Online Seminars

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The workshop continues...





Date : 15th of April, 17:00 CET

Link :

Speaker : Carlos Hoyos (University of Oviedo)

Title: Geometry, duality and odd transport in flatland


AbstractEffective theories are very useful to extract transport properties at long wavelengths, which can be done by studying the response to external sources and geometric deformations. In two dimensions one can also take advantage of particle-vortex duality which allows a similar description for Quantum Hall states and superfluids/superconductors using statistical gauge fields. I will discuss the effective theory description of two-dimensional states with broken parity and time-reversal invariance and the relation between odd transport and symmetry and topological properties of the state.



Date : 22nd of April, 17:00 CET

Link : coming soon

Speaker : Jan Zaanen (Instituut-Lorentz and University of Leiden)


Title: Holography in the lab: are the killer aps around the corner?


AbstractDealing with nature, being on the right track may have the effect that out of the blue surprises starts raining down in the laboratory. AdS/CMT may be in such a state. How ARPES disqualified the cuprate quantum critical point proving the presence of holography style strange metal phases. How graphene style nano-transport devices appear to pick up hydrodynamical electron flow in such a strange metal, seemingly implying the governance of the minimal viscosity. How transport properties in the cuprate spin stripes in very large magnetic fields reveal the fingerprints of the “second” quantum critical sector. When time- and co-authors permit, how the same stuff lingers on in the overdoped regime co-existing with an unreasonable Fermi-liquid.




Date : 24nd of April, 10:00 CET

Link : coming soon

Speaker : Li Li (Institute of Theoretical Physics, Chinese Academy of Science ITP-CAS)


Title: Intertwined orders and Fermionic Spectral Functions in Holography


AbstractSpatially modulated black holes are constructed, which allow a U(1) symmetry and translational invariance to be broken spontaneously at the same time. Our construction provides an example of a system where various orders are intertwined with each other and have a common origin. In particular, there is a dual description for the pair density wave, in which the superconducting order parameter is spatially modulated but has a zero average. The fermionic spectral function is then investigated in uni-directional striped phases, where the breaking of translational invariance can be generated either spontaneously or explicitly. Spectral weight suppression and fermi arc-like features with strong holographic lattices have been uncovered.




Date : 30th of April, 17:00 CET

Link : coming soon

Speaker : Luca Delacretaz (University of Chicago)


Title: Hydrodynamic Fluctuations


Abstract: TBA





Date : 5th of May, 16:00 CET

Link : coming soon

Speaker : Eric Mefford (École Polytechnique Paris)


Title: Transport in clean quantum critical superfluids


AbstractThe hydrodynamic regime of superfluids in systems like 4He has been well understood since the seminal work of Landau and Tisza. A fundamental assumption in much subsequent work is the low-temperature dominance of the superfluid phonon which leads to universal behavior in transport that is characterized by the phonon sound speed. I will discuss investigations of the two-fluid model of superfluids near an underlying quantum critical phase and establish criteria for the breakdown of this assumption which leads to novel transport behavior. A surprising result is the non-vanishing of the charge density of the fluid's normal component at zero temperature. I will illustrate these results with some holographic models.


Date : 12th of May, 16:00 CET

Link : coming soon

Speaker : Chandan Setty(University of Florida)


Title: Pairing instability on Luttinger Surfaces : SYK thermodynamics from a condensed matter perspective


AbstractSuperconductivity results from an instability of the Fermi surface -- contour of poles of the single particle propagator -- to an infinitesimally small attractive inter-particle attraction. In this talk, I will instead discuss the analogous problem on a model Luttinger Surface -- contour of zeros of the Green function.   

Unlike a Fermi surface, in the presence of an attractive potential, the model exhibits a quantum phase transition from a non-Fermi liquid to a superconducting state. Crucially,  pair-fluctuations close to the transition resemble well-studied models with gravity duals such as SYK. I will discuss implications of this result to microscopic models describing  Mott physics.



Date : 19th of May, 16:00 CET

Link : coming soon

Speaker : Davison Richard (Heriot-Watt University)


Title: Relations between transport and chaos in holographic theories


AbstractI will describe recent work illustrating general relations between the transport properties and chaotic properties of quantum field theories with holographic duals. I will firstly show how a simple analysis of near-horizon dynamics yields exact constraints on the spectrum of collective excitations. I will then describe how this can be exploited to identify a universal feature in the spectrum, and its implications for the collective transport properties of strongly interacting field theories with gravity duals.







Date : 26th of May, 16:00 CET

Link : coming soon

Speaker : Grozdanov Saso (MIT & University of Ljubljana)


Title: Generalised global symmetries and applications


AbstractGeneralised global symmetries or higher-form symmetries are a novel concept in quantum field theories that enables the formulation of a conservation of higher-dimensional objects. While standard (zero-form) symmetries act on local operators, a one-form symmetry can act on the one-dimensional Wilson line. These symmetries can be discrete, continuous, broken, anomalous, etc. In Nature, the simplest realisation of a continuous one-form symmetry stems from the conservation of the number of magnetic flux lines due to the absence of magnetic monopoles. The fact that such symmetries must play a crucial role in the formulation of effective field theories has led to the first, and so far best understood application: the theory of magnetohydrodynamics, which is the theory of long-range excitations in magnetised plasmas. In this review talk, I will first discuss the mathematical details of generalised global symmetries. I will then focus on the new theory of magnetohydrodynamics and summarise how it interpolates between previously known theories (standard non-relativistic magnetohydrodynamics, force-free electrodynamics, dynamics of fermions in the lowest Landau level) and enables to find their systematic corrections. The presentation of other applications of generalised global symmetries will include generic string liquids, superfluids and the theory of elasticity. Finally, I will show how generalised global symmetries can be implemented in AdS/CFT and discuss how the construction of the holographic dual to a plasma with dynamical magnetic fields gives rise to a strongly coupled field theory with dynamical photons and extends magnetohydrodynamics into the ultraviolet regime.



Date : TBA

Link : coming soon

Speaker : Martin Ammon (University of Jena)

Title: Anomalous hydrodynamics and strong external magnetic fields


Abstract: TBA





Date : TBA

Link : coming soon

Speaker : Sebastian Grieninger (University of Jena)


Title: TBA


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