Tuesday, June 12, 2012

1206.2266 (O. V. Gamayun et al.)

Magnetic field driven instability in planar NJL model in real-time
formalism
   [PDF]

O. V. Gamayun, E. V. Gorbar, V. P. Gusynin
It is known that the symmetric (massless) state of the Nambu--Jona-Lasinio model in 2+1 dimensions in a magnetic field B is not the ground state of the system at zero temperature due to the presence of a negative, linear in &|\sigma+i\pi|$, term in the effective potential for the composite fields $\sigma\sim\bar{\psi}\psi$ and $\pi\sim\bar{\psi}i\gamma^5\psi$, while the quadratic term is always positive (a tachyon is absent). We find that finite temperature is a necessary ingredient for the tachyonic instability of the symmetric state to occur. Utilizing the Schwinger--Keldysh real-time formalism we calculate the dispersion relations for the fluctuation modes of the composite fields $\sigma$ and $\pi$. We demonstrate the presence of the tachyonic instability of the symmetric state for coupling constant that exceeds a certain critical value which vanishes as temperature tends to zero in accordance with the phenomenon of magnetic catalysis.
View original: http://arxiv.org/abs/1206.2266

No comments:

Post a Comment