3,015 research outputs found
Evolution of the Great Tehuelche Paleolake in the Torres del Paine National Park of Chilean Patagonia during the Last Glacial Maximum and Holocene
Indexación: Web of Science; ScieloRESUMEN. Una serie de morrenas glaciares se distribuyen desde el margen oriental de la cuenca de drenaje Torres del Paine a cerca del actual margen de los Campos de Hielo Patagónico, junto con una serie de terrazas lacustres regional continuos relacionados con las fluctuaciones glaciales. La geomorfología, apoyada por la evidencia de sedimentos del lago, indica la existencia de un único paleolago proglacial en esta zona, aquí denominado el Gran Tehuelche paleolago. Este concepto ayuda a aclarar la cronología de eventos glaciales y conduce a una mejor comprensión de la evolución del sistema hidrológico de la zona de Torres del Paine. Avances glaciales referidos anteriormente como ocurrieron A, B y C durante el Último Máximo Glacial y alimentados con la Gran Tehuelche paleolago con agua de deshielo, que le permite alcanzar su máxima extensión. El descubrimiento de trombolitos en Laguna Amarga sugiere que el drenaje de la paleolago hacia el fiordo de Última Esperanza tuvo lugar en 7113 Cal. años AP, después de la fusión de una barrera de hielo que existía durante el avance glacial antes. Esto dio lugar al desarrollo de un sistema hidrológico fluvio-lacustre complejo que persiste hasta nuestros días.
Palabras clave: Patagonia, último máximo glacial, Younger Dryas, trombolitos.
RESUMEN. Un grupo de morrenas glaciales estan Distribuidas desde el margen Este de la cuenca de drenaje de Torres del Paine Hacia el margen real de los Campos de Hielo Patagónicos. Las morrenas se observan en conjunto con las Naciones Unidas Grupo de terrazas Lacustres Regionales, las Cuales estan vinculadas y una las fluctuaciones glaciales. La geomorfología y Evidencias de sedimentos Lacustres indicano la existence De unico ONU lago proglacial, referido En Este Estudio de Como Gran Paleolago Tehuelche. Este Concepto ayuda a clarificar la cronología de los eventos glaciales y permite Una mejor Comprensión de la Evolución del Sistema hidrológico del sector de Torres del Paine. Los eventos glaciales, previamente Referidos Como Avance A, B y C, ocurrieron Durante el Último Máximo Glacial y alimentaron con Aguas de fusión al Gran Paleolago Tehuelche, permitiéndole Alcanzar su alcalde extensión. El Descubrimiento de trombolitos en Laguna Amarga sugiere Que El desagüe del paleolago Ocurrió Hace 7.113 Cal. Por años AP el Seno de Última Esperanza, producto de la fusión De Una barrera glaciar existente Durante los Avances glaciales Anteriores. LUEGO del drenaje sí Desarrollo en Un complejo Sistema hidrológico Que Persiste Hasta el presente.
Palabras clave: Patagonia, Último Máximo Glacial, Dryas Temprano, Trombolitos.http://ref.scielo.org/wgc2q
Quantum fields and "Big Rip" expansion singularities
The effects of quantized conformally invariant massless fields on the
evolution of cosmological models containing a ``Big Rip'' future expansion
singularity are examined. Quantized scalar, spinor, and vector fields are found
to strengthen the accelerating expansion of such models as they approach the
expansion singularity.Comment: 7 pages; REVTeX
Full time nonexponential decay in double-barrier quantum structures
We examine an analytical expression for the survival probability for the time
evolution of quantum decay to discuss a regime where quantum decay is
nonexponential at all times. We find that the interference between the
exponential and nonexponential terms of the survival amplitude modifies the
usual exponential decay regime in systems where the ratio of the resonance
energy to the decay width, is less than 0.3. We suggest that such regime could
be observed in semiconductor double-barrier resonant quantum structures with
appropriate parameters.Comment: 6 pages, 5 figure
Systematic challenges for future gravitational wave measurements of precessing binary black holes
The properties of precessing, coalescing binary black holes are presently
inferred through comparison with two approximate models of compact binary
coalescence. In this work we show these two models often disagree substantially
when binaries have modestly large spins () and modest mass ratios
(). We demonstrate these disagreements using standard figures of
merit and the parameters inferred for recent detections of binary black holes.
By comparing to numerical relativity, we confirm these disagreements reflect
systematic errors. We provide concrete examples to demonstrate that these
systematic errors can significantly impact inferences about astrophysically
significant binary parameters. For the immediate future, parameter inference
for binary black holes should be performed with multiple models (including
numerical relativity), and carefully validated by performing inference under
controlled circumstances with similar synthetic events.Comment: 12 pages, 9 figure
Transient tunneling effects of resonance doublets in triple barrier systems
Transient tunneling effects in triple barrier systems are investigated by
considering a time-dependent solution to the Schr\"{o}dinger equation with a
cutoff wave initial condition. We derive a two-level formula for incidence
energies near the first resonance doublet of the system. Based on that
expression we find that the probability density along the internal region of
the potential, is governed by three oscillation frequencies: one of them refers
to the well known Bohr frequency, given in terms of the first and second
resonance energies of the doublet, and the two others, represent a coupling
with the incidence energy . This allows to manipulate the above frequencies
to control the tunneling transient behavior of the probability density in the
short-time regim
Deformation Quantization: Quantum Mechanics Lives and Works in Phase-Space
Wigner's quasi-probability distribution function in phase-space is a special
(Weyl) representation of the density matrix. It has been useful in describing
quantum transport in quantum optics; nuclear physics; decoherence (eg, quantum
computing); quantum chaos; "Welcher Weg" discussions; semiclassical limits. It
is also of importance in signal processing.
Nevertheless, a remarkable aspect of its internal logic, pioneered by Moyal,
has only emerged in the last quarter-century: It furnishes a third,
alternative, formulation of Quantum Mechanics, independent of the conventional
Hilbert Space, or Path Integral formulations. In this logically complete and
self-standing formulation, one need not choose sides--coordinate or momentum
space. It works in full phase-space, accommodating the uncertainty principle.
This is an introductory overview of the formulation with simple illustrations.Comment: LaTeX, 22 pages, 2 figure
Ysovar: The First Sensitive, Wide-area, Mid-infrared Photometric Monitoring of the Orion Nebula Cluster
We present initial results from time-series imaging at infrared wavelengths of 0.9 deg^2 in the Orion Nebula Cluster (ONC). During Fall 2009 we obtained 81 epochs of Spitzer 3.6 and 4.5 μm data over 40 consecutive days. We extracted light curves with ~3% photometric accuracy for ~2000 ONC members ranging from several solar masses down to well below the hydrogen-burning mass limit. For many of the stars, we also have time-series photometry obtained at optical (I_c) and/or near-infrared (JK_s ) wavelengths. Our data set can be mined to determine stellar rotation periods, identify new pre-main-sequence eclipsing binaries, search for new substellar Orion members, and help better determine the frequency of circumstellar disks as a function of stellar mass in the ONC. Our primary focus is the unique ability of 3.6 and 4.5 μm variability information to improve our understanding of inner disk processes and structure in the Class I and II young stellar objects (YSOs). In this paper, we provide a brief overview of the YSOVAR Orion data obtained in Fall 2009 and highlight our light curves for AA-Tau analogs—YSOs with narrow dips in flux, most probably due to disk density structures passing through our line of sight. Detailed follow-up observations are needed in order to better quantify the nature of the obscuring bodies and what this implies for the structure of the inner disks of YSOs
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