Lena Ostrowski

Lena Ostrowski is a computational scientist whose work sits where physics, numerical analysis, and optimization meet: the inverse problem of inferring a hidden field — a subsurface velocity model, a tissue's stiffness, a contaminant's source — from indirect, noisy measurements. Over two decades she has built and broken solvers for full-waveform inversion in seismic exploration, for tomographic reconstruction in medical imaging, and for parameter estimation in groundwater and environmental flow.

For most of those years the hardest part of every project was the same: deriving, implementing, and debugging the adjoint equations that supply the gradient. She wrote adjoints by hand, checked them against finite differences, and watched projects stall for months on a single sign error in a chain rule. When reverse-mode automatic differentiation matured into tools a working scientist could actually use, she recognized it for what it was — not a machine-learning fashion, but a quiet revolution in how the adjoint method is practiced. The gradient that once cost a graduate student a season now came, exact, almost for free. The mathematics did not change; the labor did.

Her teaching and her writing grew out of that shift. She is known for a plain, exacting style: she motivates a tool only by what it measurably buys, states the mathematics precisely, and refuses to let a reconstruction stand without the verification that earns it — the gradient check, the convergence study, the honest error bar. She is equally clear about the limits. When a problem is low-dimensional, or has a clean closed-form Jacobian, or yields to a dedicated solver, she says so and reaches for the classical method. That candor — knowing when a program should not be differentiated through at all — is, in her view, the mark of a practitioner rather than an enthusiast.

She writes for the working scientist who wants the method and the runnable code in one place, with nothing hand-waved and every result reproducible from the code that computed it. She lives in Poland.