Novel lattice simulations for transport coefficients in gauge theories


Seminar on Theory of hadronic matter under extreme conditions

Date and Time: Wednesday, 14 February 2018, at 2:30 PM

Venue: Blokhintsev Hall (4th floor), Bogoliubov Laboratory of Theoretical Physics

Seminar topic: “Novel lattice simulations for transport coefficients in gauge theories”

Speaker: Felix Ziegler (Institute for Theoretical Physics, Heidelberg University)


Transport coefficients, such as the temperature-dependent shear and bulk viscosities, are essential QCD ingredients in the hydrodynamical description of relativistic heavy-ion collisions. The extraction of the transport coefficients from lattice simulations is extremely challenging since a reliable spectral reconstruction from Euclidean data at low frequencies is required. In standard simulations at finite temperature this reconstruction is based on the discrete Matsubara frequencies, and is exponentially hard: the thermal part of the low frequency information is hidden in the thermal decay of the Euclidean data at large frequencies.
In order to overcome this limitation, we apply the novel approach for thermal fields on the lattice [1] to gauge fields [2]. The formalism operates in a non-compact imaginary time domain that leads to continuous imaginary time frequencies. The quantum evolution is formulated as an initial value problem and the thermal initial conditions are supplied by a standard lattice simulation.
We present results for the energy momentum tensor correlation function in SU(2) Yang-Mills theory in the confined and deconfined phase. Convergence properties to the standard results at nite Matsubara frequencies are discussed. Moreover we show first results for the corresponding spectral functions obtained via the Bayesian BR method [3]. We assess the viability of the method applied to gauge fields and its ability to provide a robust estimate for transport coefficients.

[1] J.M. Pawlowski, A. Rothkopf, arXiv:1610.09531 [hep-lat]
[2] J.M. Pawlowski, A. Rothkopf and F. Ziegler (in progress)
[3] Y.Burnier, A.Rothkopf, PRL 111, 182003 (2013)