20th Capra Meeting on Radiation Reaction in General Relativity

US/Eastern
Room 011, Sitterson Hall (Dept. of Physics & Astronomy and the CoSMS Institute, University of North Carolina at Chapel Hill)

Room 011, Sitterson Hall

Dept. of Physics & Astronomy and the CoSMS Institute, University of North Carolina at Chapel Hill

Description

Invited Speakers

• Aaron Zimmerman
• Jonathan Gair
• Niels Warburton
• Andrea Taracchini
• Maarten van de Meent
• Alexandre Le Tiec
• Barry Wardell

20th Capra Meeting at University of North Carolina at Chapel Hill

Since the inaugural meeting in 1998 (held at Caltech’s Capra Ranch near San Diego) the Capra meetings have been bringing together relativists interested in the problem of radiation reaction in general relativity and its application to extreme-mass-ratio inspirals (EMRIs) as astrophysical sources of gravitational waves. The meetings address an important open problem in gravitational theory, made particularly relevant by the recent LIGO detections of merging black holes and the exciting prospect of directly observing gravitational waves from EMRIs with a future space-based detector.

The 20th Capra Meeting on Radiation Reaction in General Relativity will be hosted by the Physics Department at the University of North Carolina at Chapel Hill and by the Institute for Cosmology, Subatomic Matter & Symmetries (CoSMS). The meeting will be held June 19-23, 2017. As usual, the program will focus on aspects of the self-force in general relativity but will also seek to explore connections to other approaches to the two-body problem. Following the Capra tradition, the meeting will be informal. There will be no registration fee and no proceedings. The program will include a few invited review talks, short contributed presentations (20 to 30 minutes), and open discussions. Contributed talks on all aspects of the radiation reaction problem (including related topics such as EMRI astrophysics or data analysis) are welcome.

Participants
• Aaron Zimmerman
• Alexandre LE TIEC
• Andrea Taracchini
• Anna Heffernan
• Barry Wardell
• Bernard Schutz
• Bernard Whiting
• Carlos Lousto
• Charles Evans
• Chris Clemens
• Christopher Munna
• David Brown
• Dillon Morse
• Dinesh Singh
• Gabe Perez-Giz
• Hector Chen
• Huan Yang
• Jezreel Castillo
• Joe Marincel
• John Wilkerson
• Jonathan Gair
• Jonathan Thompson
• Jonathan Thornburg
• Jordan Moxon
• Joseph Rudmin
• Justin Vines
• Karl Simon Revelar
• Karna Morey
• Leor Barack
• M. F. Ian Vega
• Maarten van de Meent
• Marc Casals
• Martin Gibson
• Niels Warburton
• Paul Anderson
• Peter Diener
• Richard Dudley
• Seth Hopper
• Steven Christensen
• Steven Dorsher
• Thomas Osburn
• Yota Watanabe
• Zach Nasipak
• Zachary Mark
• Zaf Jagoo
• Monday, 19 June
• 08:30 08:45
Coffee, Pastries & Name Tags 15m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 08:45 08:52
Welcome and Opening Remarks 7m Room 011, Sitterson Hall (UNC)

Room 011, Sitterson Hall

UNC

Speaker: Senior Associate Dean Prof. Chris Clemens
• 08:52 09:00
Welcome and Opening Remarks 8m Room 011, Sitterson Hall (UNC)

Room 011, Sitterson Hall

UNC

Speaker: CoSMS Institute Director Prof. John Wilkerson
• 09:00 09:50
Update on LIGO 50m Sitterson 011 (UNC)

Sitterson 011

UNC

TBA
Speaker: Aaron Zimmerman (Canadian Institute for Theoretical Astrophysics)
• 10:00 10:50
Prospects for observing extreme-mass-ratio inspirals with LISA 50m Sitterson 011 (UNC)

Sitterson 011

UNC

TBD
Speaker: Dr. Jonathan Gair (University of Edinburgh)
• 11:00 11:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 11:30 11:55
Solving for binary inspiral dynamics using renormalization group methods 25m Sitterson 011 (UNC)

