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From Chiral EFT to Perturbative QCD: A Bayesian Model Mixing Approach to Symmetric Nuclear Matter

Talk by Alexandra Semposki from Ohio University on April 16, 2024 Abstract: Constraining the equation of state (EOS) of strongly interacting, dense matter is the focus of intense experimental, observational, and theoretical effort. Chiral effective field theory (ChEFT) can describe the EOS at densities up to twice nuclear saturation density (n0), while perturbative QCD (pQCD) can be applied to properties of deconfined quark matter. The uncertainty due to truncation of the perturbative series at a finite order can be quantified for both theories using a single methodology, developed by the BUQEYE collaboration, that I will explain in my talk. However, this still leaves uncertainty quantification for the EOS in the intermediate region between 2n0 and (20-40)n0 as an unsolved problem. To bridge this gap between ChEFT and pQCD, we employ Bayesian model mixing (BMM) techniques we are developing for the BAND collaboration’s cyberinfrastructure framework. Specifically, we combine Gaussian random variables that constitute the predictions from each theory for the pressure as a function of the density in symmetric nuclear matter. In this FRIB theory seminar, I will present results from our recent arXiv submission for the pressure and speed of sound squared of symmetric nuclear matter. These results were obtained from the application of two BMM approaches: a pointwise approach, and a correlated approach implemented via a Gaussian process (GP), the latter of which allows for inclusion of full covariance information from both theories to the model mixing. I will also discuss extensions of this work for future improvements and applications to neutron-rich matter.