14,020 research outputs found
Surface Plasmons and Topological Insulators
We study surface plasmons localized on interfaces between topologically
trivial and topologically non-trivial time reversal invariant materials in
three dimensions. For the interface between a metal and a topological insulator
the magnetic polarization of the surface plasmon is rotated out of the plane of
the interface; this effect should be experimentally observable by exciting the
surface plasmon with polarized light. More interestingly, we argue that the
same effect also is realized on the interface between vacuum and a doped
topological insulator with non-vanishing bulk carrier density.Comment: 6 pages, 1 figure; v2: typo in eq. (27) correcte
Stability of quasi-linear hyperbolic dissipative systems
In this work we want to explore the relationship between certain eigenvalue
condition for the symbols of first order partial differential operators
describing evolution processes and the linear and nonlinear stability of their
stationary solutions.Comment: 16 pages, Te
EFFECT OF CONTACT ANGLE AND TANK GEOMETRY ON THE CONFIGURATION OF THE LIQUID-VAPOR INTERFACE DURING WEIGHTLESSNESS
Effect of contact angle and space vehicle tank geometry on configuration of rocket propellant liquid-vapor interface during weightlessnes
A non-main-sequence secondary in SY Cancri
Simultaneous spectroscopic and photometric observations of the Z Cam type
dwarf nova SY Cancri were used to obtain absolute flux calibrations. A
comparison of the photometric calibration with a wide slit spectrophotometric
calibration showed that either method is equally satisfactory. A radial
velocity study of the secondary star, made using the far red NaI doublet,
yielded a mass ratio q = 0.68; this is very different from the value of 1.13
quoted in the literature. Using the new lower mass ratio, and constraining the
mass of the white dwarf to be within reasonable limits, then leads to a mass
for the secondary star that is substantially less than would be expected for
its orbital period if it satisfied a main-sequence mass-radius relationship. We
find a spectral type of M0 that is consistent with that expected for a
main-sequence star of the low mass we have found. However, in order to fill its
Roche lobe, the secondary must be significantly larger than a main sequence
star of that mass and spectral type. The secondary is definitely not a normal
main-sequence star.Comment: 13 pages, 9 figures, 6 tables, accepted for publication in MNRA
Localizing merging black holes with sub-arcsecond precision using gravitational-wave lensing
The current gravitational-wave localization methods rely mainly on sources
with electromagnetic counterparts. Unfortunately, a binary black hole does not
emit light. Due to this, it is generally not possible to localize these objects
precisely. However, strongly lensed gravitational waves, which are forecasted
in this decade, could allow us to localize the binary by locating its lensed
host galaxy. Identifying the correct host galaxy is challenging because there
are hundreds to thousands of other lensed galaxies within the sky area spanned
by the gravitational-wave observation. However, we can constrain the lensing
galaxy's physical properties through both gravitational-wave and
electromagnetic observations. We show that these simultaneous constraints allow
one to localize quadruply lensed waves to one or at most a few galaxies with
the LIGO/Virgo/Kagra network in typical scenarios. Once we identify the host,
we can localize the binary to two sub-arcsec regions within the host galaxy.
Moreover, we demonstrate how to use the system to measure the Hubble constant
as a proof-of-principle application.Comment: 5 pages (main text) + 5 pages (methods+references), 5 figures.
Accepted to MNRA
Global existence and exponential decay for hyperbolic dissipative relativistic fluid theories
We consider dissipative relativistic fluid theories on a fixed flat, compact,
globally hyperbolic, Lorentzian manifold. We prove that for all initial data in
a small enough neighborhood of the equilibrium states (in an appropriate
Sobolev norm), the solutions evolve smoothly in time forever and decay
exponentially to some, in general undetermined, equilibrium state. To prove
this, three conditions are imposed on these theories. The first condition
requires the system of equations to be symmetric hyperbolic, a fundamental
requisite to have a well posed and physically consistent initial value
formulation. The second condition is a generic consequence of the entropy law,
and is imposed on the non principal part of the equations. The third condition
is imposed on the principal part of the equations and it implies that the
dissipation affects all the fields of the theory. With these requirements we
prove that all the eigenvalues of the symbol associated to the system of
equations of the fluid theory have strictly negative real parts, which in fact,
is an alternative characterization for the theory to be totally dissipative.
Once this result has been obtained, a straight forward application of a general
stability theorem due to Kreiss, Ortiz, and Reula, implies the results above
mentioned.Comment: 10 pages, Late
Visualisation Tools for Multi-Perspective, Cross-Sector, Long-Term Infrastructure Performance Evaluation
Across different infrastructure sectors there are systems that help to monitor the current and near-future operation
and performance of a particular system. Whilst Supervisory Control and Data Acquisition (SCADA) systems are critical
to maintaining acceptable levels of functionality, they do not provide insights over the longer timescales across which
strategic investment decisions play out. To understand how individual or multiple, interdependent, infrastructure
sectors perform over longer timescales, capacity/demand modelling is required. However, the outputs of such
models are often a complex high-dimensionality result-set, and this complexity is further compounded when crosssector
evaluation is required. To maximise utility of such models, tools are required that can process and present
key outputs. In this paper we describe the development of prototype tools for infrastructure performance evaluation
in relation to different strategic decisions and the complex outputs generated from capacity and demand models of
five infrastructure sectors (energy, water, waste water, solid waste, transport) investigated within the UK Infrastructure
Transitions Research Consortium (ITRC). By constructing tools that expose various dimensions of the model outputs,
a user is able to take greater control over the knowledge discovery process
3-D mesoscale MHD simulations of magnetospheric cusp-like configurations: cusp diamagnetic cavities and boundary structure
We present results from mesoscale simulations of the magnetospheric cusp
region for both strongly northward and strongly southward interplanetary
magnetic field (IMF). Simulation results indicate an extended region of
depressed magnetic field and strongly enhanced plasma β which exhibits a
strong dependence on IMF orientation. These structures correspond to
the Cusp Diamagnetic Cavities (CDC's). The typical features of these CDC's are
generally well reproduced by the simulation. The inner boundaries between the
CDC and the magnetosphere are gradual transitions which form a clear funnel
shape, regardless of IMF orientation. The outer CDC/magnetosheath boundary
exhibits a clear indentation in both the x-z and y-z planes for
southward IMF, while it is only indented in the x-z plane for northward,
with a convex geometry in the y-z plane. The outer boundary represents an
Alfvénic transition, mostly consistent with a slow-shock, indicating that
reconnection plays an important role in structuring the high-altitude cusp
region
Two small-volume electrochemical cells for the measurement of surface enhanced Raman scattering
Two electrochemical cells, for performing surface enhanced Raman scattering (SERS), with submillilitre volumes are presented. One of the cells is especially developed for use in a Raman microspectrometer. The smallest cell uses only 80 mu l of sample. SER measurements are performed on 2*10-3 M adenine
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