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SUMMARY:The Cosmological Bootstrap - Enrico Pajer\, DAMTP
DTSTART:20230608T120000Z
DTEND:20230608T130000Z
UID:TALK200098@talks.cam.ac.uk
CONTACT:Jackson Fliss
DESCRIPTION:In this talk\, I will review the (boostless) cosmological boot
 strap approach to the study of cosmological correlators from inflation\, i
 n which symmetries and general physical principles such as causality\, uni
 tarity and locality substitute the traditional model-building and lead to 
 a variety of general results and new predictions for primordial signals. T
 he object of study is the field theoretic wavefunction and its wavefunctio
 ns coefficients\, from which all correlators can be (perturbatively) deriv
 ed. Wavefunction coefficients are the close analog of amplitudes in flat s
 pace and many results for amplitudes have avatars in the cosmological boot
 strap.  \nIn the first part of the talk\, I will review a few core results
 : (i) Causality implies that "off-shell" wavefunction coefficients (a.k.a.
  cosmological "in-out" Green's function) are analytic functions of off-she
 ll energies (non-perturbatively) in the lower-half complex plane\, whose s
 ingularity on the negative real axis are classified. (ii) Unitarity implie
 s an infinite set of relations between higher and lower order contribution
 s in perturbation theory known collectively as the cosmological optical th
 eorem. (iii) Manifest locality constrains wavefunction coefficients in the
  form of analytically-continued soft limits.\nIn the second part of the ta
 lk\, I discuss some phenomenological results recently derived with these t
 echniques: (1) The tree-level scalar bispectrum to all orders in derivativ
 es\; (2) The only three possible tree-level shapes of the parity-odd tenso
 r bispectrum\; (3) a no-go theorem for the parity-odd trispectrum and some
  yes-go examples and (4) the graviton trispectrum in general relativity.
LOCATION:Potter Room\, DAMTP
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