Sitterson 011

UNC

Solving the equations of motion describing a compact binary's inspiral dynamics is not easy because of stringent accuracy requirements and the long duration of the orbit. In many cases, this can be achieved using numerical integration methods but such an approach is often a computational bottleneck for gravitational wave data analysis applications like parameter estimation. Analytically, some progress can be made by averaging out the shorter time scales in the problem. However, such adiabatic approximations are often not systematic, are difficult to estimate the domain of validity of the approximate solution, and entail ambiguities that make it difficult for assessing accuracy to truth solutions. I discuss some recent and ongoing work that aims to solve these problems using renormalization group theory methods. This approach does not require or utilize any averaging procedures so that the resulting solutions describe the binary's real-time orbital configuration at every instant. The basic idea rests on naive perturbation theory which, because of radiation reaction and self-force, produces secularly growing terms in time that renormalize the initial data parameters. This process generates a flow in time (i.e., the inspiral) which is described by the renormalization group equations that, in many cases, can be solved analytically. Being based on perturbation theory, it is straightforward to provide formal errors for the validity of the resulting resummed perturbative solution. I introduce the concepts and steps by sketching out the calculation for post-Newtonian inspirals. Other astrophysical applications, including tidal dissipation and spin-locking, may be discussed if time permits.
Speaker: Chad Galley (Jet Propulsion Laboratory, California Institute of Technology)
• 12:00 12:25
Regularization via the Detweiler-Whiting Singular Field 25m Sitterson 011 (UNC)

Sitterson 011

UNC

TBD
Speaker: Dr. Anna Heffernan (University of Florida)
• 12:30 14:00
Lunch 1h 30m Chapel Hill

Chapel Hill

• 14:00 14:25
Scattering events in Schwarzschild spacetime 25m Sitterson 011 (UNC)

Sitterson 011

UNC

The recent LIGO detections of merging black holes represent the culmination of decades of research into gravitational waves (GWs). One well-known seminal work by Peters and Mathews predicted the GW luminosity of eccentric binaries to leading post-Newtonian (PN) order. Driven largely by the desire to detect GWs from inspirals, the Peters-Mathews work has subsequently been extended through 3.5PN. Less well-known is work by Taylor, which is directly analogous to the Peters-Mathews result, except for scattering binaries. This work has only been extended by one PN order. In this talk I present work exploring the overlap regime between PN and black hole perturbation theory (BHPT). The regime is particularly fertile for bound two-body motion wherein the viral theorem links the two PN parameters (speed squared and inverse separation). For scattering and plunging trajectories, however, both numerical BHPT and analytical PN techniques struggle. I will discuss a range of potential methods for analyzing unbound motion, and show some successes and failures. Finally, I will consider the potential for using BHPT to compute (unbound-motion) gauge invariants, which has been quite successful for calibrating effective-one-body models.
Speaker: Seth Hopper (Instituto Superior Técnico)
• 14:30 14:55
Eccentric Orbit EMRIs: Enhanced Method for Determining Analytical Flux Coefficients to 7 PN. 25m Sitterson 011 (UNC)

