17,269 research outputs found
Causality in classical electrodynamics
Causality in electrodynamics is a subject of some confusion, especially
regarding the application of Faraday's law and the Ampere-Maxwell law. This has
led to the suggestion that we should not teach students that electric and
magnetic fields can cause each other, but rather focus on charges and currents
as the causal agents. In this paper I argue that fields have equal status as
casual agents, and that we should teach this. Following a discussion of
causality in classical physics I will use a numerical solution of Maxwell's
equations to inform a field based causal explanation in electrodynamics.Comment: Comments welcom
Strain patterns and strain accumulation along plate margins
Observations of strain accumulation along plate margins in Japan, New Zealand, and the United States indicate that: (1) a typical maximum rate of secular strain accumulation is on the order of 0.3 ppm/a, (2) a substantial part of the strain accumulation process can be attributed to slip at depth on the major plate boundary faults, and (3) some plastic deformation in a zone 100 km or more in width is apparently involved in the strain accumulation process
Lecture Hall Theorems, q-series and Truncated Objects
We show here that the refined theorems for both lecture hall partitions and
anti-lecture hall compositions can be obtained as straightforward consequences
of two q-Chu Vandermonde identities, once an appropriate recurrence is derived.
We use this approach to get new lecture hall-type theorems for truncated
objects. We compute their generating function and give two different
multivariate refinements of these new results : the q-calculus approach gives
(u,v,q)-refinements, while a completely different approach gives odd/even
(x,y)-refinements. From this, we are able to give a combinatorial
characterization of truncated lecture hall partitions and new finitizations of
refinements of Euler's theorem
A model of a pumped continuous atom laser
We present a model of a cw atom laser based on a system of coupled GP
equations. The model incorporates continuous Raman outcoupling, pumping and
three-body recombination. The outcoupled field has minimal atomic density
fluctuations and is locally monochromatic.Comment: 10 pages, 8 eps figures, typos fixe
The Relativity Concept Inventory: development, analysis and results
We report on a concept inventory for special relativity: the development
process, data analysis methods, and results from an introductory relativity
class. The Relativity Concept Inventory tests understanding of kinematic
relativistic concepts. An unusual feature is confidence testing for each
question. This can provide additional information; for example high confidence
correlated with incorrect answers suggests a misconception. A novel aspect of
our data analysis is the use of Monte Carlo simulations to determine the
significance of correlations. This approach is particularly useful for small
sample sizes, such as ours. Our results include a gender bias that was not
present in other assessment, similar to that reported for the Force Concept
Inventory
Spatial pair correlations of atoms in molecular dissociation
We perform first-principles quantum simulations of dissociation of trapped,
spatially inhomogeneous Bose-Einstein condensates of molecular dimers.
Specifically, we study spatial pair correlations of atoms produced in
dissociation after time of flight. We find that the observable correlations may
significantly degrade in systems with spatial inhomogeneity compared to the
predictions of idealized uniform models. We show how binning of the signal can
enhance the detectable correlations and lead to the violation of the classical
Cauchy-Schwartz inequality and relative number squeezing.Comment: Final published versio
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