Forskning ved Københavns Universitet - Københavns Universitet


Hamiltonian Nullspace Shuttles

Publikation: Bidrag til tidsskriftLetterForskningfagfællebedømt

We present a method to explore the effective nullspace of nonlinear inverse problems without Monte Carlo sampling. This is based on the construction of an artificial Hamiltonian system where a model is treated as a high-dimensional particle. Depending on its initial momentum and mass matrix, the particle evolves along a trajectory that traverses the effective nullspace, thereby producing a series of alternative models that are consistent with observations and their uncertainties. Variants of the nullspace shuttle enable hypothesis testing, for example, by adding features or by producing smoother or rougher models. Furthermore, the Hamiltonian nullspace shuttle can serve as a tunable hybrid between deterministic and probabilistic inversion methods: Choosing random initial momenta, it resembles Hamiltonian Monte Carlo; requiring misfits to decrease along a trajectory, it transforms into gradient descent. We illustrate the concept with a low-dimensional toy example and with high-dimensional nonlinear inversions of seismic traveltimes and magnetic data, respectively.

TidsskriftGeophysical Research Letters
Udgave nummer2
Sider (fra-til)644-651
Antal sider8
StatusUdgivet - 28 jan. 2019

ID: 230792846