Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.Comment: Submitted to J. Stat. Mech. for the proceedings of UPON 2008 (Lyon), topic: crackling nois

On the stability of the dorsal pattern of European cave salamanders (genus Hydromantes)

Photographic identification is an emerging method for recognising wild animals. This harmless methodology allows researchers to identify \u201cnaturally marked\u201d individuals and therefore study their specific ecology and behaviour. However, before incurring potential data loss, it is recommended to test the methodology on the target species and evaluate the pros and cons. We assessed the reliability of photographic identification in adult Hydromantes salamanders from three species. Specifically, we assessed whether the dorsal pattern of adult salamanders changed over time, thus evaluating its potential use as a reliable marking methodology. We used capture-mark-recapture and controlled conditions (i.e. individuals kept in fauna boxes) to evaluate potential changes in the dorsal pattern of Hydromantes through time. We did not observe any change in the dorsal pattern in the three species during the study period. Photographic identification might be a useful marking technique for these endangered species. However, these animals are usually found in environments generally lacking light and thus, researchers must be careful in setting up proper light conditions to produce suitable pictures for individual identification of Hydromantes

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum