4,201 research outputs found
A rigorous approach to the magnetic response in disordered systems
This paper is a part of an ongoing study on the diamagnetic behavior of a
3-dimensional quantum gas of non-interacting charged particles subjected to an
external uniform magnetic field together with a random electric potential. We
prove the existence of an almost-sure non-random thermodynamic limit for the
grand-canonical pressure, magnetization and zero- field orbital magnetic
susceptibility. We also give an explicit formulation of these thermodynamic
limits. Our results cover a wide class of physically relevant random potentials
which model not only crystalline disordered solids, but also amorphous solids.Comment: 35 pages. Revised version. Accepted for publication in RM
Impact of Timanian thrusts on the Phanerozoic tectonic history of Svalbard
Presentation at "Friday seminar" at UiT The Arctic University of Norway, 13.09.2019.Despite more than a century of investigation, the relationship between basement rocks throughout the Svalbard Archipelago is still a mystery. Though these rocks display similar geochronological ages, they show significantly different metamorphic grades and structures. Thus far, Svalbard was believed to be composed of three terranes of rocks formed hundreds–thousands of kilometers apart and accreted in the mid-Paleozoic. New evidence from seismic, gravimetric, aeromagnetic, seismological, bathymetric, and field data show that these terranes might have already been accreted in the late Neoproterozoic. Notably, the data show that at least three–four, crustal-scale, WNW–ESE-striking thrust systems crosscut Spitsbergen and merge with Timanian thrusts in the northern Barents Sea and northwestern Russia. These thrusts were reactivated as sinistral-reverse oblique-slip faults and partly folded during the Caledonian and Eurekan orogenies, and reactivated as sinistral-normal faults during Devonian–Mississippian extensional collapse, thus offsetting N–S-trending Caledonian grain and post-Caledonian basins. The presence of these faults explains the juxtaposition of basement rocks of seemingly different origin throughout the Svalbard Archipelago, the distribution of Mississippian rocks and Early Cretaceous intrusions along a WNW–ESE-trending axis in central Spitsbergen, the west vergence of Cenozoic folds in Devonian rocks in central–northern Spitsbergen (previously ascribed to Late Devonian Ellesmerian contraction), the arch shape of the Cenozoic West Spitsbergen Fold-and-Thrust Belt in Brøggerhalvøya, and the strike and location of transform faults west of Spitsbergen. Further implications of this work might be that the tectonic plates constituting present-day Norwegian Arctic regions (Laurentia and Baltica) have retained their current geometry and alignment for the past 600 Ma, that the Timanian Orogeny and associated WNW–ESE-striking faults extend from northwestern Russia to Svalbard, and, possibly, to Greenland and Arctic Canada, and that the transport of Svalbard from next to Greenland in the early Cenozoic to its present position (ca. 400 km southwards) might have been accommodated exclusively by break-up and displacement along transform faults (strike-slip movements), and by top-SSW thrusting and folding (horizontal shortening) along inherited Timanian grain instead of dextral strike-slip movement along the De Geer Zone
Devonian core complex exhumation and Cenozoic decollements as alternatives to the Ellesmerian Orogeny
Poster presentation at ARCEx Annual Conference 2018, Longyearbyen, Svalbard, 09.10. - 11.10.18. https://arcex.no/arcex-2018/. The Ellesmerian Orogeny (Piepjohn et al., 2000) is a short-lived contractional–transpressional event that occurred in the
Late Devonian–Mississippian, i.e., after Devonian collapse of the Caledonides and prior to Carboniferous rifting. Thus far, this
episode of contraction–transpression was required to explain the presence of undeformed Carboniferous–Permian
sedimentary rocks on top of folded Upper Devonian strata in central Spitsbergen. The orogen is poorly constrained in other
parts of the Arctic due to the lack/poor exposure of Devonian–Carboniferous sedimentary rocks (Rippington et al., 2010). We
present an alternative model involving core complex exhumation through continuous, decreasing, Devonian–Carboniferous
extension during the collapse of the Caledonides, and (partial) strain decoupling during Cenozoic transpression in Svalbard
On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
The CDM cosmological scenario predicts that our Galaxy should
contain hundreds of stellar streams at the solar vicinity, fossil relics of the
merging history of the Milky Way and more generally of the hierarchical growth
of galaxies. Because of the mixing time scales in the inner Galaxy, it has been
claimed that these streams should be difficult to detect in configuration space
but can still be identifiable in kinematic-related spaces like the
energy/angular momenta spaces, E-Lz and Lperp-Lz, or spaces of orbital/velocity
parameters. By means of high-resolution, dissipationless N-body simulations,
containing between 25 and 35 particles, we model the
accretion of a series of up to four 1:10 mass ratio satellites then up to eight
1:100 satellites and we search systematically for the signature of these
accretions in these spaces. In all spaces considered (1) each satellite gives
origin to several independent overdensities; (2) overdensities of multiple
satellites overlap; (3) satellites of different masses can produce similar
substructures; (4) the overlap between the in-situ and the accreted population
is considerable everywhere; (5) in-situ stars also form substructures in
response to the satellite(s) accretion. These points are valid even if the
search is restricted to kinematically-selected halo stars only. As we are now
entering the 'Gaia era', our results warn that an extreme caution must be
employed before interpreting overdensities in any of those spaces as evidence
of relics of accreted satellites. Reconstructing the accretion history of our
Galaxy will require a substantial amount of accurate spectroscopic data, that,
complemented by the kinematic information, will possibly allow us to
(chemically) identify accreted streams and measure their orbital properties.
