Browsing by Subject "hep-th"

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  • Alanen, Janne; Keski-Vakkuri, Esko; Kraus, Per; Suur-Uski, Ville (2009)
    We compute AC electrical transport at quantum Hall critical points, as modeled by intersecting branes and gauge/gravity duality. We compare our results with a previous field theory computation by Sachdev, and find unexpectedly good agreement. We also give general results for DC Hall and longitudinal conductivities valid for a wide class of quantum Hall transitions, as well as (semi)analytical results for AC quantities in special limits. Our results exhibit a surprising degree of universality; for example, we find that the high frequency behavior, including subleading behavior, is identical for our entire class of theories.
  • Herranen, Matti; Kainulainen, Kimmo; Matti Rahkila, Pyry (2010)
    We reformulate and extend our recently introduced quantum kinetic theory for interacting fermion and scalar fields. Our formalism is based on the coherent quasiparticle approximation (cQPA) where nonlocal coherence information is encoded in new spectral solutions at off-shell momenta. We derive explicit forms for the cQPA propagators in the homogeneous background and show that the collision integrals involving the new coherence propagators need to be resummed to all orders in gradient expansion. We perform this resummation and derive generalized momentum space Feynman rules including coherent propagators and modified vertex rules for a Yukawa interaction. As a result we are able to set up self-consistent quantum Boltzmann equations for both fermion and scalar fields. We present several examples of diagrammatic calculations and numerical applications including a simple toy model for coherent baryogenesis.
  • Keranen, V; Keski-Vakkuri, E; Nowling, S; Yogendran, K P (2009)
    We construct dark soliton solutions in a holographic model of a relativistic superfluid. We study the length scales associated with the condensate and the charge density depletion, and find that the two scales differ by a non-trivial function of the chemical potential. By adjusting the chemical potential, we study the variation of the depletion of charge density at the interface.
  • Jokela, Niko; Lifschytz, Gilad; Lippert, Matthew (2014)
  • Ihl, Matthias; Jokela, Niko; Zingg, Tobias (2016)
    Anyons have garnered substantial interest theoretically as well as experimentally. Due to the intricate nature of their interactions, however, even basic notions such as the equation of state for any kind of anyon gas have eluded a profound understanding so far. Using holography as a guiding principle, we propose a general method for an alternative quantization of electromagnetic degrees of freedom in the gravitational dual to obtain an effective physical description of strongly correlated anyonic systems. We then demonstrate the application of this prescription in a toy model of an anyonic fluid at finite charge density and magnetic field, dual to a dyonic black brane in AdS_4, and compute the equation of state and various transport coefficients explicitly.
  • Keränen, Ville; Keski-Vakkuri, Esko; Nowling, Sean; P. Yogendran, K. (2010)
    We begin an investigation of inhomogeneous structures in holographic superfluids. As a first example, we study domain wall like defects in the 3+1 dimensional Einstein-Maxwell-Higgs theory, which was developed as a dual model for a holographic superconductor. In [1], we reported on such "dark solitons" in holographic superfluids. In this work, we present an extensive numerical study of their properties, working in the probe limit. We construct dark solitons for two possible condensing operators, and find that both of them share common features with their standard superfluid counterparts. However, both are characterized by two distinct coherence length scales (one for order parameter, one for charge condensate). We study the relative charge depletion factor and find that solitons in the two different condensates have very distinct depletion characteristics. We also study quasiparticle excitations above the holographic superfluid, and find that the scale of the excitations is comparable to the soliton coherence length scales.
  • Panero, Marco (2012)
    Generalizations of QCD in which the number of colors N is taken to infinity are characterized by profound mathematical properties, with far-reaching implications for fundamental problems and for phenomenological issues alike. In this contribution, after a brief introduction to the theoretical motivation for studying the large-N limit, the role of lattice computations in large-N gauge theories is discussed, and a selection of interesting results obtained in recent years is highlighted. Finally, some promising research directions for future studies are pointed out.
  • Caselle, Michele; Castagnini, Luca; Feo, Alessandra; Gliozzi, Ferdinando; Panero, Marco (2010)
  • Caselle, Michele; Castagnini, Luca; Feo, Alessandra; Gliozzi, Ferdinando; Panero, Marco (2011)
  • Caselle, Michele; Feo, Alessandra; Panero, Marco; Pellegrini, Roberto (2011)