Post-Minkowskian Effective Field Theory for Conservative Binary Dynamics

We develop an Effective Field Theory (EFT) formalism to solve for the conservative dynamics of binary systems in gravity via Post-Minkowskian (PM) scattering data. Our framework combines a systematic EFT approach to compute the deflection angle in the PM expansion, together with the 'Boundary-to-Bound' (B2B) dictionary introduced in [1910.03008, 1911.09130]. Due to the nature of scattering processes, a remarkable reduction of complexity occurs both in the number of Feynman diagrams and type of integrals, compared to a direct EFT computation of the potential in a PM scheme. We provide two illustrative examples. Firstly, we compute all the conservative gravitational observables for bound orbits to 2PM, which follow from only one topology beyond leading order. The results agree with those in [1910.03008, 1911.09130], obtained through the 'impetus formula' applied to the classical limit of the one loop amplitude in Cheung et al. [1808.02489]. For the sake of comparison we reconstruct the conservative Hamiltonian to 2PM order, which is equivalent to the one derived in [1808.02489] from a matching calculation. Secondly, we compute the scattering angle due to tidal effects from the electric- and magnetic-type Love numbers at leading PM order. Using the B2B dictionary we then obtain the tidal contribution to the periastron advance. We also construct a Hamiltonian including tidal effects at leading PM order. Although relying on (relativistic) Feynman diagrams, the EFT formalism developed here does not involve taking the classical limit of a quantum amplitude, neither integrals with internal massive fields, nor additional matching calculations, nor spurious ('super-classical') infrared singularities. By construction, the EFT approach can be automatized to all PM orders.Comment: 40 pages. 3 figure

The Full-Color Two-Loop Four-Gluon Amplitude in N=2\mathcal{N} = 2 Super-QCD

We present the fully integrated form of the two-loop four-gluon amplitude in $\mathcal{N} = 2$ supersymmetric quantum chromodynamics with gauge group SU$(N_c)$ and with $N_f$ massless supersymmetric quarks (hypermultiplets) in the fundamental representation. Our result maintains full dependence on $N_c$ and $N_f$, and relies on the existence of a compact integrand representation that exhibits the duality between color and kinematics. Specializing to the $\mathcal{N} = 2$ superconformal theory, where $N_f = 2N_c$ , we obtain remarkably simple amplitudes that have an analytic structure close to that of $\mathcal{N} = 4$ super-Yang-Mills theory, except that now certain lower-weight terms appear. We comment on the corresponding results for other gauge groups.Comment: 5 pages + refs, 1 figure, 2 ancillary file

Conservative Dynamics of Binary Systems to Third Post-Minkowskian Order from the Effective Field Theory Approach

We derive the conservative dynamics of non-spinning binaries to third Post-Minkowskian order, using the Effective Field Theory (EFT) approach introduced in [2006.01184] together with the Boundary-to-Bound dictionary developed in [1910.03008, 1911.09130]. The main ingredient is the scattering angle, which we compute to ${\cal O}(G^3)$ via Feynman diagrams. Adapting to the EFT framework powerful tools from the amplitudes program, we show how the associated (master) integrals are bootstrapped to all orders in velocities via differential equations. Remarkably, the boundary conditions can be reduced to the same integrals that appear in the EFT with Post-Newtonian sources. For the sake of comparison, we reconstruct the Hamiltonian and the classical limit of the scattering amplitude. Our results are in perfect agreement with those in Bern et al. [1901.04424, 1908.01493].Comment: 7 pages. 1 figure. v2: Typos and misprints fixed (notably in Eq. 19). To appear in Phys. Rev. Let

Conservative Tidal Effects in Compact Binary Systems to Next-to-Leading Post-Minkowskian Order

Using the Effective Field Theory approach together with the Boundary-to-Bound map, we compute the next-to-leading order (NLO) Post-Minkowskian (PM) tidal effects in the conservative dynamics of compact binary systems. We derive the mass and current quadrupole and, for the first time, octupole corrections to the binding energy for circular orbits at ${\cal O}(G^3)$. Our results are consistent with the test-body limit as well as the existent Post-Newtonian literature. We also reconstruct a Hamiltonian incorporating tidal effects to NLO in the PM expansion and find complete agreement with the recent derivation of its quadrupolar part using the classical limit of scattering amplitudes.Comment: 5+4 pages. 1 figur

Machine Learning Post-Minkowskian Integrals

We study a neural network framework for the numerical evaluation of Feynman loop integrals that are fundamental building blocks for perturbative computations of physical observables in gauge and gravity theories. We show that such a machine learning approach improves the convergence of the Monte Carlo algorithm for high-precision evaluation of multi-dimensional integrals compared to traditional algorithms. In particular, we use a neural network to improve the importance sampling. For a set of representative integrals appearing in the computation of the conservative dynamics for a compact binary system in General Relativity, we perform a quantitative comparison between the Monte Carlo integrators VEGAS and i-flow, an integrator based on neural network sampling.Comment: 26 pages + references, 3 figures, 3 table

