Fermion Number Conservation Isn't Fermion Conservation

A nonperturbative regularization of the Standard Model may have a superficially undesirable exact global U(1) symmetry corresponding to exact fermion number conservation. We argue that such a formulation can still have the desired physics of fermion nonconservation, i.e. fermion particle creation and annihilation by sphaleron transitions. We illustrate our reasoning in massless axial QED in 1+1 dimensions.Comment: 3 pages to appear in the proceedings of Lattice '93, Dallas, Texas, 12-16 October 1993, comes as a single uuencoded postscript file (LaTeX source available from the authors), ITFA 93-3

Visiting a Farm: An Exploratory Study of the Social Construction of Animal Farming in Norway and the Netherlands based on Sensory Perception

Most citizens in modern societies have little personal knowledge or experience of animal farming. This study explores the social construction of animal farming by studying how citizens perceive and evaluate modern farming after visiting a farm in real life. We wanted to understand how (non-farming) citizens develop an opinion of modern dairy farming when experiencing dairy farming in real life and practice, and how they translate what they see, smell and feel into an evaluative perception and mental image. We therefore conducted dairy farm visits with citizen panels in Norway and the Netherlands and asked the panel members to register what they saw, heard, smelled and felt and what they appreciated (or not) on the farm. The aspects that respondents registered could be grouped into four themes: the animals and their products, the rural landscape, farm practices and the farmer. When respondents described their experiences of these aspects on a specific farm, they appeared to look at them from three angles: modernity, tradition and naturality. Most respondents wanted farms to be modern, traditional as well as natural, but they were ready to negotiate and to accept compromises. Many respondents considered the farmer to be responsible for reconciling modernity, tradition and naturality. By taking different topics and issues into account and looking at animal farms from multiple angles, the respondents’ developed a balanced and nuanced opinion of animal farming. The image that they constructed was not dualistic (arcadia versus factory) but pluralistic, thus at the same time more complex but also more flexible than expected. We expect that the development of a pluralistic image and balanced opinion was facilitated through the direct experience of dairy farming and farm life. The article starts with a theoretical analysis and aims to contribute to recent debates in rural sociology in two ways: 1) it studies how material experience and mental perception interact in the construction of an evaluative image of animal farming; and 2) it explores the social construction of animal farming as embedded into to the construction of nature, rurality and human-animal relationships. It concludes by discussing the contribution of the findings to the ongoing theoretical debate in this fiel

Emissivity measurements of reflective surfaces at near-millimeter wavelengths

We have developed an instrument for directly measuring the emissivity of reflective surfaces at near-millimeter wavelengths. The thermal emission of a test sample is compared with that of a reference surface, allowing the emissivity of the sample to be determined without heating. The emissivity of the reference surface is determined by one’s heating the reference surface and measuring the increase in emission. The instrument has an absolute accuracy of Δe = 5 x 10^-4 and can reproducibly measure a difference in emissivity as small as Δe = 10^-4 between flat reflective samples. We have used the instrument to measure the emissivity of metal films evaporated on glass and carbon fiber-reinforced plastic composite surfaces. We measure an emissivity of (2.15 ± 0.4) x 10^-3 for gold evaporated on glass and (2.65 ± 0.5) x 10^-3 for aluminum evaporated on carbon fiber-reinforced plastic composite

Study of low gravity propellant transfer Quarterly progress report, 23 Dec. 1970 - 30 Apr. 1971

Bellows, metallic diaphragm, and paddle vortex subcritical transfer systems designs and high pressure systems analyses for orbital space station cryogen

Form and function of barbels in Osteoglossum bicirrhosum (Pisces Osteoglossidae) during aquatic surface respiration

The barbels on the lower jaw of Osteoglossum bicirrhosum have a different shape from those of other teleosts. A thin longitudinal fold along the shaft is characteristic. The barbel consists of dermal tissue surrounded by a thin epidermal layer. O. bicirrhosum lacks accessory respiratory organs for breathing air. At oxygen concentrations at or below 2 ppm, young individuals begin "aquatic surface respiration" (ASR). While engaged in this behaviour, the fishes swim constantly at a regular speed with the barbels in a fixed position, the lower jaws motionless, and the opercula in continuous motion. This enables the fishes to survive for hours at oxygen concentrations of less than 0.5 ppm. Observations of the currents around the barbels reveal their hydrodynamic function in light of the current theories. The barbels improve the flow of surface water into the mouth

Fermion production despite fermion number conservation

Lattice proposals for a nonperturbative formulation of the Standard Model easily lead to a global U(1) symmetry corresponding to exactly conserved fermion number. The absence of an anomaly in the fermion current would then appear to inhibit anomalous processes, such as electroweak baryogenesis in the early universe. One way to circumvent this problem is to formulate the theory such that this U(1) symmetry is explicitly broken. However we argue that in the framework of spectral flow, fermion creation and annihilation still in fact occurs, despite the exact fermion number conservation. The crucial observation is that fermions are excitations relative to the vacuum, at the surface of the Dirac sea. The exact global U(1) symmetry prohibits a state from changing its fermion number during time evolution, however nothing prevents the fermionic ground state from doing so. We illustrate our reasoning with a model in two dimensions which has axial-vector couplings, first using a sharp momentum cutoff, then using the lattice regulator with staggered fermions. The difference in fermion number between the time evolved state and the ground state is indeed in agreement with the anomaly. A study of the vacuum energy shows that the perturbative counterterm needed for restoration of gauge invariance is insufficient in a nonperturbative setting. For reference we also study a closely related model with vector couplings, the Schwinger model, and we examine the emergence of the $\theta$-vacuum structure of both theories.Comment: 31 pages, LaTeX + uuencoded figs file (=5 PS figs). UvA-ITFA 94-17, UCSD/PTH 94-0