Seminars on t-, T- & 𝜇-dependence in Quantum Field Theory

Welcome to the home page of the online seminars on t-, T- & 𝜇-dependence in Quantum Field Theory! (

This is a joint initiative of the Gravity, Quantum Fields and Information group at the Albert Einstein Institute in Potsdam (Michal Heller, Johannes Knaute, Viktor Svensson), CERN (Urs Wiedemann, Wilke van der Schee, Aleksas Mazeliauskas), the University of Barcelona (David Mateos), Utrecht University (Umut Gürsoy), University of Oxford (Jorge Casalderrey Solana), University of Regensburg (Andreas Schäfer), University of Helsinki (Aleksi Vuorinen), University of Oviedo (Carlos Hoyos Badajoz), Brookhaven National Laboratory (Raju Venugopalan) and Bielefeld University (Sören Schlichting).

Our aim is to provide an online platform for researchers working on this topic all around the globe to present their work from anywhere they like! (Office, home, restaurant, airport, or even the beach.) We hope this seminar series can make a small contribution towards cutting down costs, unnecessary travel, and carbon emissions.

How does it work? A link to the virtual seminar room for each talk is sent out to participating groups via our mailing list. Anyone with the link can tune-in remotely to the live stream, ask questions, and participate in discussion. 

In addition, the talks are typically recorded and posted on our YouTube channel:, in case you miss the live stream, and/or want to revisit the talk.

If you are interested in being added to the mailing list to receive information (including the link to the virtual seminar room) please contact

Group seminars
The full spectrum of our other joint group seminars is available under the following links: (Quantum Gravity & Information) (Tensor Networks in High Energy Physics)


Upcoming Seminars

5. Raju Venugopalan

When: Friday, April. 24th @ 15:30 CET (Berlin-time)
Title: TBA

4. Jürgen Berges

When: Friday, April. 3rd @ 15:30 CET (Berlin-time)
Title: TBA


Past Seminars

3. Simone Montangero

When: Friday, Feb. 14th @ 15:30 CET (Berlin-time)
Title: Tensor network methods applied to high energy physics problems
Abstract: We briefly introduce tensor network methods, a classical numerical approach that promises to become a powerful tool to support future quantum simulations and computations, providing guidance, benchmarking and verification of the quantum computation and simulation results. We review some of the latest achievements we obtained: the gauge-invariant formulation of tensor networks and their application to abelian and non-abelian, one- and two-dimensional lattice gauge theories in regimes where Monte Carlo methods efficiency is hindered by the sign problem. Finally, we present the application of tensor network machine learning techniques to the event classification of LHCb simulated data.

2. Paul Chesler

When: Thursday, Dec. 12th @ 15:30 CET (Berlin-time)
Title: Searching for quark matter cores with binary neutron star inspirals
Abstract: I will discuss the feasibility of detecting quark matter cores in merging neutron stars with ground-based gravitational-wave detectors. I will argue that the existence of quark matter cores can be confirmed at the 70% confidence level with as few as several tens of detections. Likewise, with such a sample, some models of quark matter cores can be excluded with high confidence.

1. Paul Romatschke (Opening seminar of the series)

When: Thursday, Nov. 14th @ 15:30 CET (Berlin-time)
Title: Pure CFT Thermodynamics and Fractional Degrees of Freedom
Abstract: "Pure" CFTs are CFTs that have vanishing trace of the energy-momentum tensor for all values of the coupling. A famous example for a pure CFT is N=4 SYM in 3+1 dimensions, which has the property that its entropy density at infinite coupling is exactly 3/4 of the Stefan-Boltzmann limit (the entropy at intermediate coupling is not known exactly, nor is monotonicity in the coupling established). In this talk I will present other examples of pure CFTs in 2+1 dimensions which can be solved exactly in the large N limit for all values of the coupling. It is found that for these pure CFTs the entropy density is monotonically decreasing as a function of the coupling. Furthermore, I show that for a large class of CFTs (not only pure CFTs), the strong/weak ratio for the entropy density is a simple fraction bounded from below by 4/5. I entertain the hypothesis for CFTs at infinite coupling, the degrees of freedom contributing to the entropy density are fractional.