相关论文: In a hot, chirally symmetric phase, $\pi^0$ doesn'…

Using constituent quarks coupled to a linear sigma model at nonzero temperature, I show that many anomalous mesonic amplitudes, such as $\pi^0 \rightarrow \gamma \gamma$, vanish in a chirally symmetric phase. Processes which are allowed,…

We use the 2-dimensional $\sigma$ model as a toy model to study the behavior of anomalous amplitudes in the limit where the constituent quark mass is small. Symmetry arguments tell that the $\pi^o\to\gamma$ amplitude should vanish if $m\to…

At zero temperature, in the chiral limit the amplitude for pi0 to decay into two photons is directly related to the coefficient of the axial anomaly. At any nonzero temperature, this direct relationship is lost: while the coefficient of the…

First we summarize the quark-level linear $\sigma$ model compositeness conditions and verify that indeed $m_\sigma = 2 m_q$ when $m_\pi = 0$ and $N_c=3$, rather than in the $N_c\to\infty$ limit, as is sometimes suggested. Later we show that…

If the phase transition of $QCD$ at nonzero temperature is dominated by the (approximate) restoration of chiral symmetry, then the transition might be characterized using a gauged linear sigma model. Assuming that vector meson dominance…

The chiral phase transition at a certain critical temperature is a restoration mechanism of the chiral symmetry, broken by the nonzero mass of quarks and mesons. The transition can be studied through several models, among which are the…

We discuss chiral theories of constituent quarks interacting with bosons at high temperatures. In the chirally symmetric phase we demonstrate by applying functional methods the presence of effective anomalous couplings for e.g. $\pi \sigma…

In vacuum, in the chiral limit the coupling of a pion to two on-shell photons is directly related to the coefficient of the axial anomaly in QED. This relationship is lost at any nonzero temperature. Explicit calculations show that the…

Chiral theories of constituent quarks interacting with bosons and photons at high temperatures are studied. In the expected chirally symmetric phase effective electromagnetic anomalous couplings for e.g. $\pi \sigma \to \gamma \gamma, ~…

Properties and temperature behavior of pi and sigma bound states are studied in the framework of the nonlocal model with a separable interaction kernel based on the quark Dyson-Schwinger and the meson Bethe-Salpeter equations. M_pi(T),…

The linear O($N$) sigma model undergoes a symmetry restoring phase transition at finite temperature. We show that the nonlinear O($N$) sigma model also undergoes a symmetry restoring phase transition; the critical temperatures are the same…

We present models where $\gamma_+$ and $\gamma_-$, the exponents of the susceptibility in the high and low temperature phases, are generically different. In these models, continuous symmetries are explicitly broken down by discrete…

We discuss the global symmetries of the high temperature phase of QCD with $N_f$ massless quarks. We show that the $U(N_f) \times U(N_f)$ symmetries are only violated by operators of dimension $\geq 3 N_f$. For $N_f > 2$ this implies that…

The $\eta \to \pi^+ \pi^- \pi^0 \gamma$ decay is discussed in the general context of Chiral Perturbation Theory (ChPT), assuming that the low--energy constants (counter--terms) are saturated by vector-meson resonances. The $\eta \to \pi^+…

A confined quark model study in a couple of chirally anomalous processes is presented in comparison with effective meson Lagrangian approaches of various kind. The processes considered are \pi^0 \to \gamma \gamma and \gamma \to \pi^+ \pi^-…

We consider the form of the chiral symmetry breaking piece of the effective potential in the linear sigma model. Surprisingly, it allows for a second local minimum at both zero and finite temperature. Even though chiral symmetry is not…

We explore a possible phase where chiral $SU(2)_L \times SU(2)_R$ symmetry is spontaneously broken while its center $Z_2$ symmetry remains unbroken and its consequence on thermal quantities. In this phase, chiral symmetry breaking is driven…

We study the chiral phase transition in the linear sigma model with 2 quark flavors and $N_c$ colors. One-loop calculations predict a first-order phase transition at both $\mu=0$ and $\mu\neq 0$. We also discuss the phase diagram and make a…

The Heat Kernel Method is applied to the constituent quark model. We calculate the effect of thermal quark fluctuations on the meson action and the resulting quark condensate and pi pi-scattering amplitude at finite temperature. The quarks…

The three-dimensional four-fermion model with a Z_2 chiral symmetry and N=4 fermion species in the system is investigated numerically at non-zero temparature and chemical potential. The phase diagram in the (chemical potential, temperature)…