31,903 research outputs found
Ambipolar Filamentation of Turbulent Magnetic Fields : A numerical simulation
We present the results of a 2-D, two fluid (ions and neutrals) simulation of
the ambipolar filamentation process, in which a magnetized, weakly ionized
plasma is stirred by turbulence in the ambipolar frequency range. The higher
turbulent velocity of the neutrals in the most ionized regions gives rise to a
non-linear force driving them out of these regions, so that the initial
ionization inhomogeneities are strongly amplified. This effect, the ambipolar
filamentation, causes the ions and the magnetic flux to condense and separate
from the neutrals, resulting in a filamentary structure.Comment: 8 pages, 6 figures, accepted for publication in A&
Entanglement Content of Quantum Particle Excitations II. Disconnected Regions and Logarithmic Negativity
In this paper we study the increment of the entanglement entropy and of the (replica) logarithmic negativity in a zero-density excited state of a free massive bosonic theory, compared to the ground state. This extends the work of two previous publications by the same authors. We consider the case of two disconnected regions and find that the change in the entanglement entropy depends only on the combined size of the regions and is independent of their connectivity. We subsequently generalize this result to any number of disconnected regions. For the replica negativity we find that its increment is a polynomial with integer coefficients depending only on the sizes of the two regions. The logarithmic negativity turns out to have a more complicated functional structure than its replica version, typically involving roots of polynomials on the sizes of the regions. We obtain our results by two methods already employed in previous work: from a qubit picture and by computing four-point functions of branch point twist fields in finite volume. We test our results against numerical simulations on a harmonic chain and find excellent agreement
The SEALS Yardsticks for Ontology Management
This paper describes the rst SEALS evaluation campaign
over ontology engineering tools (i.e., the SEALS Yardsticks for Ontology Management). It presents the dierent evaluation scenarios dened to evaluate the conformance, interoperability and scalability of these tools, and the test data used in these scenarios
Shadowing by non uniformly hyperbolic periodic points and uniform hyperbolicity
We prove that, under a mild condition on the hyperbolicity of its periodic
points, a map which is topologically conjugated to a hyperbolic map
(respectively, an expanding map) is also a hyperbolic map (respectively, an
expanding map). In particular, this result gives a partial positive answer for
a question done by A. Katok, in a related context
Miro1 – the Missing Link to Peroxisome Motility
This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordPeroxisomes are ubiquitous, highly dynamic, multifunctional compartments in eukaryotic
cells, which perform key roles in cellular lipid metabolism and redox balance. Like other
membrane-bound organelles, peroxisomes must move in the cellular landscape to
perform localized functions, interact with other organelles and to properly distribute
during cell division. However, our current knowledge of peroxisome motility in
mammalian cells is still very limited. Recently, three independent studies have identified
Miro1 as a regulator of peroxisome motility in mammalian cells. In these studies, the
authors show that Miro1 is targeted to peroxisomes in several cell lines, in a process that
relies on its interaction with the peroxisomal chaperone Pex19. Interestingly, however,
different conclusions are drawn about which Miro1 isoforms are targeted to peroxisomes,
how it interacts with Pex19 and most importantly, the type of motility Miro1 is regulating.This work was supported by the Biotechnology and Biological Sciences Research
Council (BB/K006231/1, BB/N01541X/1) (to M.S.). I.G.C. is supported by an EMBO
Long-term Fellowship ALTF-580-2017
Unstable particles versus resonances in impurity systems, conductance in quantum wires
We compute the DC conductance for a homogeneous sine-Gordon model and an
impurity system of Luttinger liquid type by means of the thermodynamic Bethe
ansatz and standard potential scattering theory. We demonstrate that unstable
particles and resonances in impurity systems lead to a sharp increase of the
conductance as a function of the temperature, which is characterized by the
Breit-Wigner formula.Comment: 5 pages Latex, 1 figure replaced, version to appear in J. Phys.
Elliot-Yafet mechanism in graphene
The differences between spin relaxation in graphene and in other materials
are discussed. For relaxation by scattering processes, the Elliot-Yafet
mechanism, the relation between the spin and the momentum scattering times
acquires a dependence on the carrier density, which is independent of the
scattering mechanism and the relation between mobility and carrier
concentration. This dependence puts severe restrictions on the origin of the
spin relaxation in graphene. The density dependence of the spin relaxation
allows us to distinguish between ordinary impurities and defects which modify
locally the spin-orbit interaction.Comment: 4 pages + \epsilon + S
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