arXiv subjects

Ryan Benazzouk

Publications and source records attributed to Ryan Benazzouk.

2 recordsLinked to original sources

arXiv2026

Exploiting floating point emulation in tensor contractions in relativistic coupled cluster theory

In this manuscript we outline a computational strategy to leverage a vendor-optimized implementation of the Ozaki scheme I for floating point emulation as part of an implementation of the Transpose-Transpose-GEMM-Transpose (TTGT) pattern for tensor contractions, and assess its potential to accelerate two of the most expensive tensor contractions appearing in relativistic coupled cluster theory in high-end accelerators such as the NVIDIA Blackwell B200 system in which there is a strong differential in the performance of computations for double and lower precision datatypes. Our results indicate that this emulation-based TTGT strategy can provide significant speedups compared to runs without emulation, and can be competitive with state-of-the-art, vendor-optimized tensor contraction libraries using native double precision as compute datatype. More importantly, our scheme provides a path towards easily allowing users to tune the desired accuracy in the tensor contraction steps, including cases where precision between single and double is sufficient for the application.

physics.chem-ph↗

arXiv2025

Wichmann-Kroll vacuum polarization density in a finite Gaussian basis set

This work further develops the calculation of QED effects in a finite Gaussian basis. We focus on the non-linear $α(Zα)^{n\ge 3}$ contribution to the vacuum polarization density, computing the energy shift of 1s$_{1/2}$ states of hydrogen-like ions. Our goal is to improve the numerical computations to achieve a precision comparable to that of Green's function methods reported in the literature. To do so, an analytic expression for the linear contribution to the vacuum polarization density is derived using Riesz projectors. Alternative formulations of the vacuum polarization density and their relation is discussed. The convergence of the finite Gaussian basis scheme is investigated, and the numerical difficulties that arise are characterized. In particular, an error analysis is performed to assess the method's robustness to numerical noise. We then report a strategy for computing the energy shift with sufficient precision to enable a sensible extrapolation of the partial-wave expansion. A key feature of the procedure is the use of even-tempered basis sets, allowing for an extrapolation towards the complete basis set limit.

quant-ph↗