Heavy Fermion Screening Effects and Gauge Invariance

We show that the naively expected large virtual heavy fermion effects in low energy processes may be screened if the process under consideration contains external gauge bosons constrained by gauge invariance. We illustrate this by a typical example of the process $\gamma\gamma\to b \bar{b}$. Phenomenological implications are also briefly indicated.Comment: a miss-print fixed, 7 pages, LaTex, no figure

Resonance in Strong WW Rescattering in Massive SU(2) Gauge Theory

We investigate the effects of WW rescattering through strong anomalous four-vector boson couplings. In the I=1, J=1 channel, we find a resonance with a mass of approximately 200 GeV and a width of less than 12 GeV. In an application to pion physics we find a small correction to the KSRF relation.Comment: 21 pages, extended discussion, some minor change

Exact αs\alpha _s Calculation of b→s+γb\rightarrow s + \gamma , \ b→s+gb\rightarrow s + g

We present an exact $\alpha_s$ calculation of the Wilson coefficients associated with the dipole moment operators. We also give an estimate of the branching ratio for $b\rightarrow s \gamma$. We find that higher dimensional effects are under control within $9\%$ for $BR(b\rightarrow s \gamma)=(4.3\pm 0.37 )\times 10^{-4}$.Comment: 12 pages (plain TeX), 2 postscript figures available upon request. UM-TH-93-20 , IP-ASTP-29-9

Corrections to oblique parameters induced by anomalous vector boson couplings

We study quadratically divergent radiative corrections to the oblique parameters at LEP1 induced by non-standard vector boson self-couplings. We work in the Stueckelberg formalism and regulate the divergences through a gauge-invariant higher derivative scheme. Using consistency arguments together with the data we find a limit on the anomalous magnetic moment Delta kappa of the W-boson, |Delta kappa| <= 0.26.Comment: 32 pages, LaTeX; cross reference corrected, minor beautifications, version to be published in Phys.Rev.

Single-Top-Quark Production via W-Gluon Fusion at Next-to-Leading Order

Single-top-quark production via W-gluon fusion at hadron colliders provides an opportunity to directly probe the charged-current interaction of the top quark. We calculate the next-to-leading-order corrections to this process at the Fermilab Tevatron, the CERN Large Hadron Collider, and DESY HERA. Using a b-quark distribution function to sum collinear logarithms, we show that there are two independent corrections, of order 1/[ln(m_t^2/m_b^2)] and alpha_s. This observation is generic to processes involving a perturbatively derived heavy-quark distribution function at an energy scale large compared with the heavy-quark mass.Comment: 19 pages, 9 figures, small update to Phys. Rev. D versio

Do Two Symmetry Breaking Transitions in Photosynthetic Light Harvesting Complexes Form One, Two or More Kibble Zurek Model Topological Defects?

Kibble and Zurek proposed that rapid symmetry breaking transitions in the hot, early universe could result in causally disconnected topological defects such as cosmic strings. This type of first order transition has analogues in certain second order transitions present in condensed matter such as liquid crystals, super fluids, and charge density waves in terms of flux tubes or vortices. Recently, we discovered that Rhodopseudomonas acidophilus photosynthetic light harvesting complex might have different types of coherent ground and excited states, suggesting that there are two different symmetry breaking transitions. The B 850 ground states comprise eight identical rings each containing 18 bacteriochlorophyll components, and each ring has undergone a Bose Einstein phase transition to a charge density wave that lowers the energy. The excited state coherence results from polariton formation from the non-crossing of bosons, here an extension of exciton theory. The result is short-lived quasi-particles with very low mass that can form an unusual BEC. We suggest the oriented, circular B 850 and enclosed singlet B 875 compounds create a new cavity structure with some attributes of a nano pillar. Since both the ground and excited states should contain solitons, we envisage three fast light pulse experiments could be able to map both the Kibble Zurek Model phase transitions and energy transfers as a function of light intensity and time in this complex at room temperature

Ongoing mumps outbreak in a student population with high vaccination coverage, Netherlands, 2010.

Since December 2009, mumps incidence has increased in the Netherlands. As of 20 April 2010, 172 cases have been notified on the basis of laboratory confirmation or linkage to a laboratory-confirmed case. Of these, 112 were students, the majority of whom had been vaccinated (81%). Although outbreaks in vaccinated populations have been described before, risk factors for exposure and susceptibility, and dose-dependent vaccine effectiveness in a student population of this nature are relatively unknown

Transmission of Supersymmetry Breaking from a 4-Dimensional Boundary

In the strong-coupling limit of the heterotic string theory constructed by Horava and Witten, an 11-dimensional supergravity theory is coupled to matter multiplets confined to 10-dimensional mirror planes. This structure suggests that realistic unification models are obtained, after compactification of 6 dimensions, as theories of 5-dimensional supergravity in an interval, coupling to matter fields on 4-dimensional walls. Supersymmetry breaking may be communicated from one boundary to another by the 5-dimensional fields. In this paper, we study a toy model of this communication in which 5-dimensional super-Yang-Mills theory in the bulk couples to chiral multiplets on the walls. Using the auxiliary fields of the Yang-Mills multiplet, we find a simple algorithm for coupling the bulk and boundary fields. We demonstrate two different mechanisms for generating soft supersymmetry breaking terms in the boundary theory. We also compute the Casimir energy generated by supersymmetry breaking.Comment: 26 pages, latex + 7 eps figures, final correction

Are Amphipod invaders a threat to the regional biodiversity? Conservation prospects for the Loire River

The impact of invasions on local biodiversity is well established, but their impact on regional biodiversity has so far been only sketchily documented. To address this question, we studied the impact at various observation scales (ranging from the microhabitat to the whole catchment) of successive arrivals of non-native amphipods on the amphipod assemblage of the Loire River basin in France. Amphipod assemblages were studied at 225 sites covering the whole Loire catchment. Non-native species were dominant at all sites in the main channel of the Loire River, but native species were still present at most of the sites. We found that the invaders have failed to colonize most of tributaries of the Loire River. At the regional scale, we found that since the invaders first arrived 25 years ago, the global amphipod diversity has increased by 33% (from 8 to 12 species) due to the arrival of non-native species. We discuss the possibility that the lack of any loss of biodiversity may be directly linked to the presence of refuges at the microhabitat scale in the Loire channel and in the tributaries, which invasive species have been unable to colonize. The restoration of river quality could increase the number of refuges for native species, thus reducing the impact of invader