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SUMMARY:Paolo di Vecchia\,  Classical observables  of General Relativity f
 rom scattering amplitudes
DTSTART:20260330T113000Z
DTEND:20260330T123000Z
DTSTAMP:20260710T080000Z
UID:indico-event-9630@indico.fysik.su.se
DESCRIPTION:In the first part of the seminar I   will  consider the elas
 tic scattering of two massive particles\, describing two black holes\, and
   I  will show how to compute  the eikonal up to two-loop order\, corre
 sponding to third Post-Minkowskian (3PM) order\, that contains all the cla
 ssical information. From it I will compute the first observable that is th
 e classical deflection angle. \nIn the second part of the seminar I will 
 consider inelastic processes with the emission of soft gravitons. In this 
 case the eikonal becomes an operator containing the creation and annihilat
 ion operators of the gravitons. The case of soft gravitons can be treated 
 following the Bloch-Nordsieck approach and\, in this case\, I will be comp
 uting  two other observables: the zero-frequency limit (ZFL) of the spect
 rum 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 m
 odes localised at $\\omega=0$.\n \nIn the third part of the seminar  I w
 ill be discussing soft theorems with one graviton emission\, first briefly
  at tree level\, and then at loop level following the approach of  Weinbe
 rg from 1965 and comparing it with a more recent approach by Laddha\, Saha
 \,  Sahoo and Sen.  I  will compute  the universal soft terms of the w
 aveform\, that are  $\\frac{1}{\\omega}$\, $\\log \\omega$ and $\\omega \
 \log^2 \\omega$\, first at the tree and one-loop level and then  also at 
 two-loop   level.  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   terms are resummed. \nFinally\, if I have time left\, I  will 
 study the high energy limit. In particular\, since the graviton is the mas
 sless particle with the highest spin\, we expect universality at high ener
 gy in any gravitational amplitude. I will show that universality at high e
 nergy is satisfied both in the elastic and inelastic case\, but this happe
 ns in the inelastic case in a very non trivial way. I will end with some c
 onclusions and with a list of open problems.\n \n\nhttps://indico.fysik.s
 u.se/event/9630/
LOCATION:Albano 3: 6228 - Mega (22 seats) (Albano Building 3)
URL:https://indico.fysik.su.se/event/9630/
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