456,071 research outputs found
Transmission coefficient and two-fold degenerate discrete spectrum of spin-1 bosons in a double-step potential
The scattering of spin-1 bosons in a nonminimal vector double-step potential
is described in terms of eigenstates of the helicity operator and it is shown
that the transmission coefficient is insensitive to the choice of the
polarization of the incident beam. Poles of the transmission amplitude reveal
the existence of a two-fold degenerate spectrum. The results are interpreted in
terms of solutions of two coupled effective Schr\"{o}dinger equations for a
finite square well with additional -functions situated at the borders.Comment: arXiv admin note: substantial text overlap with arXiv:1203.119
Dynamic System Adaptation by Constraint Orchestration
For Paradigm models, evolution is just-in-time specified coordination
conducted by a special reusable component McPal. Evolution can be treated
consistently and on-the-fly through Paradigm's constraint orchestration, also
for originally unforeseen evolution. UML-like diagrams visually supplement such
migration, as is illustrated for the case of a critical section solution
evolving into a pipeline architecture.Comment: 19 page
Joint Formation of QSOs and Spheroids: QSOs as clocks of star formation in Spheroids
Direct and indirect observational evidence leads to the conclusion that high
redshift QSOs did shine in the core of early type proto-galaxies during their
main episode of star formation. Exploting this fact, we derive the rate of
formation of this kind of stellar systems at high redshift by using the QSO
Luminosity Function. The elemental proportions in elliptical galaxies, the
descendents of the QSO hosts, suggest that the star formation was more rapid in
more massive objects. We show that this is expected to occur in Dark Matter
haloes, when the processes of cooling and heating is considered. This is also
confirmed by comparing the observed sub-mm counts to those derived by coupling
the formation rate and the star formation rate of the spheroidal galaxies with
a detailed model for their SED evolution. In this scenario SCUBA galaxies and
Lyman Break Galaxies are early type proto-galaxies forming the bulk of their
stars before the onset of QSO activity.Comment: 13 pages, 8 figures, accepted by MNRAS, major revision of the
formalis
Multi-layer model for the web graph
This paper studies stochastic graph models of the WebGraph. We present a new model that describes the WebGraph as an ensemble of different regions generated by independent stochastic processes (in the spirit of a recent paper by Dill et al. [VLDB 2001]). Models such as the Copying Model [17] and Evolving Networks Model [3] are simulated and compared on several relevant measures such as degree and clique distribution
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