222 research outputs found
Future sea level contribution from Antarcticainferred from CMIP5 model forcing and itsdependence on precipitation ansatz
Various observational estimates indicate growing mass loss at Antarctica's margins but also heavier precipitation across the continent. In the future, heavier precipitation fallen on Antarctica will counteract any stronger iceberg discharge and increased basal melting of floating ice shelves driven by a warming ocean. Here, we use from nine CMIP5 models future projections, ranging from strong mitigation efforts to business-as-usual, to run an ensemble of ice-sheet simulations. We test, how the precipitation boundary condition determines Antarctica's sea-level contribution. The spatial and temporal varying climate forcings drive ice-sheet simulations. Hence, our ensemble inherits all spatial and temporal climate patterns, which is in contrast to a spatial mean forcing. Regardless of the applied boundary condition and forcing, some areas will lose ice in the future, such as the glaciers from the West Antarctic Ice Sheet draining into the Amundsen Sea. In general the simulated ice-sheet thickness grows in a broad marginal strip, where incoming storms deliver topographically controlled precipitation. This strip shows the largest ice thickness differences between the applied precipitation boundary conditions too. On average Antarctica's ice mass shrinks for all future scenarios if the precipitation is scaled by the spatial temperature anomalies coming from the CMIP5 models. In this approach, we use the relative precipitation increment per degree warming as invariant scaling constant. In contrast, Antarctica gains mass in our simulations if we apply the simulated precipitation anomalies of the CMIP5 models directly. Here, the scaling factors show a distinct spatial pattern across Antarctica. Furthermore, the diagnosed mean scaling across all considered climate forcings is larger than the values deduced from ice cores. In general, the scaling is higher across the East Antarctic Ice Sheet, lower across the West Antarctic Ice Sheet, and lowest around the Siple Coast. The latter is located on the east side of the Ross Ice Shelf
Behaviour of Magnetic Tubes in Neutron Star's Interior
It is found from Maxwell's equations that the magnetic field lines are good
analogues of relativistic strings. It is shown that the super-conducting
current in the neutron star's interior causes local rotation of magnetic flux
tubes carrying quantized flux.Comment: 6 pages, no figure
Chiral models in dilaton-Maxwell gravity
We study symmetry properties of the Einstein-Maxwell theory nonminimaly
coupled to the dilaton field. We consider a static case with pure electric
(magnetic) Maxwell field and show that the resulting system becomes a nonlinear
sigma-model wich possesses a chiral representation. We construct the
corresponding chiral matrix and establish a representation which is related to
the pair of Ernst-like potentials. These potentials are used for separation of
the symmetry group into the gauge and nongauge (charging) sectors. New
variables, which linearize the action of charging symmetries, are also
established; a solution generation technique based on the use of charging
symmetries is formulated. This technique is used for generation of the
elecricaly (magneticaly) charged dilatonic fields from the static General
Relativity ones.Comment: 9 pages in LaTex; published in Gen. Rel. Grav. 32 (2000) pp 1389-139
Quasi-normal modes of warped black holes and warped AdS/CFT correspondence
We analytically calculate the quasi-normal modes of various perturbations of
spacelike stretched and null warped black holes. From AdS/CFT
correspondence, these quasi-normal modes are expected to appear as the poles in
momentum space of retarded Green functions of dual operators in CFT at finite
temperature. We find that this is indeed the case, after taking into account of
the subtle identification of quantum numbers. The subtlety comes from the fact
that only after appropriate coordinate transformation the asymptotic geometries
of warped black holes are the same as the ones of warped spacetimes. We
show that in general the quasi-normal modes are in good agreement with the
prediction of the warped AdS/CFT correspondence, up to a constant factor. As a
byproduct, we compute the conformal dimensions of boundary operators dual to
the perturbations. Our result gives strong support to the conjectured warped
AdS/CFT correspondence.Comment: 26 pages; typos corrected, references added; more clarifications,
match the version to appear in JHE
Gross hematuria as the presentation of an inguinoscrotal hernia: a case report
<p>Abstract</p> <p>Introduction</p> <p>Several complications have been reported with inguinal hernias. Although hematuria and flank pain, either as the presentation or as a complication of inguinal hernia, are infrequent, this condition may lead to the development of obstructive uropathy, which can have diverse manifestations.</p> <p>Case presentation</p> <p>A 71-year-old Iranian man with Persian ethnicity presented with new onset episodes of gross hematuria and left-sided flank pain. A physical examination revealed a large and non-tender inguinal hernia on his left side. An initial workup included an abdominal ultrasound, an intravenous pyelogram and cystoscopy, which showed left hydronephrosis and a bulging on the left-side of his bladder wall. On further evaluation, computed tomography confirmed that his sigmoid colon was the source of the pressure effect on his bladder, resulting in hydroureteronephrosis and hematuria. No tumoral lesion was evident. Herniorrhaphy led to the resolution of his signs and symptoms.</p> <p>Conclusion</p> <p>Our case illustrates a rare presentation of inguinal hernia responsible for gross hematuria and unilateral hydronephrosis. Urologic signs and symptoms can be caused by the content of inguinal hernias. They can also present as complications of inguinal hernias.</p
Type D spacetimes and the Weyl double copy
We study the double-copy relation between classical solutions in gauge theory and gravity, focusing on four-dimensional vacuum metrics of algebraic type D, a class that includes several important solutions. We present a double copy of curvatures that applies to all spacetimes of this typeâthe Weyl double copyârelating the curvature of the spacetime to an electromagnetic field strength. We show that the Weyl double copy is consistent with the previously known KerrâSchild double copy, and in fact resolves certain ambiguities of the latter. The most interesting new example of the classical double copy presented here is that of the C-metric. This well-known solution, which represents a pair of uniformly accelerated black holes, is mapped to the LiĂ©nardâWiechert potential for a pair of uniformly accelerated charges. We also present a new double-copy interpretation of the EguchiâHanson instanton
Dynamics and stability of the Godel universe
We use covariant techniques to describe the properties of the Godel universe
and then consider its linear response to a variety of perturbations. Against
matter aggregations, we find that the stability of the Godel model depends
primarily upon the presence of gradients in the centrifugal energy, and
secondarily on the equation of state of the fluid. The latter dictates the
behaviour of the model when dealing with homogeneous perturbations. The
vorticity of the perturbed Godel model is found to evolve as in almost-FRW
spacetimes, with some additional directional effects due to shape distortions.
We also consider gravitational-wave perturbations by investigating the
evolution of the magnetic Weyl component. This tensor obeys a simple plane-wave
equation, which argues for the neutral stability of the Godel model against
linear gravity-wave distortions. The implications of the background rotation
for scalar-field Godel cosmologies are also discussed.Comment: Revised version, to match paper published in Class. Quantum Gra
Cinema-going trajectories in the digital age
The activity of cinema-going constantly evolves and gradually integrates the use of digital data and platforms to become more engaging for the audiences. Combining methods from the fields of Human Computer Interaction and Film Studies, we conducted two workshops seeking to understand cinema audiencesâ digital practices and explore how the contemporary cinema-going experience is shaped in the digital age. Our findings suggest that going to the movies constitutes a trajectory during which cinemagoers interact with multiple digital platforms. At the same time, depending on their choices, they construct unique digital identities that represent a set of online behaviours and rituals that cinemagoers adopt before, while and after cinema-going. To inform the design of new, engaging cinemagoing experiences, this research establishes a preliminary map of contemporary cinema-going including digital data and platforms. We then discuss how audiences perceive the potential improvement of the experience and how that would lead to the construction of digital identities
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