299 research outputs found
Restoring size consistency of approximate functionals constructed from the adiabatic connection
Approximate exchange-correlation functionals built by modeling in a
non-linear way the adiabatic connection (AC) integrand of density functional
theory have many attractive features, being virtually parameters-free and
satisfying different exact properties, but they also have a fundamental flaw:
they violate the size-consistency condition, crucial to evaluate interaction
energies of molecular systems. We show that size consistency in the AC-based
functionals can be restored in a very simple way at no extra computational
cost. Results on a large set of benchmark molecular interaction energies show
that functionals based on the interaction strength interpolation approximations
are significantly more accurate than the second-order perturbation theory.Comment: 6 pages, 3 figure
Data-driven acceleration of Photonic Simulations
Designing modern photonic devices often involves traversing a large parameter
space via an optimization procedure, gradient based or otherwise, and typically
results in the designer performing electromagnetic simulations of correlated
devices. In this paper, we present an approach to accelerate the Generalized
Minimal Residual (GMRES) algorithm for the solution of frequency-domain
Maxwell's equations using two machine learning models (principal component
analysis and a convolutional neural network) trained on simulations of
correlated devices. These data-driven models are trained to predict a subspace
within which the solution of the frequency-domain Maxwell's equations lie. This
subspace can then be used for augmenting the Krylov subspace generated during
the GMRES iterations. By training the proposed models on a dataset of grating
wavelength-splitting devices, we show an order of magnitude reduction () in the number of GMRES iterations required for solving frequency-domain
Maxwell's equations
Periodic mass loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD50064
We aim to interpret the photometric and spectroscopic variability of the
luminous blue variable supergiant HD\,50064 ().CoRoT space photometry
and follow-up high-resolution spectroscopy, with a time base of 137\,d and
169\,d, respectively, was gathered, analysed and interpreted using standard
time series analysis and light curve modelling methods as well as spectral line
diagnostics.The space photometry reveals one period of 37\,d, which undergoes a
sudden amplitude change with a factor 1.6. The pulsation period is confirmed in
the spectroscopy, which additionally reveals metal line radial velocity values
differing by km\,s depending on the spectral line and on the
epoch. We estimate \teff13\,500\,K, \logg1.5 from the equivalent
width of Si lines. The Balmer lines reveal that the star undergoes episodes of
changing mass loss on a time scale similar to the changes in the photometric
and spectroscopic variability, with an average value of (in M\,yr). We tentatively interpret the 37\,d
period as due to a strange mode oscillation.Comment: 4 pages, accepted for publication in Astronomy & Astrophysics Letter
Optimal generation of indistinguishable photons from non-identical artificial molecules
We show theoretically that nearly indistinguishable photons can be generated
with non-identical semiconductor-based sources. The use of virtual Raman
transitions and the optimization of the external driving fields increases the
tolerance to spectral inhomogeneity to the meV energy range. A trade-off
emerges between photon indistinguishability and efficiency in the
photon-generation process. Linear (quadratic) dependence of the coincidence
probability within the Hong-Ou-Mandel setup is found with respect to the
dephasing (relaxation) rate in the semiconductor sources
Trace N-glycans including sulphated species may originate from various plasma glycoproteins and not necessarily IgG
Proteomic
CoRoT observations of O stars: diverse origins of variability
Six O-type stars were observed continuously by the CoRoT satellite during a
34.3-day run. The unprecedented quality of the data allows us to detect even
low-amplitude stellar pulsations in some of these stars (HD 46202 and the
binaries HD 46149 and Plaskett's star). These cover both opacity-driven modes
and solar-like stochastic oscillations, both of importance to the
asteroseismological modelling of O stars. Additional effects can be seen in the
CoRoT light curves, such as binarity and rotational modulation. Some of the
hottest O-type stars (HD 46223, HD 46150 and HD 46966) are dominated by the
presence of red-noise: we speculate that this is related to a sub-surface
convection zone.Comment: 5 pages, 3 figures, conference paper. To be published in "Four
decades of Research on Massive Stars", Astronomical Society of the Pacific.
Eds. C. Robert, N. St-Louis and L. Drisse
Experimental realization of a low-noise heralded single photon source
We present a heralded single-photon source with a much lower level of
unwanted background photons in the output channel by using the herald photon to
control a shutter in the heralded channel. The shutter is implemented using a
simple field programable gate array controlled optical switch.Comment: 4 pages, 5 figure
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