Quantum effects on the inner (Cauchy) horizon of rotating black holes

All black holes in the Universe are believed to be rotating. This poses interesting questions, since rotating black hole solutions of Einstein’s equations of General Relativity possess a so-called Cauchy horizon in their interior, which threatens the predictability of Einstein’s theory. However, these exact solutions may not model sufficiently accurately black holes in Nature, which have classical matter in their neighbourhood and, furthermore, are inevitably surrounded by a quantum vacuum (which is responsible for Hawking radiation).

Theory group seminar : Properties of average distances and emergent causality

Title: Properties of average distances and emergent causality

Abstract: In the presence of a (quantum or classical) statistical ensemble of metrics one can consider averages of distances between points/events, as long as a prescription is assigned for identifying such points.

Unveiling Positrons in Galactic Cosmic Rays

The spectrum of positrons in cosmic rays is currently measured with unprecedented precision by AMS-02 up to TeV energies, and represents an unique probe for the local properties of our Galaxy. Currently, its interpretation is still debated, especially for the excess above 10 GeV which suggests the presence of a local, primary source.
Recently, the observation of extended gamma-ray halos around Galactic pulsars has opened a new window to constrain the acceleration and propagation of positrons in our Galaxy.

Multimessenger prospects for massive black hole binaries in LISA

In 2034 the Laser Interferometer Space Antenna (LISA) will detect the coalescence of massive black hole binaries (MBHBs) from 10^5 to 10^7 solar mass up to z~10. The gravitational wave (GWs) signal is expected to be accompanied by a powerful electromagnetic (EM) counterpart, from radio to X-ray, generated by the gas accreting on the binary.

Summary of workshop on High energy Cosmic Rays and Neutrinos

In this talk I'll give recent news from workshop on Cosmic Rays and Neutrinos which was organised in APC and UCLouvain. I'll show several new experimental and theoretical results presented at this workshop
from the fields of high energy neutrinos, gamma-ray astronomy and cosmic rays.

Quantum orientations in the plane: Malus’ law (1808) and Stokes parameters (1852) for polarisation of light viewed as a quantum measurement

Two aspects of Positive Operator Valued Measures (POVM) on the Euclidean plane (a basic Hilbert space!) are presented, namely their status as quantum observables and their role as quantizers in the integral quantization procedure. The compatibility of POVMs in the ensuing quantum formalism is discussed, and a Naimark dilation is found for the quantum operators. The relation with Toeplitz quantization is explained. Within this framework, we describe the linear polarization of the light with the use of Stokes parameters and its interaction with a polariser as a quantum measurement (Malus’ law).

Detecting axion dark matter with chiral magnetic effects

Observing quantum gravity in gravitational waves

Gravity can be embedded into a renormalizable theory by means of adding quadratic in curvature terms.
However, this at first leads to the presence of the Weyl ghost. It is possible to get rid of this ghost if the
locality assumption is weakened and the propagator of the graviton is represented by an entire function
of the d'Alembertian operator without new poles and zeros. Models of this type admit a cosmological
solution describing the R^2, or Starobinsky, inflation. We study graviton production after inflation in

Tests of gravity with DES Year 3 weak lensing

The new weak lensing measurements from the first three years of observation by the Dark Energy Survey offer a unique opportunity to constrain deviations from General Relativity, our theory of gravity. Weak gravitational lensing is indeed a powerful probe of the growth of structures. As such it offers a window on the laws of gravity on cosmological scales. We thus used DES Year 3 weak lensing data to test the validity of General Relativity (GR) to a new regime, and explore modifications to GR as an alternative to dark energy.

Scalar-vector gauge unification and quantum de Sitter geometry

We consider the massless minimally coupled scalar field in the de Sitter ambient space formalism as a gauge potential or connection field. We construct the scalar gauge theory by helping an arbitrary constant five-vector field B analogous to the standard gauge theory. The Lagrangian density of the interaction between the scalar and spinor fields is presented in this framework. The Yukawa potential can be extracted from this Lagrangian density at the null curvature limit by an appropriate choice of a constant five-vector field.

LABORATOIRE

ASTROPARTICULE & COSMOLOGIE

Séminaire