Double Threefold Degeneracies for Active and Sterile Neutrinos

We explore the possibility that the 3 active (doublet) neutrinos have nearly degenerate masses which are split only by the usual seesaw mechanism from 3 sterile (singlet) neutrinos in the presence of a softly broken $A_4$ symmetry. We take the unconventional view that the sterile neutrinos may be light, i.e. less than 1 keV, and discuss some very interesting and novel phenomenology, including a connection between the LSND neutrino data and solar neutrino oscillations.Comment: 8 pages, no figur

Long-range correlations and trends in Colombian seismic time series

We study long-range correlations and trends in time series extracted from the data of seismic events occurred from 1973 to 2011 in a rectangular region that contains mainly all the continental part of Colombia. The long-range correlations are detected by the calculation of the Hurst exponents for the time series of interevent intervals, separation distances, depth differences and magnitude differences. By using a modification of the classical $R/S$ method that has been developed to detect short-range correlations in time series, we find the existence of persistence for all the time series considered except for magnitude differences. We find also, by using the $DFA$ until the third order, that the studied time series are not influenced by trends. Additionally, an analysis of the Hurst exponent as a function of the number of events in the time and the maximum window size is presented.Comment: 21 pages, 6 figures, 2 figures added, types corrected, accepted to be published in Physica

Effective Lagrangian description of Higgs mediated flavor violating electromagnetic transitions: implications on lepton flavor violation

Higgs mediated flavor violating electromagnetic interactions, induced at the one--loop level by a nondiagonal $Hf_if_j$ vertex, with $f_i$ and $f_j$ charged leptons or quarks, are studied within the context of a completely general effective Yukawa sector that comprises $SU_L(2)\times U_Y(1)$--invariant operators of up to dimension--six. Exact formulae for the one--loop $\gamma f_if_j$ and $\gamma \gamma f_if_j$ couplings are presented and their related processes used to study the phenomena of Higgs mediated lepton flavor violation. The experimental limit on the $\mu \to e\gamma$ decay is used to derive a bound on the branching ratio of the $\mu \to e\gamma \gamma$ transition, which is 6 orders of magnitude stronger than the current experimental limit. Previous results on the $\tau \to \mu \gamma$ and $\tau \to \mu \gamma \gamma$ decays are reproduced. The possibility of detecting signals of lepton flavor violation at $\gamma \gamma$ colliders is explored through the $\gamma \gamma \to l_il_j$ reaction, putting special emphasis on the $\tau \mu$ final state. Using the bound imposed on the $H\tau \mu$ vertex by the current experimental data on the muon anomalous magnetic moment, it is found that about half a hundred events may be produced in the International Linear Collider.Comment: 18 pages, 12 figure

Ajuste osmótico en dos robles de clima templado [Quercus pyrenaicaWilld y Quercus petraea (Matt.) Liebl] de la Península Ibérica en respuesta a la sequía