Sitterson 011

UNC

Continuing the work of Forseth et *al*. (2016), we use high precision comparisons between perturbation theory and the post-Newtonian expansion to extract new information on eccentric orbit EMRIs to 7 PN order. Fluxes are calculated by combining the MST formalism with spectral source integration (SSI) for a multitude of orbits, whose parameters are then fit over in the PN form. This time, we perform a fit on each LMN mode individually, exploiting the patterns contained therein. The result is a significantly enhanced ability to fit for the combinations of transcendentals that appear in the higher PN orders.
Speaker: Christopher Munna (UNC Chapel Hill)
• 15:00 15:25
Progress towards multiscale EMRI approximation: zones and scales 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We present an update to the multiscale analytic approximation method for computing EMRI dynamics. The multiscale method takes advantage of the separation of the radiation-reaction timescale to the orbital timescale. By appropriately accounting for the slow evolution of the system, we suggest a framework for computing the waveform with only $\mathcal{O}(\epsilon)$ phase error. This framework will also be useful for computing quantities relevant for comparisons to Post-Newtonian or Numerical Relativity computations to second order in the mass ratio. Full second-order solution requires the introduction of puncture' regions near the horizon, near the small companion, and far from the binary, which are related to the interaction with the inspiral via a matched asymptotic expansion. We propose a geometric optics approximation for the region far from the inspiral.
Speaker: Jordan Moxon (Cornell University)
• 15:30 16:00
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 16:00 16:25
The nonspinning binary black hole merger scenario revisited 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We present the results of 14 simulations of nonspinning black hole binaries with mass ratios $q=m_1/m_2$ in the range $1/100\leq q\leq1$. For each of these simulations we perform three runs at increasing resolution to assess the finite difference errors and to extrapolate the results to infinite resolution. For $q\geq 1/6$, we follow the evolution of the binary typically for the last ten orbits prior to merger. By fitting the results of these simulations, we accurately model the peak luminosity, peak waveform frequency and amplitude, and the recoil of the remnant hole for unequal mass nonspinning binaries. We verify the accuracy of these new models and compare them to previously existing empirical formulas. These new fits provide a basis for a hierarchical approach to produce more accurate remnant formulas in the generic precessing case. They also provide input to gravitational waveform modeling and allow comparisons with perturbation theory.
Speaker: Prof. Carlos Lousto (Rochester Institute of Technology)
• 16:30 16:55
Merger Simulation Using the Parker Sochacki Method and Finite Element Analysis, in a Model Explicitly Consistent with Quantum Mechanics. 25m Sitterson 011 (UNC)

Sitterson 011

UNC

The motion of two or more sources of a gravitational field is modeled using the Parker Sochacki Method in adaptive finite element analysis. In rest frames, the metric is isotropic but not conformally flat. A metric equation for the conjugate mass-energy-momentum equation provides explicit consistency with quantum mechanics: Unitarity is preserved because Planck's Constant is invariant with metric scaling. While a metric is invariant under a local lorentz transformation, it is not invariant in under a lorentz transformation at an observer with a different metric scaling. The lorentz-transformed metric provides the affine connection for the equations of motion, which gives the velocities of the rest frames of the metrics at each point in space as seen by an observer at an arbitrary location. The equivalence principle applied to the continuity equation (or bianchi identities) for the Einstein Tensor as seen by any observer provides the equation which advances the Taylor series for the metric scaling: $G^{\mu\nu}(g^{2})_{,\nu}=0$, where the metric scaling $g$ appears in the metric equations in rest frames as $d\tau^{2}=dt^{2}/g^{2}-g^{2}d\vec{r}^{2}$ and $dm_{0}^{2}=g^{2}E^{2}-d\vec{p}^{2}/g^{2}$. This method is inherently symplectic because it uses the Parker Sochacki Method. It is inherently retarded and parallelizable because time evolution depends only on local conditions: Each processor can independently track its finite element.
Speaker: Mr. Joseph Rudmin (James Madison University)
• 17:00 18:00
Discussion 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• Tuesday, 20 June
• 08:30 09:00
Coffee & Pastries 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 09:00 09:50
Computing inspirals and waveforms using the self-force 50m Sitterson 011 (UNC)

Sitterson 011

UNC

In this talk I will review methods and results for computing inspirals and their associated waveforms in the small mass-ratio regime. To leading-order in the orbital phase evolution of the binary adiabatic flux balance techniques can be used. If we desire to track the orbital phase to better than one radian we must include post-adiabatic terms in the inspiral model. These post-adiabatic terms include first-order (in the mass ratio) conservative effects, second-order fluxes and effects from the spin of the secondary. I will discuss geodesic self-force and self-consistent models for incorporating these effects. After reviewing the progress that has been made I will conclude with a discussion of on-going efforts and future directions.
Speaker: Dr. Niels Warburton (University College Dublin)
• 10:00 10:50
First order gravitational self-force on generic bound orbits in Kerr spacetime 50m Sitterson 011 (UNC)

