The construction of Electromagnetism

Abstract We examine the construction of electromagnetism in its current form, and in an alternative form, from a point of view that combines a minimal realism with strict rational demands. We begin by discussing the requests of reason when constructing a theory and next, we follow the historical development as presented in the record of original publications, the underlying epistemology (often explained by the authors) and the mathematical constructions. The historical construction develops along socio-political disputes (mainly, the reunification of Germany and the second industrial revolution), epistemic disputes (at least two demarcations of science in conflict) and several theories of electromagnetism. Such disputes resulted in the militant adoption of the ether by some, a position that expanded in parallel with the expansion of Prussia. This way of thinking was facilitated by the earlier adoption of a standpoint that required, as a condition for understanding, the use of physical hypothesis in the form of analogies; an attitude that is antithetic to Newton's “hypotheses non fingo”. While the material ether was finally abandoned, the epistemology survived in the form of “substantialism” and a metaphysical ether: the space. The militants of the ether attributed certainties regarding the ether to Faraday and Maxwell, when they only expressed doubts and curiosity. Thus, the official story is not the real history. This was achieved by the operation of detaching Maxwell's electromagnetism from its construction and introducing a new game of formulae and interpretations. Large and important parts of Maxwell work are today not known, as for example, the rules for the transformation of the electromagnetic potentials between moving systems. When experiments showed that all the theories based in the material ether were incorrect, a new interpretation was offered: Special Relativity (SR). At the end of the transformation period a pragmatic view of science, well adapted to the industrial society, had emerged, as well as a new protagonist: the theoretical physicist. The rival theory of delayed action at distance initiated under the influence of Gauss was forgotten in the midst of the intellectual warfare. The theory is indistinguishable in formulae from Maxwell's and its earlier versions are the departing point of Maxwell for the construction of his equations. We show in a mathematical appendix that such (relational) theory can incorporate Lorentz' contributions as well as Maxwell's transformations and C. Neumann's action, without resource to the ether. Demarcation criteria was further changed at the end of the period making room for habits and intuitions. When these intuited criteria are examined by critical reason (seeking for the fundaments) they can be sharpened with the use of the Non Arbitrariness Principle, which throws light over the arbitrariness in the construction of SR. Under a fully rational view SR is not acceptable, it requires to adopt a less demanding epistemology that detaches the concept from the conception, such as Einstein's own view in this respect, inherited from Hertz. In conclusion: we have shown in this relevant exercise how the reality we accept depends on earlier, irrational, decisions that are not offered for examination but rather are inherited from the culture

A mathematically assisted reconstruction of the initial focus of the yellow fever outbreak in Buenos Aires (1871)

We discuss the historic mortality record corresponding to the initial focus of the yellow fever epidemic outbreak registered in Buenos Aires during the year 1871 as compared to simulations of a stochastic population dynamics model. This model incorporates the biology of the urban vector of yellow fever, the mosquito Aedes aegypti, the stages of the disease in the human being as well as the spatial extension of the epidemic outbreak. After introducing the historical context and the restrictions it puts on initial conditions and ecological parameters, we discuss the general features of the simulation and the dependence on initial conditions and available sites for breeding the vector. We discuss the sensitivity, to the free parameters, of statistical estimators such as: final death toll, day of the year when the outbreak reached half the total mortality and the normalized daily mortality, showing some striking regularities. The model is precise and accurate enough to discuss the truthfulness of the presently accepted historic discussions of the epidemic causes, showing that there are more likely scenarios for the historic facts.Comment: 25 pages, 12 figure

Bed load at low shields stress on arbitrarily sloping beds: Failure of the Bagnold hypothesis

Abstract According to the Bagnold hypothesis for equilibrium bedload transport, a necessary constraint for the maintenance of equilibrium bedload transport is that the fluid shear stress at the bed must be reduced to the critical, or threshold value associated with incipient motion of grains. It was shown in a companion paper to the present one, however that the Bagnold hypothesis breaks down when applied to equilibrium bedload transport on beds with transverse slopes above a relatively modest value that is well below the angle of repose. This failure motivates the abandonment of the Bagnold constraint, even for nearly horizontal beds. The constraint is replaced with an entrainment formulation, according to which a dynamic equilibrium is maintained by a balance between entrainment of bed grains into the bedload layer and deposition of bedload grains onto the bed. The entrainment function is formulated so that the entrainment rate is an increasing function of the excess of the fluid shear stress at the bed over the threshold value. The formulation is implemented with the aid of a unique set of laboratory data that characterizes equilibrium bedload transport at relatively low shear stresses for streamwise angles of bed inclination varying from nearly 0 ° to 22°. The formulation is shown to provide a description of bedload transport on nearly horizontal beds that fits the data as well as that resulting from the Bagnold constraint. The entrainment formulation has the added advantage of not requiring the unrealistically high dynamic coefficient of Coulomb friction resulting from the Bagnold constraint. Finally

VIV regimes and simplified solutions by the spectral model description

The present paper discusses technical aspects of the vortex-induced vibrations (VIVs) of structures excited by the wind in the framework of the spectral model, which is applied by many codes and guidelines for civil engineering verifications. Quantitative thresholds related to Scruton number domains, where the structural response can be considered in \u201cforced vibration\u201d or \u201clock-in\u201d regime, are proposed. In this way, the type of VIV response and its evaluation can be assessed with simple calculations that use the parameters already present in codes and guidelines. An analytical solution of the original model allows straightforward evaluations inclusive of operative criteria to properly consider structural and flow conditions concerning the coefficients governing the VIV response in the spectral description, leaving out some assumptions that are commonly adopted. Extensive numerical applications, limited here to circular cylinders and including a real full-scale chimney, allow to identify the most significant parameters of the model and the criticalities connected with their choice