S_3 and the L=1 Baryons in the Quark Model and the Chiral Quark Model

The S_3 symmetry corresponding to permuting the positions of the quarks within a baryon allows us to study the 70-plet of L=1 baryons without an explicit choice for the spatial part of the quark wave functions: given a set of operators with definite transformation properties under the spin-flavor group SU(3) x SU(2) and under this S_3, the masses of the baryons can be expressed in terms of a small number of unknown parameters which are fit to the observed L=1 baryon mass spectrum. This approach is applied to study both the quark model and chiral constituent quark model. The latter theory leads to a set of mass perturbations which more satisfactorily fits the observed L=1 baryon mass spectrum (though we can say nothing, within our approach, about the physical reasonableness of the parameters in the fit). Predictions for the mixing angles and the unobserved baryon masses are given for both models as well as a discussion of specific baryons.Comment: 24 pages, requires picte

Familial occurrence of cervical artery dissection - coincidence or sign of familial predisposition?

Background and Purpose: The etiology of spontaneous cervical artery dissection (CeAD) is poorly understood in most patients. Mild cervical trauma preceding the dissection event is a common finding, but many CeAD occur spontaneously. It is likely that genetic factors may increase the risk for CeAD. However, familial cases are excedingly rare. Familial clustering of CeAD may be accidental or associated with genetic or environmental risk factors shared between affected relatives. In this explorative study, we aim to show that specific risk factors for familial CeAD exist. Methods: Age of onset, sex, affected artery and number of recurrent CeAD were documented for familial patients and compared with published findings from patients with sporadic CeAD. Concordance of age, sex and dissected artery within the families was analyzed by correlation analysis and by analysis of variance or Kruskal-Wallis testing. Results: The study sample consisted of 9 new patients with a family history of CeAD enrolled in the Neurology Department of the University of Heidelberg or referred to Heidelberg from other centers. The study sample also included published findings from another 23 patients, in total 32 patients. The mean age of the patients with familial CeAD at their first dissections was 38.4 +/- 13.3 years. Twenty (62.5%) patients were female and 12 patients (37.5%) suffered multiple dissections. Four patients (12.5%) presented with recurrent dissections after >1 year. Patients with a familial history of CeAD were younger (p = 0.023) and presented more often with multiple dissections (p = 0.024) and recurrent dissections (p = 0.018). Age at the first event(correlation analysis p = 0.026; analysis of variance p = 0.029) and site of the dissection (correlation analysis p = 0.032; Kruskal-Wallis test p = 0.018) differed between the families, and there was no concordance of gender of affected family members (correlation analysis p = 0.500; Kruskal-Wallis test p = 0.211). Conclusions: The high prevalence of multiple dissection events and of long-term (>1 year) recurrent dissections in patients with a familial history of CeAD indicates that a specific predisposition for familial CeAD exists. Since age of onset and affected vessel differ between families, the risk profile for familial CeAD is heterogeneous. A large-scale (whole exome) sequencing analysis of 14 patients from 7 of the analyzed families is currently being performed in order to identify causative genetic variants

Low Energy Constants from High Energy Theorems

New constraints on resonance saturation in chiral perturbation theory are investigated. These constraints arise because each consistent saturation scheme must map to a representation of the full QCD chiral symmetry group. The low-energy constants of chiral perturbation theory are then related by a set of mixing angles. It is shown that vector meson dominance is a consequence of the fact that nature has chosen the lowest-dimensional nontrivial chiral representation. It is further shown that chiral symmetry places an upper bound on the mass of the lightest scalar in the hadron spectrum.Comment: 11 pages TeX and mtexsis.te

Testing consumers' acceptance for an extra-virgin olive oil with a naturally increased content in polyphenols: The case of ultrasounds extraction

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Testing consumers’ acceptance for an extra-virgin olive oil with a naturally increased content in polyphenols: The case of ultrasounds extraction

Innovation is fundamental for all agri-food companies to increase competitiveness. Being extra-virgin olive oil (EVOO) a traditional food product (TFP), the main obstacle to innovation is its traditional nature. This study evaluated consumers’ acceptance for an EVOO with a naturally increased content of poliphenols, as it has been extracted through ultrasounds. This product has been compared with a set of emerging innovations that may be introduced in the next future. To this end, a choice experiment was carried out bent on the estimation of a Latent Class Model (LCM). A nationally-representative sample of EVOO consumers were involved in a web-based interview. The LCM analysis highlighted three segments of consumers: (1) innovative; (2) traditionalist; (3) cautious. Results showed that there is cluster of consumers willing to accept this innovation, therefore its introduction on the market appears to be possibly successful

Linking solar and long baseline terrestrial neutrino experiments

We show that in the framework of three light neutrino species with hierarchical masses and assuming no fine tuning between the entries of the neutrino mass matrix, one can use the solar neutrino data to obtain information on the element $U_{e3}$ of the lepton mixing matrix. Conversely, a measurement of $U_{e3}$ in atmospheric or long baseline accelerator or reactor neutrino experiments would help discriminate between possible oscillation solutions of the solar neutrino problem.Comment: revtex, 4 pages, no figures. Discussion of the LOW solution modified; results unchanged. References adde

Topological reversibility and causality in feed-forward networks

Systems whose organization displays causal asymmetry constraints, from evolutionary trees to river basins or transport networks, can be often described in terms of directed paths (causal flows) on a discrete state space. Such a set of paths defines a feed-forward, acyclic network. A key problem associated with these systems involves characterizing their intrinsic degree of path reversibility: given an end node in the graph, what is the uncertainty of recovering the process backwards until the origin? Here we propose a novel concept, \textit{topological reversibility}, which rigorously weigths such uncertainty in path dependency quantified as the minimum amount of information required to successfully revert a causal path. Within the proposed framework we also analytically characterize limit cases for both topologically reversible and maximally entropic structures. The relevance of these measures within the context of evolutionary dynamics is highlighted.Comment: 9 pages, 3 figure

Spontaneous breaking of a global symmetry in a 331 model

In a 331 model in which the lepton masses arise from a scalar sextet it is possible to break spontaneously a global symmetry implying in a pseudoscalar majoron-like Goldstone boson. This majoron does not mix with any other scalar fields and for this reason it does not couple, at the tree level, neither to the charged leptons nor to the quarks. Moreover, its interaction with neutrinos is diagonal. We also argue that there is a set of the parameters in which that the model can be consistent with the invisible Z^0-width and that heavy neutrinos can decay sufficiently rapid by majoron emission having a lifetime shorter than the age of the universe.Comment: RevTex, 10 pages, one .eps figur

Effective String Theory of Vortices and Regge Trajectories

Starting from a field theory containing classical vortex solutions, we obtain an effective string theory of these vortices as a path integral over the two transverse degrees of freedom of the string. We carry out a semiclassical expansion of this effective theory, and use it to obtain corrections to Regge trajectories due to string fluctuations.Comment: 27 pages, revtex, 3 figures, corrected an error with the cutoff in appendix E (was previously D), added more discussion of Fig. 3, moved some material in section 9 to a new appendi

The effects of meson mixing on dilepton spectra

The effect of scalar and vector meson mixing on the dilepton radiation from hot and dense hadronic matter is estimated in different isospin channels. In particular, we study the effect of $\sigma$-$\omega$ and $\rho-a_0$ mixing and calculate the corresponding rates. Effects are found to be significant compared to standard $\pi$-$\pi$ and $K$-${\bar K}$ annihilations. While the mixing in the isoscalar channel mostly gives a contribution in the invariant mass range between the two-pion threshold and the $\omega$ peak, the isovector channel mixing induces an additional peak just below that of the $\phi$. Experimentally, the dilepton signals from $\rho$-$a_0$ mixing seem to be more tractable than those from $\sigma$-$\omega$ mixing.Comment: 10 pages, 9 figure