8,196 research outputs found
Fields in Nonaffine Bundles. I. The general bitensorially covariant differentiation procedure
The standard covariant differentiation procedure for fields in vector bundles
is generalised so as to be applicable to fields in general nonaffine bundles in
which the fibres may have an arbitrary nonlinear structure. In addition to the
usual requirement that the base space should be flat or endowed with its own
linear connection, and that there should be an ordinary gauge connection on the
bundle, it is necessary to require also that there should be an intrinsic,
bundle-group invariant connection on the fibre space. The procedure is based on
the use of an appropriate primary-field (i.e. section) independent connector
that is constructed in terms of the natural fibre-tangent-vector realisation of
the gauge connection. The application to gauged harmonic mappings will be
described in a following article.Comment: 17 page Latex file with some minor misprint corrections and added
color for article originally published in black and whit
A class of anisotropic (Finsler-) space-time geometries
A particular Finsler-metric proposed in [1,2] and describing a geometry with
a preferred null direction is characterized here as belonging to a subclass
contained in a larger class of Finsler-metrics with one or more preferred
directions (null, space- or timelike). The metrics are classified according to
their group of isometries. These turn out to be isomorphic to subgroups of the
Poincar\'e (Lorentz-) group complemented by the generator of a dilatation. The
arising Finsler geometries may be used for the construction of relativistic
theories testing the isotropy of space. It is shown that the Finsler space with
the only preferred null direction is the anisotropic space closest to isotropic
Minkowski-space of the full class discussed.Comment: 12 pages, latex, no figure
A temporal versioned object-oriented data schema model
AbstractThis paper describes in a formal way a data schema model which introduces temporal and versioning schema features in an object-oriented environment. In our model, the schema is time dependent and the history of the changes which occur on its elements are kept into version hierarchies. A fundamental assumption behind our approach is that a new schema specification should not define a new database, so that previous schema definitions are considered as alternative design specifications, and consequently, existing data can be accessed in a consistent way using any of the defined schemas
- …