2,029 research outputs found
Renormalizability of the massive Yang-Mills theory
It is shown that the massive Yang-Mills theory is on mass-shell
renormalizable. Thus the Standard Model of electroweak interactions can be
modified by removing terms with the scalar field from the Lagrangian in the
unitary gauge. The resulting electroweak theory without the Higgs particle is
on mass-shell renormalizable and unitary.Comment: 9 page
Limits on Lorentz Violation from the Highest Energy Cosmic Rays
We place several new limits on Lorentz violating effects, which can modify
particles' dispersion relations, by considering the highest energy cosmic rays
observed. Since these are hadrons, this involves considering the partonic
content of such cosmic rays. We get a number of bounds on differences in
maximum propagation speeds, which are typically bounded at the 10^{-21} level,
and on momentum dependent dispersion corrections of the form v = 1 +-
p^2/Lambda^2, which typically bound Lambda > 10^{21} GeV, well above the Planck
scale. For (CPT violating) dispersion correction of the form v = 1 + p/Lambda,
the bounds are up to 15 orders of magnitude beyond the Planck scale.Comment: 24 pages, no figures. Added references, very slight changes. Version
published in Physical Review
Dimensional Reduction applied to QCD at three loops
Dimensional Reduction is applied to \qcd{} in order to compute various
renormalization constants in the \drbar{} scheme at higher orders in
perturbation theory. In particular, the function and the anomalous
dimension of the quark masses are derived to three-loop order. Special emphasis
is put on the proper treatment of the so-called -scalars and the
additional couplings which have to be considered.Comment: 13 pages, minor changes, references adde
Nonperturbative ghost dynamics in the maximal Abelian gauge
We construct the effective potential for the ghost condensate
in the maximal Abelian gauge. This condensate is an
order parameter for a global continuous symmetry, which is spontaneously broken
since a nonvanishing value of lowers the vacuum energy.
The associated Goldstone mode turns out to be unphysical.Comment: 16 pages. v2: version accepted for publication in JHE
The Scientific and Social Activity of Professor N. N. Saltykov in Russia in 1894–1919
The scientific and social activity of Professor N. N. Saltykov in Russia in period 1894–1919 is presented
Unknotting the polarized vacuum of quenched QED
A knot-theoretic explanation is given for the rationality of the quenched QED
beta function. At the link level, the Ward identity entails cancellation of
subdivergences generated by one term of the skein relation, which in turn
implies cancellation of knots generated by the other term. In consequence, each
bare three-loop diagram has a rational Laurent expansion in the Landau gauge,
as is verified by explicit computation. Comparable simplification is found to
occur in scalar electrodynamics, when computed in the Duffin-Kemmer-Petiau
formalism.Comment: 11 pages, LaTe
Higher moments of nucleon spin structure functions in heavy baryon chiral perturbation theory and in a resonance model
The third moment of the twist-3 part of the nucleon spin structure
function is generalized to arbitrary momentum transfer and is
evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order
and in a unitary isobar model (MAID). We show how to link
as well as higher moments of the nucleon spin structure functions
and to nucleon spin polarizabilities. We compare our results with the
most recent experimental data, and find a good description of these available
data within the unitary isobar model. We proceed to extract the twist-4 matrix
element which appears in the suppressed term in the twist
expansion of the spin structure function for proton and neutron.Comment: 30 pages, 7 figure
Resummation of Singlet Parton Evolution at Small x
We propose an improvement of the splitting functions at small x which
overcomes the apparent problems encountered by the BFKL approach. We obtain a
stable expansion for the x-evolution function chi(M) near M=0 by including in
it a sequence of terms derived from the one- and two-loop anomalous dimension
gamma. The requirement of momentum conservation is always satisfied. The
residual ambiguity on the splitting functions is effectively parameterized in
terms of the value of lambda, which fixes the small x asymptotic behaviour
x^-lambda of the singlet parton distributions. We derive from this improved
evolution function an expansion of the splitting function which leads to good
apparent convergence, and to a description of scaling violations valid both at
large and small x.Comment: 16 pages, 6 figures, LaTeX with epsfig; final version, to be
published in Nucl. Phys. B. A few typos corrected for the recor
Four-loop beta function and mass anomalous dimension in Dimensional Reduction
Within the framework of QCD we compute renormalization constants for the
strong coupling and the quark masses to four-loop order. We apply the DR-bar
scheme and put special emphasis on the additional couplings which have to be
taken into account. This concerns the epsilon-scalar--quark Yukawa coupling as
well as the vertex containing four epsilon-scalars. For a supersymmetric Yang
Mills theory, we find, in contrast to a previous claim, that the evanescent
Yukawa coupling equals the strong coupling constant through three loops as
required by supersymmetry.Comment: 15 pages, fixed typo in Eq. (18
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