## Abstract

In this paper we examine 9Φ-derivable approximations in QED, General theorems tell us that the gauge dependence of the n-loop Φ-derivable approximation shows up at order g

^{2n}where g is the coupling constant. We consider the gauge dependence of the two-loop Φ-derivable approximation to the Debye mass and show that it is of order e^{4}as expected. We solve the three-loop Φ-derivable approximation in QED by expanding sum-integrals in powers of e^{2}and m/T, where m is the Debye mass which satisfies a variational gap equation. The results for the pressure and the Debye mass are accurate to order e^{5}. © 2005 The American Physical Society.Original language | English |
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Journal | Physical Review D |

Volume | 71 |

Issue number | 2 |

DOIs | |

Publication status | Published - 2005 |