The universal character of Zwanziger's horizon function in Euclidean Yang-Mills theories

In light of the recently established BRST invariant formulation of the Gribov-Zwanziger theory, we show that Zwanziger's horizon function displays a universal character. More precisely, the correlation functions of local BRST invariant operators evaluated with the Yang-Mills action supplemented with a BRST invariant version of the Zwanziger's horizon function and quantized in an arbitrary class of covariant, color invariant and renormalizable gauges which reduce to the Landau gauge when all gauge parameters are set to zero, have a unique, gauge parameters independent result, corresponding to that of the Landau gauge when the restriction to the Gribov region $\Omega$ in the latter gauge is imposed. As such, thanks to the BRST invariance, the cut-off at the Gribov region $\Omega$ acquires a gauge independent meaning in the class of the physical correlators.Comment: 14 pages. v2: version accepted by Phys.Lett.

Some remarks on the spectral functions of the Abelian Higgs Model

We consider the unitary Abelian Higgs model and investigate its spectral functions at one-loop order. This analysis allows to disentangle what is physical and what is not at the level of the elementary particle propagators, in conjunction with the Nielsen identities. We highlight the role of the tadpole graphs and the gauge choices to get sensible results. We also introduce an Abelian Curci-Ferrari action coupled to a scalar field to model a massive photon which, like the non-Abelian Curci-Ferarri model, is left invariant by a modified non-nilpotent BRST symmetry. We clearly illustrate its non-unitary nature directly from the spectral function viewpoint. This provides a functional analogue of the Ojima observation in the canonical formalism: there are ghost states with nonzero norm in the BRST-invariant states of the Curci-Ferrari model.Comment: 32 pages, 12 figure

An exact nilpotent non-perturbative BRST symmetry for the Gribov-Zwanziger action in the linear covariant gauge

We point out the existence of a non-perturbative exact nilpotent BRST symmetry for the Gribov-Zwanziger action in the Landau gauge. We then put forward a manifestly BRST invariant resolution of the Gribov gauge fixing ambiguity in the linear covariant gauge.Comment: 8 pages. v2: version accepted for publication in PhysRev

More on the non-perturbative Gribov-Zwanziger quantization of linear covariant gauges

In this paper, we discuss the gluon propagator in the linear covariant gauges in $D=2,3,4$ Euclidean dimensions. Non-perturbative effects are taken into account via the so-called Refined Gribov-Zwanziger framework. We point out that, as in the Landau and maximal Abelian gauges, for $D=3,4$, the gluon propagator displays a massive (decoupling) behaviour, while for $D=2$, a scaling one emerges. All results are discussed in a setup that respects the Becchi-Rouet-Stora-Tyutin (BRST) symmetry, through a recently introduced non-perturbative BRST transformation. We also propose a minimizing functional that could be used to construct a lattice version of our non-perturbative definition of the linear covariant gauge.Comment: 15 pages, 1 figure; V2 typos fixed and inclusion of section on the ghost propagator. To appear in PhysRev

Particle Creation by a Moving Boundary with Robin Boundary Condition

We consider a massless scalar field in 1+1 dimensions satisfying a Robin boundary condition (BC) at a non-relativistic moving boundary. We derive a Bogoliubov transformation between input and output bosonic field operators, which allows us to calculate the spectral distribution of created particles. The cases of Dirichlet and Neumann BC may be obtained from our result as limiting cases. These two limits yield the same spectrum, which turns out to be an upper bound for the spectra derived for Robin BC. We show that the particle emission effect can be considerably reduced (with respect to the Dirichlet/Neumann case) by selecting a particular value for the oscillation frequency of the boundary position

Minorities and fuel-economy standards: Differences in EPA-test vs in-use fuel economy

A vehicle`s in-use or on-the-road fuel economy often differs substantially from the miles-per-gallon estimates developed by the US Environmental Protection Agency (EPA) as part of its emissions certification program. As a result, the certification values are routinely adjusted by a set of correction factors so that the resulting estimates will better reflect in-use experience. Our analysis investigated how well the correction factors replicated the shortfall experience of all household vehicles on the road in 1985 and of those vehicles held by different population groups. Using data from the Residential Transportation Energy Consumption Survey conducted by the Energy Information Administration of the US Department of Energy, our analysis showed that fleetwide, the shortfall is larger than the EPA correction factors, and that light trucks are experiencing larger shortfalls than automobiles. Controlling for vehicle age and size class, shortfalls did not appear to differ by population group. However, African-American households appeared to select vehicles with systematically lower fuel economy (both EPA-test and on-the-road) within individual vehicle age and size class categories

Exchange Current Corrections to Neutrino--Nucleus Scattering

Relativistic exchange current corrections to neutrino--nucleus cross sections are presented assuming non--vanishing strange quark form factors for the constituent nucleons. For charged current processes the exchange current corrections can lower the impulse approximation results by 10\% while these corrections are found to be sensitive to both the nuclear density and the strange quark axial form factor of the nucleon for neutral current processes. Implications on the LSND experiment to determine this form factor are discussed.Comment: 11 pages, 2 figures, revtex 3.0, full postscript version of the file and figures available at http://www.nikhefk.nikhef.nl/projects/Theory/preprints/preprints.html To appear in Phys. Rev. Lett