arXiv subjects

Jens Kuester

Publications and source records attributed to Jens Kuester.

2 recordsLinked to original sources

arXiv1996

Calculation of Universal Amplitude Ratios in three-loop order

For the universality class of three-dimensional Ising systems the ratio of the high- and low-temperature amplitudes for the correlation length and for the susceptibility are universal quantities. They can be calculated by renormalized perturbation theory for scalar $ϕ^4$ theory in fixed dimensions $D=3$ in the symmetric phase and in the phase of broken symmetry. In this article the amplitude ratios are calculated in the three-loop approximation. Using the fixed point values of the coupling constants we obtain $f_+/f_-=2.013(28)$ and $C_+/C_-=4.72(17)$.

cond-mat↗

arXiv1996

Tadpole Summation by Dyson-Schwinger Equations

In quantum field theory with three-point and four-point couplings the Feynman diagrams of perturbation theory contain momentum independent subdiagrams, the ``tadpoles'' and ``snails''. With the help of Dyson-Schwinger equations we show how these can be summed up completely by a suitable modification of the mass and coupling parameters. This reduces the number of diagrams significantly. The method is useful for the organisation of perturbative calculations in higher orders.

hep-th↗