3,953 research outputs found
A new creep law for crushable aggregates
The authors have recently proposed a new equation for the one-dimensional (1D) normal compression line, which contains a parameter controlling the size effect on average strength. They showed that the equation held for a wide range of discrete-element modelling (DEM) simulations of crushable aggregates. This paper incorporates the time-dependence of particle strength. A new equation is proposed and examined using DEM of 1D creep. The simulations show that while the plots may seem linear on a plot of voids ratio against the logarithm of time in the traditional way, the new proposed law, which is linear when the voids ratio is also plotted on a logarithmic scale, is more appropriate. The simulations examine the influence of the size effect hardening law, the time dependence on strength and stress level. It is shown that the new equation holds for each case
A Bivariate Measure of Redundant Information
We define a measure of redundant information based on projections in the
space of probability distributions. Redundant information between random
variables is information that is shared between those variables. But in
contrast to mutual information, redundant information denotes information that
is shared about the outcome of a third variable. Formalizing this concept, and
being able to measure it, is required for the non-negative decomposition of
mutual information into redundant and synergistic information. Previous
attempts to formalize redundant or synergistic information struggle to capture
some desired properties. We introduce a new formalism for redundant information
and prove that it satisfies all the properties necessary outlined in earlier
work, as well as an additional criterion that we propose to be necessary to
capture redundancy. We also demonstrate the behaviour of this new measure for
several examples, compare it to previous measures and apply it to the
decomposition of transfer entropy.Comment: 16 pages, 15 figures, 1 table, added citation to Griffith et al 2012,
Maurer et al 199
Quantifying Self-Organization with Optimal Predictors
Despite broad interest in self-organizing systems, there are few
quantitative, experimentally-applicable criteria for self-organization. The
existing criteria all give counter-intuitive results for important cases. In
this Letter, we propose a new criterion, namely an internally-generated
increase in the statistical complexity, the amount of information required for
optimal prediction of the system's dynamics. We precisely define this
complexity for spatially-extended dynamical systems, using the probabilistic
ideas of mutual information and minimal sufficient statistics. This leads to a
general method for predicting such systems, and a simple algorithm for
estimating statistical complexity. The results of applying this algorithm to a
class of models of excitable media (cyclic cellular automata) strongly support
our proposal.Comment: Four pages, two color figure
The Active Nucleus of IC4970: A Nearby Example of Merger-Induced Cold-Gas Accretion
We present results from Chandra X-ray and Spitzer mid-infrared observations
of the interacting galaxy pair NGC6872/IC4970 in the Pavo galaxy group and show
that the smaller companion galaxy IC4970 hosts a highly obscured active
galactic nucleus (AGN). The 0.5-10 keV X-ray luminosity of the nucleus is
variable, increasing by a factor 2.9 to 1.7 x 10^{42} erg/s (bright state) on
~100 ks timescales. The X-ray spectrum of the is heavily absorbed (N_H = 3 x
10^{23} cm^{-2}) for power law models with Gamma = 1.5-2.0 and shows a clear
6.4 keV Fe Kalpha line with equivalent width of 144-195 eV. Limits on the
diffuse emission in IC4970 from Chandra X-ray data suggest that the available
power from Bondi accretion of hot interstellar gas may be an order of magnitude
too small to power the AGN. Spitzer images show that 8 micron nonstellar
emission is concentrated in the central 1 kpc of IC4970, consistent with high
obscuration in this region. The mid-infrared colors of the nucleus are
consistent with those expected for a highly obscured AGN. Taken together these
data suggest that the nucleus of IC4970 is a Seyfert 2, triggered and fueled by
cold material supplied to the central supermassive black hole as a result of
the off-axis collision of IC4970 with the cold-gas rich spiral galaxy NGC6872.Comment: 10 pages, 9 figures, submitted to ApJ, MIR flux conversion error
corrected in Table 4, MIR colors and paper text unchange
Bell's Theorem from Moore's Theorem
It is shown that the restrictions of what can be inferred from
classically-recorded observational outcomes that are imposed by the no-cloning
theorem, the Kochen-Specker theorem and Bell's theorem also follow from
restrictions on inferences from observations formulated within classical
automata theory. Similarities between the assumptions underlying classical
automata theory and those underlying universally-unitary quantum theory are
discussed.Comment: 12 pages; to appear in Int. J. General System
Lifetimes and polarizabilities of low lying lithium S, P and D states
Abstract The radiative lifetimes, scalar and tensor polarizabilities of low lying S, P and D states of lithium are obtained using a Coulomb approximation. The calculated lifetimes agree very well with the handful of experimental values listed in the literature. The ground state polarizability is also close to the measured result. This method requires substantially less computational time than ab initio theory, thereby permitting the study of nearly 40 states.
Mid-infrared Identification of 6 cm Radio Source Counterparts in the Extended Groth Strip
A new 6-cm survey of almost 0.6 square degrees to a limit of 0.55-mJy/beam
(10-sigma) finds 37 isolated radio sources and 7 radio source pairs (not
necessarily physical companions). IRAC counterparts are identified for at least
92% of the radio sources within the area of deep IRAC coverage, which includes
31 isolated sources and 6 pairs. This contrasts with an identification rate of
<74% to R<23.95 in visible light. Eight of the IRAC galaxies have power law
spectral energy distributions, implying that the mid-infrared emission comes
from a powerful AGN. The remaining 26 IRAC galaxies show stellar emission in
the mid-infrared, probably in most of these galaxies because the stellar
emission is bright enough to outshine an underlying AGN. The infrared colors
suggest that the majority of these galaxies are bulge-dominated and have
redshifts between approximately 0.5 and 1.0. Visible spectra from the DEEP2
redshift survey, available for 11 galaxies, are consistent with this
suggestion. The IRAC galaxies fall into two distinct groups in a
color-magnitude diagram, one group (the "stripe") includes all the AGN. The
other group (the "blue clump") has blue 3.6 to 8 micron colors and a small
range of 8 micron magnitudes. This separation should be useful in classifying
galaxies found in other radio surveys.Comment: Accepted by A
Formal analogies between gravitation and electrodynamics
We develop a theoretical framework that allows us to compare electromagnetism
and gravitation in a fully covariant way. This new scenario does not rely on
any kind of approximation nor associate objects with different operational
meaning as it's sometime done in the literature. We construct the
electromagnetic analogue to the Riemann and Weyl tensors and develop the
equations of motion for these objects. In particular, we are able to identify
precisely how and in what conditions gravity can be mapped to electrodynamics.
As a consequence, many of the gemometrical tools of General Relativity can be
applied to Electromagnetism and vice-versa. We hope our results would shed new
light in the nature of electromagnetic and gravitational theories.Comment: 9pages, submitted to General Relativity and Gravitatio
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