# Spectra, reconstructions and pole-skipping

- Institution: CERN
- Department: TH String Theory Seminar
- Speaker: Sašo Grozdanov
- Year: 2023
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3004523)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

The poles of two-point functions in momentum space, which can be computed and analysed using holographic methods, reveal various details of the physical properties of spectra in QFTs. In thermal QFTs, the lowest-energy (IR) gapless mode is usually described by the theory of hydrodynamics. Assuming a known dispersion relation of only a single hydrodynamic mode, I will discuss when and how the reconstruction of the complete spectrum of physical excitations is possible in the corresponding correlator. In particular, I will demonstrate our recently developed constructive algorithm based on the theorems of Darboux and Puiseux that allows for a reconstruction of all modes connected by `level-crossings' in the associated spectral curve, from IR to UV. In the second part of my talk, I will introduce the phenomenon of pole-skipping (formally, a "0/0") in such correlators and discuss how its knowledge can itself be sufficient to reconstruct the entire spectrum. .

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## Lectures

1. [Spectra, reconstructions and pole-skipping](https://invisiblenetwork.ai/learn/cern/3004523/45d4a87fe4cf), 1 h 14 min (CERN's player)