recent achievements in analytic calculations of higher order post-Newtonian Hamiltonians for spinning binary black holes and neutron stars are presented. The results of the generalized ADM formalism are put into mathematical relationship with those obtained within the Effective Field Theory approach.

Leonardo Senatore, Stanford University

On the Effective Field Theory of Inflation and on the Effective Field Theory of the Long Distance Universe

Misha Smolkin, Perimeter Institute

Tidal deformations of a Schwarzschild black hole via effective field theory approach.

In my talk I will discuss the static subsector of the black hole effective action in an arbitrary dimension. In particular, the derivation of the induced mass multipoles as a result of an external (static) gravitational field will be elucidated. In 4d these constants vanish, however in general they are non-vanishing in higher dimensions. Moreover, in certain cases they exhibit a (classical) renormalization group flow consistent with the divergences of the effective field theory.

Michele Vallisneri, California Institute of Technology

How Good is "good enough" for Gravitational-wave Templates?

After the first landmark gravitational-wave (GW) detection, GW astronomy will turn to the study of detector data to identify the physical properties of GW sources. The science payoff of GW observations must therefore depend critically on the accurate knowledge of the shapes of waveforms as functions of the source parameters. Effective-field-theory techniques have advanced and continue to advance the state of the art for the modeling of inspiraling-binary dynamics. But how far do we have to push our calculations to satisfy the needs of observations? I review current attempts to answer this question for different detectors and sources, and for the delicate problem of matching post-Newtonian and numerical-relativity waveforms.