Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimization of QCD Perturbation Theory: Results for R(e+e-) at fourth
  order   Physical quantities in QCD are independent of renormalization scheme (RS),
but that exact invariance is spoiled by truncations of the perturbation series.
"Optimization" corresponds to making the perturbative approximant, at any given
order, locally invariant under small RS changes. A solution of the resulting
optimization equations is presented. It allows an efficient algorithm for
finding the optimized result. Example results for R(e+e-)=3(Sum q_i^2)(1+R) to
fourth order (NNNLO) are given that show nice convergence, even down to
arbitrarily low energies. The Q=0 "freezing" behaviour, R=0.3+/-0.3, found at
third order is confirmed and made more precise; R=0.2+/-0.1. Low-energy results
in the MS-bar scheme, by contrast, show the typical pathologies of a
non-convergent asymptotic series.

37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
3
The categories of this paper are: physics