Holographic phase diagram of quark-gluon plasma formed in heavy-ion collisions

We use a holographic dual model for the heavy-ion collision to obtain the phase diagram of the quark-gluon plasma (QGP) formed at a very early stage just after the collision. In this dual model, colliding ions are described by the charged gravitational shock waves. Points on the phase diagram correspond to the QGP or hadronic matter with given temperatures and chemical potentials. The phase of the QGP in dual terms is related to the case where the collision of shock waves leads to the formation of a trapped surface. Hadronic matter and other confined states correspond to the absence of a trapped surface after collision. In the dual language, the multiplicity of the ion collision process is estimated as the area of the trapped surface. We show that a nonzero chemical potential reduces the multiplicity. To plot the phase diagram, we use two different dual models of colliding ions, the pointlike and the wall shock waves, and find that the results agree qualitatively (based on JHEP05(2012)117).

Strong confinement of a water monolayer induces 3D-like behavior

Hydrophobic confinement allows to supercool liquid water below its temperature of crystal homogeneous nucleation, making accessible to experiments a thermodynamic region that cannot be entered in bulk water. However, it is debated how the confinement affects each property of water when compared to bulk. Here, we investigate, using Monte Carlo simulations and a coarse-grained model of water, the low temperature phase diagram of a water monolayer confined between hydrophobic plates. By defining the appropriate order parameter and performing finite size scaling, we show that the model has a liquid-liquid critical point (LLCP), between two liquids with different density and energy, that belongs to the universality class of the the two-dimensional Ising model. Surprisingly, upon decreasing the size of the system, the universality class approaches continously the three-dimensional Ising model, as it has been found in bulk water. Therefore, our results lead to the unexpected conclusion that the smaller the confined monolayer, the closer the critical behavior to bulk water at low temperature.

Dark Matter and Fundamental Physics searches with GeV-TeV gamma-rays

Ground-based Imaging Cherenkov Telescopes (IACTs) are gamma-ray detectors for non-thermal phenomena in the VHE range (GeV-TeV). Moved by the success of the current generation of experiments, a new great project of world-wide scale is being run, dubbed CTA (Cherenkov Telescope Array). Besides gamma-ray astronomy, IACTs can also be used as observatories for fundamental physics searches (dark matter, quantum gravity, axion-like particles), and even as cosmic-ray detectors (electrons, heavy nuclei), neutrino detectors (tau-induced showers) or detector for other exotic particles. In this presentation, I will discuss the current results in these fields, and discuss some outlooks for CTA.

Exact results for static and radiative fields of a quark in N=4 super Yang-Mills

We present the main results of hep-th/1106.5412 and hep-th/1202.5292. This includes both the computation of the expectation value of the N=4 SU(N) SYM Lagrangian density operator in the presence of an infinitely heavy static particle in the symmetric representation and that of the energy radiated by an infinitely massive particle transforming in the symmetric or antisymmetric representation of the gauge group, and moving in the vacuum, to all orders in 1/N and for large ’t Hooft coupling. Next, we argue that the agreement between these two results go beyond the probe approximation, which leads us to propose an exact formula for the total energy loss by radiation of a heavy particle in the fundamental representation.