24,083 research outputs found
Sedimentation of Oblate Ellipsoids at low and Moderate Reynolds numbers
In many applications to biophysics and environmental engineering,
sedimentation of non-spherical particles for example: ellipsoids, is an
important problem. In our work, we simulate the dynamics of oblate ellipsoids
under gravity. We study the settling velocity and the average orientation of
the ellipsoids as a function of volume fraction. We see that the settling
velocity shows a local maximum at the intermmediate densities unlike the
spheres. The average orientation of the ellipsoids also shows a similar local
maximum and we observe that this local maximum disappears as the Reynolds
number is increased. Also, at small volume fractions, we observe that the
oblate ellipsoids exhibit an orientational clustering effect in alignment with
gravity accompanied by strong density fluctuations. The vertical and horizontal
fluctuations of the oblate ellipsoids are small compared to that of the
spheres
Four-dimensional gravity on supersymmetric dilatonic domain walls
We investigate the localization of four-dimensional metastable gravity in
supersymmetric dilatonic domain walls through massive modes by considering
several scenarios in the model. We compute corrections to the Newtonian
potential for small and long distances compared with a crossover scale given in
terms of the dilatonic coupling. 4D gravity behavior is developed on the brane
for distance very much below the crossover scale, while for distance much
larger, the 5D gravity is recovered. Whereas in the former regime gravity is
always attractive, in the latter regime due to non-normalizable unstable
massive graviton modes present on the spectrum, in some special cases, gravity
appears to be repulsive and signalizes a gravitational confining phase which is
able to produce an inflationary phase of the Universe.Comment: 11 pages, 4 figures, Latex. Version to appear in PL
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