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

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Mamiya Kawaguchi ◽  
Shinya Matsuzaki ◽  
Akio Tomiya
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Weak Magnetic Field ◽  
Strange Quark ◽  
Strong Field ◽  
Dense Matter ◽  
Second Order ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Matter System

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.

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

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Francesca Cuteri ◽  
Owe Philipsen ◽  
Alessandro Sciarra
Keyword(s):  
Phase Transition ◽  
Parameter Space ◽  
Chiral Limit ◽  
Lattice Parameter ◽  
Second Order ◽  
Critical Surface ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
First Order ◽  
The Continuum

Abstract 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.

scholarly journals Chiral phase transition of three flavor QCD with nonzero magnetic field using standard staggered fermions

2018 ◽  
Vol 175 ◽  
pp. 07041 ◽  
Author(s):  
Akio Tomiya ◽  
Heng-Tong Ding ◽  
Swagato Mukherjee ◽  
Christian Schmidt ◽  
Xiao-Dan Wang
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quark Mass ◽  
Chiral Condensate ◽  
Zero Magnetic Field ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Magnetic Catalysis ◽  
Staggered Fermions ◽  
The Magnetic Field

Lattice simulations for (2+1)-flavor QCD with external magnetic field demon-strated that the quark mass is one of the important parameters responsible for the (inverse) magnetic catalysis. We discuss the dependences of chiral condensates and susceptibilities, the Polyakov loop on the magnetic field and quark mass in three degenerate flavor QCD. The lattice simulations are performed using standard staggered fermions and the plaquette action with spatial sizes Nσ = 16 and 24 and a fixed temporal size Nτ = 4. The value of the quark masses are chosen such that the system undergoes a first order chiral phase transition and crossover with zero magnetic field. We find that in light mass regime, the quark chiral condensate undergoes magnetic catalysis in the whole temperature region and the phase transition tend to become stronger as the magnetic field increases. In crossover regime, deconfinement transition temperature is shifted by the magnetic field when quark mass ma is less than 0:4. The lattice cutoff effects are also discussed.

APPLICATION OF THE RENORMALIZATION GROUP TO A SECOND-ORDER QCD PHASE TRANSITION

1992 ◽  
Vol 07 (16) ◽  
pp. 3911-3925 ◽  
Author(s):  
FRANK WILCZEK
Keyword(s):  
Phase Transition ◽  
Renormalization Group ◽  
Strange Quark ◽  
Tricritical Point ◽  
Universality Class ◽  
Second Order ◽  
Chiral Phase ◽  
Quark Masses ◽  
Potential Applications ◽  
Second Order Transition

An earlier suggestion that the chiral phase transition in QCD for two flavors of massless quarks might be a second-order transition has gained credibility as a result of recent numerical simulations. One can test this hypothesis, and draw very specific quantitative consequences from it, using universality and renormalization group ideas. This hypothetical second order phase transition is in the universality class of a four component isotropic Heisenberg antiferromagnet—a model which has been investigated intensely by condensed matter physicists. Existing calculations can be adapted to yield predictions for critical exponents governing the QCD transition. The perturbation due to small equal quark masses maps onto an external staggered magnetic field; that due to unequal quark masses is effective only in second order and generates a quadratic anisotropy. Several other potential applications of the renormalization group to related questions are suggested, including a model of the tricritical point which arises with finite strange quark mass, and a model for the dynamic critical behavior.

scholarly journals FIRST AND SECOND ORDER PHASE TRANSITIONS IN MAXWELL–CHERN–SIMONS THEORY COUPLED TO FERMIONS

1996 ◽  
Vol 11 (04) ◽  
pp. 777-822 ◽  
Author(s):  
KEI-ICHI KONDO
Keyword(s):  
Phase Transition ◽  
Chiral Symmetry ◽  
Dyson Equation ◽  
Second Order ◽  
Spontaneous Breaking ◽  
Simons Theory ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Chern Simons ◽  
Chern Simons Theory

