Boundary Dynamics Driven Entanglement

We will show how it is possible to generate entangled states out of unentangled ones on a bipartite system by means of dynamical boundary conditions. The auxiliary system is defined by a symmetric but not self-adjoint Hamiltonian and the space of self-adjoint extensions of the bipartite system is studied. It is shown that only a small set of them leads to separable dynamics and they are characterized. Various simple examples illustrating this phenomenon are discussed, in particular we will analyze the hybrid system consisting on a planar quantum rotor and a spin system under a wide class of boundary conditions.Comment: 26 pages, 5 figure

A formulation of a (q+1,8)-cage

Let $q\ge 2$ be a prime power. In this note we present a formulation for obtaining the known $(q+1,8)$-cages which has allowed us to construct small $(k,g)$--graphs for $k=q-1, q$ and $g=7,8$. Furthermore, we also obtain smaller $(q,8)$-graphs for even prime power $q$.Comment: 14 pages, 2 figure

A construction of small (q-1)-regular graphs of girth 8

In this note we construct a new infinite family of $(q-1)$-regular graphs of girth $8$ and order $2q(q-1)^2$ for all prime powers $q\ge 16$, which are the smallest known so far whenever $q-1$ is not a prime power or a prime power plus one itself.Comment: 8 pages, 2 figure

Magnetostratigraphy of the Miocene continental deposits of the Montes de Castejón (central Ebro basin, Spain): geochronological and paleoenvironmental implications

A detailed magnetostratigraphic study has been carried out in the early to middle Miocene distal alluvial and lacustrine sediments of the Montes de Castejón (central Ebro Basin). The study was based on the analysis of 196 magnetostratigraphic sites sampled along a stratigraphic interval of about 240 meters. Local magnetostratigraphy yielded a sequence of 12 magnetozones (6 normal and 6 reverse) which could be correlated with the Geomagnetic Polarity Time Scale (GPTS) interval C5Cr to C5AD (between 17 and 14.3 Ma.). The sampled sedimentary sequences include the boundary between two tectosedimentary units (TSU, T5 and T6) already defined in the Ebro Basin. The magnetostratigraphy of the Montes de Castejón allows to date the T5/T6 TSU boundary at 16.14 Ma, within chron C5Cn.1n. This magnetostratigraphy also allows us to analyse in detail as well as to discuss the variations in sedimentation rates through space and time between different lacustrine environments: Outer carbonate lacustrine fringes and distal alluvial plains (Montes de Castejón sections) show higher sedimentation rates than offshore lacustrine areas (San Caprasio section, 50 km east of Montes de Castejón)

The intrinsic complexity of parametric elimination methods

This paper is devoted to the complexity analysis of a particular property, called "algebraic robustness" owned by all known symbolic methods of parametric polynomial equation solving (geometric elimination). It is shown that any parametric elimination procedure which owns this property must neccessarily have an exponential sequential time complexity.Comment: LaTeX, 12 pages. To appear in Proc. of WAIT'97, Buenos Aires, Argentina, 199

Nota previa sobre las características litoestratigráficas de las formaciones "Arenas de Utrillas" y "Lignitos de Escucha"

This paper deabs wiith the new data about the paleogeagraphy and litostratigraphy 0f the Utrillas and Escucha formations, in the area N of the type locality. Several synthetized litostratigraphic sections are correlationed, and a first isopach map is compri~sed. A sedimentary rupture has been detected at the bottom of Utrillas formation. Some data abaut the mineralogy of claysized frackion in the lsediments are given