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SUMMARY:Observing the end of inflation
DTSTART:20260716T103000Z
DTEND:20260716T113000Z
DTSTAMP:20260803T014400Z
UID:indico-event-9383@scitalks.tifr.res.in
DESCRIPTION:Speakers: Sriramkumar L. (Dept. of Physics\, IIT-Madras\, Chen
 nai.)\n\nThe primary gravitational waves (PGWs) are generated in the early
  universe from the quantum vacuum during inflation. In slow roll inflation
 \, the power spectrum (PS) of PGWs over large scales\, which leave the Hub
 ble radius during inflation\, is nearly scale-invariant. However\, over ve
 ry small scales\, which never leave the Hubble radius\, the PS of PGWs ris
 es quadratically. In this talk\, I will first show that\, over such small 
 scales\, the PS of PGWs exhibits a similar behavior even when it is evalua
 ted at any time after inflation. I will argue that the PS has to be regula
 rized in order to truncate the quadratic rise over small scales or\, equiv
 alently\, at high frequencies. Thereafter\, I will describe the method of 
 adiabatic regularization to arrive at the PS of PGWs over a wide range of 
 frequencies. Assuming instantaneous transitions from inflation to the epoc
 hs of radiation and matter domination\, I will show that the process of re
 gularization curtails the quadratic rise and the regularized PS of PGWs os
 cillates with a fixed amplitude about a vanishing mean value over small sc
 ales. Later\, considering a smoother transition from inflation to radiatio
 n domination\, I will explicitly show that the smoother transition leads t
 o a power-law suppression in the amplitude of the oscillations (about the 
 zero mean value) of the regularized PS of PGWs over scales that always rem
 ain within the Hubble radius. Finally\, using the Born approximation\, I w
 ill illustrate that\, on small scales\, the suppression in the regularized
  PS of PGWs occurs more and more sharply as the transition is smoothed fur
 ther and further. With the help of specific examples\, I will also show th
 at\, in the case of infinitely continuous transitions\, the regularized PS
  of PGWs exhibits an exponential suppression on small scales. I will concl
 ude by pointing out that the observation of the exponential drop in the PS
  of PGWs can\, in principle\, help us determine the energy scale as well a
 s the time of the end of inflation. \n\nhttps://scitalks.tifr.res.in/even
 t/9383/
LOCATION:AG-80 (Hybrid) (https://tifr-res-in.zoom.us/j/96517028121?pwd=QMd
 JVhNRIpmyN5hvb5btsXXdeBdgP2.1  Meeting ID: 965 1702 8121 Passcode: 648752)
URL:https://scitalks.tifr.res.in/event/9383/
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