MDPI - Publisher of Open Access Journals

24 pages, 907 KB

Open AccessReview

Phase Diagram of Dense Two-Color QCD at Low Temperatures

by Victor V. Braguta

Symmetry 2023, 15(7), 1466; https://doi.org/10.3390/sym15071466 - 24 Jul 2023

Cited by 8 | Viewed by 2086

This review is devoted to the modern understanding of the two-color QCD phase diagram at finite baryon density and low temperatures. First, we consider the theoretical picture of this phase diagram. It is believed that at low baryon density, two-color QCD can be described by chiral perturbation theory (ChPT), which predicts a second-order phase transition with Bose-Einstein condensation of diquarks at

μ = m_{π} / 2

. At larger baryon chemical potentials, the interactions between baryons become important, and ChPT is not applicable anymore. At sufficiently large baryon chemical potential, the Fermi sphere composed of quarks is formed, and diquarks are condensed on the surface of this sphere. In this region, two-color baryon matter reveals properties similar to those of the Quarkyonic phase. Particular attention in this review is paid to lattice studies of dense two-color QCD phase diagram. In the low-density region, the results of lattice studies are in agreement with ChPT predictions. At sufficiently large baryon densities, lattice studies observe a Fermi sphere composed of quarks and condensation of diquarks on its surface. Thus, available lattice studies support most of the theoretical predictions. Finally, we discuss the status of the deconfinement in cold dense two-color matter, which was observed in lattice simulation with staggered fermions. Full article

(This article belongs to the Special Issue Review on Quantum Field Theory)

► Show Figures

Figure 1

28 pages, 5840 KB

Open AccessArticle

Topological Vortexes, Asymptotic Freedom, and Multifractals

by Alexander Migdal

Fractal Fract. 2023, 7(5), 351; https://doi.org/10.3390/fractalfract7050351 - 25 Apr 2023

Cited by 3 | Viewed by 1822

Abstract

In this paper, we study the Kelvinons, which are monopole ring solutions to the Euler equations, regularized as the Burgers vortex in the viscous core. There is finite anomalous dissipation in the inviscid limit. However, in the anomalous Hamiltonian, some terms are growing as logarithms of Reynolds number; these terms come from the core of the Burgers vortex. In our theory, the turbulent multifractal phenomenon is similar to asymptotic freedom in QCD, with these logarithmic terms summed up by an RG equation. The small effective coupling does not imply small velocity; on the contrary, velocity is large compared to its fluctuations, which opens the way for a quantitative theory. In the leading order in the perturbation theory in this effective coupling constant, we compute running multifractal dimensions for high moments of velocity circulation, which is in good agreement with the data for quantum Turbulence and available data for classical Turbulence. The logarithmic dependence of fractal dimensions on the loop size comes from the running coupling in anomalous dimensions. This slow logarithmic drift of fractal dimensions would be barely observable at Reynolds numbers achievable at modern DNS. Full article

(This article belongs to the Special Issue Multifractals, Turbulence and Complexity in Geoscience and Space Science)

► Show Figures

Figure 1

17 pages, 1548 KB

Open AccessArticle

Local Correlation among the Chiral Condensate, Monopoles, and Color Magnetic Fields in Abelian Projected QCD

by Hideo Suganuma and Hiroki Ohata

Universe 2021, 7(9), 318; https://doi.org/10.3390/universe7090318 - 28 Aug 2021

Cited by 5 | Viewed by 1886

Abstract

Using the lattice gauge field theory, we study the relation among the local chiral condensate, monopoles, and color magnetic fields in quantum chromodynamics (QCD). First, we investigate idealized Abelian gauge systems of (1) a static monopole–antimonopole pair and (2) a magnetic flux without monopoles, on a four-dimensional Euclidean lattice. In these systems, we calculate the local chiral condensate on quasi-massless fermions coupled to the Abelian gauge field, and find that the chiral condensate is localized in the vicinity of the magnetic field. Second, using SU(3) lattice QCD Monte Carlo calculations, we investigate Abelian projected QCD in the maximally Abelian gauge, and find clear correlation of distribution similarity among the local chiral condensate, monopoles, and color magnetic fields in the Abelianized gauge configuration. As a statistical indicator, we measure the correlation coefficient r, and find a strong positive correlation of

r ≃ 0.8

between the local chiral condensate and an Euclidean color-magnetic quantity

F

in Abelian projected QCD. The correlation is also investigated for the deconfined phase in thermal QCD. As an interesting conjecture, like magnetic catalysis, the chiral condensate is locally enhanced by the strong color-magnetic field around the monopoles in QCD. Full article

(This article belongs to the Special Issue Modern Approaches to Non-Perturbative QCD and other Confining Gauge Theories)

► Show Figures

Figure 1

27 pages, 500 KB

Open AccessEditor’s ChoiceReview

Effective Field Theories

by Andrey Grozin

Particles 2020, 3(2), 245-271; https://doi.org/10.3390/particles3020020 - 31 Mar 2020

Cited by 5 | Viewed by 3419

Abstract

This paper represents a pedagogical introduction to low-energy effective field theories. In some of them, heavy particles are “integrated out” (a typical example—the Heisenberg–Euler EFT); in some, heavy particles remain but some of their degrees of freedom are “integrated out” (Bloch–Nordsieck EFT). A large part of these lectures is, technically, in the framework of QED. QCD examples, namely decoupling of heavy flavors and HQET, are discussed only briefly. However, effective field theories of QCD are very similar to the QED case, and there are just some small technical complications: more diagrams, color factors, etc. The method of regions provides an alternative view at low-energy effective theories; this is also briefly introduced. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

► Show Figures

Figure 1

10 pages, 1033 KB

Open AccessReview

Chiralspin Symmetry and Its Implications for QCD

by Leonid Glozman

Universe 2019, 5(1), 38; https://doi.org/10.3390/universe5010038 - 19 Jan 2019

Cited by 7 | Viewed by 2721

Abstract

In a local gauge-invariant theory with massless Dirac fermions, a symmetry of the Lorentz-invariant fermion charge is larger than a symmetry of the Lagrangian as a whole. While the Dirac Lagrangian exhibits only a chiral symmetry, the fermion charge operator is invariant under [...] Read more.

S U (2 N_{F})

, that includes chiral transformations as well as

S U {(2)}_{C S}

chiralspin transformations that mix the right- and left-handed components of fermions. Consequently, a symmetry of the electric interaction, which is driven by the charge density, is larger than a symmetry of the magnetic interaction and of the kinetic term. This allows separating in some situations electric and magnetic contributions. In particular, in QCD, the chromo-magnetic interaction contributes only to the near-zero modes of the Dirac operator, while confining chromo-electric interaction contributes to all modes. At high temperatures, above the chiral restoration crossover, QCD exhibits approximate

S U {(2)}_{C S}

and

S U (2 N_{F})

symmetries that are incompatible with free deconfined quarks. Consequently, elementary objects in QCD in this regime are quarks with a definite chirality bound by the chromo-electric field, without the chromo-magnetic effects. In this regime, QCD can be described as a stringy fluid. Full article

(This article belongs to the Special Issue Selected Papers from the 7th International Conference on New Frontiers in Physics (ICNFP 2018))

► Show Figures

Figure 1

Search Results (5)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (5)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI