Detecting scale anomaly in chiral phase transition of QCD: new critical endpoint pinned down

Abstract

Violation of scale symmetry, scale anomaly, being a radical concept in quantum field theory, is of importance to comprehend the vacuum structure of QCD, and should potentially contribute to the chiral phase transition in thermal QCD, as well as the chiral and U(1) axial symmetry. Though it should be essential, direct evidence of scale anomalies has never been observed in the chiral phase transition. We propose a methodology to detect a scale anomaly in the chiral phase transition, which is an electromagnetically induced scale anomaly: apply a weak magnetic field background onto two-flavor massless QCD with an extremely heavy strange quark, first observe the chiral crossover; second, adjusting the strange quark mass to be smaller and smaller, observe the second-order chiral phase transition, and then the first-order one in the massless-three flavor limit. Thus, the second-order chiral phase transition, observed as the evidence of the quantum scale anomaly, is a new critical endpoint. It turns out that this electromagnetic scale anomaly gets most operative in the weak magnetic field regime, rather than a strong field region. We also briefly address accessibility of lattice QCD, a prospected application to dense matter system, and implications to astrophysical observations, such as gravitational wave productions provided from thermomagnetic QCD-like theories.

arXiv comment23 pages, 7 figures, some references added, minor corrections made, version accepted in JHEP

References in corpus (31)

• The effects of topological charge change in heavy ion collisions: "Event by event P and CP violation"
• Chiral Magnetic and Vortical Effects in High-Energy Nuclear Collisions --- A Status Report
• The QCD phase diagram for external magnetic fields
• The QCD phase transition with physical-mass, chiral quarks
• The QCD equation of state in background magnetic fields
• Chiral phase transition temperature in (2+1)-Flavor QCD
• Chiral Properties of Strong Interactions in a Magnetic Background
• The QCD chiral transition, $\ua$ symmetry and the Dirac spectrum using domain wall fermions
• The chiral transition and U(1)_A symmetry restoration from lattice QCD using Domain Wall Fermions
• Chiral symmetry restoration, eigenvalue density of Dirac operator and axial U(1) anomaly at finite temperature
• Finite temperature study of the axial U(1) symmetry on the lattice with overlap fermion formulation
• Inverse magnetic catalysis in the linear sigma model with quarks
• Deconfinement transition in two-flavour lattice QCD with dynamical overlap fermions in an external magnetic field
• Bootstrapping phase transitions in QCD and frustrated spin systems
• Evidence of effective axial U(1) symmetry restoration at high temperature QCD
• QCD phase diagram in a magnetic background for different values of the pion mass
• Correlated Dirac Eigenvalues and Axial Anomaly in Chiral Symmetric QCD
• Chiral phase structure of three flavor QCD at vanishing baryon number density
• Magnetic catalysis and inverse catalysis for heavy pions
• Chiral transition in a magnetic field and at finite baryon density
• Magnetic susceptibility of QCD matter and its decomposition from the lattice
• Study of the axial U(1) anomaly at high temperature with lattice chiral fermions
• Lattice QCD Simulations in External Background Fields
• Inverse magnetic catalysis and regularization in the quark-meson model
• Critical point phase transition for finite temperature 3-flavor QCD with non-perturbatively O($a$) improved Wilson fermions at $N_{\mathrm{t}}=10$
• Possible Classification of the Chiral Scalar sigma-Nonet
• The Myriad Uses of Instantons
• Linking $U(2)\times U(2)$ to $O(4)$ model via decoupling
• Soft contribution to the damping rate of a hard photon in a weakly magnetized hot medium
• New critical point for QCD in a magnetic field
• Polyakov Loop Susceptibility and Correlators in the Chiral Limit

Cited by in corpus (4)

• Phase diagram of QCD in a magnetic background
• QCD phase diagram in a magnetized medium from the chiral symmetry perspective: The linear sigma model with quarks and the Nambu--Jona-Lasinio model effective descriptions
• Fate of the first-order chiral phase transition in QCD: Implications for dark QCD studied via a Nambu-Jona-Lasinio model
• First-order CP phase transition in two-flavor QCD at $\theta =\pi$ under electromagnetic scale anomaly via a Nambu-Jona-Lasinio description