2,852 research outputs found
Guardians of public morals: an examination of the effect of Victorianism on literary studies
For the purposes of this study, we must seek a narrow definition of Victorianism and describe it as that sense of moral seriousness which all Victorians shared or were expected to share. In an age which possessed no natural unity, and which experienced constant change, this one characteristic stood out as a cohesive force. Known by a multitude of synonyms--respectability, prudishness, propriety--Victorianism in this sense has been used to indicate that moral attitude which lay at the base of the strict standards we still think of as typical of nineteenth century Britain
Symmetry Decomposition of Chaotic Dynamics
Discrete symmetries of dynamical flows give rise to relations between
periodic orbits, reduce the dynamics to a fundamental domain, and lead to
factorizations of zeta functions. These factorizations in turn reduce the labor
and improve the convergence of cycle expansions for classical and quantum
spectra associated with the flow. In this paper the general formalism is
developed, with the -disk pinball model used as a concrete example and a
series of physically interesting cases worked out in detail.Comment: CYCLER Paper 93mar01
Echoes in classical dynamical systems
Echoes arise when external manipulations to a system induce a reversal of its
time evolution that leads to a more or less perfect recovery of the initial
state. We discuss the accuracy with which a cloud of trajectories returns to
the initial state in classical dynamical systems that are exposed to additive
noise and small differences in the equations of motion for forward and backward
evolution. The cases of integrable and chaotic motion and small or large noise
are studied in some detail and many different dynamical laws are identified.
Experimental tests in 2-d flows that show chaotic advection are proposed.Comment: to be published in J. Phys.
Design diversity: an update from research on reliability modelling
Diversity between redundant subsystems is, in various forms, a common design approach for improving system dependability. Its value in the case of software-based systems is still controversial. This paper gives an overview of reliability modelling work we carried out in recent projects on design diversity, presented in the context of previous knowledge and practice. These results provide additional insight for decisions in applying diversity and in assessing diverseredundant systems. A general observation is that, just as diversity is a very general design approach, the models of diversity can help conceptual understanding of a range of different situations. We summarise results in the general modelling of common-mode failure, in inference from observed failure data, and in decision-making for diversity in development.
Comparison with excavated and metal-detected finds in the wider region
When Roman objects are discovered in rivers they are commonly interpreted as accidental losses or as rubbish deposits revealed by fluvial erosion; this is in contrast to prehistoric assemblages, which are often seen as ritual offerings
Statistical analysis of coherent structures in transitional pipe flow
Numerical and experimental studies of transitional pipe flow have shown the
prevalence of coherent flow structures that are dominated by downstream
vortices. They attract special attention because they contribute predominantly
to the increase of the Reynolds stresses in turbulent flow. In the present
study we introduce a convenient detector for these coherent states, calculate
the fraction of time the structures appear in the flow, and present a Markov
model for the transition between the structures. The fraction of states that
show vortical structures exceeds 24% for a Reynolds number of about Re=2200,
and it decreases to about 20% for Re=2500. The Markov model for the transition
between these states is in good agreement with the observed fraction of states,
and in reasonable agreement with the prediction for their persistence. It
provides insight into dominant qualitative changes of the flow when increasing
the Reynolds number.Comment: 11 pages, 26 (sub)figure
Semiclassical cross section correlations
We calculate within a semiclassical approximation the autocorrelation
function of cross sections. The starting point is the semiclassical expression
for the diagonal matrix elements of an operator. For general operators with a
smooth classical limit the autocorrelation function of such matrix elements has
two contributions with relative weights determined by classical dynamics. We
show how the random matrix result can be obtained if the operator approaches a
projector onto a single initial state. The expressions are verified in
calculations for the kicked rotor.Comment: 6 pages, 2 figure
Semiclassical Quantization by Pade Approximant to Periodic Orbit Sums
Periodic orbit quantization requires an analytic continuation of
non-convergent semiclassical trace formulae. We propose a method for
semiclassical quantization based upon the Pade approximant to the periodic
orbit sums. The Pade approximant allows the re-summation of the typically
exponentially divergent periodic orbit terms. The technique does not depend on
the existence of a symbolic dynamics and can be applied to both bound and open
systems. Numerical results are presented for two different systems with chaotic
and regular classical dynamics, viz. the three-disk scattering system and the
circle billiard.Comment: 7 pages, 3 figures, submitted to Europhys. Let
Approach to ergodicity in quantum wave functions
According to theorems of Shnirelman and followers, in the semiclassical limit
the quantum wavefunctions of classically ergodic systems tend to the
microcanonical density on the energy shell. We here develop a semiclassical
theory that relates the rate of approach to the decay of certain classical
fluctuations. For uniformly hyperbolic systems we find that the variance of the
quantum matrix elements is proportional to the variance of the integral of the
associated classical operator over trajectory segments of length , and
inversely proportional to , where is the Heisenberg
time, being the mean density of states. Since for these systems the
classical variance increases linearly with , the variance of the matrix
elements decays like . For non-hyperbolic systems, like Hamiltonians
with a mixed phase space and the stadium billiard, our results predict a slower
decay due to sticking in marginally unstable regions. Numerical computations
supporting these conclusions are presented for the bakers map and the hydrogen
atom in a magnetic field.Comment: 11 pages postscript and 4 figures in two files, tar-compressed and
uuencoded using uufiles, to appear in Phys Rev E. For related papers, see
http://www.icbm.uni-oldenburg.de/icbm/kosy/ag.htm
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