Computer Simulations and the Need for Nuclear Weapon Testing

At least since 1998, we know that the main nuclear weapons states are using computer simulations aimed at having the capability of designing new nuclear weapons without conducting any nuclear test, among other relevant jobs in which computer simulations are used. Currently, three important developments have increased the power of computer simulations: a) the development of new supercomputers with a tremendous capacity for processing and realising complex jobs; b) the accumulation of billions of data useful for simulations considering the number of nuclear tests conducted in the past and the results of computer simulations, and c) the recent developments of powerful AI foundation models with billions of parameters that can be used in nuclear weapon design very successful. The dominant thesis, since 2002, is that experiments using simulants to replace nuclear materials are permitted under the Comprehensive Test Ban Treaty (CTBT). What this means is that states can develop new nuclear weapons complying with the CTBT, but this, I consider, is contrary to the goal of the CTBT and CTBTO. Nuclear proliferation was expected during the first two decades of the 21st century. However, in the current global geopolitical situation, where other forms of nuclear proliferation are observed, these computer simulations pose challenges to the CTBT and CTBTO.