51,137 research outputs found
Higher covariant derivative regulators and non-multiplicative renormalization
The renormalization algorithm based on regularization methods with two
regulators is analyzed by means of explicit computations. We show in particular
that regularization by higher covariant derivative terms can be complemented
with dimensional regularization to obtain a consistent renormalized
4-dimensional Yang-Mills theory at the one-loop level. This shows that hybrid
regularization methods can be applied not only to finite theories, like \eg\
Chern-Simons, but also to divergent theories.Comment: 12 pages, phyzzx, no figure
BRS symmetry versus supersymmetry in Yang-Mills-Chern-Simons theory
We prove that three-dimensional supersymmetric Yang-Mills-Chern-Simons
theory is finite to all loop orders. In general this leaves open the
possibility that different regularization methods lead to different finite
effective actions. We show that in this model dimensional regularization and
regularization by dimensional reduction yield the same effective action.
Consequently, the superfield approach preserves BRS invariance for this model.Comment: 27 pages, 2 figures, latex2e, uses epsfi
Higher covariant derivative Pauli-Villars regularization does not lead to a consistent QCD
We compute the beta function at one loop for Yang-Mills theory using as
regulator the combination of higher covariant derivatives and Pauli-Villars
determinants proposed by Faddeev and Slavnov. This regularization prescription
has the appealing feature that it is manifestly gauge invariant and essentially
four-dimensional. It happens however that the one-loop coefficient in the beta
function that it yields is not as it should be, but The
difference is due to unphysical logarithmic radiative corrections generated by
the Pauli-Villars determinants on which the regularization method is based.
This no-go result discards the prescription as a viable gauge invariant
regularization, thus solving a long-standing open question in the literature.
We also observe that the prescription can be modified so as to not generate
unphysical logarithmic corrections, but at the expense of losing manifest gauge
invariance.Comment: 43 pages, Latex file (uses the macro axodraw.sty, instructions of how
to get it and use it included), FTUAM 94/9, NIKHEF-H 94/2
Regularization and Renormalization of Chern-Simons Theory
We analyze some features of the perturbative quantization of Chern-Simons
theory (CST) in the Landau gauge. In this gauge the theory is known to be
perturbatively finite. We consider the renormalization scheme in which the
renormalized parameter equals the bare or classical one and show that it
constitutes a natural parametrization for the quantum theory. The reason is
that, although in this renormalization scheme the value of the Green functions
depends on the regularization used, comparison among different regularization
methods shows that the observables (Wilson loops) are the same function of the
shifted monodromy parameter for all BRS invariant regulators used so
far for CST. We also discuss a particular BRS invariant regularization
prescription in which CST is perturbatively defined as the large mass limit of
dimensionally regularized topologically massive Yang-Mills theory. With this
regularization prescription the radiative corrections induced by two-loop
contributions do not entail observable consequences since they can be
reabsorbed by a finite rescaling of the fields only. This very mechanism is
conjectured to take place at higher perturbative orders. Talk presented by G.G.
at the NATO AWR on ``Low dimensional Topology and Quantum Field Theory'', 6-13
September 1992, Cambridge (UK).Comment: 10 pages, Phyzzx, LPTHE 92-4
Non-relativistic pair annihilation of nearly mass degenerate neutralinos and charginos II. P-wave and next-to-next-to-leading order S-wave coefficients
This paper is a continuation of an earlier work (arXiv:1210.7928) which
computed analytically the tree-level annihilation rates of a collection of
non-relativistic neutralino and chargino two-particle states in the general
MSSM. Here we extend the results by providing the next-to-next-to-leading order
corrections to the rates in the non-relativistic expansion in momenta and mass
differences, which include leading P-wave effects, in analytic form. The
results are a necessary input for the calculation of the Sommerfeld-enhanced
dark matter annihilation rates including short-distance corrections at
next-to-next-to-leading order in the non-relativistic expansion in the general
MSSM with neutralino LSP.Comment: LaTeX, 16 pages (+ 36 pages Appendix), 4 figures; v2 - new appendix
with analytic results for the P-wave and rest of v^2 corrections to
annihilation rates in the wino limit added, matches published versio
New contributions to heavy quark sum rules
We analyse new contributions to the theoretical input in heavy quark sum
rules and we show that the general theory of singularities of perturbation
theory amplitudes yields the method to handle these specific features. In
particular we study the inclusion of heavy quark radiation by light quarks at
O(alpha_s^2) and non-symmetric correlators at O(alpha_s^3). Closely related, we
also propose a solution to the construction of moments of the spectral
densities at O(alpha_s^3) where the presence of massless contributions
invalidates the standard approach. We circumvent this problem through a new
definition of the moments, providing an infrared safe and consistent procedure.Comment: 15 pages, 3 figures. Version accepted for publication in The European
Journal of Physics C; several new comments and references added, conclusions
unchange
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