65 research outputs found
Canonical Noether symmetries and commutativity properties for gauge systems
For a dynamical system defined by a singular Lagrangian, canonical Noether
symmetries are characterized in terms of their commutation relations with the
evolution operators of Lagrangian and Hamiltonian formalisms. Separate
characterizations are given in phase space, in velocity space, and through an
evolution operator that links both spaces.Comment: 22 pages; some references updated, an uncited reference deleted,
minor style change
Singular lagrangians: some geometric structures along the Legendre map
New geometric structures that relate the lagrangian and hamiltonian
formalisms defined upon a singular lagrangian are presented. Several vector
fields are constructed in velocity space that give new and precise answers to
several topics like the projectability of a vector field to a hamiltonian
vector field, the computation of the kernel of the presymplectic form of
lagrangian formalism, the construction of the lagrangian dynamical vector
fields, and the characterisation of dynamical symmetries.Comment: 27 pages; minor changes, a reference update
Gauge transformations for higher-order lagrangians
Noether's symmetry transformations for higher-order lagrangians are studied.
A characterization of these transformations is presented, which is useful to
find gauge transformations for higher-order singular lagrangians. The case of
second-order lagrangians is studied in detail. Some examples that illustrate
our results are given; in particular, for the lagrangian of a relativistic
particle with curvature, lagrangian gauge transformations are obtained, though
there are no hamiltonian gauge generators for them.Comment: 22 pages, LaTe
Noether's theorem and gauge transformations. Application to the bosonic string and CP(2,n-1) model
New results on the theory of constrained systems are applied to characterize the generators of Noethers symmetry transformations. As a byproduct, an algorithm to construct gauge transformations in Hamiltonian formalism is derived. This is illustrated with two relevant examples
Gauge transformations in the Lagrangian and Hamiltonian formalisms of generally covariant theories
We study spacetime diffeomorphisms in Hamiltonian and Lagrangian formalisms
of generally covariant systems. We show that the gauge group for such a system
is characterized by having generators which are projectable under the Legendre
map. The gauge group is found to be much larger than the original group of
spacetime diffeomorphisms, since its generators must depend on the lapse
function and shift vector of the spacetime metric in a given coordinate patch.
Our results are generalizations of earlier results by Salisbury and
Sundermeyer. They arise in a natural way from using the requirement of
equivalence between Lagrangian and Hamiltonian formulations of the system, and
they are new in that the symmetries are realized on the full set of phase space
variables. The generators are displayed explicitly and are applied to the
relativistic string and to general relativity.Comment: 12 pages, no figures; REVTeX; uses multicol,fancyheadings,eqsecnum;
to appear in Phys. Rev.
Les coves litorals situades a la franja costanera entre es Mal Pas i el cap Gros
[cat] Presentam la topografia i descripció de 9 coves litorals d’Alcúdia. Es comenta la seva possible gènesi i les peculiaritats morfològiques més destacades. Documentam l’esbucament recent d’una cavitat situada a la zona. Es descriuen els jaciments del Pleistocè superior marÃ. A la cova des Fonoll Marà s’han trobat restes de vell marà (Monachus monachus), extingit el segle passat a les Illes Balears.[spa] Presentamos la topografÃa y descripción de 9 cavidades litorales de Alcúdia. Se comentan algunos aspectos genéticos y morfológicos destacables de las cavidades. Se documenta el desmantelamiento reciente de una cavidad situada en la zona. Se describen los yacimientos paleontológicos del Pleistoceno superior marino. En la cova des Fonoll MarÃ, se han hallado restos de la foca monje (Monachus monachus), extinguida el siglo pasado en las Islas Baleares
- …