A Note on MHV Amplitudes for Gravitons

We show how the maximally helicity violating (MHV) scattering amplitudes for gravitons can be related to current correlators and vertex operators in twistor space. This is similar to what happens in Yang-Mills theory and raises the possibility of a direct twistor-string-like construction for ${\cal N}=8$ supergravity.Comment: 14 pages, LaTe

Production of non-Abelian tensor gauge bosons. Tree amplitudes in generalized Yang-Mills theory and BCFW recursion relation

The BCFW recursion relation allows to calculate tree-level scattering amplitudes in generalized Yang-Mills theory and, in particular, four-particle amplitudes for the production rate of non-Abelian tensor gauge bosons of arbitrary high spin in the fusion of two gluons. The consistency of the calculations in different kinematical channels is fulfilled when all dimensionless cubic coupling constants between vector bosons (gluons) and high spin non-Abelian tensor gauge bosons are equal to the Yang-Mills coupling constant. There are no high derivative cubic vertices in the generalized Yang-Mills theory. The amplitudes vanish as complex deformation parameter tends to infinity, so that there is no contribution from the contour at infinity. We derive a generalization of the Parke-Taylor formula in the case of production of two tensor gauge bosons of spin-s and N gluons (jets). The expression is holomorhic in the spinor variables of the scattered particles, exactly as the MHV gluon amplitude is, and reduces to the gluonic MHV amplitude when s=1. In generalized Yang-Mills theory the tree level n-particle scattering amplitudes with all positive helicities vanish, but tree amplitudes with one negative helicity particle are already nonzero.Comment: 19 pages, LaTex fil

QCD Theory

Quantum Chromodynamics is an established part of the Standard Model and an essential part of the toolkit for searching for new physics at high-energy colliders. I present a status report on the theory of QCD and review some of the important developments in the past year.Comment: 10 pages, 11 figures, plenary talk presented at ICHEP04, Beijing, China, August 200

Towards an Implantable Vestibular Prosthesis: The Surgical Challenges

Published versio

Micro-Optoelectromechanical Tilt Sensor

Published versio

Spiking Chemical Sensor (SCS): A new platform for neuro-chemical sensing

Published versio

An auto-input-offset removing floating gate pseudo-differential transconductor

Published versio

A Partial-Current-Steering Biphasic Stimulation Driver for Vestibular Prostheses

Published versio

A new type of lordosis and vertebral body compression in Gilthead seabream, Sparus aurata Linnaeus, 1758: aetiology, anatomy and consequences for survival

A new type of vertebral malformation is described, consisting of deformed cartilaginous neural and haemal processes and the compression and fusion of vertebral bodies. The malformation is designated as haemal vertebral compression and fusion (haemal VCF). We studied the aetiology of the malformations and described microanatomical histopathological alterations. The malformations were detected during routine quality control in one of six monitored Gilthead sea bream populations. Haemal VCF affected the posterior part of the vertebral column (haemal vertebrae). In 20% of the deformed specimens, haemal VCF was combined with lordosis. At 35dph (days post-hatching), early anatomical signs of the haemal VCF consisted of abnormal centrum mineralization, malformed cartilaginous neural and haemal processes and developing lordotic alterations. The histological examination of the deformed individuals revealed that haemal VCF is preceded by notochord abnormalities. The frequency of deformed individuals was three times higher at 35 than at 61dph (50.3% vs. 17.2%, n=157 and n=250, respectively). No signs of repair or reversion of malformations have been observed. Thus, the steep decrease in deformities in older animals suggests that haemal VCF is linked to high mortality rates. The results are discussed in respect of the possible causative factors of haemal VCF