On the phase structure of massless many-flavour QCD with staggered fermions
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arXiv
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| Auteurs principaux: | , , , |
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| Format: | Preprint |
| Publié: |
2026
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| _version_ | 1866911532041895936 |
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| author | Klinger, Jan Philipp Kaiser, Reinhold Philipsen, Owe Schaible, Jonas |
| author_facet | Klinger, Jan Philipp Kaiser, Reinhold Philipsen, Owe Schaible, Jonas |
| contents | When the number of massless fermions exceeds a critical value $N_f^*$, QCD enters the conformal window and becomes chirally symmetric already in the vacuum. Determining $N_f^*$ from lattice simulations is challenging, since calculations are performed at finite lattice spacing, quark mass, and temporal lattice size, where both a thermal transition and an unphysical bulk transition obscure the conformal behaviour. In this work, we present results on the chiral phase boundaries in the bare lattice parameter space $(N_τ,\;β,\;am,\;N_f)$ of unimproved staggered fermions. Our analysis indicates that the chiral transition in continuum QCD is of second order for all $N_f$ up to the onset of the conformal window. By systematically studying the thermal chiral transition and its interplay with the bulk transition, we obtain a coherent picture of the lattice phase structure and suggest how the onset of the conformal window can be identified from simulations performed away from the chiral and continuum limits. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_20099 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | On the phase structure of massless many-flavour QCD with staggered fermions Klinger, Jan Philipp Kaiser, Reinhold Philipsen, Owe Schaible, Jonas High Energy Physics - Lattice When the number of massless fermions exceeds a critical value $N_f^*$, QCD enters the conformal window and becomes chirally symmetric already in the vacuum. Determining $N_f^*$ from lattice simulations is challenging, since calculations are performed at finite lattice spacing, quark mass, and temporal lattice size, where both a thermal transition and an unphysical bulk transition obscure the conformal behaviour. In this work, we present results on the chiral phase boundaries in the bare lattice parameter space $(N_τ,\;β,\;am,\;N_f)$ of unimproved staggered fermions. Our analysis indicates that the chiral transition in continuum QCD is of second order for all $N_f$ up to the onset of the conformal window. By systematically studying the thermal chiral transition and its interplay with the bulk transition, we obtain a coherent picture of the lattice phase structure and suggest how the onset of the conformal window can be identified from simulations performed away from the chiral and continuum limits. |
| title | On the phase structure of massless many-flavour QCD with staggered fermions |
| topic | High Energy Physics - Lattice |
| url | https://arxiv.org/abs/2603.20099 |