In the Maxwell–Chern–Simons theory coupled to Nf flavors of four-component fermions (or an even number of two-component fermions), we construct the gauge-covariant effective potential written in terms of two order parameters which are able to probe the breakdown of chiral symmetry and parity. In the absence of the bare Chern–Simons term, we show that the chiral symmetry is spontaneously broken for fermion flavors Nf below a certain finite critical number [Formula: see text] while the parity is not broken spontaneously. This chiral phase transition is of the second order. In the presence of the bare Chern–Simons term, on the other hand, the chiral phase transition associated with the spontaneous breaking of chiral symmetry is shown to continue to exist, although the parity is explicitly broken. However, it is shown that the existence of the bare Chern–Simons term changes the order of the chiral transition into the first order, no matter how small the bare Chern–Simons coefficient may be. This gauge-invariant result is consistent with that recently obtained through the Schwinger–Dyson equation in the nonlocal gauge.

scholarly journals LOW-MOMENTUM PION ENHANCEMENT INDUCED BY CHIRAL SYMMETRY RESTORATION

2004 ◽  
Vol 19 (03) ◽  
pp. 341-346
Author(s):  
PENGFEI ZHUANG
Keyword(s):  
Phase Transition ◽  
Chiral Symmetry ◽  
Finite Temperature ◽  
Pion Production ◽  
Dense Matter ◽  
Chiral Symmetry Restoration ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Symmetric Phase

The thermal and nonthermal pion production by sigma decay and its relation with chiral symmetry restoration in a hot and dense matter are investigated. The nonthermal decay into pions of sigma mesons which are popularly produced in chiral symmetric phase leads to a low-momentum pion enhancement as a possible signature of chiral phase transition at finite temperature and density.

scholarly journals Surface tension of dense matter at the chiral phase transition

2019 ◽  
Vol 99 (1) ◽  
Author(s):  
Eduardo S. Fraga ◽  
Maurício Hippert ◽  
Andreas Schmitt
Keyword(s):  
Phase Transition ◽  
Surface Tension ◽  
Dense Matter ◽  
Chiral Phase ◽  
Chiral Phase Transition

scholarly journals Strange quark chiral phase transition in hot2+1-flavor magnetized quark matter

2014 ◽  
Vol 90 (1) ◽  
Author(s):  
Márcio Ferreira ◽  
Pedro Costa ◽  
Constança Providência
Keyword(s):  
Phase Transition ◽  
Quark Matter ◽  
Strange Quark ◽  
Chiral Phase ◽  
Chiral Phase Transition

scholarly journals Parity Doubling and the Dense-Matter Phase Diagram under Constraints from Multi-Messenger Astronomy

Universe ◽  
2019 ◽  
Vol 5 (8) ◽  
pp. 180 ◽  
Author(s):  
Michał Marczenko ◽  
David Blaschke ◽  
Krzysztof Redlich ◽  
Chihiro Sasaki
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Low Temperature ◽  
Compact Star ◽  
Dense Matter ◽  
Mass Splitting ◽  
Baryon Density ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Characteristic Features

We extend the recently developed hybrid quark–meson–nucleon model by augmenting a six-point scalar interaction and investigate the consequences for neutron-star sequences in the mass–radius diagram. One of the characteristic features of the model is that the chiral symmetry is restored within the hadronic phase by lifting the mass splitting between chiral partner states, before quark deconfinement takes place. At low temperature and finite baryon density, the model predicts a first- or second-order chiral phase transition, or a crossover, depending on the expectation value of a scalar field, and a first-order deconfinement phase transition. We discuss two sets of free parameters, which result in compact-star mass–radius relations that are at tension with the combined constraints for maximum-mass ( 2 M ⊙ ) and the compactness (GW170817). We find that the most preferable mass–radius relations result in isospin-symmetric phase diagram with rather low temperature for the critical point of the chiral phase transition.

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