Finite Size Effects on the Chiral Phase Transition of Quantum Chromodynamics
Shen-Song Wan, Daize Li, Bonan Zhang, Marco Ruggieri
备注：
11 pages, 9 figures. A short discussion about the critical temperature versus L, including a comparison with the NJL model, has been added in the V2, in Section IV.B
We study the effect of periodic boundary conditions on chiral symmetry breaking and its restoration in Quantum Chromodynamics. As an effective model of the effective potential for the quark condensate, we use the quark-meson model, while the theory is quantized in a cubic box of size $L$. After specifying a renormalization prescription for the vacuum quark loop, we study the condensate at finite temperature, $T$, and quark chemical potential, $μ$. We find that lowering $L$ leads to a catalysis of chiral symmetry breaking. The excitation of the zero mode leads to a jump in the condensate at low temperature and high density, that we suggest to interpret as a gas-liquid phase transition that takes place between the chiral symmetry broken phase (hadron gas) and chiral symmetry restored phase (quark matter). We characterize this intermediate phase in terms of the increase of the baryon density, and of the correlation length of the fluctuations of the order parameter: for small enough $L$ the correlation domains occupy a substantial portion of the volume of the system, and the fluctuations are comparable to those in the critical region. For these reasons, we dub this phase as the {\it subcritical liquid}. The qualitative picture that we draw is in agreement with previous studies based on similar effective models. We also clarify the discrepancy on the behavior of the critical temperature versus $L$ found in different models.
We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $σ$-meson, hence we refer to these processes simply as \sugg{to} one-pion (one-$σ$) exchange\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibriu…
We suggest the idea, supported by concrete calculations within chiral models, that the critical endpoint of the phase diagram of Quantum Chromodynamics with three colors can be detected, by means of Lattice simulations of grand-canonical ensembles with a chiral chemical potential, $μ_5$, conjugated to chiral charge density. In fact, we show that a continuation of the critical endpoint of the phase diagram of Quantum Chromodynamics at finite chemical potential, $μ$, to a critical end point in the temperature-chiral chemical potential plane, is possible. This study paves the way of the mapping o…
In this thesis, we study the novel dynamic critical phenomena induced by superfluidity and the chiral magnetic effect in Quantum Chromodynamics (QCD), respectively. In particular, we find the new dynamic universality class of the high-density QCD critical point between the nuclear and quark superfluid phases beyond the conventional Hohnenberg and Halperin's classification. We also consider the second-order chiral phase transition under an external magnetic field and find that the inclusion of the chiral magnetic effect changes the dynamic universality class from the model E into model A within…
We establish that in Quantum Chromodynamics (QCD) at zero temperature, SU_{L+R}(N_F) exhibits the vector mode conjectured by Georgi and SU_{L-R}(N_F) is realized in either the Nambu-Goldstone mode or else Q_5^a is also screened from view at infinity. The Wigner-Weyl mode is ruled out unless the beta function in QCD develops an infrared stable zero.
We calculate the renormalization group flows of all perturbatively renormalizable interactions in the three-dimensional Ginzburg-Landau potential for the chiral phase transition of three-flavor quantum chromodynamics. On the contrary to the common belief we find a fixed point in the system that is able to describe a second-order phase transition in the infrared. This shows that long-standing assumptions on the transition order might be false. If the transition is indeed of second-order, our results may hint that the axial $U(1)$ symmetry restores at the transition temperature.
By the use of an effective superpotential in supersymmetric quantum chromodynamics (SQCD) with N_f flavors and N_c colors of quarks for N_f>=N_c+2, the influence of soft supersymmetry (SUSY) breakings is examined to clarify dynamics of chiral symmetry breakings near the SUSY limit. In case that SQCD triggers spontaneous chiral symmetry breakings, it is possible to show that our superpotential dynamically favors the successive formation of condensates, leaving either SU(N_f-N_c) or SU(N_f-N_c+1) unbroken as a chiral nonabelian symmetry.
Quantum chromodynamics (QCD) at sufficiently high density is expected to undergo a chiral phase transition. Understanding such a transition is of particular importance for neutron star or quark star physics. In Lagrangian SU(3) lattice gauge theory, the standard approach breaks down at large chemical potential $μ$, due to the complex action problem. The Hamiltonian formulation of lattice QCD doesn't encounter such a problem. In a previous work, we developed a Hamiltonian approach at finite chemical potential $μ$ and obtained reasonable results in the strong coupling regime. In this paper, we e…
Recently the new interest arised (hep-ph/0403139) to the chiral coefficients $L_{11}, L_{12}, L_{13}$ in the low-energy ChPT lagrangian describing the pseudoscalar meson coupling to gravity and/or light singlet dilatons. In 90ties we estimated these coefficients within the Chiral and Conformal Bosonization Model but published the results in the journal not easily accessible for the physics community. We put now our old paper to the E-archives.
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The physics of strong interactions is invariant under the exchange of left-handed and right-handed quarks, at least in the massless limit. This invariance is reflected in the chiral symmetry of quantum chromodynamics. Surprisingly, it has become clear only recently how to implement this important symmetry in lattice formulations of quantum field theories. We will discuss realizations of exact lattice chiral symmetry and give an example of the computation of a physical observable in quantum chromodynamics where chiral symmetry is important. This calculation is performed by relying on finite siz…
Light and heavy-light (b) hadrons are among the most interesting and among the most challenging quantities to calculate in lattice gauge theory. One would like to avoid discretization effects from very heavy quarks and to calculate chiral extrapolations and to calculate finite volume effects from light quarks or to minimize these effects. For this one uses effective theories: Chiral Perturbation Theory and Nonrelativistic QCD or Heavy Quark Effective Theory. Lattice results are reviewed on hadrons containing light quarks and light and b quarks, and discussed in the framework of effective theor…
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