(abridged)Comment: Accepted on A&A. A high-resolution version of the paper is available
at http://aramis.obspm.fr/~paola/ELZ/Elz.pd
The Billefjorden Fault Zone north of Spitsbergen: a major terrane boundary?
The Billefjorden Fault Zone is a major terrane boundary in the Norwegian Arctic. The fault separates basement rocks of Svalbard’s north-eastern and north-western terranes that recorded discrete Precambrian tectonothermal histories and were accreted, intensely deformed and metamorphosed during the Caledonian Orogeny. Although the fault represents a major, crustal-scale tectonic boundary, its north-ward extent is not well constrained. The present short contribution addresses this issue and presents new seismic mapping of structures and rock units north of Wijdefjorden, where the Billefjorden Fault Zone may continue. This study shows that there is no evidence for major faulting of the top-basement reflection, and therefore, that the Billefjorden Fault Zone may die out within Wijdefjorden–Austfjorden, step ≥ 20 km laterally, or be invisible on the presented seismic data. Seismic data also suggest that Caledonian basement rocks in Ny-Friesland (north-eastern terrane) are not significantly different from basement rocks below the Devonian Graben in Andrée Land (north-western terrane). Potential implica-tions include the absence of a major terrane boundary in northern Spitsbergen
Constriction – Construction, a short history of specialised wearing apparel for athletic activities from the fourteenth century to nineteenth century
During the twentieth century, clothing permits a real freedom of bodily movement. However, when examining past athletic activity, we must take into account the period approach to the body: liberty of movement is at the same time controlled by morality, gestures and clothing. The French term “tenue” initially referred to behaviour, but since the end of the eighteenth century concerns the manner of dressing, and later by extension, the “dignity of conduct”. In the past times concerned with “sporting” activities such as the HEMA (Historical European Martial Arts), physical appearance is affected by rules of etiquette imposed by morality and civility. From the Middle Ages to the nineteenth century, each period offers a different overview of the dress standards in relation to the different approaches to corporal identity, and the constriction first necessary for military activities becomes indivisible from the moral and physical construction. As a practitioner of the 21st century, the question raises about our relationship, not only with our bodies but also with past cultures. As demonstrated by some concrete examples, if it is desired to fully approach the ancient practices, it is therefore necessary to also adopt the garment, in the same way as the accessories
Creep motion of a model frictional system
We report on the dynamics of a model frictional system submitted to minute
external perturbations. The system consists of a chain of sliders connected
through elastic springs that rest on an incline. By introducing cyclic
expansions and contractions of the springs we observe a reptation of the chain.
We account for the average reptation velocity theoretically. The velocity of
small systems exhibits a series of plateaus as a function of the incline angle.
Due to elastic e ects, there exists a critical amplitude below which the
reptation is expected to cease. However, rather than a full stop of the creep,
we observe in numerical simulations a transition between a continuous-creep and
an irregular-creep regime when the critical amplitude is approached. The latter
transition is reminiscent of the transition between the continuous and the
irregular compaction of granular matter submitted to periodic temperature
changes
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