2,627 research outputs found
The simple scheme for the calculation of the anomalous dimensions of composite operators in the 1/N expansion
The simple method for the calculating of the anomalous dimensions of the
composite operators up to 1/N^2 order is developed. We demonstrate the
effectiveness of this approach by computing the critical exponents of the
and
operators in the 1/N^2 order in the nonlinear sigma model. The special
simplifications due to the conformal invariance of the model are discussed.Comment: 20 pages, Latex, uses Feynman.st
Electron Mass Anomalous Dimension at O(1/N^2_f) in Quantum Electrodynamics
The critical exponent corresponding to the renormalization of the composite
operator is computed in quantum electrodynamics at
O(1/\Nf^2) in arbitrary dimensions and covariant gauge at the non-trivial
zero of the -function in the large \Nf expansion and the exponent
corresponding to the anomalous dimension of the electron mass which is a gauge
independent object is deduced. Expanding in powers of
we check it is consistent with the known three loop perturbative
structure and determine the subsequent coefficients in the coupling constantComment: 12 pages (latex), 1 figure (available from author on request),
LTH-31
Anomalous dimension of non-singlet quark currents at O(1/Nf^2) in QCD
We compute the O(1/Nf^2) corrections to the flavour non-singlet quark
bilinear currents in QCD in arbitrary spacetime dimensions. Hence, the
anomalous dimension of the QED current is
deduced at four loops in the MSbar scheme up to one unknown parameter.Comment: 8 latex page
Status of twist-2 operator dimensions at O(1/N_f)
We review the computation of the anomalous dimensions of the twist-2
unpolarized operators in the large N_f expansion. Results are discussed for the
predominantly gluonic singlet operator and the O(1/N_f) part of the 3-loop
splitting function is given.Comment: 4 latex pages, contribution to DIS 9
Four loop MSbar mass anomalous dimension in the Gross-Neveu model
We compute the four loop term of the mass anomalous dimension in the two
dimensional Gross-Neveu model in the MSbar scheme. The absence of
multiplicative renormalizability which results when using dimensional
regularization means that the effect of the evanescent operator, which first
appears at three loops in the 4-point Green's function, has to be properly
treated in the construction of the renormalization group function. We repeat
the calculation of the three loop MSbar beta-function and construct the
beta-function of the evanescent operator coupling which corrects earlier
computations.Comment: 20 latex pages, 7 figure
The Nambu-Jona-Lasinio Model at O(1/N^2)
We write down the anomalous dimensions of the fields of the
Nambu--Jona-Lasinio model or chiral Gross Neveu model with a continuous global
chiral symmetry for the two cases and
at in a expansion.Comment: 9 latex pages, 4 figures (available on request from the author),
LTH-308, (2 eqns corrected
Plasma jet electrode has longer operating life
Water-cooled, silver-infiltrated tungsten electrode has twice the operating lifetime of the pure tungsten electrode used in plasma jet generators. This electrode reduces the erosion rate, ensures excellent heat transfer, and reduces thermal stresses
Momentum subtraction and the R-ratio
We determine the R-ratio for massless quarks in several renormalization
schemes to various loop orders. These are the momentum subtraction schemes of
Celmaster and Gonsalves as well as the minimal momentum subtraction scheme. The
dependence of the R-ratio on the schemes is analysed.Comment: 27 latex pages, 36 figures, anc directory contains txt file with
electronic version of main equation
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