Why trust cosmological simulations? A closer look from the V&V perspective

Computer simulations play an important role in current cosmology. In particular, they are used to trace the evolution of dark matter and visible galaxies for alternative cosmological models. Some problems for the currently popular concordance model, e.g., the core cusp problem, crucially involve simulations. But why should we trust such simulations? Practicing simulation scientists often answer questions of this type by referring to a battery of tests to which they subject their simulations. These tests are summarized under the label “V&V” for verification and validation. Very recently, the methods of V&V have drawn the attention of philosophers of science. The aim of this talk is to bring the philosophical literature on V&V to bear on cosmological simulations. To this purpose, I discuss the simulations in view of the so-called Sargent cycle. I argue that the verification of cosmological simulations is essential, which is evident from the fact that potential numerical artefacts are an important issue. I further analyze the tests that are used to achieve verification of the simulations and discuss the relation to the validation of the conceptual model. A main result from my analysis is that the difficulty to secure data of cosmological import is not a severe problem for the credibility of cosmological simulations