Séminaire

In the same spirit as The Oxford handbook of the history of Quantum Interpretations, the two days offer a historical overview of the contrasts that have been at the heart of quantum physics over the past 100 years. Drawing on the extensive expertise of several lecturers working in the fields of physics, history and philosophy.
Thus, the objective of these two days is to fuel the ongoing debate on the foundations of quantum mechanics by dealing with the major open questions concerning the interpretations of Quantum Mechanics.

Cosmological first-order phase transitions are said to be strongly supercooled when the nucleation temperature is much smaller than the critical temperature. They are typical of potentials which feature nearly scale-invariance, for which the bounce action decreases only logarithmically with time. The phase transition takes place slowly and the probability distribution of bubble nucleation time is maximally spread. Hubble patches which get percolated later than the average are hotter than the background after reheating and potentially collapse into black holes.

I will derive new classes of soft theorems for theories in which time symmetries (i.e., symmetries that involve the transformation of time, an example of which are Lorentz boosts) are spontaneously broken. The soft theorems involve unequal-time correlation functions with the insertion of a soft Goldstone in the far past. I will discuss explicit examples, which include the effective theory of a relativistic superfluid and inflationary cosmology.

Since the no-scalar-hair theorems of the 1970s, it has long been thought that four-dimensional, asymptotically flat black holes cannot support any kind of non-minimally coupled real scalar hair, if not for the controversial Bocharova-Bronnikov-Melnikov-Bekenstein (BBMB) black hole. However, the 2010s have seen renewed interest in the healthy, higher-order scalar-tensor theories which were described by Horndeski in 1974, and easily escape the assumptions of the no-hair arguments.

False vacuum decay (FVD) plays a vital role in many models of the early Universe, with important implications for inflation, the multiverse, and gravitational waves. However, we still lack a satisfying theoretical understanding of this process, with existing approaches working only in imaginary (Euclidean) time, and relying on numerous assumptions that have yet to be empirically tested. An exciting route forward is to use laboratory experiments which undergo transitions analogous to FVD, allowing nature to simulate all of the non-perturbative quantum effects for us.

Magnetic fields are ubiquitous on astrophysical and cosmological scales: from planets and stars to galaxies and galaxy clusters. Different observational methods infer a field strength of the order of microGauss and coherence scales reaching a few tens of kiloparsecs in galaxy clusters. Despite their ubiquity, the origin of these fields still remains unknown. It is commonly assumed that the observed fields are originated from either astrophysical or cosmological (primordial) weak seed magnetic fields that undergo efficient growth during structure formation.