One-year-old seedlings of Quercus pyrenaica and Quercus petraea were subjected in a greenhouse to three consecutive water stress cycles. Watering was withdrawn in water stressed seedlings until 5% volumetric soil water content in the two first cycles and up to 3.5% in the third one. At the end of each cycle, predawn water potential (Ψpd) was measured by a pressure bomb. Furthermore, other water parameters: osmotic potential at full (Ψπ100) and at turgor loss point (Ψπ0) as well as bulk modulus of tissue elasticity at maximum turgor (Emax), were derived from the establishment of pressure-volume curves at the end of the second and third water stress cycles. In the three drought periods there was a significant decrease of Ψpd in both species as compared to the controls which were maintained at field capacity. This decrease progressed from the first to the following cycles in Quercus pyrenaica up to –1.7 ± 0.31 MPa minimum value. In Quercus petraea the Ψpd value reached at the end of the first cycle (±1.8 ± 0.52 MPa), was no significantly different from those reached afterwards. A large decrease in Ψπ100 and Ψπ0 together with an increase of Emax were recorded in both species after the second water stress cycle, without any new significant variation in the third one. When well-watered and water-stressed seedlings were compared, Quercus pyrenaica showed a decrease in Ψπ100 of 0.8 MPa with regard to 0.3 MPa in Quercus petraea. These results show the occurrence of osmotic adjustment in both species. However, the osmoregulation capacity was higher in Quercus pyrenaica, which pointed out to a higher ability to develop mechanisms of water stress tolerance. This could be recognized as one of the physiological traits that explain why Quercus pyrenaica is better adapted to xeric conditions than Quercus petraea.Brinzales de un año de melojo y roble albar se sometiron a tres ciclos consecutivos de estrés hídrico en un invernadero. El riego se retiró en los brinzales estresados hasta un 5% de contenido hídrico volumétrico del suelo en los dos primeros ciclos, y hasta el 3.5% en el tercero. Al final de cada ciclo, el potencial hídrico al amanecer (Ψpd) se midió con una cámara de presión. Además, otros parámetros hídricos fueron derivados a partir del establecimiento de las curvas presión volumen al final del segundo y tercer ciclo de estrés hídrico: potencial osmótico a plena turgencia (Ψπ100) y en el punto de marchitez (Ψπ0), así como el módulo de elasticidad a máxima turgencia (Emax). En los tres períodos de sequía hubo una disminución significativa del Ψpd en ambas especies en comparación con las plantas control mantenidas a capacidad de campo. Esta disminución progresó desde el primer ciclo a los siguientes en el roble melojo hasta un valor mínimo de –1,7 ± 0,31 MPa. En el roble albar el valor del Ψpd alcanzado al final del primer período de estrés hídrico (–1,8 ± 0,52 MPa), no fue significativamente diferente de los alcanzados posteriormente. Una gran disminución en Ψπ100 y Ψπ0, junto con un aumento en Emax, fueron registrados en ambas especies tras el segundo ciclo de estrés hídrico, sin ninguna variación significativa en el tercero. Al comparar brinzales bien regados y estresados, Quercus pyrenaica mostró una disminución de 0.8 MPa en Ψπ100 respecto a 0.3 MPa en Quercus petraea. Estos resultados ponen de manifiesto la presencia de ajuste osmótico en ambas especies. Sin embargo, la capacidad de osmorregulación fue superior en Quercus pyrenaica, lo cual señala una mayor capacidad de puesta en marcha de mecanismos de tolerancia al estrés hídrico. Este podría ser reconocido como uno de los rasgos fisiológicos que explican porque Quercus pyrenaica está mejor adaptado que Quercus petraea a condiciones xerófitas

Comparación de métodos de estimación de ajuste de las funciones Weibull, SB de Johnson y beta a masas de Pinus pinaster, Pinus radiata y Pinus sylvestris en el noroeste de España

The purpose of this study was to compare the accuracy of the Weibull, Johnson’s SB and beta distributions, fitted with some of the most usual methods and with different fixed values for the location parameters, for describing diameter distributions in even-aged stands of Pinus pinaster, Pinus radiata and Pinus sylvestris in northwest Spain. A total of 155 permanent plots in Pinus sylvestris stands throughout Galicia, 183 plots in Pinus pinaster stands throughout Galicia and Asturias and 325 plots in Pinus radiata stands in both regions were measured to describe the diameter distributions. Parameters of the Weibull function were estimated by Moments and Maximum Likelihood approaches, those of Johnson’s SB function by Conditional Maximum Likelihood and by Knoebel and Burhart’s method, and those of the beta function with the method based on the moments of the distribution. The beta and the Johnson’s SB functions were slightly superior to Weibull function for Pinus pinaster stands; the Johnson’s SB and beta functions were more accurate in the best fits for Pinus radiata stands, and the best results of the Weibull and the Johnson’s SB functions were slightly superior to beta function for Pinus sylvestris stands. However, the three functions are suitable for this stands with an appropriate value of the location parameter and estimation of parameters method.El objetivo de este estudio fue comparar la precisión de las distribuciones Weibull, SB de Johnson y beta, ajustadas por alguno de los métodos más habituales y fijando diferentes valores para los parámetros de localización, para describir distribuciones diamétricas en masas regulares de Pinus pinaster, Pinus radiata y Pinus sylvestris en el noroeste de España. Se midieron un total de 155 parcelas permanentes en masas de Pinus sylvestris en Galicia, 183 parcelas de Pinus pinaster en Galicia y en Asturias y 325 parcelas de Pinus radiata en ambas regiones para describir sus distribuciones diamétricas. Los parámetros de la función Weibull fueron estimados por las aproximaciones de los Momentos y Máxima Verosimilitud, los de la función SB de Johnson por los estimadores condicionados de Máxima Verosimilitud y por el método de Knoebel y Burkhart, y los de la función beta por el método basado en los Momentos de la distribución. Las funciones beta y SB de Johnson fueron ligeramente superiores a la función Weibull en las masas de Pinus pinaster; las funciones SB de Johnson y beta fueron más precisas en los mejores ajustes en las masas de Pinus radiata, y los mejores resultados de las funciones Weibull y SB de Johnson fueron ligeramente superiores a los de la función beta en las masas de Pinus sylvestris. No obstante, las tres funciones son apropiadas para estas masas siempre que se elija un valor de localización y método de estimación de los parámetros apropiado