2,927 research outputs found
Polynomial and rational solutions of holonomic systems
The aim of this paper is to give two new algorithms, which are elimination
free, to find polynomial and rational solutions for a given holonomic system
associated to a set of linear differential operators in the Weyl algebra D =
k where k is a subfield of the complex numbers.Comment: 20 page
Compressible vortex loops: effect of nozzle geometry
Vortex loops are fundamental building blocks of supersonic free jets. Isolating them allows for an easier study and better understanding of such flows. The present study looks at the behaviour of compressible vortex loops of different shapes, generated due to the diffraction of a shock wave from a shock tube with different exit nozzle geometries. These include a 15 mm diameter circular nozzle, two elliptical nozzles with minor to major axis ratios of 0.4 and 0.6, a 30 × 30 mm square nozzle, and finally two exotic nozzles resembling a pair of lips with minor to major axis ratios of 0.2 and 0.5. The experiments were performed for diaphragm pressure ratios of P4/P1=4, 8, and 12, with P4 and P1 being the pressures within the high pressure and low pressure compartments of the shock tube, respectively. High-speed schlieren photography as well as PIV measurements of both stream-wise and head-on flows have been conducted
Big Bang Nucleosynthesis with Long Lived Charged Massive Particles
We consider Big Bang Nucleosynthesis (BBN) with long lived charged massive
particles. Before decaying, the long lived charged particle recombines with a
light element to form a bound state like a hydrogen atom. This effect modifies
the nuclear reaction rates during the BBN epoch through the modifications of
the Coulomb field and the kinematics of the captured light elements, which can
change the light element abundances. It is possible that the heavier nuclei
abundances such as Li and Be decrease sizably, while the ratios ,
D/H, and He/H remain unchanged. This may solve the current discrepancy
between the BBN prediction and the observed abundance of Li. If future
collider experiments found signals of a long-lived charged particle inside the
detector, the information of its lifetime and decay properties could provide
insights to understand not only the particle physics models but also the
phenomena in the early universe in turn.Comment: 20 pages, 6 figures, published version in Physical Review
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