A new method for taming tensor sum-integrals

We report on the computation of a class of massless bosonic three-loop vacuum sum-integrals which are key building blocks for an evaluation of the Debye screening mass in hot QCD. Generalizing known techniques and introducing the concept of tensor reduction by dimensionality shifts (known to the zero-temperature community since the work of Tarasov in 1996) to finite temperature, we are able to treat hitherto unaccessible cases, which will allow us to finalize the long-term project of NNLO Debye mass evaluation.Comment: 26 page

Three-loop Debye mass and effective coupling in thermal QCD

Ghisoiu I. Three-loop Debye mass and effective coupling in thermal QCD. Bielefeld: Universität Bielefeld; 2013.We determine the three-loop effective parameters of the dimensionally reduced theory of EQCD as matching coefficients to full QCD. The mass parameter \mE is interpreted as the high temperature, perturbative contribution to the Debye screening mass of chromo-electric fields and enters the pressure of QCD at the order of $g^7$. The effective coupling \gE can be used to compute the spatial string tension of QCD. However, we suspect that the effective coupling \gE obtains through renormalization contributions from higher order operators that have not yet been taken into account. Therefore our result reflects the (still divergent) contribution from the super-renormalizable EQCD Lagrangian. In addition, we present a new method for computing tensor sum-integrals and provide a generalization to the known computation techniques of spectacles-type sum-integrals

Debye screening mass of hot Yang-Mills theory to three-loop order

Peer reviewe

On high-order perturbative calculations at finite density

We discuss the prospects of performing high-order perturbative calculations in systems characterized by a vanishing temperature but finite density. In particular, we show that the determination of generic Feynman integrals containing fermionic chemical potentials can be reduced to the evaluation of three-dimensional phase space integrals over vacuum on-shell amplitudes - a result reminiscent of a previously proposed "naive real-time formalism" for vacuum diagrams. Applications of these rules are discussed in the context of the thermodynamics of cold and dense QCD, where it is argued that they facilitate an extension of the Equation of State of cold quark matter to higher perturbative orders. (C) 2016 The Author(s). Published by Elsevier B.V.Peer reviewe

A new three-loop sum-integral of mass dimension two

We evaluate a new 3-loop sum-integral which contributes to the Debye screening mass in hot QCD. While we manage to derive all divergences analytically, its finite part is mapped onto simple integrals and evaluated numerically.Comment: 15 page

Automated computation meets hot QCD

Ghisoiu I, Schroeder Y. Automated computation meets hot QCD. In: PoS. Vol LL2012. 2012: 063.We give a short review on recent progress in the field of automatedcalculations in finite-temperature field theory, where integration-by-partstechniques have proven (almost) as useful as in the zero-temperature case.Furthermore, we provide one concrete example of an evaluation of a newthree-loop master sum-integral that exhibits maximal divergence