Speaker: Friederike Ihssen (Institut für Theoretische Physik, Universität Heidelberg)
Title of Talk: On the QCD phase structure: towards locating the (real) critical end point
Abstract: Lattice simulations and functional approaches established that QCD has no phase transition at small baryon chemical potential (μ_B). Instead,
they predict a smooth crossover region from hadronic particles to the quark-gluon plasma at high temperatures (T). However, phase transitions
are expected at the conjectured critical endpoint (CEP) at larger chemical potential or in the limit of massless pions. Their precise
resolution and pinpointing the CEP remain an open task. The main computational difficulty lies in effects introduced by the large
chemical potential. In this talk, I will introduce an approach to potentially circumvent these difficulties using Lee-Yang theory:
The QCD phase transitions leave an imprint as Lee-Yang edge singularities and can be found at high temperatures T>T_c for complex
magnetisation and complex chemical potential. For an increasing real part of the chemical potential, the complex edge singularity moves
towards the real μ_B-axis, potentially allowing for an extrapolation of the critical endpoint.

As a precursor for a quantitative study in QCD we discuss the impact of fluctuations in a simple low energy effective theory, the non-linear
sigma model. We show that in this model the location of the phase transition can accurately be determined by tracking the Lee-Yang
singularities in the complex plane. I close by discussing the remaining task of extending this computation to full QCD.

Venue (HYBRID-EVENT): Goldene Box, Physikalisches Institut, INF 226, 69120 Heidelberg AND all talks will also be streamed via the permanent Zoom-link:

Meeting ID: 946 0240 1603
Passcode: 386993

13:30-14:00 talk+questions
14:00-14.15 discussion and questions
14.15-14:30 pizza



The aim of the YRC Lunch Seminar is to promote individual research done by young researchers within Isoquant and create a regular platform to socialize and share ideas.