Microcausality and positivity constrain Green's functions to be analytic in the forward light-cone with Im(ω G) > 0 in the complex domain for translation-invariant but Lorentz-breaking systems, implying integral constraints and analytic ε(ω,k), μ^{-1}(ω,k).
Retarded Correlators in Kinetic Theory: Branch Cuts, Poles and Hydrodynamic Onset Transitions
7 Pith papers cite this work. Polarity classification is still indexing.
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abstract
In this work the collective modes of an effective kinetic theory description based on the Boltzmann equation in relaxation time approximation applicable to gauge theories at weak but finite coupling and low frequencies are studied. Real time retarded two-point correlators of the energy-momentum tensor and the R-charge current are calculated at finite temperature in flat space-times for large N gauge theories. It is found that the real time correlators possess logarithmic branch cuts which in the limit of large coupling disappear and give rise to non-hydrodynamic poles that are reminiscent of quasi-normal modes in black holes. In addition to branch cuts, correlators can have simple hydrodynamic poles, generalizing the concept of hydrodynamic modes to intermediate wavelength. Surprisingly, the hydrodynamic poles cease to exist for some critical value of the wavelength and coupling reminiscent of the properties of onset transitions.
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Normal mode analysis of the relativistic Boltzmann equation for massive particles reveals coupling between sound and heat channels, mass-dependent critical wavenumbers, and an infinite branch cut for Landau damping.
Out-of-equilibrium superfluids in Bjorken, Gubser and FLRW flows reach hydrodynamic attractors after an initial-condition-dependent attractor time, with a novel nonlinear constant-anisotropy regime in Gubser evolution.
Authors derive new Kubo formulae for transport coefficients by analyzing analytic structures of stress-energy response functions in second- and third-order hydrodynamics.
Energy-energy correlators in heavy-ion collisions exhibit classical hydrodynamic scaling from collective flow at large angles within the small-angle regime, collective modes at smaller angles, and light-ray OPE at even smaller angles.
Any standalone hydrodynamic EFT is acausal and requires UV completions with transient modes to restore causality.
Non-conformal deformation via Einstein-dilaton gravity increases the radius of convergence of the derivative expansion for gapped quasinormal modes of a scalar operator in the holographic dual.
citing papers explorer
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Analyticity and positivity of Green's functions without Lorentz
Microcausality and positivity constrain Green's functions to be analytic in the forward light-cone with Im(ω G) > 0 in the complex domain for translation-invariant but Lorentz-breaking systems, implying integral constraints and analytic ε(ω,k), μ^{-1}(ω,k).
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Normal mode analysis within relativistic massive transport
Normal mode analysis of the relativistic Boltzmann equation for massive particles reveals coupling between sound and heat channels, mass-dependent critical wavenumbers, and an infinite branch cut for Landau damping.
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Superfluids in expanding backgrounds and attractor times
Out-of-equilibrium superfluids in Bjorken, Gubser and FLRW flows reach hydrodynamic attractors after an initial-condition-dependent attractor time, with a novel nonlinear constant-anisotropy regime in Gubser evolution.
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Analytic structure of stress-energy response functions and new Kubo formulae
Authors derive new Kubo formulae for transport coefficients by analyzing analytic structures of stress-energy response functions in second- and third-order hydrodynamics.
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Hydrodynamics and Energy Correlators
Energy-energy correlators in heavy-ion collisions exhibit classical hydrodynamic scaling from collective flow at large angles within the small-angle regime, collective modes at smaller angles, and light-ray OPE at even smaller angles.
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Causal UV completions of relativistic hydrodynamics
Any standalone hydrodynamic EFT is acausal and requires UV completions with transient modes to restore causality.
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Effect of non-conformal deformation on the gapped quasi-normal modes and the holographic implications
Non-conformal deformation via Einstein-dilaton gravity increases the radius of convergence of the derivative expansion for gapped quasinormal modes of a scalar operator in the holographic dual.