Cold Quantum Coffee

The Cold Quantum Coffee brings together research students at the Institute for Theoretical Physics to discuss topics revolving around phenomenology, quantum gravity, cold quantum gases, solid state systems, and everything in between. The seminar is organised by students, for students. For further questions or in case you want to give a talk, please contact one of the organisers (Maruice Beringuier, Zois Gyftopoulos, Renzo Kapust, and Fabian Zhou).

We are supported by the SFB 1225 ISOQUANT.
Date: Tuesday 16:15
Location: Seminar Room of Philosophenweg 16, ITP Heidelberg

Upcoming Talks
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Winter Semester 2025/26 Schedule
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{$\hspace{0.5cm}$} Date	{$\hspace{5cm}$} Speaker
21.10.2025
28.10.2025	Diego Buccio (University of Heidelberg)
04.11.2025	Fabian Wagner (University of Heidelberg)
11.11.2025
18.11.2025	Peter Lowdon (Goethe University Frankfurt)
25.11.2025
02.12.2025
09.12.2025
16.12.2025
13.01.2026	Maximilian Neumann (University of Heidelberg)
20.01.2026
27.01.2026	Ankur Singha (TU Berlin)
03.02.2026

Diego Buccio, 28.10.2025: Momentum running of Quadratic Gravity

Running couplings were introduced in quantum field theory to preserve perturbativity in scattering amplitudes, despite the appearance of large logs of external momenta. It is commonly believed that such logarithms are directly related to UV divergencies in one-loop perturbation theory. However, this is not completely true in higher derivative theories: on the one hand, large logs can also emerge from UV finite loop integrals due to IR effects; on the other hand, some UV divergent diagrams do not depend on external momenta. We define a new set of beta functions for quadratic gravity based on the explicit computation of large logs of momenta and discuss their features concerning the asymptotic UV behaviour of the theory and their gauge dependence.

Fabian Wagner, 04.11.2025: Quantum field theory with minimal spacetime volume

It is common lore that phenomenological quantum-gravity models with a fundamental scale, such as a minimal length, must break Lorentz invariance. In my talk, I show that a Lorentz-covariant cutoff yields a fundamental scale, a minimal spacetime volume, while preserving Lorentz invariance. Thus, such a cutoff may serve as a continuum analogue to causal sets. I construct an interacting QFT with Lorentz-covariant cutoff, and show that its correlation functions can be mapped to those of a (possibly nonlocal) QFT, which makes the phenomenology much more tractable.

Peter Lowdon, 18.11.2025: Goldstone bosons at finite temperature

Temperature has a significant effect on the properties of QFTs with spontaneously broken symmetries, in particular for the massless Goldstone bosons that exist in the vacuum state. In this talk I will discuss recent results which indicate that Goldstone modes persist at high temperatures, even if the symmetry is restored, and that they have the properties of screened massless excitations, so-called thermoparticles. This has important implications for the phase structure of QFTs at finite temperature.