Black hole perturbations in higher-order scalar-tensor theories: initial value problem and dynamical stability

We propose a physically sensible formulation of initial value problem for black hole perturbations in higher-order scalar-tensor theories. As a first application, we study monopole perturbations around stealth Schwarzschild solutions in a shift- and reflection-symmetric subclass of DHOST theories. In particular, we investigate the time evolution of the monopole perturbations by solving a two-dimensional wave equation and analyze the Vishveshwara’s classical scattering experiment, i.e., the time evolution of a Gaussian wave packet.

Light Propagation in Massive, Non-Linear, Standard-Model Extension Theories

Astrophysical observations are largely based on electromagnetic signals still read with the Maxwellian massless and linear theory, possibly an approximation of a larger theory, as Newtonian gravity is for Einsteinian gravity in weak fields. Photons are the sole free massless particles in the Standard-Model (SM). Apart from massive formalisms (de Broglie-Proca, Bopp, Stueckelberg and others), the SM Extension dresses the photon of a mass dependent from the Lorentz-Poincaré symmetry violation.

EU Underground Laboratories Workshop 28-29 April 2022

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.

2nd Joint ECFA-NuPECC-APPEC Seminar

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.

Black holes: myths and facts

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.

Direct Evidence of a Dual Cascade in Gravitational Wave Turbulence

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

Current and future constraints on cosmology and modified gravitational wave friction from binary black holes

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.

On Adiabatic Renormalization with a Physically Motivated Infrared Cut-Off

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.

Hidden symmetries of black holes

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

Ghosts without Runaway

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.

LABORATOIRE

ASTROPARTICULE & COSMOLOGIE

Séminaire