2,219 research outputs found
QED correction for H
A quantum electrodynamics (QED) correction surface for the simplest
polyatomic and polyelectronic system H is computed using an approximate
procedure. This surface is used to calculate the shifts to vibration-rotation
energy levels due to QED; such shifts have a magnitude of up to 0.25 cm
for vibrational levels up to 15~000 cm and are expected to have an
accuracy of about 0.02 cm. Combining the new H QED correction
surface with existing highly accurate Born-Oppenheimer (BO), relativistic and
adiabatic components suggests that deviations of the resulting {\it ab initio}
energy levels from observed ones are largely due to non-adiabatic effects
Learning to handle parameter perturbations in Combinatorial Optimization: An application to facility location
We present an approach to couple the resolution of Combinatorial Optimization problems with methods from Machine Learning. Specifically, our study is framed in the context where a reference discrete optimization problem is given and there exist data for many variations of such reference problem (historical or simulated) along with their optimal solution. Those variations can be originated by disruption but this is not necessarily the case. We study how one can exploit these to make predictions about an unseen new variation of the reference instance. The methodology is composed by two steps. We demonstrate how a classifier can be built from these data to determine whether the solution to the reference problem still applies to a perturbed instance. In case the reference solution is only partially applicable, we build a regressor indicating the magnitude of the expected change, and conversely how much of it can be kept for the perturbed instance. This insight, derived from a priori information, is expressed via an additional constraint in the original mathematical programming formulation. We present the methodology through an application to the classical facility location problem and we provide an empirical evaluation and discuss the benefits, drawbacks and perspectives of such an approach. Although it cannot be used in a black-box manner, i.e., it has to be adapted to the specific application at hand, we believe that the approach developed here is general and explores a new perspective on the exploitation of past experience in Combinatorial Optimization
ExoMol molecular line lists XXX: a complete high-accuracy line list for water
A new line list for HO is presented. This line list, which is
called POKAZATEL, includes transitions between rotation-vibrational energy
levels up to 41000 cm in energy and is the most complete to date. The
potential energy surface (PES) used for producing the line list was obtained by
fitting a high-quality ab initio PES to experimental energy levels with
energies of 41000 cm and for rotational excitations up to . The
final line list comprises all energy levels up to 41000 cm and
rotational angular momentum up to 72. An accurate ab initio dipole moment
surface (DMS) was used for the calculation of line intensities and reproduces
high-precision experimental intensity data with an accuracy close to 1 %. The
final line list uses empirical energy levels whenever they are available, to
ensure that line positions are reproduced as accurately as possible. The
POKAZATEL line list contains over 5 billion transitions and is available from
the ExoMol website (www.exomol.com) and the CDS database
High accuracy CO line intensities determined from theory and experiment
Atmospheric CO concentrations are being closely monitored by remote
sensing experiments which rely on knowing line intensities with an uncertainty
of 0.5\%\ or better. Most available laboratory measurements have uncertainties
much larger than this. We report a joint experimental and theoretical study
providing rotation-vibration line intensities with the required accuracy. The
{\it ab initio} calculations are extendible to all atmospherically important
bands of CO and to its isotologues. As such they will form the basis for
detailed CO spectroscopic line lists for future studies.Comment: 5 pages, 2 figures, 1 tabl
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