Chiral susceptibility in (
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)-flavor QCD

Braun, Jens; Fu, Weijie; Pawlowski, Jan M.; Rennecke, Fabian; Rosenblüh, Daniel; Yin, Shi

doi:10.1103/physrevd.102.056010

Cited by 56 publications

(86 citation statements)

References 66 publications

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“…Yet another analysis of the renormalisation group flow in a 3D effective theory [10] finds a possible symmetry breaking pattern to be U(2) L ⊗ U(2) R → U(2) V in the case of a restored U(1) A , which would amount to a second-order transition in a different universality class. Finally, a recent functional renormalisation group analysis applied to U(1) A restoration in QCD, which is in good agreement with lattice susceptibilities at finite quark masses [11], favours the O(4) scenario in the chiral limit [12].…”

Section: The Columbia Plotsupporting

confidence: 56%

On the order of the QCD chiral phase transition for different numbers of quark flavours

Cuteri

Philipsen

Sciarra

2021

J. High Energ. Phys.

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The nature of the QCD chiral phase transition in the limit of vanishing quark masses has remained elusive for a long time, since it cannot be simulated directly on the lattice and is strongly cutoff-dependent. We report on a comprehensive ongoing study using unimproved staggered fermions with Nf ∈ [2, 8] mass-degenerate flavours on Nτ ∈ {4, 6, 8} lattices, in which we locate the chiral critical surface separating regions with first-order transitions from crossover regions in the bare parameter space of the lattice theory. Employing the fact that it terminates in a tricritical line, this surface can be extrapolated to the chiral limit using tricritical scaling with known exponents. Knowing the order of the transitions in the lattice parameter space, conclusions for approaching the continuum chiral limit in the proper order can be drawn. While a narrow first-order region cannot be ruled out, we find initial evidence consistent with a second-order chiral transition in all massless theories with Nf ≤ 6, and possibly up to the onset of the conformal window at 9 ≲ $$ {N}_{\mathrm{f}}^{\ast } $$ N f ∗ ≲ 12. A reanalysis of already published $$ \mathcal{O} $$ O (a)-improved Nf = 3 Wilson data on Nτ ∈ [4, 12] is also consistent with tricritical scaling, and the associated change from first to second-order on the way to the continuum chiral limit. We discuss a modified Columbia plot and a phase diagram for many-flavour QCD that reflect these possible features.

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Section: The Columbia Plotsupporting

confidence: 56%

On the order of the QCD chiral phase transition for different numbers of quark flavours

Cuteri

Philipsen

Sciarra

2021

J. High Energ. Phys.

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“…A later high-order perturbative analysis for the case with an effectively restored Up1q A at the transition temperature finds a possibility for second-order transitions also in this case, but with a symmetry breaking pattern Up2q L b Up2q R Ñ Up2q V signalling a different universality class [28]. Finally, a recent functional renormalisation group analysis applied to Up1q A restoration in QCD, which is in good agreement with lattice susceptibilities at finite quark masses [29], favours the Op4q scenario in the chiral limit [30].…”

Section: The Chiral Transition At Zero Baryon Densitysupporting

confidence: 70%

Lattice Constraints on the QCD Chiral Phase Transition at Finite Temperature and Baryon Density

Philipsen

2021

Symmetry

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The thermal restoration of chiral symmetry in QCD is known to proceed by an analytic crossover, which is widely expected to turn into a phase transition with a critical endpoint as the baryon density is increased. In the absence of a genuine solution to the sign problem of lattice QCD, simulations at zero and imaginary baryon chemical potential in a parameter space enlarged by a variable number of quark flavours and quark masses constitute a viable way to constrain the location of a possible non-analytic phase transition and its critical endpoint. In this article I review recent progress towards an understanding of the nature of the transition in the massless limit, and its critical temperature at zero density. Combined with increasingly detailed studies of the physical crossover region, current data bound a possible critical point to μB ≳ 3T.

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“…[13,17] find a satisfactory O(4) scaling up to nearly physical pion mass, with T c = 132 +3 −6 MeV. A recent FRG study [57] confirms these findings, but with a slightly larger T c = 142 MeV in the chiral limit.…”

Section: N F = 2 + 1 and The Physical Pointmentioning

confidence: 76%

Gliding Down the QCD Transition Line, from Nf = 2 till the Onset of Conformality

2021

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We review the hot QCD transition with varying number of flavours, from two till the onset of the conformal window. We discuss the universality class for Nf=2, along the critical line for two massless light flavours, and a third flavour whose mass serves as an interpolator between Nf=2 and Nf=3. We identify a possible scaling window for the 3D O(4) universality class transition, and its crossover to a mean field behaviour. We follow the transition from Nf=3 to larger Nf, when it remains of first order, with an increasing coupling strength; we summarise its known properties, including possible cosmological applications as a model for a strong electroweak transition. The first order transition, and its accompanying second order endpoint, finally morphs into the essential singularity at the onset of the conformal window, following the singular behaviour predicted by the functional renormalisation group.

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Chiral susceptibility in ( 2+1 )-flavor QCD

Cited by 56 publications

References 66 publications

On the order of the QCD chiral phase transition for different numbers of quark flavours

On the order of the QCD chiral phase transition for different numbers of quark flavours

Lattice Constraints on the QCD Chiral Phase Transition at Finite Temperature and Baryon Density

Gliding Down the QCD Transition Line, from Nf = 2 till the Onset of Conformality

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