Differential Renormalization of Gauge Theories

The scope of constrained differential renormalization is to provide renormalized expressions for Feynman graphs, preserving at the same time the Ward identities of the theory. It has been shown recently that this can be done consistently at least to one loop for abelian and non-abelian gauge theories. We briefly review these results, evaluate as an example the gluon selfenergy in both coordinate and momentum space, and comment on anomalies.Comment: LaTex, 8 pages with 1 ps figures, talk given at the Zeuthen Workshop on Elementary Particle Physics "Loops and Legs in Gauge Theories", Rheinsberg, Germany, April 19-24, 1998, to appear in Acta Physica Polonica

CP violating effects in the decay Z -> mu^+mu^-gamma induced by ZZgamma and Zgammagamma couplings

We analyze possible CP-violating effects induced in the $Z$ decay with hard photon radiation by $\gamma ZZ$ and $\gamma\gamma Z$ anomalous vertices. We estimate the sensibility of future linear collider experiments on these couplings coming from CP-odd asymmetries associated to angular correlations of the three particle final state in $e^+e^- \to Z \to \mu^+\mu^-\gamma$. We find that a linear collider with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s} = 0.05$ TeV can place the bound $|h_1^{\gamma,Z}| < 0.92$ at the 90% confidence level for these couplings.Comment: Added references, 2 graphics 5 pages, LaTeX; typos added, 4 graphics remove

A hybrid boundary for the prediction of intake wave dynamics in IC engines

This paper concerns the calculation of wave dynamics in the intake systems of naturally aspirated internal combustion (I.C.) engines. In particular it presents a method for improving the boundary conditions required to solve the one-dimensional Euler equations that are commonly used to describe the wave dynamics in time and space. A number of conclusions are reached in this work. The first relates to the quasi-steady state inflow boundary specified in terms of ingoing and outgoing characteristics that is commonly adopted for engine simulation. This is correctly specified by using the pair of primitive variables pressure (p) and density (ρ) but will be unrealistic at frequencies above a Hemholtz number of 0.1 as only stagnation values po, ρo are used. For the case of I.C. engine intake simulations this sets a maximum frequency of around 300Hz. Above that frequency the results obtained will become increasingly unrealistic. Secondly, a hybrid time and frequency domain boundary has been developed and tested against linear acoustic theory. This agrees well with results obtained using a quasi-steady state boundary at low frequencies (Helmholtz number less than 0.1) and should remain realistic at higher frequencies in the range of Helmholtz number 0.1 - 1.84. Thirdly, the cyclic nature of the operation of the IC engine has been exploited to make use of the inverse Fourier transform to develop an analytical hybrid boundary that functions for non-sinusoidal waves in ducts. The method is self starting, does not rely on iterations over complete cycles and is entirely analytical and therefore is an improvement over earlier hybrid boundaries

Physics of Brane Kinetic Terms

Models with extra dimensions may give new effects visible at future experiments. In these models, bulk fields can develop localized corrections to their kinetic terms which can modify the phenomenological predictions in a sizeable way. We review the case in which both gauge bosons and fermions propagate in the bulk, and discuss the limits on the parameter space arising from electroweak precision data.Comment: Presented at Matter To The Deepest: Recent Developments In Physics of Fundamental Interactions, XXVII International Conference of Theoretical Physics, Ustron 15-21 September 2003, Polan

Observable contributions of new exotic quarks to quark mixing

Models with new vector-like quarks can produce observable quark mixing effects which are forbidden in the Standard Model. We classify all such models and write down the effective Lagrangian that results from integrating out the new quarks. We study the relations between neutral and charged currents and discuss how to distinguish among the different possibilities.Comment: 15 pages, 1 figure, typos corrected, version to appear in JHE