2,240 research outputs found
Measuring the effective complexity of cosmological models
We introduce a statistical measure of the effective model complexity, called
the Bayesian complexity. We demonstrate that the Bayesian complexity can be
used to assess how many effective parameters a set of data can support and that
it is a useful complement to the model likelihood (the evidence) in model
selection questions. We apply this approach to recent measurements of cosmic
microwave background anisotropies combined with the Hubble Space Telescope
measurement of the Hubble parameter. Using mildly non-informative priors, we
show how the 3-year WMAP data improves on the first-year data by being able to
measure both the spectral index and the reionization epoch at the same time. We
also find that a non-zero curvature is strongly disfavored. We conclude that
although current data could constrain at least seven effective parameters, only
six of them are required in a scheme based on the Lambda-CDM concordance
cosmology.Comment: 9 pages, 4 figures, revised version accepted for publication in PRD,
updated with WMAP3 result
Industries\u27 Proprietary Information and the Freedom of Access to State-Held Information: A Review of the Law and Its Implications for Special Interest Businesses
The Supreme Court Perspective of Media Effects as Expressed in Campaign Finance Reform
The Bipartisan Campaign Reform Act (BCRA) of 2002 amended campaign finance law by banning unlimited soft money contributions to political parties and reforming the financing of advertising close to an election. In this ruling the Court is clearly concerned with the amount of money being donated to political candidates, which leads to the appearance of impropriety in gaining access to elected officials that in turn may influence legislation. In ruling on the constitutionality of this legislation, the Supreme Court also provided insight into its view of mass media effects. In applying the principles of cultivation theory and the media framing paradigm, the groups that can fund more commercials have an advantage with voters who may believe these repeated advertisements and vote for that particular candidate. This Article posits what might be the Supreme Court\u27s view of the media effects debate by examining its ruling in McConnell v. FEC
On Information Theory, Spectral Geometry and Quantum Gravity
We show that there exists a deep link between the two disciplines of
information theory and spectral geometry. This allows us to obtain new results
on a well known quantum gravity motivated natural ultraviolet cutoff which
describes an upper bound on the spatial density of information. Concretely, we
show that, together with an infrared cutoff, this natural ultraviolet cutoff
beautifully reduces the path integral of quantum field theory on curved space
to a finite number of ordinary integrations. We then show, in particular, that
the subsequent removal of the infrared cutoff is safe.Comment: 4 page
Recommended from our members
Isoprenoids determine Th1/Th2 fate in pathogenic T cells, providing a mechanism of modulation of autoimmunity by atorvastatin.
3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is a critical enzyme in the mevalonate pathway that regulates the biosynthesis of cholesterol as well as isoprenoids that mediate the membrane association of certain GTPases. Blockade of this enzyme by atorvastatin (AT) inhibits the destructive proinflammatory T helper cell (Th)1 response during experimental autoimmune encephalomyelitis and may be beneficial in the treatment of multiple sclerosis and other Th1-mediated autoimmune diseases. Here we present evidence linking specific isoprenoid intermediates of the mevalonate pathway to signaling pathways that regulate T cell autoimmunity. We demonstrate that the isoprenoid geranylgeranyl-pyrophosphate (GGPP) mediates proliferation, whereas both GGPP and its precursor, farnesyl-PP, regulate the Th1 differentiation of myelin-reactive T cells. Depletion of these isoprenoid intermediates in vivo via oral AT administration hindered these T cell responses by decreasing geranylgeranylated RhoA and farnesylated Ras at the plasma membrane. This was associated with reduced extracellular signal-regulated kinase (ERK) and p38 phosphorylation and DNA binding of their cotarget c-fos in response to T cell receptor activation. Inhibition of ERK and p38 mimicked the effects of AT and induced a Th2 cytokine shift. Thus, by connecting isoprenoid availability to regulation of Th1/Th2 fate, we have elucidated a mechanism by which AT may suppress Th1-mediated central nervous system autoimmune disease
Generalized Hurst exponent and multifractal function of original and translated texts mapped into frequency and length time series
A nonlinear dynamics approach can be used in order to quantify complexity in
written texts. As a first step, a one-dimensional system is examined : two
written texts by one author (Lewis Carroll) are considered, together with one
translation, into an artificial language, i.e. Esperanto are mapped into time
series. Their corresponding shuffled versions are used for obtaining a "base
line". Two different one-dimensional time series are used here: (i) one based
on word lengths (LTS), (ii) the other on word frequencies (FTS). It is shown
that the generalized Hurst exponent and the derived curves
of the original and translated texts show marked differences. The original
"texts" are far from giving a parabolic function, - in contrast to
the shuffled texts. Moreover, the Esperanto text has more extreme values. This
suggests cascade model-like, with multiscale time asymmetric features as
finally written texts. A discussion of the difference and complementarity of
mapping into a LTS or FTS is presented. The FTS curves are more
opened than the LTS onesComment: preprint for PRE; 2 columns; 10 pages; 6 (multifigures); 3 Tables; 70
reference
Statistical mechanics of error exponents for error-correcting codes
Error exponents characterize the exponential decay, when increasing message
length, of the probability of error of many error-correcting codes. To tackle
the long standing problem of computing them exactly, we introduce a general,
thermodynamic, formalism that we illustrate with maximum-likelihood decoding of
low-density parity-check (LDPC) codes on the binary erasure channel (BEC) and
the binary symmetric channel (BSC). In this formalism, we apply the cavity
method for large deviations to derive expressions for both the average and
typical error exponents, which differ by the procedure used to select the codes
from specified ensembles. When decreasing the noise intensity, we find that two
phase transitions take place, at two different levels: a glass to ferromagnetic
transition in the space of codewords, and a paramagnetic to glass transition in
the space of codes.Comment: 32 pages, 13 figure
The Occurrence of Crassulacean Acid Metabolism in Epiphytic Ferns, With and Emphasis on the Vittariaceae
This is the publisher's official version. It is also available electronically from: http://www.jstor.org/stable/10.1086/430334.The potential for nighttime CO2 uptake and/or increases in tissue acidity characteristic of crassulacean acid
metabolism (CAM) was investigated, to varying degrees, in 12 species of Vittariaceae as well as in seven species
in four other families of tropical epiphytic ferns. Evidence of CAM (actually CAM cycling, i.e., diei changes in
tissue acidity without nighttime atmospheric C 0 2 uptake), though highly variable, was found in two species of
Vittariaceae. The ecophysiological significance of this finding is puzzling, because the occurrence of these
plants in deeply shaded, extremely moist habitats is rare, if not unique, among plants expressing any degree of
CAM. The results of this study confirm that CAM among the ferns is not limited to the Polypodiaceae, and
they emphasize the polyphyletic nature of the evolution of CAM among higher plants
- …