De Sitter braneworld and gravitational waves

We study the braneworld theory constructed by multi scalar fields. The model contains a smooth and infinitely large extra dimension, allowing the background fields propagating in it. We give a de Sitter solution for the four-dimensional cosmology as a good approximation to the early universe inflation. We show that the graviton has a localizable massless mode, and a series of continuous massive modes, separated by a mass gap. There could be a normalizable massive mode, depending on the background solution. The gravitational waves of massless mode evolve the same as the four dimensional theory, while that of the massive modes evolve greatly different from the massless mode.

Teleparallel gravity: Effects of torsion in 6D braneworlds

Braneworld models are interesting theoretical and phenomenological frameworks to search for new physics beyond the standard model of particles and cosmology. In this work, we discuss braneworld models whose gravitational dynamics is governed by teleparallel [Formula: see text] gravities. Here, we emphasize a codimension two-axisymmetric model, also known as a string-like brane. Likewise, in the 5D domain-wall models, the [Formula: see text] gravitational modification leads to a phase transition on the perfect fluid source providing a brane-splitting mechanism. Furthermore, the torsion changes the gravitational perturbations. The torsion produces new potential wells inside the brane core leading to a massless mode more localized around the ring structures. In addition, the torsion keeps a gapless nonlocalizable and a stable tower of massive modes in the bulk.

Quenches in initially coupled Tomonaga-Luttinger Liquids: a conformal field theory approach

We study the quantum quench in two coupled Tomonaga-Luttinger Liquids (TLLs), from the off-critical to the critical regime, relying on the conformal field theory approach and the known solutions for single TLLs. We consider a squeezed form of the initial state, whose low energy limit is fixed in a way to describe a massive and a massless mode, and we encode the non-equilibrium dynamics in a proper rescaling of the time. In this way, we compute several correlation functions, which at leading order factorize into multipoint functions evaluated at different times for the two modes. Depending on the observable, the contribution from the massive or from the massless mode can be the dominant one, giving rise to exponential or power-law decay in time, respectively. Our results find a direct application in all the quench problems where, in the scaling limit, there are two independent massless fields: these include the Hubbard model, the Gaudin-Yang gas, and tunnel-coupled tubes in cold atoms experiments.

Thick string-like braneworlds in f(T) gravity

We propose a codimension two warped braneworld model within the teleparallel [Formula: see text] gravity. Asymptotically, the bulk geometry converges to an [Formula: see text] spacetime whose cosmological constant is produced by the torsion parameters. Furthermore, the torsion induces an AdS-dS transition on the exterior region. As the torsion parameters vary, the brane undergoes a phase transition from a thick string-like brane into ring-like structures. The bulk-brane Planck mass ration is modified by the torsion. The analysis of the stress–energy condition reveals a splitting brane process satisfying the weak and strong–energy conditions for some values of the parameters. In addition, we investigate the behavior of the gravitational perturbations in this scenario. It turns out that the gravitational spectrum has a linear behavior for small masses and is independent of the torsion parameters for large masses. In the bulk, the torsion keeps a gapless nonlocalizable and stable tower of massive modes. Inside the brane core, the torsion produces new barriers and potential wells leading to small amplitude massive modes and a massless mode localized around the ring structures.

The future of gravitational theories in the era of the gravitational wave astronomy

We discuss the future of gravitational theories in the framework of gravitational wave (GW) astronomy after the recent GW detections (the events GW150914, GW151226, GW170104, GW170814, GW170817 and GW170608). In particular, a calculation of the frequency and angular dependent response function that a GW detector would see if massive modes from [Formula: see text] theories or scalar–tensor gravity (STG) were present, allowing for sources incident from any direction on the sky, is shown. In addition, through separate theoretical results which do not involve the recent GW detections, we show that [Formula: see text] theories of gravity having a third massless mode are ultimately ruled out while there is still room for STG having a third (massive or massless) mode and for [Formula: see text] theories of gravity having a third massive mode.

Recent progress in hard-thermal-loop QCD thermodynamics and collective excitations

I review recent developments in QCD thermodynamics and collective excitations from the hard-thermal-loop effective theory. I begin by motivating the discussion with open questions from heavy-ion collisions. I then discuss a finite-temperature and density calculation of QCD thermodynamics at NNLO from the hard-thermal-loop perturbation theory. Finally, I discuss a recent exploration of generalizing the hard-thermal-loop framework to the (chromo)magnetic scale g2T, from which a novel massless mode is uncovered.