44,464 research outputs found
Dielectric-Branes
We extend the usual world-volume action for a Dp-brane to the case of N
coincident Dp-branes where the world-volume theory involves a U(N) gauge
theory. The guiding principle in our construction is that the action should be
consistent with the familiar rules of T-duality. The resulting action involves
a variety of potential terms, i.e., nonderivative interactions, for the
nonabelian scalar fields. This action also shows that Dp-branes naturally
couple to RR potentials of all form degrees, including both larger and smaller
than p+1. We consider the dynamics resulting from this action for Dp-branes
moving in nontrivial background fields, and illustrate how the Dp-branes are
``polarized'' by external fields. In a simple example, we show that a system of
D0-branes in an external RR four-form field expands into a noncommutative
two-sphere, which is interpreted as the formation of a spherical D2-D0 bound
state.Comment: 33 pages, Latex, 2 ref.'s added, few typo's fixe
Fragment isospin distributions and the phase diagram of excited nuclear systems
Fragment average isospin distributions are investigated within a
microcanonical multifragmentation model in different regions of the phase
diagram. The results indicate that in the liquid phase versus is
monotonically increasing, in the phase coexistence region it has a rise and
fall shape and in the gas phase it is constant. Deviations from this behavior
may manifest at low fragment multiplicity as a consequence of mass/charge
conservation. Characterization of the "free" and "bound" phases function of
fragment charge reconfirms the neutron enrichment of the "free" phase with
respect to the "bound" one irrespectively the localization of the
multifragmentation event in the phase diagram.Comment: 23 pages, 12 figure
Methods for presentation and display of multivariate data
Methods for the presentation and display of multivariate data are discussed with emphasis placed on the multivariate analysis of variance problems and the Hotelling T(2) solution in the two-sample case. The methods utilize the concepts of stepwise discrimination analysis and the computation of partial correlation coefficients
Literature review of some selected types of results and statistical analyses of total-ozone data
The depletion of ozone in the stratosphere is examined, and causes for the depletion are cited. Ground station and satellite measurements of ozone, which are taken on a worldwide basis, are discussed. Instruments used in ozone measurement are discussed, such as the Dobson spectrophotometer, which is credited with providing the longest and most extensive series of observations for ground based observation of stratospheric ozone. Other ground based instruments used to measure ozone are also discussed. The statistical differences of ground based measurements of ozone from these different instruments are compared to each other, and to satellite measurements. Mathematical methods (i.e., trend analysis or linear regression analysis) of analyzing the variability of ozone concentration with respect to time and lattitude are described. Various time series models which can be employed in accounting for ozone concentration variability are examined
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