Formation and abundance of primordial black holes

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, a Lagrangian relativistic hydrodynamical code is used to follow the non linear evolution. 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.

Beyond the Standard Models with Cosmic Strings

Cosmic strings (CS) are topological defects formed after spontaneous breaking of a U(1) symmetry. Remarkably, thanks to the scaling regime, CS loops constitute a long-standing source of Gravitational Waves (GW) and produce a flat GW spectrum during radiation domination, spanning many orders of magnitude in frequency.

APC colloquium

Dear all,

We are very happy to welcome Andrzej M. Szelc (Royal Society University Research Fellow, the University of Manchester) at APC this week.

Andrzej will talk about the "Long- and Short-Baseline Neutrino Oscillation Experiments” (abstract and poster below) in Amphi PGG on Friday, February 7th at 11am.

Vincent and Josquin

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Title: Long- and Short-Baseline Neutrino Oscillation Experiments

Cosmology as a CFT1

Over the last decades, the emergence of conformal symmetry in gravitational systems has provided a powerful tool to investigate new aspects in classical, semi-classical and quantum general relativity.

Observational signatures of multifield inflation

Slow-roll single-field inflation constitutes the main paradigm of the
Early Universe. But this model suffers from a number of conceptual issues
that naturally lead to the consideration of multifield models of
inflation with curved field space, that have recently been under scrutiny
as realistic realizations of high-energy physics in the Early Universe.
I will show that the non-trivial internal geometry reshuffles
observational predictions from inflation, at the level of the background
(geometrical destabilisation of inflation), of linear

Relieving the Hubble tension with primordial magnetic fields

Observations with LHAASO-1/2 and the Construction Status

This is a joint seminar with the Institute of High Energy Physics in Beijing.

Composite and holographic axions

The idea that low energy fields such as Gravitons or Axions can be 
thought of as composite particles has been entertained since a long 
time. We revisit this idea motivated by the AdS/CFT correspondence. We 
focus in the case of axions and show that hidden sectors coupled to SM 
fields may provide an emergent axionic field that is a composite of the 
hidden fields (instanton density). This is a more general phenomenon 
beyond holographic theories. We study the general properties of such an 
"emergent axion", without a PQ symmetry. The construction goes beyond

Euclidean Wormholes and Holography

Inflation and Geometry

Inflation, an era of accelerated expansion of the universe prior to the radiation phase, constitutes the paradigm of primordial cosmology. Within this paradigm, the simplest single-field slow-roll models economically explain all curent data. However, the sensitivity of inflation to Planck scale physics, and the fact that ultraviolet completions of inflation invariably involve extra fields coupled to the inflaton, indicate that these models constitute at best a phenomenological description that emerges from a more realistic physical framework.

LABORATOIRE

ASTROPARTICULE & COSMOLOGIE

Théorie