1,461 research outputs found
Inconsistency of the Wolf sunspot number series around 1848
Aims. Sunspot number is a benchmark series in many studies, but may still
contain inhomogeneities and inconsistencies. In particular, an essential
discrepancy exists between the two main sunspot number series, Wolf (WSN) and
group (GSN) sunspot numbers, before 1848. The source of this discrepancy has so
far remained unresolved. However, the recently digitized series of solar
observations in 1825-1867 by Samuel Heinrich Schwabe, who was the primary
observer of the WSN before 1848, makes such an assessment possible. Methods. We
construct sunspot series, similar to WSN and GSN, but using only Schwabe's
data. These series, called WSN-S and GSN-S, respectively, were compared with
the original WSN and GSN series for the period 1835-1867 to look for possible
inhomogeneities. Results. We show that: (1) The GSN series is homogeneous and
consistent with the Schwabe data throughout the entire studied period; (2) The
WSN series decreases by roughly ~20% around 1848 caused by the change of the
primary observer from Schwabe to Wolf and an inappropriate individual
correction factor used for Schwabe in the WSN; (3) This implies a major
inhomogeneity in the WSN, which needs to be corrected by reducing its values by
20% before 1848; (4) The corrected WSN series is in good agreement with the GSN
series. This study supports the earlier conclusions that the GSN series is more
consistent and homogeneous in the earlier part than the WSN series.Comment: Published as: Leussu, R., I.G. Usoskin, R. Arlt and K. Mursula,
Inconsistency of the Wolf sunspot number series around 1848, Astron.
Astrophys., 559, A28, 201
A Waveguide for Bose-Einstein Condensates
We report on the creation of Bose-Einstein condensates of Rb in a
specially designed hybrid, dipole and magnetic trap. This trap naturally allows
the coherent transfer of matter waves into a pure dipole potential waveguide
based on a doughnut beam. Specifically, we present studies of the coherence of
the ensemble in the hybrid trap and during the evolution in the waveguide by
means of an autocorrelation interferometer scheme. By monitoring the expansion
of the ensemble in the waveguide we observe a mean field dominated acceleration
on a much longer time scale than in the free 3D expansion. Both the
autocorrelation interference and the pure expansion measurements are in
excellent agreement with theoretical predictions of the ensemble dynamics
Importance of second-order piezoelectric effects in zincblende semiconductors
We show that the piezoelectric effect that describes the emergence of an
electric field in response to a crystal deformation in III-V semiconductors
such as GaAs and InAs has strong contributions from second-order effects that
have been neglected so far. We calculate the second-order piezoelectric tensors
using density functional theory and obtain the piezoelectric field for
[111]-oriented InGaAs quantum wells of realistic dimensions and
concentration . We find that the linear and the quadratic piezoelectric
coefficients have the opposite effect on the field, and for large strains the
quadratic terms even dominate. Thus, the piezoelectric field turns out to be a
rare example of a physical quantity for which the first- and second-order
contributions are of comparable magnitude.Comment: 4 pages, 3 figures, Submitted to Phys. Rev. Let
Satisfying the Einstein-Podolsky-Rosen criterion with massive particles
In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of
quantum mechanics by devising a quantum state of two massive particles with
maximally correlated space and momentum coordinates. The EPR criterion
qualifies such continuous-variable entangled states, where a measurement of one
subsystem seemingly allows for a prediction of the second subsystem beyond the
Heisenberg uncertainty relation. Up to now, continuous-variable EPR
correlations have only been created with photons, while the demonstration of
such strongly correlated states with massive particles is still outstanding.
Here, we report on the creation of an EPR-correlated two-mode squeezed state in
an ultracold atomic ensemble. The state shows an EPR entanglement parameter of
0.18(3), which is 2.4 standard deviations below the threshold 1/4 of the EPR
criterion. We also present a full tomographic reconstruction of the underlying
many-particle quantum state. The state presents a resource for tests of quantum
nonlocality and a wide variety of applications in the field of
continuous-variable quantum information and metrology.Comment: 8 pages, 7 figure
Dynamics of F=2 Spinor Bose-Einstein Condensates
We experimentally investigate and analyze the rich dynamics in F=2 spinor
Bose-Einstein condensates of Rb87. An interplay between mean-field driven spin
dynamics and hyperfine-changing losses in addition to interactions with the
thermal component is observed. In particular we measure conversion rates in the
range of 10^-12 cm^3/s for spin changing collisions within the F=2 manifold and
spin-dependent loss rates in the range of 10^-13 cm^3/s for hyperfine-changing
collisions. From our data we observe a polar behavior in the F=2 ground state
of Rb87, while we measure the F=1 ground state to be ferromagnetic. Furthermore
we see a magnetization for condensates prepared with non-zero total spin.Comment: 4 pages, 2 figures, RevTe
Interaction of martensitic microstructures in adjacent grains
It is often observed that martensitic microstructures in adjacent polycrystal
grains are related. For example, micrographs of Arlt exhibit propagation of
layered structures across grain boundaries in the cubic-to-tetragonal phase
transformation in . Such observations are related to requirements
of compatibility of the deformation at the grain boundary. Using a
generalization of the Hadamard jump condition, this is explored in the
nonlinear elasticity model of martensitic transformations for the case of a
bicrystal with suitably oriented columnar geometry, in which the microstructure
in both grains is assumed to involve just two martensitic variants, with a
planar or non-planar interface between the grains.Comment: 6 pages, 1 figure, submitted to ICOMAT 2017 Proceeding
Second Order Correlation Function of a Phase Fluctuating Bose-Einstein Condensate
The coherence properties of phase fluctuating Bose-Einstein condensates are
studied both theoretically and experimentally. We derive a general expression
for the N-particle correlation function of a condensed Bose gas in a highly
elongated trapping potential. The second order correlation function is analyzed
in detail and an interferometric method to directly measure it is discussed and
experimentally implemented. Using a Bragg diffraction interferometer, we
measure intensity correlations in the interference pattern generated by two
spatially displaced copies of a parent condensate. Our experiment demonstrates
how to characterize the second order correlation function of a highly elongated
condensate and to measure its phase coherence length.Comment: 22 pages, 5 figure
- …