1,391 research outputs found
Conformal anomaly from gauge fields without gauge fixing
We show how the Weyl anomaly generated by gauge fields, can be computed from
manifestly gauge invariant and diffeomorphism invariant exact renormalization
group equations, without having to fix the gauge at any stage. Regularisation
is provided by covariant higher derivatives and by embedding the Maxwell field
into a spontaneously broken supergauge theory. We first provide a
realisation that leaves behind two versions of the original gauge field,
and then construct a manifestly supergauge invariant flow equation
which leaves behind only the original Maxwell field in the spontaneously broken
regime.Comment: 24 page
Exact renormalization group equation in presence of rescaling anomaly
Wilson's approach to renormalization group is reanalyzed for supersymmetric
Yang-Mills theory. Usual demonstration of exact renormalization group equation
must be modified due to the presence of the so called Konishi anomaly under the
rescaling of superfields. We carry out the explicit computation for N=1 SUSY
Yang-Mills theory with the simpler, gauge invariant regularization method,
recently proposed by Arkani-Hamed and Murayama. The result is that the
Wilsonian action S_M consists of two terms, i.e. the non anomalous term, which
obeys Polchinski's flow equation and Fujikawa-Konishi determinant contribution.
This latter is responsible for Shifman-Vainshtein relation of exact
beta-function.Comment: 19 pages, no figures; an appendix and reference added; typos
correcte
N=1* model superpotential revisited (IR behaviour of N=4 limit)
The one-loop contribution to the superpotential, in particular the
Veneziano-Yankielowicz potential in N=1 supersymmetric Yang-Mills model is
discussed from an elementary field theory method and the matrix model point of
view. Both approaches are based on the Renormalization Group variation of the
superconformal N=4 supersymmetric Yang-Mills model.Comment: 31 page
Navier-Stokes analysis of transonic cascade flow
A new kind of C-type grid is proposed, this grid is non-periodic on the wake and allows minimum skewness for cascades with high turning and large camber. Reynolds-averaged Navier-Stokes equations are solved on this type of grid using a finite volume discretization and a full multigrid method which uses Runge-Kutta stepping as the driving scheme. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. A detailed numerical study is proposed for a highly loaded transonic blade. A grid independence analysis is presented in terms of pressure distribution, exit flow angles, and loss coefficient. Comparison with experiments clearly demonstrates the capability of the proposed procedure
Ising Spin Glasses on Wheatstone-Bridge Hierarchical Lattices
Nearest-neighbor-interaction Ising spin glasses are studied on three
different hierarchical lattices, all of them belonging to the Wheatstone-Bridge
family. It is shown that the spin-glass lower critical dimension in these
lattices should be greater than 2.32. Finite-temperature spin-glass phases are
found for a lattice of fractal dimension (whose unit cell is
obtained from a simple construction of a part of the cubic lattice), as well as
for a lattice of fractal dimension close to five.Comment: Accepted for publication in Physics Letters
Multigrid calculation of three-dimensional viscous cascade flows
A 3-D code for viscous cascade flow prediction was developed. The space discretization uses a cell-centered scheme with eigenvalue scaling to weigh the artificial dissipation terms. Computational efficiency of a four stage Runge-Kutta scheme is enhanced by using variable coefficients, implicit residual smoothing, and a full multigrid method. The Baldwin-Lomax eddy viscosity model is used for turbulence closure. A zonal, nonperiodic grid is used to minimize mesh distortion in and downstream of the throat region. Applications are presented for an annular vane with and without end wall contouring, and for a large scale linear cascade. The calculation is validated by comparing with experiments and by studying grid dependency
Scheme Independence to all Loops
The immense freedom in the construction of Exact Renormalization Groups means
that the many non-universal details of the formalism need never be exactly
specified, instead satisfying only general constraints. In the context of a
manifestly gauge invariant Exact Renormalization Group for SU(N) Yang-Mills, we
outline a proof that, to all orders in perturbation theory, all explicit
dependence of beta function coefficients on both the seed action and details of
the covariantization cancels out. Further, we speculate that, within the
infinite number of renormalization schemes implicit within our approach, the
perturbative beta function depends only on the universal details of the setup,
to all orders.Comment: 18 pages, 8 figures; Proceedings of Renormalization Group 2005,
Helsinki, Finland, 30th August - 3 September 2005. v2: Published in jphysa;
minor changes / refinements; refs. adde
Colour, copies and confinement
In this paper we construct a wide class of Gribov copies in Coulomb gauge
SU(2) gauge theory. Infinitesimal copies are studied in some detail and their
non-perturbative nature is made manifest. As an application it is shown that
the copies prevent a non-perturbative definition of colour charge.Comment: 25 pages, 10 figures. Minor changes, two references added. Published
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