1,416 research outputs found
Merger Transitions in Brane--Black-Hole Systems: Criticality, Scaling, and Self-Similarity
We propose a toy model for study merger transitions in a curved spaceime with
an arbitrary number of dimensions. This model includes a bulk N-dimensional
static spherically symmetric black hole and a test D-dimensional brane
interacting with the black hole. The brane is asymptotically flat and allows
O(D-1) group of symmetry. Such a brane--black-hole (BBH) system has two
different phases. The first one is formed by solutions describing a brane
crossing the horizon of the bulk black hole. In this case the internal induced
geometry of the brane describes D-dimensional black hole. The other phase
consists of solutions for branes which do not intersect the horizon and the
induced geometry does not have a horizon. We study a critical solution at the
threshold of the brane-black-hole formation, and the solutions which are close
to it. In particular, we demonstrate, that there exists a striking similarity
of the merger transition, during which the phase of the BBH-system is changed,
both with the Choptuik critical collapse and with the merger transitions in the
higher dimensional caged black-hole--black-string system.Comment: 9 pages 2 figures; additional remarks and references are added at
Section IX "Discussion
Stability of the spiral phase in the 2D extended t-J model
We analyze the t-t'-t''-J model at low doping by chiral perturbation theory
and show that the (1,0) spiral state is stabilized by the presence of t',t''
above critical values around 0.2J, assuming t/J=3.1. We find that the (magnon
mediated) hole-hole interactions have an important effect on the region of
charge stability in the space of parameters t',t'', generally increasing
stability, while the stability in the magnetic sector is guaranteed by the
presence of spin quantum fluctuations (order from disorder effect). These
conclusions are based on perturbative analysis performed up to two loops, with
very good convergence.Comment: 7 pages, 6 figure
Multi-waveband Emission Maps of Blazars
We are leading a comprehensive multi-waveband monitoring program of 34
gamma-ray bright blazars designed to locate the emission regions of blazars
from radio to gamma-ray frequencies. The "maps" are anchored by sequences of
images in both total and polarized intensity obtained with the VLBA at an
angular resolution of ~ 0.1 milliarcseconds. The time-variable linear
polarization at radio to optical wavelengths and radio to gamma-ray light
curves allow us to specify the locations of flares relative to bright
stationary features seen in the images and to infer the geometry of the
magnetic field in different regions of the jet. Our data reveal that some
flares occur simultaneously at different wavebands and others are only seen at
some of the frequencies. The flares are often triggered by a superluminal knot
passing through the stationary "core" on the VLBA images. Other flares occur
upstream or even parsecs downstream of the core.Comment: 5 pages, including 2 figures; to be published in Journal of
Astrophysics and Astronomy, as part of proceedings of the meeting
"Multiwavelength Variability of Blazars" held in Guangzhou, China, in
September 201
CCl 4 distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation
Abstract. Atmospheric emissions of carbon tetrachloride (CCl4) are regulated by the Montreal Protocol due to its role as a strong ozone-depleting substance. The molecule has been the subject of recent increased interest as a consequence of the so-called mystery of CCl4, the discrepancy between atmospheric observations and reported production and consumption. Surface measurements of CCl4 atmospheric concentrations have declined at a rate almost 3 times lower than its lifetime-limited rate, suggesting persistent atmospheric emissions despite the ban. In this paper, we study CCl4 vertical and zonal distributions in the upper troposphere and lower stratosphere (including the photolytic loss region, 70–20 hPa), its trend, and its stratospheric lifetime using measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which operated onboard the ENVISAT satellite from 2002 to 2012. Specifically, we use the MIPAS data product generated with Version 7 of the Level 2 algorithm operated by the European Space Agency.The CCl4 zonal means show features typical of long-lived species of anthropogenic origin that are destroyed primarily in the stratosphere, with larger quantities in the troposphere and a monotonic decrease with increasing altitude in the stratosphere. MIPAS CCl4 measurements have been compared with independent measurements from other satellite and balloon-borne remote sounders, showing a good agreement between the different datasets.CCl4 trends are calculated as a function of both latitude and altitude. Negative trends of about −10 to −15 pptv decade−1 (−10 to −30 % decade−1) are found at all latitudes in the upper troposphere–lower stratosphere region, apart from a region in the southern midlatitudes between 50 and 10 hPa where the trend is positive with values around 5–10 pptv decade−1 (15–20 % decade−1). At the lowest altitudes sounded by MIPAS, we find trends consistent with those determined on the basis of long-term ground-based measurements (−10 to −13 pptv decade−1). For higher altitudes, the trend shows a pronounced asymmetry between the Northern and Southern hemispheres, and the magnitude of the decline rate increases with altitude. We use a simplified model assuming tracer–tracer linear correlations to determine CCl4 lifetime in the lower stratosphere. The calculation provides a global average lifetime of 47 (39–61) years, considering CFC-11 as the reference tracer. This value is consistent with the most recent literature result of 44 (36–58) years
Gravitational field of charged gyratons
We study relativistic gyratons which carry an electric charge. The
Einstein-Maxwell equations in arbitrary dimensions are solved exactly in the
case of a charged gyraton propagating in an asymptotically flat metric.Comment: 11 pages, some new comments and new references added. To appear in
Classical and Quantum Gravit
Self-energy of a scalar charge near higher-dimensional black holes
We study the problem of self-energy of charges in higher dimensional static
spacetimes. Application of regularization methods of quantum field theory to
calculation of the classical self-energy of charges leads to model-independent
results. The correction to the self-energy of a scalar charge due to the
gravitational field of black holes of the higher dimensional
Majumdar-Papapetrou spacetime is calculated exactly. It proves to be zero in
even dimensions, but it acquires non-zero value in odd dimensional spacetimes.
The origin of the self-energy correction in odd dimensions is similar to the
origin the conformal anomalies in quantum field theory in even dimensional
spacetimes.Comment: 9 page
Expectations and outcomes when moving from open to laparoscopic adrenalectomy: Multivariate analysis
Various authors have suggested that laparoscopic adrenalectomy (LA) leads to better surgical outcomes than open surgery. The debate is still open, however, and indications and limitations of minimally invasive surgery have not been completely established. The objective of our study was to compare surgical outcomes of LA and open adrenalectomy (OA), using multivariate analysis to adjust for potential confounding factors (e.g., size of the lesion, histology). Between 1995 and June 2000 at "Careggi" Hospital in Florence, Italy patients with an indication for adrenalectomy were treated laparoscopically if the lesion was 2 hours, blood loss greater than or equal to 500 ml) between patients operated on through a traditional approach and those who underwent LA. On the other hand, patients operated on laparoscopically have a significantly higher probability than the OA group of experiencing a better recovery from surgery (i.e., require less postoperative analgesics and return to normal activities earlier). The results of the present study show that, although LA does not add much benefit in terms of expected intraoperative outcomes, it dramatically speeds patients' recovery from surgery. The two approaches are complementary and should both be integrated into the technical background of all endocrine surgeons
A Note on the Relativistic Covariance of the Cyclic Relations
It is shown that the Evans-Vigier modified electrodynamics is compatible with
the Relativity Theory.Comment: ReVTeX file, 14pp., no figure
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