1,144 research outputs found
Undecidability and the problem of outcomes in quantum measurements
We argue that it is fundamentally impossible to recover information about
quantum superpositions when a system has interacted with a sufficiently large
number of degrees of freedom of the environment. This is due to the fact that
gravity imposes fundamental limitations on how accurate measurements can be.
This leads to the notion of undecidability: there is no way to tell, due to
fundamental limitations, if a quantum system evolved unitarily or suffered
wavefunction collapse. This in turn provides a solution to the problem of
outcomes in quantum measurement by providing a sharp criterion for defining
when an event has taken place. We analyze in detail in examples two situations
in which in principle one could recover information about quantum coherence: a)
"revivals" of coherence in the interaction of a system with the environment and
b) the measurement of global observables of the system plus apparatus plus
environment. We show in the examples that the fundamental limitations due to
gravity and quantum mechanics in measurement prevent both revivals from
occurring and the measurement of global observables. It can therefore be argued
that the emerging picture provides a complete resolution to the measurement
problem in quantum mechanics.Comment: 14 pages, Latex, one figure, version to appear in Foundations of
Physic
Environment of 1 ≤ z ≤ 2 MIR selected obscured and unobscured AGNs in the Extended Chandra Deep Field South
Context. In unified models, different types of active galaxy nuclei (AGN) correspond to a single class of objects, where their observed differences are solely due to the different orientations of the obscuring material around the central inner regions. Recent studies also show that this obscuring material can even extend at galactic scales due to debris from galaxy interactions and/or mergers. In standard unified models the different AGN types are expected to show similar galaxy environments. Aims. We aim to investigate properties and environment of obscured and unobscured AGNs selected from mid-infrared (MIR) bands from the Multiwavelength Survey by Yale-Chile (MUSYC), in order to test the unified model and evolutionary scenarios. Methods. The sample of AGNs was selected from images obtained with the Infrared Array Camera (IRAC) mounted on the Spitzer Space Telescope, based on their MIR colors centered at wavelengths [3.6], [4.5], [5.8] and [8.0] microns. We selected two samples of AGNs with redshifts in the range 1 ≤ z ≤ 2 and rest-frame absolute magnitudes Mv ≤ -21: obscured and unobscured AGNs by means of a simple optical-MIR color cut criterion (R - [4:5] = 3:05.) Results. We find that obscured AGNs are intrinsically optically faint in the R band, suggesting that luminous IR-selected AGNs have a significant dust extinction. From a cross-correlation with several X-ray surveys, we find that the majority of the AGNs in our sample have X-ray luminosities similar to those found in Seyfert-like galaxies. We study the properties of galaxies surrounding these two samples. Neighbouring galaxies located close to (~200 kpc) obscured AGNs tend to have redder colors, compared to the local environment of unobscured AGNs. Results obtained from a KS test show that the two color distributions are different at ~95% confidence level. We find that obscured AGNs are located in denser local galaxy environments compared to the unobscured AGN sample. Conclusions. Our results suggest that AGN obscuration can occur at galactic scales, possibly due to galaxy interactions or mergers, and that the simple unified model based solely on the local torus orientation may not be sufficient to explain all the observations.Fil: Bornancini, Carlos Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Taormina, Mónica Silvia. Polish Academy of Sciences. Nicolaus Copernicus Astronomical Center; Polonia. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Garcia Lambas, Diego Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin
AGN spiral galaxies in groups: effects of bars
AIMS: We explore properties of barred active spiral galaxies in groups and clusters selected from the Sloan Digital Sky Survey data release 7 (SDSS-DR7), with the aim of assessing the effects of bars on active galactic nuclei (AGN) and the role of the high density environment.
METHODS: We identified barred active galaxies that reside in groups and clusters by cross-correlating the total barred AGN sample with the SDSS-DR7 group catalog. With the goal of providing a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distributions was also constructed.
