Charge/color breaking minima and A-parameter bounds in supersymmetric models

In supersymmetric models, the requirement that the global potential minimum not violate color and/or electric charge invariance implies restrictions on the parameters of the model. We reassess and improve upon constraints on the A parameter that have been obtained previously in the literature. In particular, we demonstrate that no universally applicable bound which is either necessary or sufficient can be given.     

Decay of Z′ in W+W− and Higgs modes

We show that Z′ → WW and into Higgs mode are valuable probes of the symmetry breaking mechanism in gauge theories. Results are derived for a decay of an arbitrary Z′ from string inspired E₆ theory.     

The relationship between the crystallographic order and electronic structure of mercury thin films

Thin (1–7 monolayer) well ordered, disordered, and liquid Hg overlayers on Ag (100) have been investigated with angle resolved photoemission and low energy electron diffraction. The well ordered overlayers exhibit new electronic states as a result of the strained, cubic, overlayer crystallographic structure. The photoemission cross section of the electronic states depends on the overlayer long range crystallographic order and cannot be explained by photoelectron diffraction. The new electronic states depend upon the long range crystallographic order of the overlayer not simply the local crystallographic symmetry, a heretofore unreported result.     

Higgs boson pair production from gluon fusion

We calculate Higgs-boson pair production from gluon fusion at future hadron colliders. We find that the box diagram is appreciably larger then the triangle diagram for Higgs-boson masses which are experimentally accessible. This obscures the observation of the three-Higgs-boson vertex, which is present in the latter diagram.     

Where are the missing V0V0′ in γγ reactions?

The measured cross sections ofγγ→V⁰V^0′ are inconsistent with the measurements of the γγ total hadronic cross section above 2 GeV. Higher cross sections for γγ→ϱ⁰ϱ⁰ or additional V⁰V^0′ final states are needed to solve this inconsistency.     

The ultratough peeling of elastic tapes from viscoelastic substrates

The peeling of an elastic thin tape from a flat smooth viscoelastic substrate is investigated. Based on a Green function approach and on the translational invariance, a closed form analytical solution is proposed, which takes into account the viscoelastic dissipation in the substrate material.We find that peeling is prevented from taking place, only when the external force is smaller than the one predicted by Kendall's formula for elastic tapes on rigid substrates. However, we also find that, regardless of the value of the applied force, steady state detachment may occur when the elastic tape is sufficiently stiff. In this case, the constant peeling velocity can be modulated by properly defining the geometrical parameters and the material properties of tape and viscoelastic foundation. On the other hand, for relatively high peeling angles or compliant tapes a threshold value of the peeling force is found, above which the steady-state equilibrium is no longer possible and unstable detachment occurs.The present study contributes to shed light on the behavior of pressure sensitive adhesives in contact with viscoelastic substrates like the human skin. At the same time, it can be considered a first step towards a better understanding of the effect of viscoelastic dissipation on the fracture behavior of solids.     

Risk-sensitive and risk-neutral control for continuous-time hidden Markov models

In this paper the optimal control of a continuous-time hidden Markov model is discussed. The risk-sensitive problem involves a cost function which has an exponential form and a risk parameter, and is solved by defining an appropriate information state and dynamic programming. As the risk parameter tends to zero, the classical risk-neutral optimal control problem is recovered. The limits are proved using viscosity solution methods.The first author wishes to acknowledge the funding of the activities of the Cooperative Research Centre for Robust and Adaptive Systems by the Australian Commonwealth Government under the Cooperative Research Centers Program. The support of NSERC Grant A7964 is acknowledged by the second author, as is the hospitality of the Department of Systems Engineering and the Cooperative Research Centre for Robust and Adaptive Systems, Australian National University, in July 1993.     

Photoacoustic infrared spectroscopy and thermophysical properties of syncrude cokes

This paper presents and interprets photoacoustic (PA) infrared spectra and four different thermophysical properties (thermal conductivity, thermal diffusivity, volumetric specific heat and thermal effusivity) for four sets of hydrocarbon cokes. A total of 12 samples, with varying histories, were analyzed. These cokes are a by-product of the upgrading of bitumen to Syncrude Sweet Blend (a blend of hydrotreated components), and were obtained from several locations in the thermal cokers operated by Syncrude Canada Ltd. in Fort McMurray, Alberta, Canada. PA infrared spectroscopy provides detailed information on the amount and type of residual aromatic hydrocarbons in cokes; aliphatic hydrocarbons are sometimes detected in smaller quantities. Three of the thermophysical properties (thermal conductivity, diffusivity and effusivity) display systematic differences among the cokes. On the other hand, volumetric specific heat hardly varies, a phenomenon that accounts for the observed proportionality between thermal diffusivity and conductivity. Analogous relationships exist between thermal effusivity and both thermal conductivity and thermal diffusivity for these cokes. The magnitudes of these three thermophysical properties tend to increase as aromatics contents, determined by PA spectroscopy, decrease.This revised version was published online in November 2005 with corrections to the Cover Date.     

Trace‐level screening of dichlorophenols in processed dairy milk by headspace gas chromatography

A headspace gas chromatographic approach based on flame ionization detection has been successfully developed for the determination of parts‐per‐billion levels of 2,4‐dichlorophenol and 2,6‐dichlorophenol in processed dairy milk. Under the right environmental conditions, these compounds are produced as products of the reductive dechlorination of pentachlorophenol. Maintaining a highly inert chromatographic system and employing a recently commercialized inert capillary column permits the analysis of 2,4‐dichlorophenol and 2,6‐dichlorophenol without derivatization. Further, a detection limit improvement of more than a factor of two was achieved by adding sodium sulfate to substantially decrease the solute partition coefficient in the matrix. A detection limit of 1 ng/g and a limit of quantitation of 2 ng/g were attained, and complete analysis can be conducted in < 13 min. Reproducibility of area counts over a range from 20 to 200 ng/g and over a period of 2 days were found to be less than 6% (n = 20). A linear range from 5 to 500 ng/g with a correlation coefficient of at least 0.9992 was obtained for 2,4‐dichlorophenol and 2,6‐dichlorophenol. Spike recoveries from 10 to 500 ng/g for all the analytes range from 92 to 102%.