Sitterson 011

UNC

In this talk I will review the metric reconstruction machinery used for frequency domain calculations of the first order gravitational self-force on bound geodesics in Kerr spacetime. In particular, I will focus on how each step in this process is affect by relinquishing the up/down reflection symmetry of equatorial orbits, and moving to generic (inclined and eccentric) orbits. If the cluster and coding gods are willing, I will present some fresh preliminary results for the gravitational self-force on an inclined and eccentric orbit.
Speaker: Dr. Maarten van de Meent (AEI Potsdam-Golm)
• 11:00 11:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 11:30 11:55
Time-domain metric reconstruction for self-force applications 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We present a new method for self-force calculation in Kerr, based on a time-domain reconstruction of the metric perturbation from curvature scalars. The approach is computationally cheaper than existing time-domain methods based on a direct integration of the linearised Einstein's equations in the Lorenz gauge. It also avoids instability issues that plague those methods. At the same time, it retains the utility and flexibility of a time-domain treatment, allowing calculations for any type of orbits (including highly eccentric or unbound ones) and the possibility of self-consistently evolving the orbit under the effect of the self-force. Here we formulate our method for Kerr, and present a first numerical implementation in Schwarzschild.
Speaker: Prof. Leor Barack (University of Southampton)
• 12:00 12:25
Evolution of small-mass-ratio binaries with a spinning secondary 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We calculate the evolution and gravitational-wave emission of a spinning compact object inspiraling into a substantially more massive (non-rotating) black hole. We extend our previous model for a non-spinning binary [Phys. Rev. D 93, 064024] to include the Mathisson-Papapetrou-Dixon spin-curvature force. Using a generalized osculating element prescription we compute inspirals where the spin and orbital angular momentum are not parallel and the orbital plane precesses. For spin-aligned binaries we calculate the dephasing of the inspiral and associated waveforms with respect to models that do not include spin-curvature effects.
Speaker: Dr. Thomas Osburn (Oxford College of Emory University)
• 12:30 14:00
Lunch 1h 30m Chapel Hill

Chapel Hill

• 14:00 14:25
Transient Instabilities of Nearly Extremal Black holes 25m Sitterson 011 (UNC)

Sitterson 011

UNC

I will review recent work on the near-horizon perturbations of nearly extremal Kerr black holes. These perturbations experience transient growth, resulting in a "ring up" to strongly enhanced amplitudes. These transient instabilities connect directly to the slowly growing instabilities of extremal horizons, and may have observable consequences.
Speaker: Aaron Zimmerman (Canadian Institute for Theoretical Astrophysics)
• 14:30 14:55
Scalar self-force and QNM excitation for highly eccentric orbits in Kerr spacetime 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We present a computation of the self-force for a scalar-field particle on a bound eccentric orbit (which need not be a geodesic) in Kerr spacetime. Our main interest is in the case of highly eccentric orbits; here we present results for eccentricities as high as $0.98$. We use a Lorenz-gauge Barack-Golbourn-Vega-Detweiler effective-source regularization followed by an $e^{im\phi}$ ("m-mode") Fourier decomposition and a separate time-domain numerical evolution in $2{+}1$ dimensions for each $m$. We introduce a finite worldtube which surrounds the particle worldline and define our evolution equations in a piecewise manner so that the effective source is only used within the worldtube. Viewed as a spatial region the worldtube moves to follow the particle's orbital motion. Our numerical evolution uses Berger-Oliger mesh refinement with 4th~order finite differencing in space and time. We use slices of constant Boyer-Lindquist time near the black hole, deformed (following Zenginoglu) so as to be asymptotically hyperboloidal and compactified near the horizon and near $\mathcal{J}^+$. Our present implementation is restricted to equatorial geodesic orbits, but this restriction is not fundamental. For those configurations where the central black hole is highly spinning, the particle's periastron passage is near to or within the light ring, and the orbital eccentricity is $\ge 0.4$, we find that the particle's periastron passage excites quasinormal modes of the background (Kerr) spacetime, causing large oscillations (wiggles'') in the self-force on the outgoing leg of the orbit, and smaller but still detectable oscillations in the radiated field at $\mathcal{J}^+$.
Speaker: Dr. Jonathan Thornburg (Indiana University, Astronomy Dept)
• 15:00 15:25
Towards the self-consistent evolution of a scalar charge around a Schwarzschild black hole. 25m Sitterson 011 (UNC)

