BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Enrico Pajer (Cambridge) DTSTART:20210608T100000Z DTEND:20210608T110000Z DTSTAMP:20260513T222341Z UID:CCTP_HEP/52 DESCRIPTION:Title: A Timeless History of Time\nby Enrico Pajer (Cambridge) as part of C CTP HEP Seminars\n\n\nAbstract\nCosmological observations give us the uniq ue opportunity to\nprobe the fundamental laws of physics at very high ener gies as well as\nthe perturbative regime of quantum gravity. Unfortunately \, due to the\ncreativity of theorists and the paucity of data about the p rimordial\nuniverse\, there is a huge number of models compatible with all \nmeasurements\, featuring a wide variety of mechanisms\, symmetries\, and \nspectra of particles.The reason can be traced back to the fact that we\n don't observe the time evolution during inflation\, but only its final\nou tcome.\n\nIn this talk I will report on the recent progress in developing a\ncompletely new "bootstrap" approach to derive predictions from the very \nearly universe that make no reference to time and the un-observable time \nevolution. The bootstrap approach builds directly upon the fundamental\n pillars of physics. In particular\, I will present the recent\nbreakthroug hs in understanding the consequence of unitarity for\ncosmological correla tors to all orders in perturbation theory\, as well\nas the footprint of ( bulk) locality. I will show how these principles\ncan be used to derive ma ny classical and new inflationary predictions\nassociated with primordial non-Gaussianity in a way that is both\ncomputationally simpler and concept ually more transparent. This includes\na reconstruction formula that relat es de Sitter correlators to\namplitudes for massless particles\, cosmologi cal partial-energy recursion\nrelations and a "timeless" differential repr esentation of the\nperturbative wavefunction. This approach makes no refer ence to de Sitter\nboosts\, which are broken by a large amount in models t hat predict large\nnon-Gaussianity.\n LOCATION:https://researchseminars.org/talk/CCTP_HEP/52/ END:VEVENT END:VCALENDAR