Lattice QCD Phase Diagram In and Away from the Strong Coupling Limit

Forcrand, Philippe de; Langelage, Jens; Philipsen, Owe; Unger, Wolfgang

doi:10.1103/physrevlett.113.152002

Cited by 113 publications

(149 citation statements)

References 33 publications

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“…For example, complex Langevin dynamics has recently been successfully used for full QCD at finite density albeit on still rather small lattices [3]. Strong-coupling techniques can either be used together with hopping parameter expansions for very heavy quarks [4,5] or to derive a graph representation valid also for light quarks but without continuum limit [6,7]. More direct evidence of a first-order transition analogous to that of nuclear matter has so far only been seen in G 2 -QCD at finite density, a QCD-like theory with fermionic baryons but without sign problem which can therefore be simulated with standard lattice techniques [8,9].…”

Section: Introductionmentioning

confidence: 99%

Chiral mirror-baryon-meson model and nuclear matter beyond mean-field approximation

2015

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We consider a chiral baryon-meson model for nucleons and their parity partners in mirror assignment interacting with pions, sigma and omega mesons to describe the liquid-gas transition of nuclear matter together with chiral symmetry restoration in the high density phase. Within the mean-field approximation the model is known to provide a phenomenologically successful description of the nuclear-matter transition. Here, we go beyond this approximation and include mesonic fluctuations by means of the functional renormalization group. While these fluctuations do not lead to major qualitative changes in the phase diagram of the model, beyond mean-field, one is no-longer free to adjust the parameters so as to reproduce the binding energy per nucleon, the nuclear saturation density, and the nucleon sigma term all at the same time. However, the prediction of a clear first-order chiral transition at low temperatures inside the high baryon-density phase appears to be robust.

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Section: Introductionmentioning

confidence: 99%

Chiral mirror-baryon-meson model and nuclear matter beyond mean-field approximation

2015

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“…For gauge theories, such a relation would certainly improve our understanding of confinement and dynamical mass gap generation. It would also extend the applicability of Diagrammatic Monte-Carlo studies of non-Abelian lattice gauge theories, which are so far limited to the regime of unphysically strong bare coupling constants [20].…”

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confidence: 99%

Complex Path Integrals and Saddles in Two-Dimensional Gauge Theory

2016

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We study numerically the saddle point structure of two-dimensional (2D) lattice gauge theory, represented by the Gross-Witten-Wadia unitary matrix model. The saddle points are in general complex-valued, even though the original integration variables and action are real. We confirm the trans-series/instanton gas structure in the weak-coupling phase, and identify a new complex-saddle interpretation of non-perturbative effects in the strong-coupling phase. In both phases, eigenvalue tunneling refers to eigenvalues moving off the real interval, into the complex plane, and the weakto-strong coupling phase transition is driven by saddle condensation. Introduction: Path integral saddle points are physically important in quantum mechanics, matrix models, quantum field theory (QFT) and string theory, and are deeply related to the typical asymptotic nature of weak coupling perturbative expansions. Such relations are central to the concept of resurgence, whereby different saddles are intertwined by monodromy properties that connect them and account for Stokes phases. The theory of resurgence has recently provided new insights into matrix models and string theories [1][2][3][4][5][6], and has been applied to asymptotically free QFTs and sigma models [7][8][9][10], and localizable SUSY QFTs [11]. One motivation for such QFT studies is to find a practical numerical implementation of a semiclassical expansion that could provide a Picard-Lefschetz thimble decomposition of gauge theory, either in the continuum or on the lattice, especially for theories with a sign problem [12,13]. A unifying theme in these studies, and in related work [14][15][16][17], is the appreciation that complex saddles are important, in particular in the context of phase transitions, even though the original 'path integral' may be a sum over only real configurations.

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“…Note that the onset transition to nuclear matter in the strong coupling limit coincides with the chiral transition, with its endpoint sitting on top of the chiral tricritical point. More recently the leading gauge corrections to O(β) have been evaluated as well [27]. At finite values of β the two transitions begin to become distinct.…”

Section: A 4d Effective Lattice Theory For Coarse Latticesmentioning

confidence: 99%

Towards a theoretical description of dense QCD

Philipsen¹

2017

EPJ Web Conf.

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Abstract. The properties of matter at finite baryon densities play an important role for the astrophysics of compact stars as well as for heavy ion collisions or the description of nuclear matter. Because of the sign problem of the quark determinant, lattice QCD cannot be simulated by standard Monte Carlo at finite baryon densities. I review alternative attempts to treat dense QCD with an effective lattice theory derived by analytic strong coupling and hopping expansions, which close to the continuum is valid for heavy quarks only, but shows all qualitative features of nuclear physics emerging from QCD. In particular, the nuclear liquid gas transition and an equation of state for baryons can be calculated directly from QCD. A second effective theory based on strong coupling methods permits studies of the phase diagram in the chiral limit on coarse lattices.

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Lattice QCD Phase Diagram In and Away from the Strong Coupling Limit

Cited by 113 publications

References 33 publications

Chiral mirror-baryon-meson model and nuclear matter beyond mean-field approximation

Chiral mirror-baryon-meson model and nuclear matter beyond mean-field approximation

Complex Path Integrals and Saddles in Two-Dimensional Gauge Theory

Towards a theoretical description of dense QCD

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