1,967 research outputs found
Dynamically assisted Sauter-Schwinger effect in inhomogeneous electric fields
Via the worldline instanton method, we study electron-positron pair creation
by a strong electric field of the profile superimposed by a
weaker pulse . If the temporal Keldysh parameter
exceeds a threshold value which depends on the spatial Keldysh parameter , we
find a drastic enhancement of the pair creation probability -- reporting on
what we believe to be the first analytic non-perturbative result for the
interplay between temporal and spatial field dependences in the
Sauter-Schwinger effect.Comment: 13 pages, 4 figure
The combination of spatial access methods and computational geometry in geographic database systems
Geographic database systems, known as geographic information systems (GISs) particularly among non-computer scientists, are one of the most important applications of the very active research area named spatial database systems. Consequently following the database approach, a GIS hag to be seamless, i.e. store the complete area of interest (e.g. the whole world) in one database map. For exhibiting acceptable performance a seamless GIS hag to use spatial access methods. Due to the complexity of query and analysis operations on geographic objects, state-of-the-art computational geomeny concepts have to be used in implementing these operations. In this paper, we present GIS operations based on the compuational geomeny technique plane sweep. Specifically, we show how the two ingredients spatial access methods and computational geomeny concepts can be combined fĂŒr improving the performance of GIS operations. The fruitfulness of this combination is based on the fact that spatial access methods efficiently provide the data at the time when computational geomeny algorithms need it fĂŒr processing. Additionally, this combination avoids page faults and facilitates the parallelization of the algorithms.
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