720 research outputs found
O(1/N_f) Corrections to the Thirring Model in 2<d<4
The Thirring model, that is, a relativistic field theory of fermions with a
contact interaction between vector currents, is studied for dimensionalities
2<d<4 using the 1/N_f expansion, where N_f is the number of fermion species.
The model is found to have no ultraviolet divergences at leading order provided
a regularization respecting current conservation is used. Explicit O(1/N_f)
corrections are computed, and the model shown to be renormalizable at this
order in the massless limit; renormalizability appears to hold to all orders
due to a special case of Weinberg's theorem. This implies there is a universal
amplitude for four particle scattering in the asymptotic regime. Comparisons
are made with both the Gross-Neveu model and QED.Comment: 22 pages in plain TeX, with 7 figs included using psfig.tex (Minor
conceptual changes - algebra unaffected
Heterotic non-linear sigma models with anti-de Sitter target spaces
We calculate the beta function of non-linear sigma models with S^{D+1} and
AdS_{D+1} target spaces in a 1/D expansion up to order 1/D^2 and to all orders
in \alpha'. This beta function encodes partial information about the spacetime
effective action for the heterotic string to all orders in \alpha'. We argue
that a zero of the beta function, corresponding to a worldsheet CFT with
AdS_{D+1} target space, arises from competition between the one-loop and
higher-loop terms, similarly to the bosonic and supersymmetric cases studied
previously in hep-th/0512355. Various critical exponents of the non-linear
sigma model are calculated, and checks of the calculation are presented.Comment: 36 pages, 7 figure
UV finiteness of 3D Yang-Mills theories with a regulating mass in the Landau gauge
We prove that three-dimensional Yang-Mills theories in the Landau gauge
supplemented with a infrared regulating, parity preserving mass term are
ultraviolet finite to all orders. We also extend this result to the
Curci-Ferrari gauge.Comment: 6 page
Review of Aircraft Altitude Errors Due to Static-Pressure Source and Description of Nose-Boom Installations for Aerodynamic Compensation of Error
A brief review of airplane altitude errors due to typical pressure installations at the fuselage nose, the wing tip, and the vertical fins is presented. A static-pressure tube designed to compensate for the position errors of fuselage-nose installations in the subsonic speed range is described. This type of tube has an ogival nose shape with the static-pressure orifices located in the low-pressure region near the tip. The results of wind-tunnel tests of these compensated tubes at two distances ahead of a model of an aircraft showed the position errors to be compensated to within 1/2 percent of the static pressure through a Mach number range up to about 1.0. This accuracy of sensing free-stream static pressure was extended up to a Mach number of about 1.15 by use of an orifice arrangement for producing approximate free-stream pressures at supersonic speeds and induced pressures for compensation of error at subsonic speeds
Off-diagonal mass generation for Yang-Mills theories in the maximal Abelian gauge
We investigate a dynamical mass generation mechanism for the off-diagonal
gluons and ghosts in SU(N) Yang-Mills theories, quantized in the maximal
Abelian gauge. Such a mass can be seen as evidence for the Abelian dominance in
that gauge. It originates from the condensation of a mixed gluon-ghost operator
of mass dimension two, which lowers the vacuum energy. We construct an
effective potential for this operator by a combined use of the local composite
operators technique with algebraic renormalization and we discuss the gauge
parameter independence of the results. We also show that it is possible to
connect the vacuum energy, due to the mass dimension two condensate discussed
here, with the non-trivial vacuum energy originating from the condensate ,
which has attracted much attention in the Landau gauge.Comment: 15 pages. Revtex. 1 .eps figure. Talk given by D.Dudal at XXV
Encontro Nacional de Fisica de Particulas e Campos, Caxambu, Minas Gerais,
Brasil, 24-28 Aug 2004. To appear in Brazilian Journal of Physic
The asymmetry of the dimension 2 gluon condensate: the zero temperature case
We provide an algebraic study of the local composite operators A_\mu
A_\nu-\delta_{\mu\nu}/d A^2 and A^2, with d=4 the spacetime dimension. We prove
that these are separately renormalizable to all orders in the Landau gauge.
This corresponds to a renormalizable decomposition of the operator A_\mu A_\nu
into its trace and traceless part. We present explicit results for the relevant
renormalization group functions to three loop order, accompanied with various
tests of these results. We then develop a formalism to determine the zero
temperature effective potential for the corresponding condensates, and recover
the already known result for \neq 0, together with <A_\mu
A_\nu-\delta_{\mu\nu}/d A^2>=0, a nontrivial check that the approach is
consistent with Lorentz symmetry. The formalism is such that it is readily
generalizable to the finite temperature case, which shall allow a future
analytical study of the electric-magnetic symmetry of the condensate,
which received strong evidence from recent lattice simulations by Chernodub and
Ilgenfritz, who related their results to 3 regions in the Yang-Mills phase
diagram.Comment: 25 page
Phase transition and critical behaviour of the d=3 Gross-Neveu model
A second order phase transition for the three dimensional Gross-Neveu model
is established for one fermion species N=1. This transition breaks a paritylike
discrete symmetry. It constitutes its peculiar universality class with critical
exponent \nu = 0.63 and scalar and fermionic anomalous dimension \eta_\sigma =
0.31 and \eta_\psi = 0.11, respectively. We also compute critical exponents for
other N. Our results are based on exact renormalization group equations.Comment: 4 pages, 1 figure; v4 corresponds to the published articl
Non-linear sigma models with anti-de Sitter target spaces
We present evidence that there is a non-trivial fixed point for the AdS_{D+1}
non-linear sigma model in two dimensions, without any matter fields or
additional couplings beyond the standard quadratic action subject to a
quadratic constraint. A zero of the beta function, both in the bosonic and
supersymmetric cases, appears to arise from competition between one-loop and
higher loop effects. A string vacuum based on such a fixed point would have
string scale curvature. The evidence presented is based on fixed-order
calculations carried to four loops (corresponding to O(\alpha'^3) in the
spacetime effective action) and on large D calculations carried to O(D^{-2})
(but to all orders in \alpha'). We discuss ways in which the evidence might be
misleading, and we discuss some features of the putative fixed point, including
the central charge and an operator of negative dimension. We speculate that an
approximately AdS_5 version of this construction may provide a holographic dual
for pure Yang-Mills theory, and that quotients of an AdS_3 version might stand
in for Calabi-Yau manifolds in compactifications to four dimensions.Comment: 44 pages, 4 figures. v2: references adde
Renormalization group aspects of the local composite operator method
We review the current status of the application of the local composite
operator technique to the condensation of dimension two operators in quantum
chromodynamics (QCD). We pay particular attention to the renormalization group
aspects of the formalism and the renormalization of QCD in various gauges.Comment: 13 latex pages, talk presented at RG0
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