Research

I work in theoretical research at the interface between particle physics and cosmology, especially on models of the early universe and their experimental signatures, baryogenesis, dark matter, primordial gravitational waves and Higgs boson cosmology. My main contributions to this field have been:

• to reconcile the existence of extra spatial dimensions with standard Friedmann cosmological expansion [3].
• to propose the lightest Kaluza-Klein particle as a viable dark matter candidate [9, 10, 11].
• to study the nature of the electroweak phase transition in various extensions of the Standard Model [2, 16, 22] and the consequences of a modified cosmological expansion at the electroweak epoch. In [41, 58, 60, 61], we have outlined the peculiar cosmological properties characterizing some models of strong dynamics at the TeV scale. In particular, we motivated the mechanism of cold baryogenesis in this context [42].
• to show that detection of a stochastic background of Gravity Waves at the space-interferometer LISA would be a major experimental implication of the Randall-Sundrum model [22].
• I have been particularly interested in the possibility of probing early universe phase transitions with upcoming gravity wave experiments [21] and I have been for instance advertising the relevance of LISA for electroweak scale physics [21, 52].
• I have been involved in analytic calculations of the gravity wave spectrum produced during first order phase transitions [25, 30, 32] and in studies of the energy budget associated with bubble growth [35].
• I have also been working on collider phenomenological studies. I have studied the LHC prospects for pair production and decay of new heavy bottom quarks [23]. In [27] we proposed a refined analysis (in the same-sign dilepton channel) that applies as well to the pair-production of new quarks carrying electric charge Q_e=5/3, which are well-motivated in a class of composite Higgs models. I have been interested in searching for new physics in LHC events involving top quarks especially four-top production [36, 37, 38]. Effective field theory (EFT) approaches to top quark pair production, same-sign top pair production (in relation with the $t\bar{t}$ forward-backward asymmetry) and t tbar H production were investigated respectively in [39] , [40] and [44]. I have co-supervised PhD students Lea Gauthier and Romain Kukla for their analysis related to top partners and search for four-top events at the LHC with the ATLAS detector.
• As far as dark matter (DM) is concerned, I have also investigated the case of heavy Dirac neutrinos [14, 17, 24] and contributed to review chapters in the book ``Particle dark matter" [31]. In [33, 46], we showed that in a well-motivated class of WIMP models connected to the top quark, large gamma ray lines are naturally expected from DM annihilations in the center of our galaxy. In [45], we computed all one-loop annihilation channels responsible for gamma ray lines and continuum in a large class of DM models and studied in details prospects for indirect detection with gamma-ray telescopes.
• In [43], we provided the first detailed study of the effect of dark matter/anti dark matter oscillations during freese-out, showing how these oscillations reopen the parameter space of asymmetric dark matter and naturally enable TeV scale asymmetric dark matter to have the correct relic abundance.
• In [47], we proposed a theory of baryogenesis does not require B nor L violation beyond the SM. Our idea is to use instead the Higgs chemical potential to link an asymmetry in a new physics sector to the visible matter asymmetry, ultimately biasing sphalerons into generating B+L. We call this mechanism Ê``Higgsogenesis''. Inversely, we proposed that a Higgs asymmetry can generate asymmetric dark matter.
• In [50], I showed that strong CP violation from the QCD axion can explain the matter antimatter asymmetry of the universe in the context of cold baryogenesis.
• In [51], we showed that the mechanism of cosmological relaxation of the electroweak scale addressing the hierarchy problem up to 10^8 GeV does not require any new physics at the EW scale. In [55], we discussed constraints on the relaxion mechanism from string theory. In [62], we showed how the relaxion mechanism can be implemented independently from inflation.
• In [53, 54, 56, 57, 59, 60, 61, 63], we initiated works on flavour cosmology and the flavour-EW symmetry breaking interplay.