131,923 research outputs found
Some Surprising Properties of Power Indices
A troubling aspect about power indices is how the values assigned to players can depend upon the index. As shown, the problem is more severe; different indices can generate radically different rankings; e.g., a 15-player game exists with over a trillion different strict power index rankings of the players. It is shown that certain indices always share the same ranking, but this assertion depends on the number of players; e.g., the Shapley and Banzhaf rankings agree with three players, but with more players they can even have opposite rankings. It is also shown how changes in certain assumptions affect the outcomes. This includes demonstrating how the rankings change when players drop out of a game.
Effects of the network structural properties on its controllability
In a recent paper, it has been suggested that the controllability of a
diffusively coupled complex network, subject to localized feedback loops at
some of its vertices, can be assessed by means of a Master Stability Function
approach, where the network controllability is defined in terms of the spectral
properties of an appropriate Laplacian matrix. Following that approach, a
comparison study is reported here among different network topologies in terms
of their controllability. The effects of heterogeneity in the degree
distribution, as well as of degree correlation and community structure, are
discussed.Comment: Also available online at: http://link.aip.org/link/?CHA/17/03310
A CRITICAL REAPPRAISAL OF SOME VOTING POWER PARADOXES
Power indices are meant to assess the power that a voting rule confers a priori to each of the decision makers who use it. In order to test and compare them, some authors have proposed "natural" postulates that a measure of a priori voting power "should" satisfy, the violations of which are called "voting power paradoxes". In this paper two general measures of factual success and decisiveness based on the voting rule and the voters' behavior, and some of these postulates/paradoxes test each other. As a result serious doubts on the discriminating power of most voting power postulates are cast.Voting power, decisiveness, success, voting rules, voting behavior, postulates, paradoxes.
Confinement and Condensates Without Fine Tuning in Supergravity Duals of Gauge Theories
We discuss a solution of the equations of motion of five-dimensional gauged
type IIB supergravity that describes confining SU(N) gauge theories at large N
and large 't Hooft parameter. We prove confinement by computing the Wilson
loop, and we show that our solution is generic, independent of most of the
details of the theory. In particular, the Einstein-frame metric near its
singularity, and the condensates of scalar, composite operators are universal.
Also universal is the discreteness of the glueball mass spectrum and the
existence of a mass gap. The metric is also identical to a generically
confining solution recently found in type 0B theory.Comment: 19 pages, Late
Chandra Observations of X-ray Weak Narrow-Line Seyfert 1 Galaxies
We present Chandra observations of 17 optically-selected, X-ray weak
narrow-line Seyfert 1 (NLS1) galaxies. These objects were optically identified
by Williams et al. (2002) in the Sloan Digital Sky Survey Early Data Release,
but were not found in the ROSAT All-Sky Survey (RASS) despite having optical
properties similar to RASS-detected NLS1s. All objects in this sample were
detected by Chandra and exhibit a range of 0.5-2 keV photon indices
Gamma=1.1-3.4. One object was not detected in the soft band, but has a best-fit
Gamma=0.25 over the full 0.5-8 keV range. These photon indices extend to values
far below what are normally observed in NLS1s. A composite X-ray spectrum of
the hardest objects in this sample does not show any signs of absorption,
although the data do not prohibit one or two of the objects from being highly
absorbed. We also find a strong correlation between Gamma and L_1keV; this may
be due to differences in L_bol/L_Edd among the NLS1s in this sample. Such
variations are seemingly in conflict with the current paradigm that NLS1s
accrete near the Eddington limit. Most importantly, this sample shows that
strong, ultrasoft X-ray emission is not a universal characteristic of NLS1s; in
fact, a substantial number may exhibit weak and/or low-Gamma X-ray emission.Comment: Minor changes, added section on X-ray weakness. 25 pages incl. 6
figures, 3 tables, accepted to Ap
Radio continuum observations of local star-forming galaxies using the Caltech Continuum Backend on the Green Bank Telescope
We observed radio continuum emission in 27 local (D < 70 Mpc) star-forming
galaxies with the Robert C. Byrd Green Bank Telescope between 26 GHz and 40 GHz
using the Caltech Continuum Backend. We obtained detections for 22 of these
galaxies at all four sub-bands and four more marginal detections by taking the
average flux across the entire bandwidth. This is the first detection (full or
marginal) at these frequencies for 22 of these galaxies. We fit spectral energy
distributions (SEDs) for all of the four-sub-band detections. For 14 of the
galaxies, SEDs were best fit by a combination of thermal free-free and
nonthermal synchrotron components. Eight galaxies with four-sub-band detections
had steep spectra that were only fit by a single nonthermal component. Using
these fits, we calculated supernova rates, total number of equivalent O stars,
and star formation rates within each ~23 arcsecond beam. For unresolved
galaxies, these physical properties characterize the galaxies' recent star
formation on a global scale. We confirm that the radio-far-infrared correlation
holds for the unresolved galaxies' total 33 GHz flux regardless of their
thermal fractions, though the scatter on this correlation is larger than that
at 1.4 GHz. In addition, we found that for the unresolved galaxies, there is an
inverse relationship between the ratio of 33 GHz flux to total far-infrared
flux and the steepness of the galaxy's spectral index between 1.4 GHz and 33
GHz. This relationship could be an indicator of the timescale of the observed
episode of star formation.Comment: 36 pages, 9 figures; accepted for publication in ApJ. First and
second author affiliation updated to reflect departmental name chang
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