1,298 research outputs found
Euclidean asymptotic expansions of Green functions of quantum fields (II) Combinatorics of the asymptotic operation
The results of part I (hep-ph/9612284) are used to obtain full asymptotic
expansions of Feynman diagrams renormalized within the MS-scheme in the regimes
when some of the masses and external momenta are large with respect to the
others. The large momenta are Euclidean, and the expanded diagrams are regarded
as distributions with respect to them. The small masses may be equal to zero.
The asymptotic operation for integrals is defined and a simple combinatorial
techniques is developed to study its exponentiation. The asymptotic operation
is used to obtain the corresponding expansions of arbitrary Green functions.
Such expansions generalize and improve upon the well-known short-distance
operator-product expansions, the decoupling theorem etc.; e.g. the low-energy
effective Lagrangians are obtained to all orders of the inverse heavy mass. The
obtained expansions possess the property of perfect factorization of large and
small parameters, which is essential for meaningful applications to
phenomenology. As an auxiliary tool, the inversion of the R-operation is
constructed. The results are valid for arbitrary QFT models.Comment: one .sty + one .tex (LaTeX 2.09) + one .ps (GSview) = 46 pp. Many
fewer misprints than the journal versio
Landau equations and asymptotic operation
The pinched/non-pinched classification of intersections of causal
singularities of propagators in Minkowski space is reconsidered in the context
of the theory of asymptotic operation as a first step towards extension of the
latter to non-Euclidean asymptotic regimes. A highly visual
distribution-theoretic technique of singular wave fronts is tailored to the
needs of the theory of Feynman diagrams. Besides a simple derivation of the
usual Landau equations in the case of the conventional singularities, the
technique naturally extends to other types of singularities e.g. due to linear
denominators in non-covariant gauges etc. As another application, the results
of Euclidean asymptotic operation are extended to a class of quasi-Euclidean
asymptotic regimes in Minkowski space.Comment: 15p PS (GSview), IJMP-A (accepted
The BFKL Pomeron within Physical Renormalization Schemes and Scales
In this lecture the next-to-leading order (NLO) corrections to the QCD
Pomeron intercept obtained from the Balitsky-Fadin-Kuraev-Lipatov (BFKL)
equation are discussed. It is shown that the BFKL Pomeron intercept when
evaluated in non-Abelian physical renormalization schemes with
Brodsky-Lepage-Mackenzie (BLM) optimal scale setting does not exhibit the
serious problems encountered in the modified minimal subtraction (bar{MS})
scheme. The results obtained provide an opportunity for applications of the NLO
BFKL resummation to high-energy phenomenology.
One of such applications for virtual gamma-gamma total cross section shows a
good agreement with preliminary data at CERN LEP.Comment: Presented at XXXXV PNPI Winter School, Repino, St.Petersburg, Russia,
19-25 Feb., 2001; Latex, 16 pages, 5 figure
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