Dear all,
From Monday 19th February to the wednesday 21th, we will receive Ville Vaskonen who has worked a lot in the fields of early universe phase transitions and black holes phenomenology. Do not hesitate to pass by our offices if you want to discuss with him.
He will give a talk on Tuesday the 20th at 14:00 in the Sancton room:
Black holes and gravitational waves from slow phase transitions
The Universe may have deviated from the radiation-dominated expansion during the earliest epochs and the processes causing that can have interesting observable consequences. In this talk, I will focus on strongly supercooled phase transitions that cause a secondary period of exponential expansion of the Universe. I will describe a class of particle physics models where such transitions can happen and discuss the observable consequences of the process in the form of gravitational waves (GWs) and primordial black holes (PBHs). I will show that if the transition is slow the GW signal generated by colliding bubble walls and fluid shells can be very strong and potentially gives a good fit to the GW background recently discovered in the pulsar timing array data. I will also show that such slow transitions lead to the formation of a large PBH abundance that can constitute all dark matter and a secondary GW signal that dominates over the signal formed by the bubble walls and fluid shells if the transition is sufficiently slow.
I hope to see you there,
Kind regards,
Miguel
