23,951 research outputs found
Comment on "A note on the construction of the Ermakov-Lewis invariant"
We show that the basic results on the paper referred in the title [J. Phys.
A: Math. Gen. v. 35 (2002) 5333-5345], concerning the derivation of the Ermakov
invariant from Noether symmetry methods, are not new
THE CASE OF A QUEER ISOQUANT: INCREASING MARGINAL RATES OF SUBSTITUTION OF GRAIN FOR ROUGHAGE IN CATTLE FINISHING
Livestock Production/Industries,
X-ray and radio prompt emission from a hypernova SN 2002ap
Here we report on combined X-ray and radio observations of SN 2002ap with
XMM-Newton ToO observation and GMRT observations aided with VLA published
results. In deriving the X-ray flux of SN 2002ap we account for the
contribution of a nearby source, found to be present in the pre-SN explosion
images obtained with Chandra observatory. We also derive upper limits on mass
loss rate from X-ray and radio data. We suggest that the prompt X-ray emission
is non-thermal in nature and its is due to the repeated compton boosting of
optical photons. We also compare SN's early radiospheric properties with two
other SNe at the same epoch.Comment: 4 pages, 5 figures. Uses espcrc2.sty. To appear in proceedings of
symposium on X-ray astronomy "The Restless High-Energy Universe", May 2003,
Amsterdam, The Netherlands, eds. E.P.J. van den Heuvel, J.J.M. in 't Zand,
and R.A.M.J. Wijer
College Football Rankings and Market Efficiency
The results in this paper show that various college football ranking systems have useful independent information for predicting the outcomes of games. Optimal weights for the systems are estimated, and the use of these weights produces a predictive system that is more accurate than any of the individual systems. The results also provide a fairly precise estimate of the size of the home field advantage. These results may be of interest to the Bowl Championship Series in choosing which teams to play in the national championship game. The results also show, however, that none of the systems, including the optimal combination, contains any useful information that is not in the final Las Vegas point spread. It is argued in the paper that this is a fairly strong test of the efficiency of the college football betting market.Football rankings, Predictive information
Anxiety and Learning in Dynamic and Static Clock Game Experiments
In clock games, agents receive differently-timed private signals when an asset value is above its fundamental. The price crashes to
the fundamental when K of N agents have decided to sell. If selling decisions are private, bubbles can be sustained because people
delay selling, after receiving signals, knowing that others will delay too. Our results replicate the main features of the one previous
experimental study of clock game (in two subject pools): Selling delays are shorter than predicted, but converge toward equilibrium
predictions over repeated trials. We also find that delays are shorter in a dynamic game in which selling decisions unfold over time,
compared to a static equivalent in which subjects precommit to selling decisions. A model of learning with growing anxiety after
signal arrival can reproduce the empirical observations of shorter-than-predicted delay, smaller delay after later signal arrival, and
shorter delays in dynamic games
Mode-matching without root-finding: Application to a dissipative silencer
This article presents an analytic mode-matching approach suitable for modelling the propagation of sound in a two-dimensional, three-part, ducting system. The approach avoids the need to the find roots of the characteristic equation for the middle section of the duct (the component) and is readily applicable to a broad class of problems. It is demonstrated that the system of equations, derived via analytic mode-matching, exhibits certain features which ensure that they can be re-cast into a form that is independent of the roots of the characteristic equation for the component. The precise details of the component are irrelevant to the procedure; it is required only that there exists an orthogonality relation, or similar, for the eigenmodes corresponding to the propagating wave-forms in this region. The method is applied here to a simple problem involving acoustic transmission through a dissipative silencer of the type commonly found in heating ventilation and air-conditioning (HVAC) ducts. With reference to this example, the silencer transmission loss is computed, and the power balance for the silencer is investigated and is shown to be an identity that is necessarily satisfied by the system of equations, regardless of the level of truncation
Analysis of a parallel multigrid algorithm
The parallel multigrid algorithm of Frederickson and McBryan (1987) is considered. This algorithm uses multiple coarse-grid problems (instead of one problem) in the hope of accelerating convergence and is found to have a close relationship to traditional multigrid methods. Specifically, the parallel coarse-grid correction operator is identical to a traditional multigrid coarse-grid correction operator, except that the mixing of high and low frequencies caused by aliasing error is removed. Appropriate relaxation operators can be chosen to take advantage of this property. Comparisons between the standard multigrid and the new method are made
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