RESULTS: We found that the fraction of barred AGN galaxies in groups and clusters (≈38%) is higher than those in the total barred AGN sample (≈28%), indicating that AGN spiral galaxies in groups are more likely to be barred than those in the field. We also found that barred AGN galaxies are more concentrated towards the group centers than the other unbarred AGN group members. In addition, barred AGN host galaxies show an excess of population dominated by red colors, with respect to the control sample, suggesting that bars produce an important effect on galaxy colors of AGN hosts. The groups of AGN galaxies with and without bars show similar virial masses; however, the host groups of the barred AGN exhibit a larger fraction of red colors than the host groups of the corresponding unbarred active galaxies in the control sample. Color-magnitude relations of both host groups of AGN differ significantly: the host group colors of barred active galaxies display distributions spreading toward red populations, at the same (Mr)Group, with respect to the host groups of the unbarred AGN objects. This trend is more significant in less massive groups than in groups with MVirial> 1013.5M⊙. Barred active galaxies show an excess of nuclear activity compared to galaxies without bars in the control sample. We found that barred active galaxies located farther from the group-center have stronger Lum[OIII], while the nuclear activity in AGN galaxies without bars remain approximately constant with the group-centric distance. In addition, for both AGN samples, nuclear activity increases in bluer host groups however, barred active objects systematically show higher Lum[OIII] values, irrespective of the global group colors. Our findings suggest that the efficiency of bars to transport material towards the more central regions of the AGN galaxies in high density environments reveals an important dependence on the localization of objects within the group/cluster and on the host group colors.Fil: Alonso Giraldes, Maria Sol. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Coldwell Lloveras, Georgina Vanesa. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia Lambas, Diego Rodolfo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin
The Titanosaur Sauropods from the late Campanian–early Maastrichtian Allen Formation of Salitral Moreno, Río Negro, Argentina
The dinosaur record of the Salitral Moreno locality (Río Negro Province, Argentina) is characterized by a high diversity of herbivore taxa, among them hadrosaurs, ankylosaurs, and titanosaur sauropods, but carnivores are rare, consisting of only a few fragmentary bones of small forms. Titanosaurs are represented by Rocasaurus muniozi and Aeolosaurus sp., and at least four other taxa, represented by fragmentary material. The elements preserved include a cervical, dorsal and caudal vertebrae, chevron, humerii, ulnae, radii, metacarpal, femora, tibiae, metatarsal, ischia, pubis, and ilium. The Allen Formation is thought to be correlated with the Marília Formation in Brazil, and their faunas have certain elements in common such as aeolosaurines, but saltasaurines and hadrosaurs, are known exclusively from the Allen Formation. These ab− sences, and particularly that of the saltasaurines, may be because those sauropods originated late in the Cretaceous, probably in southern South America (Northern Patagonia?), and they did not have time to disperse to northern South America.Fil: Garcia, Rodolfo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Salgado, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rio Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiologia y Geologia; Argentin
A new limit for the NW Río de la Plata Craton Border at about 24°S (Argentina) detected by Magnetotellurics
Old South American structures constitute a puzzle where the Río de la Plata Craton is the most important clue in the assembly of SW Gondwana. The present study is aimed at characterizing the western border of the Río de la Plata Craton on the basis of magnetotelluric studies. Magnetotelluric (MT) data were acquired along an approximately NW-SE 750km profile at about 24ºS, from the Sub-Andean Ranges in the province of Salta (NW) to the Formosa Province frontier (SE) next to Paraguay River. Distortion and structure dimensionality analysis indicates that MT responses are two-dimensional with a NS strike orientation, consistent with the regional geological strike. A 2-D inversion of the data provided a model showing a lateral discontinuity, possibly associated with cratonic structures. The high resistivity observed (>5000ohm·m), from about the middle of the profile toward its eastern end, may be interpreted as the terranes accreted to the Río de la Plata Craton during Neoproterozoic to Cambrian times, or as the Río de la Plata Craton itself. Along the profile from the surface to a depth of about 10km the resistivity model shows a significant resistivity variation in the structure. The resistive block identified at the western end of the profile represents the Sub-Andean system. The markedly enhanced low-resistivity structure (~1 to 10ohm·m) corresponds to a sedimentary pile whose thickness decreases from NW to SE.Fil: Favetto, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Rocha, Veronica. Universidad Nacional de Salta. Facultad de Cs.naturales. Escuela de Geología; ArgentinaFil: Pomposiello, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Garcia, Rodolfo Fernando. Universidad Nacional de Salta. Facultad de Cs.naturales. Escuela de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barcelona, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentin
Dentition of titanosaurs (Dinosauria, Sauropoda) from the Upper Cretaceous of Río Negro province, Argentina: morphology, implantation and replacement
