9,017 research outputs found
Indefatigable
17 short moments for piano and electronics.
Inspired by the practice of ink painting, this gestural piano piece explores angular piano writing, combined with sound recordings of ink painting
Baryogenesis via Dark Matter-Induced Symmetry Breaking in the Early Universe
We put forward a new proposal for generating the baryon asymmetry of the
universe by making use of the dynamics of a scalar field
coupled to dark matter. High dark matter densities cause the
symmetry to break spontaneously so that the field acquires a large vacuum
expectation value. The symmetry is restored when the density redshifts below a
critical value, resulting in the coherent oscillation of the scalar field. A
net number can be generated either via baryon number-conserving couplings
to the standard model or through small symmetry-violating operators and the
subsequent decay of the scalar condensate.Comment: 13 pages, 4 figures, updated to reflect published versio
Taxonomy and biogeography of the genera Oedaleus fieber and Gastrimargus saussure (Orthoptera: Acrididae)
Imperial Users onl
Te Ruru Light festival 2019 - Direction/Curation
This free community event includes interactive light installations, immersive performances, building projections, a dedicated kids' zone, and much more
Unsteady turbulent buoyant plumes
We model the unsteady evolution of turbulent buoyant plumes following
temporal changes to the source conditions. The integral model is derived from
radial integration of the governing equations expressing the conservation of
mass, axial momentum and buoyancy. The non-uniform radial profiles of the axial
velocity and density deficit in the plume are explicitly described by shape
factors in the integral equations; the commonly-assumed top-hat profiles lead
to shape factors equal to unity. The resultant model is hyperbolic when the
momentum shape factor, determined from the radial profile of the mean axial
velocity, differs from unity. The solutions of the model when source conditions
are maintained at constant values retain the form of the well-established
steady plume solutions. We demonstrate that the inclusion of a momentum shape
factor that differs from unity leads to a well-posed integral model. Therefore,
our model does not exhibit the mathematical pathologies that appear in
previously proposed unsteady integral models of turbulent plumes. A stability
threshold for the value of the shape factor is identified, resulting in a range
of its values where the amplitude of small perturbations to the steady
solutions decay with distance from the source. The hyperbolic character of the
system allows the formation of discontinuities in the fields describing the
plume properties during the unsteady evolution. We compute numerical solutions
to illustrate the transient development following an abrupt change in the
source conditions. The adjustment to the new source conditions occurs through
the propagation of a pulse of fluid through the plume. The dynamics of this
pulse are described by a similarity solution and, by constructing this new
similarity solution, we identify three regimes in which the evolution of the
transient pulse following adjustment of the source qualitatively differ.Comment: 41 pages, 16 figures, under consideration for publication in Journal
of Fluid Mechanic
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