Dynamics of Binary Systems to Fourth Post-Minkowskian Order from the Effective Field Theory Approach

We present the contribution from potential interactions to the dynamics of non-spinning binaries to fourth Post-Minkowskian (4PM) order. This is achieved by computing the scattering angle to ${\cal O}(G^4)$ using the effective field theory approach and deriving the bound radial action through analytic continuation. We reconstruct the Hamiltonian and center-of-mass momentum in an isotropic gauge. The (three-loop) integrals involved in our calculation are computed via differential equations, including a sector yielding elliptic integrals. As a prelude of radiation-reaction effects, using the universal link between potential and tail terms, we also report: 1) The instantaneous energy flux at ${\cal O}(G^3)$; 2) The contribution to the 4PM unbound/bound radial action(s) depending on logarithms of the binding energy; 3) The (scheme-independent) logarithmic contribution to the 4PM non-local tail Hamiltonian for circular orbits. Our results in the potential region are in agreement with the recent derivation from scattering amplitudes. We also find perfect agreement in the overlap with the state-of-the-art in Post-Newtonian theory.Comment: 9 pages, 1 figure. 1 ancillary file (txt format

Radiation Reaction and Gravitational Waves at Fourth Post-Minkowskian Order

We obtain the total impulse in the scattering of non-spinning binaries in general relativity at fourth Post-Minkowskian order, i.e. ${\cal O}(G^4)$, including linear, nonlinear, and hereditary radiation-reaction effects. We derive the total radiated spacetime momentum as well as the associated energy flux. The latter can be used to compute gravitational-wave observables for generic (un)bound orbits. We employ the ("in-in") Schwinger-Keldysh worldline effective field theory framework in combination with modern "multi-loop" integration techniques from collider physics. The complete results are in agreement with various partial calculations in the Post-Newtonian/Minkowskian expansion.Comment: 6 pages + Refs + Supplemental. 1 figure and 1 table. 1 computer-readable ancillary fil

Scattering Amplitudes in Supersymmetric Quantum Chromodynamics and Gravity

Quantum field theory is a theoretical framework for the description of nature in terms of fundamental particles, fields and their interactions. In the quantum regime, elementary scattering processes are observables in many experiments and studied in theoretical physics. The theoretical understanding of scattering amplitudes is often based on a perturbative analysis in powers of the coupling strength of the fundamental forces. Whereas the computation of scattering amplitudes has been dominated by Feynman diagram constructions for a long time, new methods have lead to a multitude of novel results in the last 20-30 years. Thereafter discoveries of new representations, dualities and construction methods have enormously increased our understanding of the mathematical structure of scattering amplitudes. In this thesis we focus on a particular structure of gauge theory amplitudes known as the color-kinematics duality. Closely tied to this duality is the double copy construction of gravitational amplitudes, and a set of identities among basic building blocks of the gauge theory, the BCJ identities. Using methods developed for the study of this duality, we obtain new results for scattering amplitudes in non-maximal supersymmetric Yang-Mills coupled to massless fundamental matter at one and two loops. We immediately construct amplitudes in supergravity theories via the double copy. Furthermore, we include methods and results for the integration of gauge theory amplitudes and the ultraviolet structure of supergravity amplitudes. In a second part we present ideas related to the identification of basic building blocks that underlie the construction of  scattering amplitudes. A decomposition of gauge theory amplitudes into color- and kinematic-dependent contributions exposes a set of primitive objects. Relations among these objects allow us to identify a minimal set of independent kinematic building blocks

Scattering Amplitudes in Supersymmetric Quantum Chromodynamics and Gravity

Quantum field theory is a theoretical framework for the description of nature in terms of fundamental particles, fields and their interactions. In the quantum regime, elementary scattering processes are observables in many experiments and studied in theoretical physics. The theoretical understanding of scattering amplitudes is often based on a perturbative analysis in powers of the coupling strength of the fundamental forces. Whereas the computation of scattering amplitudes has been dominated by Feynman diagram constructions for a long time, new methods have lead to a multitude of novel results in the last 20-30 years. Thereafter discoveries of new representations, dualities and construction methods have enormously increased our understanding of the mathematical structure of scattering amplitudes. In this thesis we focus on a particular structure of gauge theory amplitudes known as the color-kinematics duality. Closely tied to this duality is the double copy construction of gravitational amplitudes, and a set of identities among basic building blocks of the gauge theory, the BCJ identities. Using methods developed for the study of this duality, we obtain new results for scattering amplitudes in non-maximal supersymmetric Yang-Mills coupled to massless fundamental matter at one and two loops. We immediately construct amplitudes in supergravity theories via the double copy. Furthermore, we include methods and results for the integration of gauge theory amplitudes and the ultraviolet structure of supergravity amplitudes. In a second part we present ideas related to the identification of basic building blocks that underlie the construction of  scattering amplitudes. A decomposition of gauge theory amplitudes into color- and kinematic-dependent contributions exposes a set of primitive objects. Relations among these objects allow us to identify a minimal set of independent kinematic building blocks