28,925 research outputs found
Time scales for fission at finite temperature
The concept of the "transient effect" is examined in respect of a "mean first
passage time". It is demonstrated that the time the fissioning system stays
inside the barrier is much larger than suggested by the transient time, and
that no enhancement of emission of neutrons over that given by Kramers' rate
formula ought to be considered.Comment: 6 pages, LaTex, 3 postscript figures; Keywords: Decay rate, transient
effect, mean first passage time; "Symposium on Nuclear Clusters",
Rauischholzhausen, Germany, 5-9 August 200
Pro-Lie Groups: A survey with Open Problems
A topological group is called a pro-Lie group if it is isomorphic to a closed
subgroup of a product of finite-dimensional real Lie groups. This class of
groups is closed under the formation of arbitrary products and closed subgroups
and forms a complete category. It includes each finite-dimensional Lie group,
each locally compact group which has a compact quotient group modulo its
identity component and thus, in particular, each compact and each connected
locally compact group; it also includes all locally compact abelian groups.
This paper provides an overview of the structure theory and Lie theory of
pro-Lie groups including results more recent than those in the authors'
reference book on pro-Lie groups. Significantly, it also includes a review of
the recent insight that weakly complete unital algebras provide a natural
habitat for both pro-Lie algebras and pro-Lie groups, indeed for the
exponential function which links the two. (A topological vector space is weakly
complete if it is isomorphic to a power of an arbitrary set of copies of
. This class of real vector spaces is at the basis of the Lie theory of
pro-Lie groups.) The article also lists 12 open questions connected with
pro-Lie groups.Comment: 19 page
Seeing is Believing: Dynamic Evolution of Gene Families
Department of Integrative Biology, Center for Computational Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712Supported by National Science Foundation Grants IOS- 0843712 and IOS-1354942 (to H.A.H.) and DBI-0939454 for the BEACON Center for the Study of Evolution in Action.Integrative Biolog
Sharp rate of average decay of the Fourier transform of a bounded set
We prove that the spherical mean of the Fourier transform of the
characteristic function of a bounded convex set (without any additional
assumptions) or a bounded set with a C^{3/2} boundary decays at infinity at the
same rate as the Fourier transform of the characteristic function of the ball.Comment: 10 pages. GAFA (to appear
Investigation of nonlinear motion simulator washout schemes
An overview is presented of some of the promising washout schemes which have been devised. The four schemes presented fall into two basic configurations; crossfeed and crossproduct. Various nonlinear modifications further differentiate the four schemes. One nonlinear scheme is discussed in detail. This washout scheme takes advantage of subliminal motions to speed up simulator cab centering. It exploits so-called perceptual indifference thresholds to center the simulator cab at a faster rate whenever the input to the simulator is below the perceptual indifference level. The effect is to reduce the angular and translational simulation motion by comparison with that for the linear washout case. Finally, the conclusions and implications for further research in the area of nonlinear washout filters are presented
The effect of electron-electron correlation on the attoclock experiment
We investigate multi-electron effects in strong-field ionization of Helium
using a semi-classical model that, unlike other commonly used theoretical
approaches, takes into account electron-electron correlation. Our approach has
an additional advantage of allowing to selectively switch off different
contributions from the parent ion (such as the remaining electron or the
nuclear charge) and thereby investigate in detail how the final electron angle
in the attoclock experiment is influenced by these contributions. We find that
the bound electron exerts a significant effect on the final electron momenta
distribution that can, however, be accounted for by an appropriately selected
mean field. Our results show excellent agreement with other widely used
theoretical models done within a single active electron approximation
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