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J. Doyle

Publications and source records attributed to J. Doyle.

3 recordsLinked to original sources
arXiv2008

Magnetic trapping of silver and copper, and anomolous spin relaxation in the Ag-He system

We have trapped large numbers of copper and silver atoms using buffer gas cooling. Up to 3x10^12 copper atoms and 4x10^13 silver atoms are trapped. Lifetimes are as long as 5 s, limited by collisions with the buffer gas. Ratios of elastic to inelastic collision rates with He are >~ 10^6, suggesting copper and silver are favorable for use in ultracold applications. The temperature dependence of the silver-helium-3 collision rate varies as T^5.8. We find that this temperature dependence is inconsistent with the behavior predicted for relaxation arising from the spin-rotation interaction, and conclude that the silver-helium-3 system displays anomalous collisional behavior in the multiple-partial wave regime. Lifetimes of laser ablated gold in helium-3 buffer gas are too short to permit trapping.

physics.atom-ph↗
arXiv2005

Highly optimized tolerance and power laws in dense and sparse resource regimes

Power law cumulative frequency $(P)$ vs. event size $(l)$ distributions $P(\geq l)\sim l^{-α}$ are frequently cited as evidence for complexity and serve as a starting point for linking theoretical models and mechanisms with observed data. Systems exhibiting this behavior present fundamental mathematical challenges in probability and statistics. The broad span of length and time scales associated with heavy tailed processes often require special sensitivity to distinctions between discrete and continuous phenomena. A discrete Highly Optimized Tolerance (HOT) model, referred to as the Probability, Loss, Resource (PLR) model, gives the exponent $α=1/d$ as a function of the dimension $d$ of the underlying substrate in the sparse resource regime. This agrees well with data for wildfires, web file sizes, and electric power outages. However, another HOT model, based on a continuous (dense) distribution of resources, predicts $α= 1+ 1/d $. In this paper we describe and analyze a third model, the cuts model, which exhibits both behaviors but in different regimes. We use the cuts model to show all three models agree in the dense resource limit. In the sparse resource regime, the continuum model breaks down, but in this case, the cuts and PLR models are described by the same exponent.

physics.soc-ph↗