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We demonstrate a simple method to improve the Lewenstein model for the description of high-order harmonic generation (HHG). It is shown that HHG spectra can be expressed as the product of a returning electron wave packet and the…

Atomic Physics · Physics 2007-07-31 Anh-Thu Le , Toru Morishita , C. D. Lin

High-order harmonic generation (HHG) is investigated for H$_2^+$ and its isotopomers under seven- and ten-cycle trapezoidal laser pulses at 800 nm wavelength and $I$=4$\times 10^{14}$ W$/$cm$^2$ intensity. We solved numerically…

Atomic Physics · Physics 2016-03-03 H. Ahmadi , M. Vafaee , A. Maghari

This work proposes a scalable probabilistic latent variable model based on Gaussian processes (Lawrence, 2004) in the context of multiple observation spaces. We focus on an application in astrophysics where data sets typically contain both…

Astrophysics of Galaxies · Physics 2025-02-28 Vidhi Lalchand , Anna-Christina Eilers

A recurrent theme in functional analysis is the interplay between the theory of positive definite functions, and their reproducing kernels, on the one hand, and Gaussian stochastic processes, on the other. This central theme is motivated by…

Functional Analysis · Mathematics 2012-08-15 Daniel Alpay , Palle Jorgensen

Gaussian processes are probabilistic models that are commonly used as functional priors in machine learning. Due to their probabilistic nature, they can be used to capture the prior information on the statistics of noise, smoothness of the…

Computation · Statistics 2024-02-02 Ahmad Farooq , Cristian A. Galvis-Florez , Simo Särkkä

In this work, we propose a novel generative model for mapping inputs to structured, high-dimensional outputs using structured conditional normalizing flows and Gaussian process regression. The model is motivated by the need to characterize…

Machine Learning · Computer Science 2022-12-16 Natalie Klein , Nishant Panda , Patrick Gasda , Diane Oyen

Molecular calculations in quantum Monte Carlo frequently employ a mixed basis consisting of contracted and primitive Gaussian functions. While standard basis sets of varying size and accuracy are available in the literature, we demonstrate…

Chemical Physics · Physics 2015-05-14 F. R. Petruzielo , Julien Toulouse , C. J. Umrigar

We present ab initio calculations using the $R$-matrix with time dependence (RMT) method for high-order harmonic generation (HHG) in argon in a short, intense pulse regime. The calculations employ a $6$-cycle $\sin^2$ pulse at $850$ nm with…

Atomic Physics · Physics 2026-04-23 Aaron T. Bondy , Klaus Bartschat

This work is concerned with the construction of Gaussian Beam (GB) solutions for the numerical approximation of wave equations, semi-discretized in space by finite difference schemes. GB are high-frequency solutions whose propagation can be…

Analysis of PDEs · Mathematics 2023-06-12 Umberto Biccari , Enrique Zuazua

The selection rules of high harmonic generation (HHG) are investigated using three-dimensional time-dependent density functional theory (TDDFT). From the harmonic spectra obtained with various real molecules and different forms of laser…

Atomic Physics · Physics 2016-09-28 Xi Liu , Xiaosong Zhu , Liang Li , Yang Li , Qingbin Zhang , Pengfei Lan , Peixiang Lu

Gaussian kernels can be an efficient and accurate tool for multivariate interpolation. In practice, high accuracies are often achieved in the flat limit where the interpolation matrix becomes increasingly ill-conditioned. Stable evaluation…

Numerical Analysis · Mathematics 2019-12-12 Katharina Kormann , Caroline Lasser , Anna Yurova

The use of Gaussian processes (GPs) is supported by efficient sampling algorithms, a rich methodological literature, and strong theoretical grounding. However, due to their prohibitive computation and storage demands, the use of exact GPs…

Statistics Theory · Mathematics 2022-07-27 Kelly R. Moran , Matthew W. Wheeler

A representation of polymer self-consistent field theory equivalent to quantum density functional theory is given in terms of non-orthogonal basis sets. Molecular integrals and self-consistent equations for spherically symmetric systems…

Atomic Physics · Physics 2026-02-05 Phil A. LeMaitre , Russell B. Thompson

This work explores the application of the fast assembly and formation strategy from [8, 17] to trimmed bi-variate parameter spaces. Two concepts for the treatment of basis functions cut by the trimming curve are investigated: one employs a…

Computational Engineering, Finance, and Science · Computer Science 2023-08-29 Benjamin Marussig

High harmonic generation (HHG) is an extremely nonlinear effect, where a medium is driven by a strong laser field, generating coherent broadband radiation with photon energies ranging up to the X-ray and pulse durations reaching attosecond…

Optics · Physics 2020-10-20 Alexey Gorlach , Ofer Neufeld , Nicholas Rivera , Oren Cohen , Ido Kaminer

We give a detailed account of an $\it{ab}$ $\it{initio}$ spectral approach for the calculation of energy spectra of two active electron atoms in a system of hyperspherical coordinates. In this system of coordinates, the Hamiltonian has the…

Computation of high frequency solutions to wave equations is important in many applications, and notoriously difficult in resolving wave oscillations. Gaussian beams are asymptotically valid high frequency solutions concentrated on a single…

Analysis of PDEs · Mathematics 2009-06-17 Hailiang Liu , James Ralston

A theoretical model for high-order harmonic generation (HHG) in bulk solids is considered. Our approach treats laser-induced inter- and intraband currents on an equal footing. The sum of these currents is the source of the high-order…

Quantum Physics · Physics 2017-07-12 Peter Foldi

This work further develops the calculation of QED effects in a finite Gaussian basis. We focus on the non-linear ${\alpha}(Z{\alpha})^{n\ge 3}$ contribution to the vacuum polarization density, computing the energy shift of 1s$_{1/2}$ states…

Quantum Physics · Physics 2025-12-19 Ryan Benazzouk , Maen Salman , Trond Saue

A basis set of generalized nonspherical Gaussian functions (GGTOs) is presented and discussed. As a first example we report on Born-Oppenheimer energies of the hydrogen molecule. Although accurate results have been obtained, we conclude…

Chemical Physics · Physics 2009-10-31 T. Detmer , P. Schmelcher , L. S. Cederbaum