Chiral Perturbation Theory with tensor sources

We construct the most general chirally-invariant Lagrangian for mesons in the presence of external sources coupled to the tensor current \bar{\psi}\sigma_{\mu\nu}\psi. In order to have only even terms in the chiral expansion, we consider the new source of O(p^2). With this choice, we build the even-parity effective Lagrangian up to the p^6-order (NLO). While there are only 4 new terms at the p^4-order, at p^6-order we find 78 terms for n_f=2 and 113 terms for n_f=3. We provide a detailed discussion on the different mechanisms that ensure that our final set of operators is complete and non-redundant. We also examine the odd-parity sector, to conclude that the first operators appear at the p^8-order (NNLO).Comment: 23 pages, one figure; typos corrected, one paragraph added, new section added, references added, published versio

Dispersion Relation Bounds for pi pi Scattering

Axiomatic principles such as analyticity, unitarity and crossing symmetry constrain the second derivative of the pi pi scattering amplitudes in some channels to be positive in a region of the Mandelstam plane. Since this region lies in the domain of validity of chiral perturbation theory, we can use these positivity conditions to bound linear combinations of \bar{l}_1 and \bar{l}_2. We compare our predictions with those derived previously in the literature using similar methods. We compute the one-loop pi pi scattering amplitude in the linear sigma model (LSM) using the MS-bar scheme, a result hitherto absent in the literature. The LSM values for \bar{l}_1 and \bar{l}_2 violate the bounds for small values of m_sigma/m_pi. We show how this can occur, while still being consistent with the axiomatic principles.Comment: 12 pages, 8 figures. Two references added, a few minor changes. Published versio

Is the Theta+ a K pi N bound state?

Following a recent suggestion that the $\Theta ^+$ could be a $K \pi N$ bound state we perform an investigation under the light of the meson meson and meson baryon dynamics provided by the chiral Lagrangians and using methods currently employed to dynamically generate meson and baryon resonances by means of unitary extensions of chiral perturbation theory. We consider two body and three body forces and examine the possibility of a bound state below the three particle pion-kaon-nucleon and above the kaon-nucleon thresholds. Although we find indeed an attractive interaction in the case of isospin I=0 and spin-parity $1/2^+$, the interaction is too weak to bind the system. If we arbitrarily add to the physically motivated potential the needed strength to bind the system and with such strong attraction evaluate the decay width into $K N$, this turns out to be small. A discussion on further work in this direction is done.Comment: Change of title and few sentences, size of two graphs. References adde

Statistical procedures for spatial point pattern recognition

Spatial structures in the form of point patterns arise in many different contexts, and in most of them the key goal concerns the detection and recognition of the underlying spatial pattern. Particularly interesting is the case of pattern analysis with replicated data in two or more experimental groups. This paper compares design-based and model-based approaches to the analysis of this kind of spatial data. Basic questions about pattern detection concern estimating the properties of the underlying spatial point process within each experimental group, and comparing the properties between groups. The paper discusses how either approach can be implemented in the specific context of a single-factor replicated experiment and uses simulations to show how the model-based approach can be more efficient when the underlying model assumptions hold, but potentially misleading otherwise

Tinautius exilis sp. n. (Coleoptera, Carabidae, Pterostochini) de la Alpujarra almeriense (SE España)

A new troglobitic species belonging to the genus Tinautius Mateu 1997, from the Sierra de Cazorla in the province of Jaen is described. This new species (T. exilis n. sp.) was found in the Alpujarra mountains in Almería. It is anophthalmous and differs from the anterior species in several morphological features. The female genitalia and the particular shape of the metatrochant enable simple differentiation with the two species of the genus Tinautius known to date.Se describe una nueva especie troglobia perteneciente al género Tinautius Mateu 1997, procedente de la Sierra de Cazorla, provincia de Jaén. La nueva especie (T. exilis sp. n.) proviene de la Alpujarra almeriense. Es anoftalma y difiere de T. troglobius por diferentes caracteres morfológicos y anatómicos. La genitalia femenina y la especial conformación del metatrocánter permiten separar fácilmente las dos especies de Tinautius conocidas hasta ahora