The matter that surrounds us and that we are made off consists of atomic nuclei. These are composite particles bound together by the strong force. While we know the fundamental theory of the strong interactions, quantum chromodynamics, nuclei cannot be calculated in this framework. Rather, first principles calculations of these fundamental constituents of matter rely on the observed particles, neutrons and protons, and their interactions given in terms of chiral effective field theory as developed by Nobel laureate Steven Weinberg. However, despite many decades of developing nuclear many-body methods, ab initio calculations along the nuclear chart are not yet possible, except for the framework of nuclear lattice effective field theory (NLEFT) employed here. This rather novel method combines the effective nuclear forces with stochastic methods to solve the many-body problem. Such stochastic methods are often used in particle and condensed matter physics, but so far not in the realm of nuclear structure and reactions.
This projects aims at providing methods to investigate nuclei along the nuclear charts, their structure and reactions
and providing answers to a set of questions. These are: Frist, what are the limits of stability of nuclei? Adding additional protons and neutrons to a given nucleus final leads to the case that stability is lost. The precise location of these drip lines is pertinent to the study of element generation as investigated at radioactive beam facilities worldwide. The second set of questions concerns the third dimension of the nuclear chart, the study of the formation of hyper nuclei, where a neutron is substituted by a Lambda hyperon, which contains one valence strange quark, adding an extra dimension to the light up and down quarks. Our method shows a very mild scaling with atomic number $A$, quite in contrast to the conventional methods. This will allow us to map out the third dimension of the nuclear chart. Related to this is the influence of strangeness on the neutron matter equation of state, that is of prime importance to understanding the generation of gravitational waves in the mergers of two neutron stars. Third, the element generation in the Big Bang and in stars exhibits some fine-tuning, that is so far not understood. In our framework, we can vary the fundamental parameters of the Standard Model like the quark masses or the electromagnetic fine-structure constant, that governs the repulsion between the charged constituents of the nuclei, the protons. While these parameters can not be modified in experiment, our simulations allow to address alternative version of the universe with modified parameters, allowing to eventually address the question of how accidental life on Earth really is?