Se describe la anatomía observada en un fragmento de dentario de titanosaurio saurópodo de la Formación Anacleto (Cretácico Superior de la provincia de Río Negro), compuesto por siete alvéolos. Dentro de los alvéolos se hallan dientes funcionales así como dientes de reemplazo en sucesivos estadio de desarrollo. Al menos en la porción preservada del dentario es posible advertir un patrón de reemplazo alternante de los dientes. La histología de este ejemplar, permite observar la naturaleza de los tejidos involucrados en la inserción dentaria (hueso alveolar, cemento y ligamento periodontal). De esta misma formación y de la suprayacente Formación Allen, se describen morfológicamente numerosos dientes aislados. A partir de los dientes analizados, se propone una clasificación para los diferentes tipos de facetas de desgaste: 1) Dientes con una única facetas: - sobre el lado labial - sobre el lado lingual centrada o lateral. 2) Con dos facetas: - la mayor sobre el lado labial y la menor lingual - la mayor sobre el lado lingual y la menor labial - la mayor sobre el lado lingual y la menor mesial o distal. 3) Con tres facetas: - una sobre la cara lingual, otra mesial y otra distal - una sobre la cara lingual, otra labial y otra mesial o distal - una faceta labial, otra mesial y distal. 4) Con cuatro facetas: - una menor labial, otra mayor lingual y dos laterales, mesial y distal. Finalmente se propone una hipótesis de cómo se habrían originado mencionadas facetas de desgaste.A fragment of dentary of a titanosaur sauropod from the Anacleto Formation (Upper Cretaceous of the Río Negro Province) is described. Inside the alveoli, functional and replacement teeth in successive “premature” stages are observed. At least in the preserved portion, an alternate teeth replacement pattern is observed. The histological analysis of this specimen allowed identifying the attachment dental tissues (alveolar bone, cementum and periodontal ligament). Numerous isolated teeth from the same unit and from the overlying Allen Formation are described. Based on these, a classification of the wear facets is proposed: 1) Teeth with only one facet: on the labial side, on the lingual side, or on the lateral side. 2) Teeth with two facets: the bigger on the labial side and the smaller on the lingual side; the bigger on the lingual side and the smaller on the labial side; the bigger on the lingual side and the smaller on the mesial or distal edge. 3) Teeth with three facets: one on the lingual side, the others on the mesial and distal edges; one on the lingual side, the others on the labial and mesial or distal edges; one on the labial side, the others on the mesial and distal edges. 4) Teeth with four facets: the smaller on the labial side, the bigger on the lingual side, and two lateral facets, one on the mesial and the other on the distal edges. Finally, we propose a hypothesis about the origin of the wear facets.Fil: Garcia, Rodolfo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Museo de Geologia y Paleontologia; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Museo de Geologia y Paleontologia; Argentin
IMPLICACIONES IDEOLÓGICAS, EPISTEMOLÓGICAS Y COGNITIVAS DE LA PROPUESTA DE REFORMA PETROLERA EN MÉXICO
En el debate que se ha generado en torno a la propuesta de reforma petrolera, están implícitos elementos ideológicos, teóricos y cognitivos que se ponen en juego por dos frentes en la controversia, la parte nacionalista y la parte privatizadora. En este documento se realiza una valoración crítica de tales posturas rescatando los aspectos más sobresalientes de las ideologías, las teorías económicas (neoclásica y nuevo institucionalismo) que sirven de sustento y las implicaciones cognitivas presentes en las posturas. Esto con la finalidad de que el lector cuente con un panorama más amplio y un marco analítico necesario para tomar mejores decisiones al respecto.En el debate que se ha generado en torno a la propuesta de reforma petrolera, están implícitos elementos ideológicos, teóricos y cognitivos que se ponen en juego por dos frentes en la controversia, la parte nacionalista y la parte privatizadora. En este documento se realiza una valoración crítica de tales posturas rescatando los aspectos más sobresalientes de las ideologías, las teorías económicas (neoclásica y nuevo institucionalismo) que sirven de sustento y las implicaciones cognitivas presentes en las posturas. Esto con la finalidad de que el lector cuente con un panorama más amplio y un marco analítico necesario para tomar mejores decisiones al respecto
The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion
We present an analysis of photometric and spectroscopic observations of the
symbiotic binary system RX Pup with the aims of developing a reliable binary
for the system and identifying mechanisms responsible for its spectacular
activity. The binary is composed of a long-perod Mira variable surrounded by a
thick dust shell and a hot white dwarf companion. The hot component produces
practically all activity observed in the UV, optical and radio range, while
variable obscuration of the Mira by circumstellar dust is responsible for
long-term changes in the near-IR magnitudes. The observations show RX Pup
underwent a nova-like eruption during the last three decades. The hot component
contracted in radius at roughly constant luminosity from 1975 to 1986, and was
the source of a strong stellar wind which prevented it from accreting material
lost in the Mira wind. Around 1988/9 the hot component turned over in the HR
diagram and by 1991 its luminosity had faded by a factor of about 30 with
respect to the maximum plateau value and the hot wind had practically ceased.
By 1995 the nova remnant started to accrete material from the Mira wind, as
indicated by a general increase in intensity of the optical continuum and HI
emission. The quiescent spectrum resembles the quiescent spectra of symbiotic
recurrent novae, and its intensity indicates the hot component must accrete as
much as about 1 per cent of the Mira wind, which is more or less the amount
predicted by Bondi-Hoyle theory. The earliest observational records from the
1890s suggest that another nova-like eruption of RX Pup occurred around 1894.Comment: 23 pages, 12 figues, MNRAS - accepte
“NIVEL DE SOBRECARGA DEL CUIDADOR PRIMARIO ASOCIADO A DETERIORO COGNITIVO EN PACIENTES CON ENFERMEDAD PULMONAR OBSTRUCTIVA CRÓNICA, EN EL CENTRO MEDICO LIC. ADOLFO LÓPEZ MATEOS.”
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