Seminars
# Classical general relativity from the double copy and the kinematic algebra of Yang-Mills theory

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https://infn-it.zoom.us/j/82247215673?pwd=em1GRklEYngwMGVBbVVBb2VoL1pvdz09
### https://infn-it.zoom.us/j/82247215673?pwd=em1GRklEYngwMGVBbVVBb2VoL1pvdz09

Description

Scattering amplitudes of elementary particles exhibit a

fascinating simplicity, which is entirely obscured in textbook

Feynman-diagram computations. While these quantities find their primary

application to collider physics, describing the dynamics of the tiniest

particles in the universe, they also characterise the interactions among

some of its heaviest objects, such as black holes. Violent collisions

among black holes occur where tremendous amounts of energy are emitted,

in the form of gravitational waves. 100 years after having been

predicted by Einstein, their extraordinary direct detection in 2015

opened a fascinating window of observation of our universe at extreme

energies never probed before, and it is now crucial to develop novel

efficient methods for highly needed high-precision predictions. Thanks

to their inherent simplicity, amplitudes are ideally suited to this

task. I will begin by reviewing the computation of a very familiar

quantity Newton's potential, from scattering amplitudes and unitarity.

I will then explain how to compute directly observable quantities such

as the scattering angle for light or for gravitons passing by a heavy

mass such as a black hole. These computations are further simplified

thanks to a remarkable, yet still mysterious connection between

scattering amplitudes of gluons (in Yang-Mills theory) and those of

gravitons (in Einstein's General relativity), known as the "double

copy", whereby the latter amplitudes can be expressed, schematically, as

sums of squares of the former -- a property that cannot be possibly

guessed by simply staring at the Lagrangians of the two theories. I will

conclude by discussing the prospects of performing computations in

Einstein gravity to higher orders in Newton's constant using a new,

gauge-invariant version of the double copy, and as an example I will

briefly discuss the computation of the scattering angle for classical

black hole scattering to third post-Minkowskian order (or O(G^3) in

Newton's constant G).