Transport in Anisotropic Superfluids: A Holographic Description

title: Drag force in a strongly coupled anisotropic plasma
abstract: 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: 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: Quarkonium dissociation by anisotropy
abstract: A bstractWe compute the screening length for quarkonium mesons moving through an anisotropic, strongly coupled $ \mathcal{N} $ = 4 super Yang-Mills plasma by means of its gravity dual. We present the results for arbitrary velocities and orientations of the mesons, as well as for arbitrary values of the anisotropy. The anisotropic screening length 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. For generic motion we find that: (i) mesons dissociate above a certain critical value of the anisotropy, even at zero temperature; (ii) there is a limiting velocity for mesons in the plasma, even at zero temperature; (iii) in the ultra-relativistic limit the screening length scales as (1 − v2)ϵ with ϵ = 1/2, in contrast with the isotropic result ϵ = 1/4.

title: New transport properties of anisotropic holographic superfluids
abstract: A bstractWe complete the analysis of transport phenomena in p-wave superfluids within gauge/gravity duality, using the SU(2) Einstein-Yang-Mills model with backreaction. In particular, we analyze the fluctuation modes of helicity zero in addition to the helicity one and two modes studied earlier. We compute a further transport coefficient, associated to the first normal stress difference, not previously considered in the holographic context. In the unbroken phase this is related to a minimally coupled scalar on the gravity side. Moreover we find transport phenomena related to the thermoelectric and piezoelectric effects, in particular in the direction of the condensate, as well as the flexoelectric effect. These are similar to phenomena observed in condensed matter systems.

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: Supersymmetric partners for the associated Lamé potentials
abstract: The general solution of the stationary Schrödinger equation for the associated Lamé potentials with an arbitrary real energy is found. The supersymmetric partners are generated by employing seed solutions for factorization energies inside the gaps.

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 .

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.