The Roberge-Weiss transition as a probe for conformality in many-flavor QCD

Fuente: arXiv
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Autores principales: D'Elia, Massimo, Nacci, Marco, Zambello, Kevin
Formato: Preprint
Publicado: 2026
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author D'Elia, Massimo
Nacci, Marco
Zambello, Kevin
author_facet D'Elia, Massimo
Nacci, Marco
Zambello, Kevin
contents We consider the problem of identifying the onset of the conformal window for QCD with $N_f$ massless flavors in the fundamental representation, and propose a new effective method to determine it from lattice simulations. This method is based on the investigation of the so-called Roberge-Weiss transition temperature $T_{RW}$, which is encountered at specific values of the imaginary baryon chemical potential, and can also be interpreted as the inverse of the critical spatial size at which charge conjugation is spontaneously broken in a finite box. Since $T_{RW}$ corresponds to a genuine phase transition for any value of the quark masses, it is a well-defined quantity; we argue that the critical $N_f$ at which $T_{RW}$ vanishes in the chiral limit coincides with the onset of the conformal window. We implement our proposal by investigating QCD with $N_f = 8$ flavors, discretized via stout improved staggered fermions and the tree-level improved Symanzik pure gauge action, at Euclidean temporal extents $N_t = 8, 10, 12, 16, 24$. In this case, we find evidence that $T_{RW}$ already vanishes in the chiral limit, indicating that $N_f = 8$ is already in the conformal window.
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id arxiv_https___arxiv_org_abs_2604_07284
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Roberge-Weiss transition as a probe for conformality in many-flavor QCD
D'Elia, Massimo
Nacci, Marco
Zambello, Kevin
High Energy Physics - Lattice
High Energy Physics - Theory
We consider the problem of identifying the onset of the conformal window for QCD with $N_f$ massless flavors in the fundamental representation, and propose a new effective method to determine it from lattice simulations. This method is based on the investigation of the so-called Roberge-Weiss transition temperature $T_{RW}$, which is encountered at specific values of the imaginary baryon chemical potential, and can also be interpreted as the inverse of the critical spatial size at which charge conjugation is spontaneously broken in a finite box. Since $T_{RW}$ corresponds to a genuine phase transition for any value of the quark masses, it is a well-defined quantity; we argue that the critical $N_f$ at which $T_{RW}$ vanishes in the chiral limit coincides with the onset of the conformal window. We implement our proposal by investigating QCD with $N_f = 8$ flavors, discretized via stout improved staggered fermions and the tree-level improved Symanzik pure gauge action, at Euclidean temporal extents $N_t = 8, 10, 12, 16, 24$. In this case, we find evidence that $T_{RW}$ already vanishes in the chiral limit, indicating that $N_f = 8$ is already in the conformal window.
title The Roberge-Weiss transition as a probe for conformality in many-flavor QCD
topic High Energy Physics - Lattice
High Energy Physics - Theory
url https://arxiv.org/abs/2604.07284