The Wonder of Colors and the Principle of Ariadne

The Principle of Ariadne, formulated in 1988 ago by Walter Carnielli and Carlos Di Prisco and later published in 1993, is an infinitary principle that is independent of the Axiom of Choice in ZF, although it can be consistently added to the remaining ZF axioms. The present paper surveys, and motivates, the foundational importance of the Principle of Ariadne and proposes the Ariadne Game, showing that the Principle of Ariadne, corresponds precisely to a winning strategy for the Ariadne Game. Some relations to other alternative. set-theoretical principles are also briefly discussed

Dynamics of viscous dissipative gravitational collapse: A full causal approach

The Misner and Sharp approach to the study of gravitational collapse is extended to the viscous dissipative case in, both, the streaming out and the diffusion approximations. The dynamical equation is then coupled to causal transport equations for the heat flux, the shear and the bulk viscosity, in the context of Israel--Stewart theory, without excluding the thermodynamics viscous/heat coupling coefficients. The result is compared with previous works where these later coefficients were neglected and viscosity variables were not assumed to satisfy causal transport equations. Prospective applications of this result to some astrophysical scenarios are discussed.Comment: 22 pages Latex. To appear in Int. J. Mod. Phys. D. Typos correcte

Intermodal vs. conventional logistic of refrigerated products: a case study from Southern to Northern Europe

Most of perishable goods, such as fruit and vegetables, are transported in Europe by truck and clogging up the main road networks. The increasing demand for freight transport and the environmental concerns all indicate the necessity to embrace new means of transport such as the intermodal one. The intermodal transport uses swap bodies and reefer containers that allow for the use of interchangeable truck, train, and ship to reduce direct and external costs. Nowadays, the utilization of exclusive truck transport is due to its considerable flexibility and often to the disregard of the motor vehicle regulations during transport. This research aims to analyze some essential readjustments that must be made in order to increase efficiency in the logistic of refrigerated fruit and vegetables. To do so, some hypotheses were analyzed and formulated in which the strategic use of the truck was recognized and inserted as part of an intermodal transport system. The transport options of a combined use of ships and trains in association with trucks were evaluated with respect to the current prevalent solution of exclusive use of trucks. Such options were evaluated by comparing them under different itineraries hypotheses (from south Italy, Sicily to Germany, Munich) on the base of costs and transit-times parameters. This was done mainly throughout interviewing sector-relevant transport operators. The results of the comparison between the intermodal and conventional transport was shown to be economically more convenient with respect to both legal and illegal transport by exclusive truck transport, presenting lower per unit costs (swap body or semi-trailer, containing the same amount of goods). Moreover, the intermodal solution scores equal or higher transit times in the comparison with the “transit by regulation compliance” and much higher transit times if compared with the “illegal” option. Therefore, the regulation compliance aspect would partially promote the use of intermodal options in a future fair competition. In addition, besides reducing the direct costs, it produces several other positive effects in terms of external costs to the society such as to reduce road crashes, noises, atmospheric emissions and greenhouse effect. A more efficient system should plan an integrated system of arrival and departure organizing together the schedules of ships and trains dedicated to perishable goods and increasing the transported amounts. Furthermore, another idea is to stipulate commercial agreements with train operators, applying a reduction on the base price, by ensuring the delivery of a block train for an arranged period.   Keywords: Intermodal, freight logisticcentre, truck haulage, rail hub; terminal

Some analytical models of radiating collapsing spheres

We present some analytical solutions to the Einstein equations, describing radiating collapsing spheres in the diffusion approximation. Solutions allow for modeling physical reasonable situations. The temperature is calculated for each solution, using a hyperbolic transport equation, which permits to exhibit the influence of relaxational effects on the dynamics of the system.Comment: 17 pages Late