Old results and recent developments on the theoretical description of elementary particles with "continuous" spin will be reviewed. At free level, these fields are described by unitary irreducible representations of the isometry group (either Poincare or anti de Sitter group) with an infinite number of physical degrees of freedom per spacetime point. We will mention a list of new results, in particular on their cubic interactions, as well as important issues that remain open.

In the next few years, we are going to probe the low-redshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy. A particularly useful description of dark energy is through the Effective Field Theory of Dark Energy, which assumes that dark energy is the Goldstone boson of broken time translations. Such a formalism makes it easy to ensure that predicted signatures are consistent with well-established principles of physics.

In this seminar I will describe a holographic approach to QCD where 
conformal symmetry is broken explicitly in the UV by a relevant operator 
O. This operator maps to a five dimensional scalar field, the dilaton, 
with a massive term. Implementing also the IR constraint found by 
Gursoy, Kiritsis and Nitti, an approximate linear glueball spectrum is 
obtained which is consistent with lattice data. Finally, I will describe 
the evolution of the model parameters with the conformal dimension of O. 
This will suggest a map between the QCD anomaly and the trace anomaly of 

What is the holographic dual of an ordinary solid? Using insight from effective field theory (EFT), I will argue that an answer is provided by an SO(d) magnetic monopole in (d+1)-dimensional AdS space. We call such field configuration “solidon”. The low-energy spectrum of the boundary theory can be derived analytically from the gravity dual, and the result confirms that the effective theory consists of a set of phonons having dispersion relations that match those expected from EFT.

Random matrices are ubiquitous in modern theoretical physics and provide insights on a wealth of phenomena, from the spectra of heavy nuclei to the theory of strong interactions or random two dimensional surfaces. The backbone of all the analytical results in matrix models is their 1/N expansion (where N is the size of the matrix). Despite early attempts in the '90, the generalization of this 1/N expansion to higher dimensional random tensor models has proven very challenging.