A Hamiltonian functional for the linearized Einstein vacuum field equations

By considering the Einstein vacuum field equations linearized about the Minkowski metric, the evolution equations for the gauge-invariant quantities characterizing the gravitational field are written in a Hamiltonian form by using a conserved functional as Hamiltonian; this Hamiltonian is not the analog of the energy of the field. A Poisson bracket between functionals of the field, compatible with the constraints satisfied by the field variables, is obtained. The generator of spatial translations associated with such bracket is also obtained.Comment: 5 pages, accepted in J. Phys.: Conf. Serie

Reproductive behavior of the Yellow-crowned parrot (Amazona ochrocephala) in Western Panama

We studied the breeding biology of the Panamanian subspecies of the Yellow-crowned Parrot, Amazona ochrocephala panamensis, during 1997-1999 in the province of Chiriquí, Panama, to provide basic information regarding the breeding behavior and reproductive success of these parrots in their natural habitat. We recorded parrot behaviors throughout the reproductive period, monitored nest success, and characterized occupied and non-occupied tree cavities. All breeding attempts involved a male-female pair. Clutch size ranged from 2 to 4 eggs, which were incubated only by the female, beginning when the first egg was laid. Incubation averaged 25 days and the eggs hatched asynchronously. During the incubation period, females remained inside the nest for long periods of time, though they often departed from the nest area during early mornings and late afternoons, presumably to forage; during this period, males were not observed entering the nest, though they often remained nearby. During the nestling period, males contributed significantly to feeding the offspring. Pairs nested in trees that were in good or fair condition, and did not favor cavities in any one tree species. As found in many other field studies of parrots, breeding success was low. Only 10% (1997-1998) and 14% (1998-1999) of the nests survived poaching and natural predation. Because nest poaching was the primary cause of breeding failure and poses a serious threat to population viability, we also present data on poaching techniques and the local trade of nestling parrots. Overall, the pool of breeding adults is likely made up of aging individuals that are not being replaced, setting the stage for a rapid population decline

A single scaling parameter as a first approximation to describe the rainfall pattern of a place: application on Catalonia

As well as in other natural processes, it has been frequently observed that the phenomenon arising from the rainfall generation process presents fractal self-similarity of statistical type, and thus, rainfall series generally show scaling properties. Based on this fact, there is a methodology, simple scaling, which is used quite broadly to find or reproduce the intensity–duration–frequency curves of a place. In the present work, the relationship of the simple scaling parameter with the characteristic rainfall pattern of the area of study has been investigated. The calculation of this scaling parameter has been performed from 147 daily rainfall selected series covering the temporal period between 1883 and 2016 over the Catalonian territory (Spain) and its nearby surroundings, and a discussion about the relationship between the scaling parameter spatial distribution and rainfall pattern, as well as about trends of this scaling parameter over the past decades possibly due to climate change, has been presented.Peer ReviewedPostprint (author's final draft

Analysis of extreme rainfall in Barcelona using a microscale rain gauge network

Extreme storms registered by the urban rain gauge network installed and supported by CLABSA (Clavegueram de Barcelona S. A.) in Barcelona in the period 1994–2001 have been investigated. Eleven rain events presenting intensities for durations between 5 min and 24 h with return periods equal to or larger than 5 years for any of the network gauges have been found. A cluster analysis has yielded four main classes of extreme rainfall events in this area, related to the meteorological scales involved: local (18%), mesoscale (37%) and synoptic storms (27%), as well as more complex rain events originated by multiscale mechanisms acting together (18%). An intensity index to classify extreme rainfall events in order to their complexity and severity, taking into account the contribution of the different scales implied in the rainfall processes, has been calculated. The frequency distribution of the intensity index values obtained for the urban network has resulted very similar to that calculated for rain data recorded by the Jard´ı gauge of the Observatory Fabra of Barcelona during 1927–1992 inclusive.Postprint (published version

Quality control process of the daily rainfall series available in Catalonia from 1855 to the present

The quality control of weather data is a necessity and a responsibility of meteorological services that store, distribute, and use these data. In the present work, a newly designed quality control procedure for daily rainfall data is presented after it has been adjusted and tested with more than 10^7 data from 1726 daily rainfall measurement sites in Catalonia. It is applicable to data from different origins (e.g., automatic weather stations or manual historical measurements). The procedure is focused on relative comparison of daily data with reference stations that are automatically selected after an initial estimation of their quality and a proximity study regarding location and correlation. The presented procedure has been verified taking advantage of an available network in the study area that has been routinely quality controlled by technicians of the Meteorological Service of Catalonia. The newly designed quality control procedure for daily precipitation yields good results, especially for extreme values: type I error under 10% is found for values up to 150 mm (error decreasing for lower values) and type II error is under 16% when reported values are twice a measure of 50 mm or more (error decreasing for more extreme values). After the application of the quality control procedure, a selection of series with the minimum desired quality is achieved.Peer ReviewedPostprint (author's final draft

Periodic signals from the Circinus region: two new cataclysmic variables and the ultraluminous X-ray source candidate GC X-1

The examination of two 2010 Chandra ACIS exposures of the Circinus galaxy resulted in the discovery of two pulsators: CXO J141430.1-651621 and CXOU J141332.9-651756. We also detected 26-ks pulsations in CG X-1, consistently with previous measures. For ~40 other sources, we obtained limits on periodic modulations. In CXO J141430.1-651621, which is ~2 arcmin outside the Circinus galaxy, we detected signals at 6120(1) s and 64.2(5) ks. In the longest observation, the source showed a flux of ~1.1e-13 erg/cm^2/s (absorbed, 0.5-10 keV) and the spectrum could be described by a power-law with photon index ~1.4. From archival observations, we found that the luminosity is variable by ~50 per cent on time-scales of weeks-years. The two periodicities pin down CXO J141430.1-651621 as a cataclysmic variable of the intermediate polar subtype. The period of CXOU J141332.9-651756 is 6378(3) s. It is located inside the Circinus galaxy, but the low absorption indicates a Galactic foreground object. The flux was ~5e-14 erg/cm^2/s in the Chandra observations and showed ~50 per cent variations on weekly/yearly scales; the spectrum is well fit by a power law ~0.9. These characteristics and the large modulation suggest that CXOU J141332.9-651756 is a magnetic cataclysmic variable, probably a polar. For CG X-1, we show that if the source is in the Circinus galaxy, its properties are consistent with a Wolf-Rayet plus black hole binary. We consider the implications of this for ultraluminous X-ray sources and the prospects of Advanced LIGO and Virgo. In particular, from the current sample of WR-BH systems we estimate an upper limit to the detection rate of stellar BH-BH mergers of ~16 events per yr.Comment: 17 pages, 7 figures, 6 tables; accepted for publication in MNRA

The Process of the Transfer of Hate Speech to Demonization and Social Polarization

We are living through a time of major political changes due to the rise of populist leaders and the resurgence of extreme ideological movements. The emergence of this phenomenon is due, to a large extent, to the ease with which these political actors can disseminate and spread their messages without any limits through social networks, leaving aside the former "fourth power" of the media as filterers and reinterpreters of information. Generally, the formula used by these leaders and movements is usually based on symbolic social division and polarization through hate speeches that allow demonizing their adversaries while antagonizing the issuers: a discursive "us" against "them" based on verbal violence to dehumanize an "exogroup." We want to discuss the importance of understanding the process of communicational transfer - which begins with hate speech and evolves into demonization and social polarization - as a strategic basis for creating an ideal scenario for the growth and strengthening of populist discourse, which is reductionist and simplifying in nature