1,537 research outputs found
Local Density of States in a Dirty Normal Metal connected to a Superconductor
A superconductor in contact with a normal metal not only induces
superconducting correlations, known as proximity effect, but also modifies the
density of states at some distance from the interface. These modifications can
be resolved experimentally in microstructured systems. We, therefore, study the
local density of states of a superconductor - normal metal
heterostructure. We find a suppression of at small energies, which
persists to large distances. If the normal metal forms a thin layer of
thickness , a minigap in the density of states appears which is of the
order of the Thouless energy . A magnetic field suppresses
the features. We find good agreement with recent experiments of Gu\'eron {\it
et al.}Comment: 5 pages, RevTeX, 7 Figures (included), Submitted to PRB. Revised
version: One figure changed, missprints correcte
Manned geosynchronous mission requirements and systems analysis study add-on
An MOTV mission model was constructed in order to establish the baseline condition for SOC basing. A mission model to reflect satellite servicing was extended. Yearly traffic was projected. Driver missions were categorized. Cost trades and sensitivity to traffic rates were performed and service equipment needs were identified
The role of string-like, supramolecular assemblies in reentrant supernematic liquid crystals
Using a combination of isothermal-isobaric Monte Carlo and microcanonical
molecular dynamics we investigate the relation between structure and
self-diffusion in various phases of a model liquid crystal using the
Gay-Berne-Kihara potential. These molecules are confined to a mesoscopic
slit-pore with atomically smooth substrate surfaces. As reported recently [see
M. G. Mazza {\em et al.}, Phys. Rev. Lett. {\bf 105}, 227802 (2010)], a
reentrant nematic (RN) phase may form at sufficiently high pressures/densities.
This phase is characterized by a high degree of nematic order and a
substantially enhanced self-diffusivity in the direction of the director
which exceeds that of the lower-density nematic and an
intermittent smectic A phase by about an order of magnitude. Here we
demonstrate that the unique transport behavior in the RN phase may be linked to
a confinement-induced packing effect which causes the formation of
supramolecular, string-like conformations. The strings consist of several
individual molecules that are capable of travelling in the direction of
as individual "trains" consisting of chains of molecular "cars".
Individual trains run in parallel and may pass each other at sufficiently high
pressures.Comment: 24 page
Non-liftable Calabi-Yau spaces
We construct many new non-liftable three-dimensional Calabi-Yau spaces in
positive characteristic. The technique relies on lifting a nodal model to a
smooth rigid Calabi-Yau space over some number field as introduced by the first
author and D. van Straten.Comment: 16 pages, 5 tables; v2: minor corrections and addition
A simple remark on a flat projective morphism with a Calabi-Yau fiber
If a K3 surface is a fiber of a flat projective morphisms over a connected
noetherian scheme over the complex number field, then any smooth connected
fiber is also a K3 surface. Observing this, Professor Nam-Hoon Lee asked if the
same is true for higher dimensional Calabi-Yau fibers. We shall give an
explicit negative answer to his question as well as a proof of his initial
observation.Comment: 8 pages, main theorem is generalized, one more remark is added,
mis-calculation and typos are corrected etc
Probabilistic computer model of optimal runway turnoffs
Landing delays are currently a problem at major air carrier airports and many forecasters agree that airport congestion will get worse by the end of the century. It is anticipated that some types of delays can be reduced by an efficient optimal runway exist system allowing increased approach volumes necessary at congested airports. A computerized Probabilistic Runway Turnoff Model which locates exits and defines path geometry for a selected maximum occupancy time appropriate for each TERPS aircraft category is defined. The model includes an algorithm for lateral ride comfort limits
The temperature dependence of FeRh's transport properties
The finite-temperature transport properties of FeRh compounds are
investigated by first-principles Density Functional Theory-based calculations.
The focus is on the behavior of the longitudinal resistivity with rising
temperature, which exhibits an abrupt decrease at the metamagnetic transition
point, between ferro- and antiferromagnetic phases. A detailed
electronic structure investigation for K explains this feature and
demonstrates the important role of (i) the difference of the electronic
structure at the Fermi level between the two magnetically ordered states and
(ii) the different degree of thermally induced magnetic disorder in the
vicinity of , giving different contributions to the resistivity. To
support these conclusions, we also describe the temperature dependence of the
spin-orbit induced anomalous Hall resistivity and Gilbert damping parameter.
For the various response quantities considered the impact of thermal lattice
vibrations and spin fluctuations on their temperature dependence is
investigated in detail. Comparison with corresponding experimental data finds
in general a very good agreement
Gravitating Opposites Attract
Generalizing previous work by two of us, we prove the non-existence of
certain stationary configurations in General Relativity having a spatial
reflection symmetry across a non-compact surface disjoint from the matter
region. Our results cover cases such that of two symmetrically arranged
rotating bodies with anti-aligned spins in () dimensions, or
two symmetrically arranged static bodies with opposite charges in 3+1
dimensions. They also cover certain symmetric configurations in
(3+1)-dimensional gravity coupled to a collection of scalars and abelian vector
fields, such as arise in supergravity and Kaluza-Klein models. We also treat
the bosonic sector of simple supergravity in 4+1 dimensions.Comment: 13 pages; slightly amended version, some references added, matches
version to be published in Classical and Quantum Gravit
The Action of Instantons with Nut Charge
We examine the effect of a non-trivial nut charge on the action of
non-compact four-dimensional instantons with a U(1) isometry. If the instanton
action is calculated by dimensionally reducing along the isometry, then the nut
charge is found to make an explicit non-zero contribution. For metrics
satisfying AF, ALF or ALE boundary conditions, the action can be expressed
entirely in terms of quantities (including the nut charge) defined on the fixed
point set of the isometry. A source (or sink) of nut charge also implies the
presence of a Misner string coordinate singularity, which will have an
important effect on the Hamiltonian of the instanton.Comment: 25 page
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