Sitterson 011

UNC

Using the effective source approach and the Discontinuous Galerkin method we have developed a very accurate time domain code for the evolution of a scalar charge in orbit around a Schwarzschild black hole. In the first incarnation of the code, only geodesic motion could be handled, but we have now added the ability to handle arbitrarily accelerated orbits. In this talk I will present code tests based on comparisons with frequency domain results for constant accelerated circular orbits and accelerated eccentric orbits that are periodic. Finally I will present new results for a case that can not be handled in the frequency domain: the case of a particle on a circular geodesic that experiences a short acceleration event (at constant radius) before returning to circular geodesic motion. I will also discuss the prospect of using this code for self-consistent evolutions where the field and the particle orbit are evolved together.
Speaker: Peter Diener (Louisiana State University)
• 15:30 16:00
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 16:00 16:25
Scalar self-force for generic bound orbits on Kerr 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We perform scalar self-force calculations for inclined, eccentric orbits of a small, compact body in Kerr spacetime. To implement these calculations with arbitrary numerical precision, we generalize spectral source integration (SSI) techniques by introducing the Mino time parameter and extending mode decompositions to include a polar frequency for inclined motion. Calculations are conducted using a Mathematica code that implements these SSI techniques along with the Mano, Suzuki, and Takasugi (MST) formalism to determine the inhomogeneous wave function solutions to the Teukolsky equation. This allows us to improve the accuracy of previous calculations in the literature. We also probe the extended parameter space for various orbital inclinations. Further extension to the gravitational case is also considered.
Speaker: Zach Nasipak (The University of North Carolina at Chapel Hill)
• 16:30 16:55
Self-force on a scalar charge in circular orbits about a Reissner-Nordstr\"{o}m black hole 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We calculate the self-force exerted on a scalar charge in a circular orbit about a Reissner-Nordstr\"{o}m black hole via mode-sum regularization. We also compute the radiative fluxes towards infinity and down the black hole. We pay particular attention to the dependence of the self-force and radiative fluxes on the black hole's charge-to-mass ratio, the controlling parameter of the Reissner-Nordstr\"{o}m geometry. We find that as the black hole approaches extremality, the radiative fluxes, and the self-force decreases.
Speaker: Mr. Jezreel Castillo (National Institute of Physics, University of the Philippines Diliman)
• 17:00 17:30
Discussion 30m Sitterson 011 (UNC)

Sitterson 011

UNC

• Wednesday, 21 June
• 08:30 09:00
Coffee & Pastries 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 09:00 09:50
Progress at second order 50m Sitterson 011 (UNC)

Sitterson 011

UNC

I discuss the status of second-order self-force formulations and computations, which will be necessary for accurate models of EMRIs. In the first part of the talk, I describe recent progress on the foundations of the theory. A principal feature of the second-order field equations is that the retarded field does not have a distributionally well-defined source, instead having a free boundary value in a region around the small object. This challenge has historically been addressed using a puncture scheme. However, it can also be eliminated entirely with a judicious choice of gauge, which may radically simplify future numerical work. In the second part of the talk, I describe ongoing work to numerically implement a second-order, two-timescale puncture scheme for quasicircular orbits in Schwarzschild spacetime. This will lead into the talk by Wardell.
Speaker: Adam Pound (University of Southampton)
• 10:00 10:50
Effective Source Calculations Through Second Perturbative Order 50m Sitterson 011 (UNC)

Sitterson 011

UNC

TBD
Speaker: Dr. Barry Wardell (University College Dublin)
• 11:00 11:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 11:30 11:55
Effective source formulations in the Regge-Wheeler gauge 25m Sitterson 011 (UNC)

Sitterson 011

UNC

In this status talk, I discuss progress being made to adapt effective-source regularization techniques to a first-order calculation in the Regge-Wheeler gauge.
Speaker: Mr. Jonathan Thompson (University of Florida)
• 12:00 12:25
A near-horizon expansion of second-order black hole perturbations 25m Sitterson 011 (UNC)

Sitterson 011

UNC

The first detection of gravitational waves (GWs) from merger of binary black hole (BH) by advanced LIGO has opened a new window to test general relativity. In the future, extreme-mass-ratio inspirals (EMRIs), in which stellar-mass compact objects of mass $\mu$ spiral into a supermassive black holes (SMBHs) of mass $M$, are expected to be observed by LISA. Such systems can be expressed by using the BH perturbation approach, where we expand equations in the mass ratio $\mu/M$. In order to extract physical parameters from GW observations, the second-order perturbations must be considered. However, naive calculations lead to a divergence of the second-order perturbations around boundaries. In this talk, we will seek a counterterm to avoid such a divergence around the event horizon of the SMBH.
Speaker: Dr. Kei Yamada (Kyoto Universiry)
• 12:30 14:00
Lunch 1h 30m Chapel Hill

