Anisotropic pressure of magnetized QGP within an improved quasiparticle model

In the present work we extend the improved quasi-particle model to study the magnetized QCD matter. We first introduce a classical background field B(T, eB) in the effective Lagrangian and deal with the infinity of vacuum energy in the presence of a strong magnetic field. The formula for pressure for (2+1)-flavor quark gluon plasma(QGP) can be obtained based on ensemble theory.Subsequently, we focus on the study of the total pressure in the parallel and perpendicular directions, including pure field contributions. We find that the total longitudinal pressure decreases and the total transverse pressure increases with the magnetic field increasing. We have discovered that the transverse pressure can exceed the longitudinal pressure under the presence of a strong magnetic fields, which is opposite to the conclusion obtained without the pure-field effect. Moreover the total transverse pressure is seen to increase with magnetic field,which contradicts the conclusion neglecting the pure-field effect. Our study shows that the pure field has significant contributions for the anisotropic pressure, which is consistent with the conclusions of relevant studies in recent years.