# What is Ab initio?

**Ab initio** approaches in nuclear physics attempt to characterize the atomic nucleus from the bottom up by solving the non-relativistic Schrodinger equation for all component nucleons and their interactions. For very light nuclei (up to four nucleons), this is done precisely, but for heavier nuclei, certain well-controlled estimates are used.

However, in comparison to the nuclear shell model, ab initio approaches offer a more fundamental approach. Ab initio treatment of heavier nuclei, such as nickel, has recently become possible thanks to recent advances.

The complexity of the inter-nucleon interaction poses a substantial hurdle in the ab initio approach. Although quantum chromodynamics (QCD) is non-perturbative in the low-energy regime relevant to nuclear physics. The strong nuclear force suggests deriving from the strong interaction represented by QCD. This makes it difficult to apply QCD directly to describe inter-nucleon interactions (see lattice QCD), hence a model implement instead.

Chiral effective field theory is the basis for the most advanced models. All interactions consistent with the symmetries of QCD include in this effective field theory (EFT), which sort by the size of their participation.

Nucleons and pions, rather than quarks and gluons, are the degrees of freedom in this theory. Low-energy constants are parameters in the effective theory. It calculates from scattered data.

Chiral EFT indicates the presence of many-body forces. The most notable of the three-nucleon relationship call a key component of the nuclear many-body issue.

The SchrÃ¶dinger equation solves after getting a Hamiltonian trending styles HH (depending on chiral EFT or other models.

Here the symbol in the equation is the many-body wavefunction of the A nucleons in the nucleus, and the vert Psi range is the many-body wavefunction of the A nucleons in the nucleus. Different ab initio methods devise to quantitatively find solutions to this problem.