All future seminars

Number of entries: 2

19
October 2018

Primordial black hole formation and abundance: dependence on the shape of the inflationary power spectrum


Start: 12:15h
Speaker: Ilia Musco (Institut de Ciències del Cosmos (ICCUB))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)

Primordial black holes can form in the early Universe from the collapse of cosmological perturbations after the cosmological horizon crossing. They are possible candidates for the dark matter as well as for the seeds of supermassive black holes observed today in the centre of galaxies. In calculations…
Start: 12:15h
Speaker: Ilia Musco (Institut de Ciències del Cosmos (ICCUB))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)

Primordial black holes can form in the early Universe from the collapse of cosmological perturbations after the cosmological horizon crossing. They are possible candidates for the dark matter as well as for the seeds of supermassive black holes observed today in the centre of galaxies. In calculations of spherically symmetric collapse, using a large curvature perturbation in the super horizon regime, the initial conditions are specified using the gradient expansion approximation in the long wave length limit. The non linear evolution is then simulated using a Lagrangian relativistic hydrodynamical code. If the perturbation is larger than  a threshold depending on the equation of state and on the specific shape of the perturbation, a black hole is formed. In this talk I will discuss the dependence of PBH formation from the initial shape of the curvature profile showing the relation between the threshold amplitude and the steepness of the perturbation which is linked to the amplitude of the pressure gradients that are developing during the collapse. I will show how to derive the initial curvature profile form the shape of the inflationary power spectrum, which affects also the abundance of PBHs. Depending on the model, a proper calculation, using the shape of the power spectrum, shows that the abundance of PBHs is significantly increased by several order of magnitudes compared to previous estimations.
09
November 2018

Voyager probing dark matter


Start: 12:15h
Speaker: Mathieu Boudaud (Laboratoire de Physique Théorique et Hautes Energies )
Place: Sala Alberto Lobo (ICE building, Campus UAB)

About 40 years after its launch in 1977, the famous Voyager-1 spacecraft has crossed the heliopause in 2012 and is now exploring the local interstellar medium while sending us unprecedented data. This opens up a new avenue to probe local dark matter via cosmic ray electrons and positrons in the sub-GeV…
Start: 12:15h
Speaker: Mathieu Boudaud (Laboratoire de Physique Théorique et Hautes Energies )
Place: Sala Alberto Lobo (ICE building, Campus UAB)

About 40 years after its launch in 1977, the famous Voyager-1 spacecraft has crossed the heliopause in 2012 and is now exploring the local interstellar medium while sending us unprecedented data. This opens up a new avenue to probe local dark matter via cosmic ray electrons and positrons in the sub-GeV energy range. After describing a novel semi-analytical method (pinching method) which provides us a complete description of the transport of electrons and positrons at low energy, I’ll present predictions for both the secondary astrophysical background and the pair production mechanisms relevant to dark matter particles annihilation or decay down to the MeV mass range. We combined the constraints from the Voyager and AMS-02 data to get novel and robust limits covering a very extended dark matter particle mass range, from MeV to TeV. For velocity dependent annihilation processes (p-wave), we make use of the Eddington method to compute the phase space distribution function of dark matter particles from the most recent constrained mass model of the Galaxy. Primordial black holes are alternative and also well-motivated candidates for dark matter. Black holes with a mass smaller than ~10^17 g are expected to inject electrons and positrons in the Galaxy through Hawking radiation. I’ll show that Voyager is sensitive to signatures from such black holes and I’ll present novel constraints on the contribution of primordial black holes to dark matter in this mass window. Though extracted from a completely different and new probe, these bounds have a strength similar to those obtained with the extragalactic gamma ray background.
Institute of Space Sciences (IEEC-CSIC)

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Phone: +34 93 737 9788
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya