Events Daily

Wednesday, February 15, 2023

HEP Journal Club
Event Type: Other
Time: 12:30 PM - 1:30 PM
Location: 726 Broadway, 940, CCPP Seminar

Cosmology as a weak gravitational field and the trans-Planckian problem
Alberto Nicolis, Columbia
Event Type: HEP Seminar
Time: 2:00 PM - 3:00 PM
Location: 726 Broadway, 940, CCPP Seminar
Abstract: The so-called trans-Planckian problem is the statement that in present-day cosmological observables there could be signatures of physics beyond the Planck scale, because of the exponential "stretching" of modes that took place during inflation. A popular counterargument is that, as long the Hubble rate during inflation is sub-Planckian, the expansion of the universe is adiabatic as far as trans-Planckian modes are concerned, and thus can only have exponentially small effects on them. We give quantitative support to this view by performing explicit computations in a new set of coordinates, which highlights that, for local physics, the expansion of the universe can be dealt with in perturbation theory.