2,144 research outputs found
Kinematic Segregation of Flowing Grains in Sandpiles
We study the segregation of granular mixtures in two-dimensional silos using
a set of coupled equations for surface flows of grains. We study the thick flow
regime, where the grains are segregated in the rolling phase. We incorporate
this dynamical segregation process, called kinematic sieving, free-surface
segregation or percolation, into the theoretical formalism and calculate the
profiles of the rolling species and the concentration of grains in the bulk in
the steady state. Our solution shows the segregation of the mixture with the
large grains being found at the bottom of the pile in qualitative agreement
with experiments.Comment: 6 pages, 3 figures, http://polymer.bu.edu/~hmakse/Home.htm
Boundary dynamics of asymptotically flat 3D gravity coupled to higher spin fields
We construct a two-dimensional action principle invariant under a spin-three
extension of BMS group. Such a theory is obtained through a reduction of
Chern-Simons action with a boundary. This procedure is carried out by imposing
a set of boundary conditions obtained from asymptotically flat spacetimes in
three dimensions. When implementing part of this set, we obtain an analog of
chiral WZW model based on a contraction of . The remaining part of the boundary conditions imposes
constraints on the conserved currents of the model, which allows to further
reduce the action principle. It is shown that a sector of this latter theory is
related to a flat limit of Toda theory.Comment: 16 pages, no figure
Asymptotically flat spacetimes in 3D bigravity
We report that a class of three-dimensional bimetric theories contain
asymptotically flat solutions. These spacetimes can be cast in a set of
asymptotic conditions at null infinity which are preserved under the infinite
dimensional BMS group. Moreover, the algebra of the canonical generators
exhibits a central extension. The possibility that these solutions describe
regular black holes is also discussed.Comment: 6 page
Astroparticle Physics at Eastern Colombia
We present the emerging panorama of Astroparticle Physics at Eastern
Colombia, and describe several ongoing projects, most of them related to the
Latin American Giant Observatory (LAGO) Project. This research work is carried
out at the Grupo de Investigaciones en Relatividad y Gravitaci\'on of
Universidad Industrial de Santander.Comment: 19 pages, 8 figure
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