Physics and Astronomy Colloquium

The twin mysteries of dark energy and dark matter are driving the
development and refinement of cosmological observations to remarkable
levels. Next-generation cosmological surveys aim to exploit structure
formation probes of the dynamics of the Universe at accuracy levels of the
order of fractions of a percent. In order for these ambitious targets to
be reached, theory must keep pace with observational advances: Weak
gravitational lensing as a probe of the mass distribution offers a
prominent example where observations are already theory-limited. In this
talk I will describe some of these hurdles, and present recent work on how
they can be overcome.