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J. A. Gracey

Publications and source records attributed to J. A. Gracey.

At least 127 records · Page 7Linked to original sources
arXiv2003

The anomalous dimension of the gluon-ghost mass operator in Yang-Mills theory

The local composite gluon-ghost operator $({1/2}A^{aμ}A_μ^{a}+α\bar{c}^{a}c^{a})$ is analysed in the framework of the algebraic renormalization in SU(N) Yang-Mills theories in the Landau, Curci-Ferrari and maximal abelian gauges. We show, to all orders of perturbation theory, that this operator is multiplicatively renormalizable. Furthermore, its anomalous dimension is not an independent parameter of the theory, being given by a general expression valid in all these gauges. We also verify the relations we obtain for the operator anomalous dimensions by explicit 3-loop calculations in the MSbar scheme for the Curci-Ferrari gauge.

hep-th↗
arXiv2003

Three loop anomalous dimension of the second moment of the transversity operator in the MSbar and RI' schemes

We compute the anomalous dimension of the second moment of the transversity operator, \barψ σ^{μν} D^ρψ, at three loops in both the MSbar and RI' schemes. As a check on the result we also determine the O(1/N_f) critical exponent of the n-th moment of the transversity operator in d-dimensions in the large N_f expansion and determine leading order information on the n dependence of the anomalous dimension at three and four loops in MSbar. In addition the RI' anomalous dimension of the non-singlet twist-2 operator, \barψ γ^μD^νψ, is also determined.

hep-ph↗
arXiv2003

More on ghost condensation in Yang-Mills theory: BCS versus Overhauser effect and the breakdown of the Nakanishi-Ojima annex SL(2,R) symmetry

We analyze the ghost condensates , and in Yang-Mills theory in the Curci-Ferrari gauge. By combining the local composite operator formalism with the algebraic renormalization technique, we are able to give a simultaneous discussion of , and , which can be seen as playing the role of the BCS, respectively Overhauser effect in ordinary superconductivity. The Curci-Ferrari gauge exhibits a global continuous symmetry generated by the Nakanishi-Ojima (NO) algebra. This algebra includes, next to the (anti-)BRST transformation, a SL(2,R) subalgebra. We discuss the dynamical symmetry breaking of the NO algebra through these ghost condensates. Particular attention is paid to the Landau gauge, a special case of the Curci-Ferrari gauge.

hep-th↗
arXiv2003

Three loop anomalous dimension of non-singlet quark currents in the RI' scheme

We renormalize QCD at three loops in the modified regularization invariant, RI', scheme in arbitrary covariant gauge and deduce that the four loop beta-function is equivalent to the MSbar result. The anomalous dimensions of the scalar, vector and tensor currents are then determined in the RI' scheme at three loops by considering the insertion of the operator in a quark two-point function. The expression for the scalar current agrees with the quark mass anomalous dimension and we deduce an expression for the four loop RI' mass anomalous dimension in arbitrary covariant gauge and for any Lie group.

hep-ph↗
arXiv2003

A determination of and the non-perturbative vacuum energy of Yang-Mills theory in the Landau gauge

We discuss the 2-point-particle-irreducible (2PPI) expansion, which sums bubble graphs to all orders, in the context of SU(N) Yang-Mills theory in the Landau gauge. Using the method we investigate the possible existence of a gluon condensate of mass dimension two, , and the corresponding non-zero vacuum energy. This condensate gives rise to a dynamically generated mass for the gluon.

hep-th↗
arXiv2002

Three loop MSbar renormalization of the Curci-Ferrari model and the dimension two BRST invariant composite operator in QCD

The massless Curci-Ferrari model with N_f flavours of quarks is renormalized to three loops in the MSbar scheme in an arbitrary covariant gauge with parameter alpha. The renormalization of the BRST invariant dimension two composite operator, 1/2 (A^a_μ)^2 - alpha \bar{c}^a c^a, which corresponds to the mass operator in the massive Curci-Ferrari model, is determined by renormalizing the Green's function where the operator is inserted in a ghost two-point function. Consequently the anomalous dimension of the QCD Landau gauge operator, 1/2 (A^a_μ)^2, and the (gauge independent) photon mass anomalous dimension in QED are both deduced at three loops.

hep-th↗
arXiv2002

Critical exponent omega at O(1/N) in O(N) x O(m) spin models

We compute the O(1/N) correction to the stability critical exponent, omega, in the Landau-Ginzburg-Wilson model with O(N) x O(m) symmetry at the stable chiral fixed point and the stable direction at the unstable antichiral fixed point. Several constraints on the O(1/N) coefficients of the four loop perturbative beta-functions are computed.

hep-th↗
arXiv2002

Chiral exponents in O(N) x O(m) spin models at O(1/N^2)

The critical exponents corresponding to chirality are computed at O(1/N^2) in d-dimensions at the stable chiral fixed point of a scalar field theory with an O(N) x O(m) symmetry. Pade-Borel estimates for the exponents are given in three dimensions for the Landau-Ginzburg-Wilson model at m = 2.

cond-mat↗
arXiv2002

Crossover exponent in O(N) phi^4 theory at O(1/N^2)

The critical exponent phi_c, derived from the anomalous dimension of the bilinear operator responsible for crossover behaviour in O(N) phi^4 theory, is calculated at O(1/N^2) in a large N expansion in arbitrary space-time dimension d = 4 - 2 epsilon. Its epsilon expansion agrees with the known O(epsilon^4) perturbative expansion and new information on the structure of the five loop exponent is provided. Estimates of phi_c and the related crossover exponents beta_c and gamma_c, using Pade-Borel resummation, are provided for a range of N in three dimensions.

cond-mat↗
arXiv2002

Dynamical mass generation by source inversion: calculating the mass gap of the chiral Gross-Neveu model

We probe the U(N) chiral Gross-Neveu model with a source-term $JłΨΨ$. We find an expression for the renormalization scheme and scale invariant source $\hat{J}$, as a function of the generated mass gap. The expansion of this function is organized in such a way that all scheme and scale dependence is reduced to one single parameter $d$. We obtain a non-perturbative mass gap as the solution of $\hat{J}=0$. A physical choice for $d$ gives good results for $N>2$. The self-consistent minimal sensitivity condition gives a slight improvement.

hep-th↗
arXiv2001

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 $\barψ σ^{μν} ψ$ is deduced at four loops in the MSbar scheme up to one unknown parameter.

hep-ph↗
arXiv2001

Four loop wave function renormalization in the non-abelian Thirring model

We compute the anomalous dimension of the fermion field with N_f flavours in the fundamental representation of a general Lie colour group in the non-abelian Thirring model at four loops. The implications on the renormalization of the two point Green's function through the loss of multiplicative renormalizability of the model in dimensional regularization due to the appearance of evanescent four fermi operators are considered at length. We observe the appearance of one new colour group Casimir, d_F^{abcd} d_F^{abcd}, in the final four loop result and discuss its consequences for the relation of the Knizhnik-Zamolodchikov critical exponents in the Wess Zumino Witten Novikov model to the non-abelian Thirring model. Renormalization scheme changes are also considered to ensure that the underlying Fierz symmetry broken by dimensional regularization is restored.

hep-th↗
arXiv2000

On the n -> 0 limit of gamma_gg(a) in QCD

We consider the n -> 0 limit of the DGLAP splitting function gamma_gg(a) at all orders in the strong coupling constant, a, by analysing the leading order large N_f form of the associated d-dimensional critical exponent. We show that for unpolarized scattering the pole at n = 0 which appears in successive orders in perturbation theory is absent in the resummed expression.

hep-ph↗