Theoretical Cosmology meetings

To actively encourage the field of theoretical cosmology and to set an informal stage for the exchange of ideas, the Dutch theoretical cosmology community organizes Friday afternoon meetings approximately 6 times a year — usually on the first Friday of the month. The meetings typically start in the afternoon with a main speaker, followed by a short break to continue with another seminar or journal club discussion on some topic of current interest. We end the afternoon with drinks. The supporting institutes in Leiden, Amsterdam, Groningen, Utrecht where recently joined by the strings and cosmology group in Leuven and take turns in hosting the event.

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Leiden Winter 2017

03/02/2017 @ 12:00 - 18:00

Leiden University, February 3, 2017

Casimir room (Oort building, Room 276, the Institute Lorentz coffee room)

14:00-15:00 Talk by J. Magueijo (Imperial College)
Title: The critical geometry of a thermal Big Bang
We explore the space of scalar-tensor theories containing two non-conformal metrics, and find a discontinuity pointing to a “critical” cosmological solution. Due to the different maximal speeds of propagation for matter and gravity, the cosmological fluctuations start off inside the horizon even without inflation, and will more naturally have a thermal origin (since there is never vacuum domination). The critical model makes an unambiguous, non-tuned prediction for the spectral index of the scalar fluctuations: ns = 0.96478(64). Considering also that no gravitational waves are produced, we have unveiled the most predictive model on offer. The model has a simple geometrical interpretation as a probe 3-brane embedded in an EAdS2 × E3 geometry.

15:00 – 15:30 Coffee

15:30 -16:30 Talk by J. Garcia-Bellido (IFT Madrid)
Title: Gravitational Waves from Primordial Black Holes as Dark Matter
20 years ago, we predicted that primordial black holes (PBH) would form via the gravitational collapse of matter associated with peaks in the spectrum of matter fluctuations, and that they could constitute all of the dark matter today. Last year, we predicted the mass distribution of PBH, which peaks at 50 Msun and whose tails could be responsible for the seeds of galaxies. LIGO has recently detected gravitational waves from the inspiraling of three black hole binaries. We propose that LIGO has actually detected dark matter in the form of PBH, and predict that within 10 years, an array of GW detectors (i.e. LIGO, VIRGO, KAGRA, INDIGO, etc.) could be used to determine the mass and spin distribution of PBH dark matter. Furthermore, the stochastic GW background from inspiralling PBH will potentially be detected by LISA and PTA, and will open a new window into the Early Universe.

16:30- 17:30 Borrel


12:00 - 18:00
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