Chapel Hill

• 14:00 15:30
Focused Discussion (A. Pound & B. Wardell): Progress and challenges at second order 1h 30m Sitterson 011 (UNC)

Sitterson 011

UNC

• 15:30 16:00
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 16:00 16:25
Overcharging Higher-dimensional Black holes using point particles 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We investigate the possibility of overcharging charged spherically-symmetric black holes in spacetime dimensions D > 4 by the capture of a charged particle. We generalize Wald’s classic result that extremal black holes cannot be overcharged. For nearly extremal black holes, we study how D affects the overcharging parameter space first discovered by Hubeny in D = 4. We find that overcharging becomes difficult for nearly-extremal black holes in the large D-limit.
Speaker: Mr. Karl Simon Revelar (University of the Philippines)
• 16:30 16:55
General-Relativistic Dynamics of an Extreme Mass-Ratio Binary with an External Body 25m Sitterson 011 (UNC)

Sitterson 011

UNC

We study the dynamics of a hierarchical three-body system in the general-relativistic regime:an extreme mass-ratio inner binary under the tidal influence of an external body. The inner binary consists of a central Schwarzschild black hole and a test body moving around it. We discover three types of tidal effects on the orbit of the test body. First, the angular moment of the inner binary precesses around the angular momentum of the outer binary. Second, the tidal field drives a `transient resonance" when the radial and azimuthal frequencies are commensurable.In contrast with resonances driven by the gravitational self-force, this tidal-driven resonance may boost the orbital angular momentum. Finally, as an orbit-dynamical effect during the non-resonant phase, we calculate the correction to the Innermost Stable Circular (mean) Orbit due to the tidal interaction. Hierarchical three-body systems are potential sources for future space-based gravitational wave missions and the tidal effects that we find could contribute significantly to their waveform.
Speaker: Dr. Huan Yang (Princeton University)
• 17:00 17:30
Discussion 30m Sitterson 011 (UNC)

Sitterson 011

UNC

• 18:00 20:30
Reception & Dinner 2h 30m DuBose House, UNC Rizzo Conference Center, 150 Dubose Home Lane, Chapel Hill, NC 27517

DuBose House, UNC Rizzo Conference Center, 150 Dubose Home Lane, Chapel Hill, NC 27517

• Thursday, 22 June
• 08:30 09:00
Coffee & Pastries 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 09:00 09:50
The laws of binary black hole mechanics: an update 50m Sitterson 011 (UNC)

Sitterson 011

UNC

The classical laws of black hole mechanics can be extended to binary systems of compact objects. I will first review the various zeroth and first laws of mechanics that have been established in the context of exact general relativity, in the post-Newtonian approximation and in black hole perturbation theory, for binary systems of black holes and/or point particles. I will then discuss various applications of these laws of binary mechanics.
Speaker: Alexandre Le Tiec (Observatoire de Paris)
• 10:00 10:50
Effective-one-body modeling of binary black holes in the era of gravitational-wave astronomy 50m Sitterson 011 (UNC)

Sitterson 011

UNC

The direct observation and characterization of gravitational waves from the coalescence of binary black holes by the LIGO and Virgo Collaborations is a testament to the crucial role played by waveform modeling in these discoveries. I will review the effective-one-body approach to describing the whole process of inspiral, merger and ringdown. This model implements the idea of a unified description of the dynamics of compact binaries, from the comparable-mass regime to the test-particle limit, with the goal of incorporating analytical and numerical information from different areas of relativity. I will highlight synergetic efforts with black-hole perturbation theory and gravitational self-force. I will also discuss applications of this model to the data analysis of the first gravitational-wave detections.
Speaker: Dr. Andrea Taracchini (Max Planck Institute for Gravitational Physics Potsdam)
• 11:00 11:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 11:30 11:55
Scattering of two spinning black holes and effective-one-body mappings 25m Sitterson 011 (UNC)

