Lattice Field Theory

Institut für Physik
Mathematisch-Naturwissen­schaft­liche Fakultät
Humboldt-Universität zu Berlin

HU+DESY Lattice Seminars

This seminar series is organised jointly by the NIC Research Group at DESY Zeuthen and the Theory of Elementary Particles and Computational Theoretical Physics research groups of the Institute for Physics at Humboldt University. For questions please contact Dr. Andreas Risch (DESY Zeuthen).

During the current semester, seminars are held virtually on Zoom generally on Mondays at 13:00. Due to the participation of international speakers some seminars may start at 15:00. Please check the individual dates.

The Zoom connection details will be announced via the lat-bb mailing list.

iCal link: https://indico.desy.de/export/categ/873.ics?from=-31d
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For past events, visit the Indico page.

Strings and glueballs in 4D SU(N) gauge theories

Speaker: Dr Athenodorou, Andreas (The Cyprus Institute)
Date: Monday, June 27, 2022
Time: 1:00 pm (Europe/Berlin)
Links: Indico iCal

I will present our recent results on the flux-tube spectrum as well as the glueball spectrum for $SU(N)$ lattice gauge theories in $3+1$ dimensions. Regarding flux-tubes, we have performed calculations for $N=3,5,6$ and for various values of spin, parity and longitudinal momentum. Long flux-tubes can be thought of as infinitesimally thin strings; hence their spectrum is expected to be described by an effective string theory. Furthermore, the flux-tube's internal structure makes possible the existence of massive states in addition to string modes. Our calculations demonstrate that although most states exhibit a spectrum which can be approximated adequately by Nambu-Goto there is strong evidence for the existence of a massive axion on the world-sheet of the QCD flux-tube as well as a bound state of two such axions. Regarding glueballs, we extracted spectra from $N=2$ to $N=12$ which enables us to extrapolate to $N=\infty$. Our main aim was to calculate the lightest glueball masses for all different configurations of the quantum numbers of spin, parity and charge conjugation. This provides a major update on the spectrum of glueballs in the planar limit.

Composite massless vector particles and other surprises in GUTs

Speaker: Prof. Maas, Axel (Karl-Franzens-Universität Graz)
Date: Monday, July 4, 2022
Time: 1:00 pm (Europe/Berlin)
Links: Indico iCal

Grand-unified theories (GUTs) are often treated perturbatively, using a Brout-Englert-Higgs effect to determine their spectra down to the electroweak scale. However, field-theoretically the physical spectrum needs to be constructed from manifestly gauge-invariant, and thus composite, particles, even at weak coupling. Consequently, lattice simulations show qualitative discrepancies between the perturbatively expected spectrum and the actual one in (toy) GUTs.

Nonetheless, a mechanism developed by Fröhlich, Morchio and Strocchi allows to analytically determine the correct spectrum, and is confirmed by the lattice results. This allows to extend the investigation to realistic GUTs, and rules out many popular scenarios.

In the talk both the analytical background and the relevant lattice results will be reviewed, giving an overview over the current understanding of the phenomena.

tba

Speaker: Mr Chimirri, Leonardo (DESY Zeuthen)
Date: Monday, July 18, 2022
Time: 1:00 pm (Europe/Berlin)
Links: Indico iCal