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Boris Kastening

Publications and source records attributed to Boris Kastening.

27 records · Page 2Linked to original sources
arXiv1999

Recursive Graphical Construction of Feynman Diagrams and Their Multiplicities in phi^4- and in phi^2A-Theory

The free energy of a field theory can be considered as a functional of the free correlation function. As such it obeys a nonlinear functional differential equation which can be turned into a recursion relation. This is solved order by order in the coupling constant to find all connected vacuum diagrams with their proper multiplicities. The procedure is applied to a multicomponent scalar field theory with a phi^4-self-interaction and then to a theory of two scalar fields phi and A with an interaction phi^2 A. All Feynman diagrams with external lines are obtained from functional derivatives of the connected vacuum diagrams with respect to the free correlation function. Finally, the recursive graphical construction is automatized by computer algebra with the help of a unique matrix notation for the Feynman diagrams.

hep-th↗
arXiv1998

Five-Loop Vacuum Energy Beta Function in phi^4 Theory with O(N)-Symmetric and Cubic Interactions

The beta function of the vacuum energy density is analytically computed at the five-loop level in O(N)-symmetric phi^4 theory, using dimensional regularization in conjunction with the MSbar scheme. The result for the case of a cubic anisotropy is also given. It is pointed out how to also obtain the beta function of the coupling and the gamma function of the mass from vacuum graphs. This method may be easier than traditional approaches.

hep-ph↗
arXiv1998

Corrections to oblique parameters induced by anomalous vector boson couplings

We study quadratically divergent radiative corrections to the oblique parameters at LEP1 induced by non-standard vector boson self-couplings. We work in the Stueckelberg formalism and regulate the divergences through a gauge-invariant higher derivative scheme. Using consistency arguments together with the data we find a limit on the anomalous magnetic moment Delta kappa of the W-boson, |Delta kappa| <= 0.26.

hep-ph↗
arXiv1996

Four-Loop Vacuum Energy Beta Function in O(N) Symmetric Scalar Theory

The beta function of the vacuum energy density is computed at the four-loop level in massive O(N) symmetric phi^4 theory. Dimensional regularization is used in conjunction with the MSbar scheme and all calculations are in momentum space in the massive theory. The result is beta_v = g N/4+g^3 N(N+2)/96+g^4 N(N+2)(N+8)[12 zeta(3)-25]/1296+o(g^5).

hep-ph↗
arXiv1995

The Free Energy of Hot Gauge Theories with Fermions Through g^5

We compute the free energy density $F$ for gauge theories, with fermions, at high temperature and zero chemical potential. In the expansion $F=T^4 [c_0+c_2 g^2+c_3 g^3+(c'_4\ln g+c_4)g^4+ (c'_5\ln g+c_5)g^5+O(g^6)]$, we determine $c'_5$ and $c_5$ analytically by calculating two- and three-loop diagrams. The $g^5$ term constitutes the first correction to the $g^3$ term and is for the non-Abelian case the last power of $g$ that can be computed within perturbation theory. We find that the $g^5$ term receives no contributions from overlapping double-frequency sums and that $c'_5$ vanishes.

hep-ph↗
arXiv1994

A New Gauge for Computing Effective Potentials in Spontaneously Broken Gauge Theories

A new class of renormalizable gauges is introduced that is particularly well suited to compute effective potentials in spontaneously broken gauge theories. It allows one to keep free gauge parameters when computing the effective potential from vacuum graphs or tadpoles without encountering mixed propagators of would-be-Goldstone bosons and longitudinal modes of the gauge field. As an illustrative example several quantities are computed within the Abelian Higgs model, which is renormalized at the two-loop level. The zero temperature effective potential in the new gauge is compared to that in $R_ξ$ gauge at the one-loop level and found to be not only easier to compute but also to have a more convenient analytical structure. To demonstrate renormalizability of the gauge for the non-Abelian case, the renormalization of an SU(2)-Higgs model with completely broken gauge group and of an SO(3)-Higgs model with an unbroken SO(2) subgroup is outlined and renormalization constants are given at the one-loop level.

hep-ph↗