Sitterson 011

UNC

The net results of scattering processes can be seen to fully encode the gauge-invariant content of (unbound and bound) two-body dynamics. We present new results for the scattering of two spinning black holes (BHs), with an arbitrary mass ratio and with generic spin orientations, in the first post-Minkowskian (1PM) approximation to general relativity---to linear order in G, but to all orders in 1/c, and to all orders in both BHs' spins. The results are seen to fully reproduce and "resum" the linear-in-G parts of all previous post-Newtonian results for spinning-binary-BH dynamics, through 4PN order. The results also reveal a complete equivalence at 1PM order, under simple mappings, between arbitrary-mass-ratio two-spinning-BH dynamics and both (i) the dynamics of a spinning test BH (with all of the spin-induced BH multipoles) in a Kerr spacetime, and more surprisingly (ii) geodesic (point-test-mass) motion in a Kerr spacetime. We discuss implications for effective-one-body models and preview the situation at 2PM order.
Speaker: Dr. Justin Vines (Max Planck Institute for Gravitational Physics)
• 12:00 12:30
Research Collaborations 30m Sitterson 011 (UNC)

Sitterson 011

UNC

• 12:30 14:00
Lunch 1h 30m Chapel Hill

Chapel Hill

• 14:00 15:00
Focused Discussion (J. Vines): EOB 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• 15:00 15:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 15:30 15:45
Discussion on EMRI/IMRI using numerical relativity 15m Room 011, Sitterson Hall

Room 011, Sitterson Hall

Dept. of Physics & Astronomy and the CoSMS Institute, University of North Carolina at Chapel Hill

When mass ratios are not very extreme, perturbation theory becomes difficult. Standard numerical relativity codes, however, are inefficient unless the objects are of comparable mass, because the time-step and grid size are fixed by the smaller object. However, the smaller the mass ratio, the less important is the dynamics of the smaller object. I propose therefore a discussion on how to do numerical relativity by excising the smaller object and replacing it with a parametrized analytic solution. The boundary of the excised region becomes a (timelike) boundary of the numerically integrated domain. The boundary condition can be a matching condition of the external geometry to an internal solution in the excised region that has no inherent dynamics. It can be tidally distorted but this would be treated as an adiabatic perturbation on the external timescale. The matching boundary is, from the point of view of the inner solution, in the far-field of the compact body. This method has heritage as far back as EIH but is most closely associated with the way Futamase approached the point-particle limit of the PN problem for two compact objects, where the orbit solution was obtained by boundary matching to "inner" solutions for the compact objects: Physical Review D, vol. 32, (1985) pp. 2566-2574. Unlike for the PN problem, however, in the EMRI/IMRI problem there is no scaling on velocity; the only small parameter is the mass ratio.
Speaker: Prof. Bernard Schutz (Cardiff University and AEI)
• 15:45 16:30
Focused Discussion: EMRI/IMRI Using Numerical Relativity 45m Sitterson 011 (UNC)

Sitterson 011

UNC

• 16:30 17:00
Capra roundup: perspective and prospects. 30m Sitterson 011 (UNC)

Sitterson 011

UNC

I will try to summarize my perspective on where we stand with respect to the Capra mission, mention some highlights from the preceding talks, and give a list of topics I consider worthy for group discussion during the remaining days of the meeting.
Speaker: Prof. Bernard Whiting (University of Florida)
• 17:00 17:30
Discussion 30m Sitterson 011 (UNC)

Sitterson 011

UNC

• Friday, 23 June
• 08:30 09:00
Coffee & Pastries 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 09:00 10:00
Research Collaborations 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• 10:00 11:00
Focused Discussion: Analytic Function Expansion Methods 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• 11:00 11:30
Break 30m Sitterson Lobby (UNC)

Sitterson Lobby

UNC

• 11:30 12:30
Focused Discussion: Unstable Modes in Lorenz Gauge 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• 12:30 14:00
Lunch 1h 30m Chapel Hill

Chapel Hill

• 14:00 15:00
Focused Discussion: Long-Term Evolution 1h Sitterson 011 (UNC)

Sitterson 011

UNC

• 15:00 18:00
Research Collaborations 3h Sitterson 011 (UNC)

Sitterson 011

UNC

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