Toward an ecological aesthetics: music as emergence

In this article we intend to suggest some ecological based principles to support the possibility of develop an ecological aesthetics. We consider that an ecological aesthetics is founded in concepts as “direct perception”, “acquisition of affordances and invariants”, “embodied embedded perception” and so on. Here we will purpose that can be possible explain especially soundscape music perception in terms of direct perception, working with perception of first hand (in a Gibsonian sense). We will present notions as embedded sound, detection of sonic affordances and invariants, and at the end we purpose an experience with perception/action paradigm to make soundscape music as emergence of a self-organized system

Equivalence between different classical treatments of the O(N) nonlinear sigma model and their functional Schrodinger equations

In this work we derive the Hamiltonian formalism of the O(N) non-linear sigma model in its original version as a second-class constrained field theory and then as a first-class constrained field theory. We treat the model as a second-class constrained field theory by two different methods: the unconstrained and the Dirac second-class formalisms. We show that the Hamiltonians for all these versions of the model are equivalent. Then, for a particular factor-ordering choice, we write the functional Schrodinger equation for each derived Hamiltonian. We show that they are all identical which justifies our factor-ordering choice and opens the way for a future quantization of the model via the functional Schrodinger representation.Comment: Revtex version, 17 pages, substantial change

Hidden symmetries in the two-dimensional isotropic antiferromagnet

We discuss the two-dimensional isotropic antiferromagnet in the framework of gauge invariance. Gauge invariance is one of the most subtle useful concepts in theoretical physics, since it allows one to describe the time evolution of complex physical systesm in arbitrary sequences of reference frames. All theories of the fundamental interactions rely on gauge invariance. In Dirac's approach, the two-dimensional isotropic antiferromagnet is subject to second class constraints, which are independent of the Hamiltonian symmetries and can be used to eliminate certain canonical variables from the theory. We have used the symplectic embedding formalism developed by a few of us to make the system under study gauge-invariant. After carrying out the embedding and Dirac analysis, we systematically show how second class constraints can generate hidden symmetries. We obtain the invariant second-order Lagrangian and the gauge-invariant model Hamiltonian. Finally, for a particular choice of factor ordering, we derive the functional Schr\"odinger equations for the original Hamiltonian and for the first class Hamiltonian and show them to be identical, which justifies our choice of factor ordering.Comment: To appear in Volume 43 of the Brazilian Journal of Physic

Testing two alternatives theories to dark matter with the Milky Way dynamics

Two alternative theories to dark matter are investigated by testing their ability to describe consistently the dynamics of the Milky Way. The first one refers to a modified gravity theory having a running gravitational constant and the second assumes that dark matter halos are constituted by a Bose-Einstein condensation. The parameters of each model as well as those characterizing the stellar subsystems of the Galaxy were estimated by fitting the rotation curve of the Milky Way. Then, using these parameters, the vertical acceleration profile at the solar position was computed and compared with observations. The modified gravity theory overestimates the vertical acceleration derived from stellar kinematics while predictions of the Bose-Einstein condensation halo model are barely consistent with observations. However, a dark matter halo based on a collisionless fluid satisfies our consistency test, being the best model able to describe equally well the rotation curve and the vertical acceleration of the Galaxy.Comment: 16 pages, 4 figures, Accepted in Gen. Rel. Gra

Canonical transformation for stiff matter models in quantum cosmology

In the present work we consider Friedmann-Robertson-Walker models in the presence of a stiff matter perfect fluid and a cosmological constant. We write the superhamiltonian of these models using the Schutz's variational formalism. We notice that the resulting superhamiltonians have terms that will lead to factor ordering ambiguities when they are written as operators. In order to remove these ambiguities, we introduce appropriate coordinate transformations and prove that these transformations are canonical using the symplectic method.Comment: Revtex4 Class, 3 pages, No Figure