Non-Involutive Constrained Systems and Hamilton-Jacobi Formalism

In this work we discuss the natural appearance of the Generalized Brackets in systems with non-involutive (equivalent to second class) constraints in the Hamilton-Jacobi formalism. We show how a consistent geometric interpretation of the integrability conditions leads to the reduction of degrees of freedom of these systems and, as consequence, naturally defines a dynamics in a reduced phase space.Comment: 12 page

Hamilton-Jacobi Approach for First Order Actions and Theories with Higher Derivatives

In this work we analyze systems described by Lagrangians with higher order derivatives in the context of the Hamilton-Jacobi formalism for first order actions. Two different approaches are studied here: the first one is analogous to the description of theories with higher derivatives in the hamiltonian formalism according to [Sov. Phys. Journ. 26 (1983) 730; the second treats the case where degenerate coordinate are present, in an analogy to reference [Nucl. Phys. B 630 (2002) 509]. Several examples are analyzed where a comparison between both approaches is made

General Relativity in two dimensions: a Hamilton-Jacobi constraint analysis

We will analyze the constraint structure of the Einstein-Hilbert first-order action in two dimensions using the Hamilton-Jacobi approach. We will be able to find a set of involutive, as well as a set of non-involutive constraints. Using generalized brackets we will show how to assure integrability of the theory, to eliminate the set of non-involutive constraints, and to build the field equations

Electromagnetic Field in Some Anisotropic Stiff Fluid Universes

The electromagnetic field is studied in a family of exact solutions of the Einstein equations whose material content is a perfect fluid with stiff equation of state (p = $\epsilon$ ). The field equations are solved exactly for several members of the family.Comment: 6 pages, REVTEX,no figure

Cosmic Strings from N=2, D=5 Supergravity

Exact solutions of N=2 supergravity in five dimensions are found in the metric with cylindrical symmetry, a particular case corresponds to the exterior of a cosmic string.Comment: 5 pages, plain LATEX,no figure

On the excessive role of technocracy (from a Gadamerian perspective)

The role of experts grows in the present and that is, in part, justifiable: as complexity rises, the ones who deliberate feel the need of the help of those who have know-how in specific fields. The question that must be asked revolves around the type of expectations developed in modern societies regarding what experts can do. Though specialization is not a peculiarity of our time (the process can be observed since human beings became sedentary); it has presently gained specific characteristics. Two aspects of modern life are particularly significant on that matter: (i.) the fact that the economic system is based on excitation of new needs (and no longer on the demand for satisfaction of needs); (ii.) the growing pursuit for total administration of conflicts. These factors are constitutive of what Gadamer sees as a great threat to our civilization: the excessive emphasis given in our time to the human ability to adapt. A specific ability is demanded from individuals: the capability of making an apparatus functions properly. Less resistance and more adaptability is requested, and because of that, autonomous thought - that is, not determined by the function it has in a system – is devalued. The threat we currently face is that the abilities of a good technocrat become the only qualities demanded from those who are responsible for practical decisions (especially in politics and law). Teleological reason, that guides the activity of specialists (and requires know-how in a specific area and consists in choosing means to reach a previously established goal), should not substitute practical reason, as the former requires adaptability to experience (not to a plan that was previously established) and is grounded on solidarity. In order to discuss the limits of the activity of specialists, the paper looks back to phrónesis and the way ancient Greeks set boundaries - this exercise should help raising new questions revolving the matter