Heterodon nasicus

Number of Pages: 10Integrative BiologyGeological Science

Playing with fermion couplings in Higgsless models

We discuss the fermion couplings in a four dimensional SU(2) linear moose model by allowing for direct couplings between the left-handed fermions on the boundary and the gauge fields in the internal sites. This is realized by means of a product of non linear $\sigma$-model scalar fields which, in the continuum limit, is equivalent to a Wilson line. The effect of these new non local couplings is a contribution to the $\epsilon_3$ parameter which can be of opposite sign with respect to the one coming from the gauge fields along the string. Therefore, with some fine tuning, it is possible to satisfy the constraints from the electroweak data.Comment: Latex file, 20 pages, 4 eps figure

EVALUATION OF THE POSSIBLE THREAT OF NAFTA ON U.S. CATFISH INDUSTRY USING A TRADITIONAL IMPORT DEMAND FUNCTION

The effects of increased exports from NAFTA member countries on the U.S. domestic catfish industry were evaluated. Results showed that the quantity of catfish imported will fall if the domestic price of catfish falls relative to the import price. Past imports have no effect on present imports. The income elasticity was negative indicating that imported catfish may be an inferior good. Doubling present levels of imports from NAFTA member countries is not a threat to the U.S. catfish industry.International Relations/Trade,

An Extension of the Electroweak Model with Decoupling at Low Energy

We present a renormalizable model of electroweak interactions containing an extra $SU(2)'_L\otimes SU(2)'_R$ symmetry. The masses of the corresponding gauge bosons and of the associated Higgs particles can be made heavy by tuning a convenient vacuum expectation value. According to the way in which the heavy mass limit is taken we obtain a previously considered non-linear model (degenerate BESS) which, in this limit, decouples giving rise to the Higgsless Standard Model (SM). Otherwise we can get a model which decouples giving the full SM. In this paper we argue that in the second limit the decoupling holds true also at the level of radiative corrections. Therefore the model discussed here is not distinguishable from the SM at low energy. Of course the two models differ deeply at higher energies.Comment: 13+2 pages, LaTe

Gauge covariance and the fermion-photon vertex in three- and four- dimensional, massless quantum electrodynamics

In the quenched approximation, the gauge covariance properties of three vertex Ans\"{a}tze in the Schwinger-Dyson equation for the fermion self energy are analysed in three- and four- dimensional quantum electrodynamics. Based on the Cornwall-Jackiw-Tomboulis effective action, it is inferred that the spectral representation used for the vertex in the gauge technique cannot support dynamical chiral symmetry breaking. A criterion for establishing whether a given Ansatz can confer gauge covariance upon the Schwinger-Dyson equation is presented and the Curtis and Pennington Ansatz is shown to satisfy this constraint. We obtain an analytic solution of the Schwinger-Dyson equation for quenched, massless three-dimensional quantum electrodynamics for arbitrary values of the gauge parameter in the absence of dynamical chiral symmetry breaking.Comment: 17 pages, PHY-7143-TH-93, REVTE

Production of Z' and W' via Drell-Yan processes in the 4D Composite Higgs Model at the LHC

We present an analysis of both the Neutral Current (NC) and Charged Current (CC) Drell-Yan processes at the LHC within a 4 Dimensional realization of a Composite Higgs model studying the cross sections and taking into account the possible impact of the extra fermions present in the spectrum.Comment: Conference proceeding, XII IFAE Edition, 3-5 April 2013, Cagliari. 2 pages, 2 figures; v2 typo correcte

Economies of Size for Conventional Tillage and No-till Wheat Production

Production costs and economies of size for both conventional tillage and no-till wheat production were determined. The reduction in the price of glyphosate after the patent expired improved the relative economics of no-till for continuous monoculture winter wheat. Production costs differ across farm size and by production system.Crop Production/Industries,

Nitrification-denitrification in WSP: a mechanism for permanent nitrogen removal in maturation ponds

A pilot-scale primary maturation pond was spiked with 15N-labelled ammonia (15NH4Cl) and 15N labelled nitrite (Na15NO2), in order to improve current understanding of the dynamics of inorganic nitrogen transformations and removal in WSP systems. Stable isotope analysis of δ15N showed that nitrification could be considered as an intermediate step in WSP, which is masked by simultaneous denitrification, under conditions of low algal activity. Molecular microbiology analysis showed that denitrification can be considered a feasible mechanism for permanent nitrogen removal in WSP, which may be supported either by ammonia-oxidising bacteria (AOB) or by methanotrophs, in addition to nitrite-oxidising bacteria (NOB). However, the relative supremacy of the denitrification process over other nitrogen removal mechanisms (e.g., biological uptake) depends upon phytoplanktonic activity