Théorie

Black hole information loss and the measurement problem in quantum theory

We will briefly review the issue of "information loss" during the Hawking evaporation of a black hole, and argue that the quantum dynamical reduction theories, which have been developed to address the  measurement problem in quantum mechanics,  possess the elements to diffuse the ``paradox”  at the qualitative and at the quantitative level, leading to what seems to be an overall coherent picture.

 

Factorization of IR Dynamics: Soft Black Hole Hair as Soft Wigs

Conserved charges associated with large gauge symmetries and Bondi-Metzer-Sachs symmetries of asymptotically Minkowski spacetime have been recently shown to give new "soft hair" for black holes --beyond mass, charge and angular momentum.  In this talk, I will outline a study of the constraint on dynamics due to these new symmetries. I will prove that they only constrain long-time, infrared dynamics, in a way that is completely factorizable. Factorization implies in particular that soft hair does not constrain the ``hard" physical processes that account for black hole microstates.

Post-Newtonian order gravitational radiation

Post-Newtonian theory enables us to predict the waveform of the gravitational waves emitted by a system of two compact objects coalescing in its inspiral phase. State-of-the-art works provide the phase of the expected signal up to 3.5PN (i.e. up to 1/c^7). Comparison with numerical relativity, as well as the promising evolution of gravitational wave detectors incite us to pursue this computation to a higher order. In our current attempt, we are reaching the phase of the signal at the 4.5PN order (i.e. 1/c^9). For this purpose, the flux emitted by such a system has to be known at 4.5PN.

Revisiting supernova neutrino phenomenology with non-standard neutrino self-interactions

Neutrino self-interactions are known to lead to non-linear collective flavor oscillations in a core-collapse supernova. In this talk, I will point out new possible effects of non-standard self-interactions (NSSI) of neutrinos on flavor conversions in a two-flavor framework. I will show that, for a single-energy neutrino-antineutrino ensemble, a flavor instability is generated even in normal hierarchy for large enough NSSI.

Consistency relations of the large scale structure and how to break them

Upcoming cosmological experiments intend to exploit the large scale structure of the Universe to get a better understanding of the observed cosmic acceleration. By measuring the power spectrum, one can constrain the equation of state of dark energy, and galaxy surveys promise great improvement over the current constraints. Galaxy surveys can also be used to gather cosmological information beyond cosmic acceleration. For example, one can derive consistency relations that can relate the bispectrum to the power spectrum for example.

Dark energy without dark energy: Observational tests and theoretical challenges

I will give an overview of the timescape cosmology. It is assumed that inhomogeneities - voids, walls and filaments - modify the average background geometry of the universe, which is no longer a simple solution of Einstein's equations with homogeneous dust. To obtain a viable phenomenology without dark energy, I provide a framework for interpreting Buchert's backreaction formalism, by revisiting fundamental issues relating to the definition of gravitational energy in a complex geometry. Cosmic acceleration is realized as an apparent effect due both to backreaction

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