Séminaire

The EU Underground Laboratories Workshop will be held at the Gran Sasso Laboratory, Italy, on April 28-29.

The Workshop aims to reinforce the network between EU Underground Laboratories in order to develop a strong synergy to face next generation experiments for rare events searches. The meeting will focus on reviewing the existing facilities and planned new ones for supporting research activities, strategy for collaboration and work load sharing, training and networking, interaction with the APPEC community.

The Second Joint ECFA-NuPECC-ApPEC Seminar (JENAS) will be held from May 3rd to 6th, 2022 in Madrid  
The seminar is a prestigious joint meeting of particle, nuclear and astroparticle physics scientific communities exploring synergies and highlighting recent achievements and challenges.

The participants represent scientists of the three communities, the funding agencies (important for our field) as well as big international projects and collaborations. 

After recalling the definition of a black hole and its basic properties (mass, angular momentum and area), the seminar will focus on links between black holes and gravitational waves. In particular black hole thermodynamics will be discussed in connection with gravitational wave emission, as well as the so-called black hole information paradox.

Contact kleyde@apc.in2p3.fr for zoom meeting details. 

In this seminar I will present the first direct numerical simulation of gravitational wave turbulence (Galtier & Nazarenko, PRL 127, 131101, 2021). General relativity equations are solved numerically in a periodic box with a diagonal metric tensor depending on two space coordinates only (Hadad-Zakharov metric) and with an additional small-scale

Gravitational wave (GW) standard sirens are well-established probes with which one can measure cosmological parameters, and are complementary to other probes like the cosmic microwave background or supernovae standard candles. I will focus on dark GW sirens, specifically binary black holes (BBHs) for which there is only GW data. Relying on the assumption of a source mass model for the BBH distribution, we consider four models that are representative of the BBH population observed so far.

Within the framework of the inflationary paradigm, it is well-known that correlation functions (or in general bi-linear observables) of quantum fields on a curved background suffer from divergences. In general, the presence of ultraviolet (UV) divergences due to fluctuations on arbitrary short scales is a common aspect of quantum field theory.

I will discuss classes of hidden symmetries of gravity and their consequences for black holes and compact objects. 

I will discuss our recent work Phys.Rev.Lett. 128 (2022) 4, 041301 in which we present a simple class of mechanical models where a canonical degree freedom interacts with another one with a negative kinetic term, i.e., with a ghost. We prove analytically that the classical motion of the system is completely stable for all initial conditions, notwithstanding that the conserved Hamiltonian is unbounded from below and above. Numerical computations fully supported this.

Light dark matter candidates, such as axions and hidden photons, call for new ideas in direct detection. I discuss the recently proposed strategy of searching for e.g. axions using tunable cryogenic plasmas. The plasma haloscope enables resonant conversion by matching the axion mass to a plasma frequency, therefore converting axions to plasmons. Metamaterials are promising candidates, as the plasma frequency can be tuned. Besides axions, other dark matter candidates, such as hidden photons and scalars, can be successfully targeted with a plasma haloscope.

Black holes with masses ~1 Msun cannot be produced via stellar evolution. A popular scenario of their formation involves transmutation of neutron stars - by accumulation of dark matter triggering gravitational collapse in the star centers. We show that this scenario can be realized in the models of bosonic dark matter despite the apparently contradicting requirements on the interactions of dark matter particles: on the one hand, they should couple to neutrons strongly enough to be captured inside the neutron stars, on the other, their loop-induced self-interactions impede collapse.