10,599 research outputs found
Quantum-Liouville and Langevin Equations for Gravitational Radiation Damping
From a forward--backward path integral, we derive a master equation for the
emission and absorption of gravitons by a massive quantum object in a heat bath
of gravitons. Such an equation could describe collapse phenomena of dense
stars. We also present a useful approximate Langevin equation for such a
system.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper (including all PS fonts) at
http://www.physik.fu-berlin.de/~kleinert/31
A generalization of Gabriel's Galois covering functors II: 2-categorical Cohen-Montgomery duality
Given a group , we define suitable 2-categorical structures on the class
of all small categories with -actions and on the class of all small
-graded categories, and prove that 2-categorical extensions of the orbit
category construction and of the smash product construction turn out to be
2-equivalences (2-quasi-inverses to each other), which extends the
Cohen-Montgomery duality.Comment: 31 pages. I moved the Sec of G-GrCat into Sec 3, and added Lem 5.6. I
added more explanations in the proof of Cor 7.6 with (7.5). I added Def 7.7
and Lem 7.8 with the necessary additional assumptions in Props 7.9 and 7.11.
I added Lem 8.8 with a short proof, Rmk 8.9 and the proof of Lem 8.10. The
final publication is available at Springer via
http://dx.doi.org/10.1007/s10485-015-9416-
Wind-tunnel investigation of boundary-layer control by suction on NACA 655-424 airfoil with double slotted flap
Lava channel formation during the 2001 eruption on Mount Etna: evidence for mechanical erosion
We report the direct observation of a peculiar lava channel that was formed
near the base of a parasitic cone during the 2001 eruption on Mount Etna.
Erosive processes by flowing lava are commonly attributed to thermal erosion.
However, field evidence strongly suggests that models of thermal erosion cannot
explain the formation of this channel. Here, we put forward the idea that the
essential erosion mechanism was abrasive wear. By applying a simple model from
tribology we demonstrate that the available data agree favorably with our
hypothesis. Consequently, we propose that erosional processes resembling the
wear phenomena in glacial erosion are possible in a volcanic environment.Comment: accepted for publication in Physical Review Letter
Radiation reaction and the self-force for a point mass in general relativity
A point particle of mass m moving on a geodesic creates a perturbation h, of
the spacetime metric g, that diverges at the particle. Simple expressions are
given for the singular m/r part of h and its quadrupole distortion caused by
the spacetime. Subtracting these from h leaves a remainder h^R that is C^1. The
self-force on the particle from its own gravitational field corrects the
worldline at O(m) to be a geodesic of g+h^R. For the case that the particle is
a small non-rotating black hole, an approximate solution to the Einstein
equations is given with error of O(m^2) as m approaches 0.Comment: 4 pages, RevTe
Using Topography to Meet Wildlife and Fuels Treatment Objectives in Fire-Suppressed Landscapes
Past forest management practices, fire suppression, and climate change are increasing the need to actively manage California Sierra Nevada forests for multiple environmental amenities. Here we present a relatively low-cost, repeatable method for spatially parsing the landscape to help the U.S. Forest Service manage for different forest and fuel conditions to meet multiple goals relating to sensitive species, fuels reduction, forest products, water, carbon storage, and ecosystem restoration. Using the Kings River area of the Sierra Nevada as a case study, we create areas of topographically-based units, Landscape Management Units (LMUs) using a three by three matrix (canyon, mid-slope, ridge-top and northerly, southerly, and neutral aspects). We describe their size, elevation, slope, aspect, and their difference in inherent wetness and solar radiation. We assess the predictive value and field applicability of LMUs by using existing data on stand conditions and two sensitive wildlife species. Stand conditions varied significantly between LMUs, with canyons consistently having the greatest stem and snag densities. Pacific fisher (Martes pennanti) activity points (from radio telemetry) and California spotted owl (Strix occidentalis occidentalis) nests, roosts, and sightings were both significantly different from uniform, with a disproportionate number of observations in canyons, and fewer than expected on ridge-tops. Given the distinct characteristics of the LMUs, these units provide a relatively simple but ecologically meaningful template for managers to spatially allocate forest treatments, thereby meeting multiple National Forest objectives. These LMUs provide a framework that can potentially be applied to other fire-dependent western forests with steep topographic relief
Quasiexcitons in Incompressible Quantum Liquids
Photoluminescence (PL) has been used to study two-dimensional incompressible
electron liquids in high magnetic fields for nearly two decades. However, some
of the observed anomalies coincident with the fractional quantum Hall effect
are still unexplained. We show that emission in these systems occurs from
fractionally charged "quasiexciton" states formed from trions correlated with
the surrounding electrons. Their binding and recombination depend on the state
of both the electron liquid and the involved trion, predicting discontinuities
in PL and sensitivity to sample parameters.Comment: 4 pages, 4 figure
Representation theory of some infinite-dimensional algebras arising in continuously controlled algebra and topology
In this paper we determine the representation type of some algebras of
infinite matrices continuously controlled at infinity by a compact metrizable
space. We explicitly classify their finitely presented modules in the finite
and tame cases. The algebra of row-column-finite (or locally finite) matrices
over an arbitrary field is one of the algebras considered in this paper, its
representation type is shown to be finite.Comment: 33 page
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