Drag force in a strongly coupled anisotropic plasma
A bstractWe calculate the drag force experienced by an infinitely massive quark propagating at constant velocity through an anisotropic, strongly coupled $ \mathcal{N} = 4 $ plasma by means of its gravity dual. We find that the gluon cloud trailing behind the quark is generally misaligned with the quark velocity, and that the latter is also misaligned with the force. The drag coefficient μ can be larger or smaller than the corresponding isotropic value depending on the velocity and the direction of motion. In the ultra-relativistic limit we find that generically μ ∝ p. We discuss the conditions under which this behaviour may extend to more general situations.

title: Towards collisions of inhomogeneous shockwaves in AdS
abstract: A bstractWe perform a numerical simulation of the evolution of inhomogeneities with transverse profile in a collision of gravitational shockwaves in asymptotically anti-de Sitter spacetime. This constitutes a step closer towards an accurate holographic description of the thermalization of a strongly coupled plasma, which can model the dynamics of heavy ion collisions. The results indicate that the considered inhomogeneities typically become hydrodynamical earlier or at the same moment when hydrodynamics applies to the background, even though they decay slowly.

title: Using black hole physics to compute the energy loss of a quark in strongly coupled QCD
abstract: The AdS/CFT duality can be applied to study strongly coupled regimes of QCD, such as the quark-gluon plasma. Gravity is a key factor in the understanding of the duality and an intriguing correspondence between the gravitational properties of higher-dimensional black holes and quark/gluon physics can be established. In this context, I will show that the dual theory allows us to identify a new mechanism for the energy loss of a deconfined quark in this plasma, which can be described as Cherenkov radiation of vectorial mesons. The corresponding results might be observed in heavy-ion collision experiments.

title: Jet quenching in a strongly coupled anisotropic plasma
abstract: A bstractThe jet quenching parameter of an anisotropic plasma depends on the relative orientation between the anisotropic direction, the direction of motion of the parton, and the direction along which the momentum broadening is measured. We calculate the jet quenching parameter of an anisotropic, strongly coupled $ \mathcal{N} = 4 $ plasma by means of its gravity dual. We present the results for arbitrary orientations and arbitrary values of the anisotropy. The anisotropic value can be larger or smaller than the isotropic one, and this depends on whether the comparison is made at equal temperatures or at equal entropy densities. We compare our results to analogous calculations for the real-world quark-gluon plasma and find agreement in some cases and disagreement in others.

title: Cherenkov mesons as in-medium quark energy loss
abstract: We recently showed that a heavy quark moving sufficiently fast through a quark-gluon plasma may lose energy by Cherenkov-radiating mesons . Here we review our previous holographic calculation of the energy loss in $ \mathcal{N} = 4 $ Super Yang-Mills and extend it to longitudinal vector mesons and scalar mesons. We also discuss phenomenological implications for heavy-ion collision experiments. Although the Cherenkov energy loss is an $ \mathcal{O}\left(  \left/ {{{N_c}}} \right.}} \right) $ effect, a ballpark estimate yields a value of dE/dx for Nc = 3 which is comparable to that of other mechanisms.

title: Nonlocal SUSY deformations of periodic potentials
abstract: Irreducible 2-order Darboux transformations are applied to the periodic Schrödinger’s operators. It is shown that for the pairs of factorization energies inside of the same forbidden band they can create new non-singular potentials with periodicity defects and bound states embedded into the spectral gaps. The method is applied to the Lamé and periodic piece-wise transparent potentials. An interesting phenomenon of translational Darboux invariance reveals nonlocal aspects of the supersymmetric deformations. PACS: 03.65.Ge; 03.65.Fd; 03.65.Ca

title: Varying electric charge in multiscale spacetimes
abstract: We derive the covariant equations of motion for Maxwell field theory and electrodynamics in multi-scale spacetimes with weighted Laplacian. An effective spacetime- dependent electric charge of geometric origin naturally emerges from the theory, thus giving rise to a varying fine-structure constant. The theory is compared with other varying- coupling models, such as those with a varying electric charge or varying speed of light. The theory is also confronted with cosmological observations, which can place constraints on the characteristic scales in the multi-fractional measure. We note that the model considered here is fundamentally different from those previously proposed in the literature, either of the varying-e or varying-c persuasion.

title: Exact solution of Dirac electron in graphene under SUSY generated magnetic fields
abstract: We use supersymmetry transformations to obtain new one parameter family of inhomogeneous magnetic fields B = B(x, λ)ez for which the massless Dirac electron possesses exact solution. The inhomogeneity appearing in B(x, λ) can be controlled by the parameter λ. The obtained magnetic fields are interpreted as deformed variants of some physically attainable well known magnetic fields. The particular example, when a constant magnetic field is deformed, is considered to show that equidistant Landau levels exist even in the presence of an infinite number of specially designed inhomogeneous magnetic fields.

title: New hydrogen-like potentials
abstract: Using the modified factorization method employed in , we construct a new class of radial potentials whose spectrum for l=0 coincides exactly with that of the hydrogen atom. A limiting case of our family coincides with the potentials previously derived by Abraham and Moses .