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SUMMARY:Gr.IV seminar: Paolo Di Vecchia - "Classical observables of Genera
 l Relativity from scattering amplitudes "
DTSTART:20260511T140000Z
DTEND:20260511T150000Z
DTSTAMP:20260503T183600Z
UID:indico-event-51990@agenda.infn.it
DESCRIPTION:I will be using scattering amplitudes\, instead of the  Lagra
 ngian of General Relativity (GR)\,  to compute classical observables in G
 R.   In the first part of the seminar I   will  consider the elastic s
 cattering of two massive particles\, describing two black holes\, and  I
   will show how to compute  the eikonal up to two-loop order\, correspon
 ding to third Post-Minkowskian (3PM) order\, that contains all the classic
 al information. From it I will compute the first observable that is the cl
 assical deflection angle. In the second part of the seminar I will conside
 r inelastic processes with the emission of soft gravitons. In this case th
 e eikonal becomes an operator containing the creation and annihilation ope
 rators of the gravitons. The case of soft gravitons can be treated followi
 ng the Bloch-Nordsieck approach and\, in this case\, I will be computing 
  two other observables: the zero-frequency limit (ZFL) of the spectrum dE/
 d\\omega of the emitted radiation and the angular momentum loss at 2PM and
  3PM.  I will consider  also the case in which there are static modes lo
 calised at $\\omega=0$.In the third part of the seminar  I will be discus
 sing soft theorems with one graviton emission\, first briefly at tree leve
 l\, and then at loop level following the approach of  Weinberg from 1965 
 and comparing it with a more recent approach by Laddha\, Saha\,  Sahoo an
 d Sen.  I  will compute  the universal soft terms of the waveform\, tha
 t are  $\\frac{1}{\\omega}$\, $\\log \\omega$ and $\\omega \\log^2 \\omeg
 a$\, first at the tree and one-loop level and then  also at two-loop   l
 evel.  Then I will present a guess for the terms $\\omega^n \\log^{n+1} \
 \omega$ for $n=2\, 3 …$ and I will give a formula where all these   ter
 ms are resummed. Finally\, if I have time left\, I  will study the high e
 nergy limit. In particular\, since the graviton is the massless particle w
 ith the highest spin\, we expect universality at high energy in any gravit
 ational amplitude. I will show that universality at high energy is satisfi
 ed both in the elastic and inelastic case\, but this happens in the inelas
 tic case in a very non trivial way. I will end with some conclusions and w
 ith a list of open problems.\n\nhttps://agenda.infn.it/event/51990/
LOCATION:0M03
URL:https://agenda.infn.it/event/51990/
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