Théorie

Astronomical sources are observed nowadays across different domains of electromagnetic spectrum (from radio to gamma-rays) and different astronomical "messengers" (photons, neutrinos, gravitational waves). Combining different types of observational data we have learned that some types of sources operate huge high-energy particle accelerators / colliders boosting particle energies to ten million times higher energies than reached at the Large Hadron Collider at CERN. 

The AdS/CFT correspondence give a new perspective both at strong coupling physics of quantum field theory and the nature of the gravitational interaction. This thesis will deal with analysing the physics of gauge theories at finite temperature and density, their phase diagrams and their consequences for the physics of neutron stars, strange stars,  black holes,  cosmological fluids and strange metals.

Scientific context

Cosmological inflation is a period of accelerated expansion that occurred at very high energy in the early Universe. During this epoch, vacuum quantum fluctuations were amplified to become large-scale cosmological perturbations that seeded the cosmic microwave background (CMB) anisotropies and the large-scale structure of our Universe.

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The future gamma-ray experiment CTA plans to measure the fluxes of blazars in the energy range from 30 GeV to 100 TeV with sensitivity 10 times superior to present measurements. Intergalactic magnetic fields can be measured through observations of the secondary photons through time delay in blazar flairs, signatures in spectra and extended emission around the point sources.

A major progress has been made in neutrino physics after the discovery of the neutrino oscillations. Crucial questions are being addressed experimentally and should receive an answer soon, including the absolute neutrino mass and mass ordering, the existence of sterile neutrinos and of CP violation in the lepton sector. Intriguing open issues also concern how neutrinos modify their flavor in astrophysical environments.

The origin of  very high energy astrophysical neutrinos recently discovered by IceCube experiment  at South Pole is still unknown.

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Context: 

L'objectif de la thèse est d'étudier les possibilités d'extensions d'un formalisme permettant de considérer des équations de champs en espace-temps courbes à quatre dimensions à partir d'équations de champs dans l'espace plat R6 Plus précisément il s'agirait d'étudier le possibilité de théories de champs dans R6 muni de la métrique (+,+,-,-,-,-) et leurs restrictions, en particulier, aux espaces de Robertson-Walker. L'intérêt d'un tel formalisme étant la possibilité d'utiliser le cadre a priori plus simple d'un espace plat pour l'étude de champs classiques et quantiques. Les différents résultats obtenus dans ce cadre peuvent donner lieu à des problématiques diverses de théorie des champs ou de formalisme.

The direct detection of Gravitational Waves (GWs) by the ground-based LIGO interferometers in 2015 has opened up gravitational wave astronomy in the regime of high-frequencies.  New sources have already been found – namely black-holes with masses larger than those expected from remnants of supernovae explosions and stellar evolution – and it is likely that other unexpected phenomena will be revealed by GW observations in the low redshift universe.