7,043 research outputs found
Thermoplasmonics: Quantifying plasmonic heating in single nanowires
Plasmonic absorption of light can lead to significant local heating in
metallic nanostructures, an effect that defines the sub-field of
thermoplasmonics and has been leveraged in diverse applications from biomedical
technology to optoelectronics. Quantitatively characterizing the resulting
local temperature increase can be very challenging in isolated nanostructures.
By measuring the optically-induced change in resistance of metal nanowires with
a transverse plasmon mode, we quantitatively determine the temperature increase
in single nanostructures, with the dependence on incident polarization clearly
revealing the plasmonic heating mechanism. Computational modeling explains the
resonant and nonresonant contributions to the optical heating and the dominant
pathways for thermal transport. These results, obtained by combining electronic
and optical measurements, place a bound on the role of optical heating in prior
experiments, and suggest design guidelines for engineered structures meant to
leverage such effects.Comment: 17 pages, 4 figures + 3 pages supporting materia
Microelectromagnets for Trapping and Manipulating Ultracold Atomic Quantum Gases
We describe the production and characterization of microelectromagnets made
for trapping and manipulating atomic ensembles. The devices consist of 7
fabricated parallel copper conductors 3 micrometer thick, 25mm long, with
widths ranging from 3 to 30 micrometer, and are produced by electroplating a
sapphire substrate. Maximum current densities in the wires up to 6.5 * 10^6 A /
cm^2 are achieved in continuous mode operation. The device operates
successfully at a base pressure of 10^-11 mbar. The microstructures permit the
realization of a variety of magnetic field configurations, and hence provide
enormous flexibility for controlling the motion and the shape of Bose-Einstein
condensates.Comment: 4 pages, 3 figure
New results on superconformal quivers
All superconformal quivers are shown to satisfy the relation c = a and are
thus good candidates for being the field theory living on D3 branes probing CY
singularities. We systematically study 3 block and 4 block chiral quivers which
admit a superconformal fixed point of the RG equation. Most of these theories
are known to arise as living on D3 branes at a singular CY manifold, namely
complex cones over del Pezzo surfaces. In the process we find a procedure of
getting a new superconformal quiver from a known one. This procedure is termed
"shrinking" and, in the 3 block case, leads to the discovery of two new models.
Thus, the number of superconformal 3 block quivers is 16 rather than the
previously known 14. We prove that this list exausts all the possibilities. We
suggest that all rank 2 chiral quivers are either del Pezzo quivers or can be
obtained by shrinking a del Pezzo quiver and verify this statement for all 4
block quivers, where a lot of "shrunk'' del Pezzo models exist.Comment: 51 pages, many figure
Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble
As the number of spins in an ensemble is reduced, the statistical uctuations
in its polarization eventually exceed the mean thermal polarization. This
transition has now been surpassed in a number of recent nuclear magnetic
resonance experiments, which achieve nanometer-scale detection volumes. Here,
we measure nanometer- scale ensembles of nuclear spins in a KPF6 sample using
magnetic resonance force microscopy. In particular, we investigate the
transition between regimes dominated by thermal and statistical nuclear
polarization. The ratio between the two types of polarization provides a
measure of the number of spins in the detected ensemble
Effect of a Remedy Limitation Clause on Specific Performance: S.E.S. Importers, Inc. v. Pappalardo
Anomalous dimensions and splitting functions beyond the next-to-next-to-leading order
We report on recent progress on the splitting functions for the evolution of
parton distributions and related quantities, the (lightlike) cusp anomalous
dimensions, in perturbative QCD. New results are presented for the four-loop
(next-to-next-to-next-to-leading order, N^3LO) contributions to the
flavour-singlet splitting functions and the gluon cusp anomalous dimension. We
present first results, the moments N=2 and N=3, for the five-loop (N^4LO)
non-singlet splitting functions.Comment: 10 pages, LaTeX (PoS style), 3 eps-figures. Contribution to the
proceedings of `Loops & Legs 2018', St. Goar (Germany), April/May 201
Brane Tilings and Exceptional Collections
Both brane tilings and exceptional collections are useful tools for
describing the low energy gauge theory on a stack of D3-branes probing a
Calabi-Yau singularity. We provide a dictionary that translates between these
two heretofore unconnected languages. Given a brane tiling, we compute an
exceptional collection of line bundles associated to the base of the
non-compact Calabi-Yau threefold. Given an exceptional collection, we derive
the periodic quiver of the gauge theory which is the graph theoretic dual of
the brane tiling. Our results give new insight to the construction of quiver
theories and their relation to geometry.Comment: 46 pages, 37 figures, JHEP3; v2: reference added, figure 13 correcte
Exceptional Collections and del Pezzo Gauge Theories
Stacks of D3-branes placed at the tip of a cone over a del Pezzo surface
provide a way of geometrically engineering a small but rich class of
gauge/gravity dualities. We develop tools for understanding the resulting
quiver gauge theories using exceptional collections. We prove two important
results for a general quiver gauge theory: 1) we show the ordering of the nodes
can be determined up to cyclic permutation and 2) we derive a simple formula
for the ranks of the gauge groups (at the conformal point) in terms of the
numbers of bifundamentals. We also provide a detailed analysis of four node
quivers, examining when precisely mutations of the exceptional collection are
related to Seiberg duality.Comment: 26 pages, 1 figure; v2 footnote 2 amended; v3 ref adde
Cosmogenic radionuclides on LDEF: An unexpected Be-10 result
Following the discovery of the atmospheric derived cosmogenic radionuclide Be-7 on the Long Duration Exposure Facility (LDEF), a search began for other known nuclides produced by similar mechanisms. None of the others have the narrow gamma-ray line emission of Be-7 decay which enabled its rapid detection and quantification. A search for Be-10 atoms on LDEF clamp plates using accelerator mass spectrometry is described. An unexpected result was obtained
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