# RIKEN Seminar

## "From anomalous correlations to dark matter: the effects of higher topological charge"

#### Presented by Fabian Rennecke, BNL

Thursday, May 21, 2020, 9:00 am — Bluejeans link: https://bluejeans.com/651508428

Topological gauge field configurations play an important role in the phenomenology of QCD. The axial anomaly is inextricably linked to topological effects. They give rise to anomalous meson masses, affect the order of the chiral phase transition, and lead to the chiral magnetic effect which is relevant for condensed matter and heavy-ion physics. On the flip side, topological gauge field configurations can also give rise to CP violating effects in QCD. A potential resolution of this strong CP problem involves a new particle, the axion. Incidentally, axions are also viable dark matter candidates and their properties are largely determined by the distribution of topological charge in QCD. At high energies in the deconfined regime, the topological structure of QCD is well described by a dilute gas of instantons. In this regime all the effects mentioned above are typically studied based on instantons of unit topological charge. As discussed in this talk, there are also effects uniquely related to instantons of higher topological charge. On the one hand, they give rise to higher-order anomalous quark correlations which manifest themselves in anomalous hadronic interactions. On the other hand, they modify the distribution of topological charge. This, in turn, affects the properties of axions and can lead to a topological mechanism to increase the amount of axion dark matter.

Hosted by: Yuta Kikuchi

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