Nuclear Reactions Important for Astrophysics from \textit{Ab Initio} Theory

In recent years, significant progress has been made in \textit{ab initio} nuclear structure and dynamics calculations employing Hamiltonians constructed within chiral effective field theory. We have developed an approach, the No-Core Shell Model with Continuum (NCSMC) [1,2], capable of describing both bound and unbound states in light nuclei in a unified way. We will discuss applications of NCSMC to nuclear reactions important for astrophysics and present results for the neutron radiative capture reactions $^{\mathrm{8}}$Li(n,$\gamma )^{\mathrm{9}}$Li and $^{\mathrm{14}}$C(n,$\gamma )^{\mathrm{15}}$C, for the proton radiative capture reactions $^{\mathrm{11}}$C(p,$\gamma )^{\mathrm{12}}$N and $^{\mathrm{7}}$Be(p,$\gamma )^{\mathrm{8}}$B as well as for the $^{\mathrm{3}}$He($\alpha \gamma )^{\mathrm{7}}$Be radiative alpha capture. The $^{\mathrm{7}}$Be(p,$\gamma )^{\mathrm{8}}$B and $^{\mathrm{3}}$He($\alpha \gamma )^{\mathrm{7}}$Be reactions in particular play a role in Solar nucleosynthesis and neutrino physics and have been subject of numerous experimental investigations including ongoing measurements at TRIUMF.~Finally, we will highlight our recent calculations hinting at a possible near-threshold $S$-wave resonance in $^{\mathrm{6}}$He$+$p [3] that might have implications for astrophysics. [1] S. Baroni, P. Navr\'{a}til, and S. Quaglioni, PRL \textbf{110}, 022505 (2013). [2] P. Navr\'{a}til, S. Quaglioni, G. Hupin, C. Romero-Redondo, A. Calci, Phys. Scr \textbf{91}, 053002 (2016). [3] M. Vorabbi, P. Navr\'{a}til, S. Quaglioni, G. Hupin, PRC \textbf{100}, 024304 (2019).