31,589 research outputs found
Time-Scale and Noise Optimality in Self-Organized Critical Adaptive Networks
Recent studies have shown that adaptive networks driven by simple local rules
can organize into "critical" global steady states, providing another framework
for self-organized criticality (SOC). We focus on the important convergence to
criticality and show that noise and time-scale optimality are reached at finite
values. This is in sharp contrast to the previously believed optimal zero noise
and infinite time scale separation case. Furthermore, we discover a noise
induced phase transition for the breakdown of SOC. We also investigate each of
the three new effects separately by developing models. These models reveal
three generically low-dimensional dynamical behaviors: time-scale resonance
(TR), a new simplified version of stochastic resonance - which we call steady
state stochastic resonance (SSR) - as well as noise-induced phase transitions.Comment: 4 pages, 6 figures; several changes in exposition and focus on
applications in revised versio
Ages of Type Ia Supernovae Over Cosmic Time
We derive empirical models for galaxy mass assembly histories, and convolve
these with theoretical delay time distribution (DTD) models for Type Ia
supernovae (SNe Ia) to derive the distribution of progenitor ages for all SNe
Ia occurring at a given epoch of cosmic time. In actively star-forming
galaxies, the progression of the star formation rate is shallower than a
SN Ia DTD, so mean SN Ia ages peak at the DTD peak in all star-forming
galaxies at all epochs of cosmic history. In passive galaxies which have ceased
star formation through some quenching process, the SN Ia age distribution peaks
at the quenching epoch, which in passive galaxies evolves in redshift to track
the past epoch of major star formation. Our models reproduce the SN Ia rate
evolution in redshift, the relationship between SN Ia stretch and host mass,
and the distribution of SN Ia host masses in a manner qualitatively consistent
with observations. Our model naturally predicts that low-mass galaxies tend to
be actively star-forming while massive galaxies are generally passive,
consistent with observations of galaxy "downsizing". Consequently, the mean
ages of SNe Ia undergo a sharp transition from young ages at low host mass to
old ages at high host mass, qualitatively similar to the transition of mean SN
Ia Hubble residuals with host mass. The age discrepancy evolves with redshift
in a manner currently not accounted for in SN Ia cosmology analyses. We thus
suggest that SNe Ia selected only from actively star-forming galaxies will
yield the most cosmologically uniform sample, due to the homogeneity of young
SN Ia progenitor ages at all cosmological epochs.Comment: 15 pages, 15 figures, accepted for publication in MNRA
Alterations of the CARD15/NOD2 gene and the impact on management and treatment of Crohn's disease patients
The recent identification of the CARD15/NOD2 gene as a susceptibility locus for Crohn's disease represents an important step towards the delineation of the immuno-pathogenesis of inflammatory bowel disease. CARD15 functions as an intracellular receptor for bacterial components and thus represents an important link between inflammatory bowel disease and innate immunity. Three major CARD15/NOD2 gene mutations have been associated with Crohn's disease in Caucasians in several independent studies. Together, they explain about 20% of the genetic susceptibility for Crohn's disease. Genotype-phenotype analyses demonstrated an association of these mutations with ileum-specific disease, an increased incidence of the fibrostenotic phenotype and an earlier age of disease onset. Beside these associations, no other relationship between the CARD15/NOD2 genotype and disease behavior or response to treatment has been detailed so far. Thus, the clinical impact of knowing the patient's genotype is limited at this time. Screening for CARD15 mutations in order to identify high-risk individuals or to introduce an individualized disease management is therefore currently not recommended. Copyright (C) 2003 S. Karger AG, Basel
Thermal Quantum Fields without Cut-offs in 1+1 Space-time Dimensions
We construct interacting quantum fields in 1+1 dimensional Minkowski space,
representing neutral scalar bosons at positive temperature. Our work is based
on prior work by Klein and Landau and Hoegh-KrohnComment: 48 page
Testing Gravity-Driven Collapse of the Wavefunction via Cosmogenic Neutrinos
It is pointed out that the Diosi-Penrose ansatz for gravity-induced quantum
state reduction can be tested by observing oscillations in the flavor ratios of
neutrinos originated at cosmological distances. Since such a test would be
almost free of environmental decoherence, testing the ansatz by means of a next
generation neutrino detector such as IceCube would be much cleaner than by
experiments proposed so far involving superpositions of macroscopic systems.
The proposed microscopic test would also examine the universality of
superposition principle at unprecedented cosmological scales.Comment: 4 pages; RevTeX4; Essentially the version published in PR
The Reeh-Schlieder property for thermal field theories
We show that the Reeh-Schlieder property w.r.t. the KMS-vector is a direct
consequence of locality, additivity and the relativistic KMS-condition. The
latter characterises the thermal equilibrium states of a relativistic quantum
field theory. The statement remains vaild even if the given equilibrium state
breaks spatial translation invariance.Comment: plain tex, 10 page
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