An update on fine-tunings in the triple-alpha process

Abstract

The triple-alpha process, whereby evolved stars create carbon and oxygen, is believed to be fine-tuned to a high degree. Such fine-tuning is suggested by the unusually strong temperature dependence of the triple-alpha reaction rate at stellar temperatures. This sensitivity is due to the resonant character of the triple-alpha process, which proceeds through the so-called "Hoyle state" of ${}^{12}$C with spin-parity $0^{+}$. The question of fine-tuning can be studied within the {\it ab initio} framework of nuclear lattice effective field theory, which makes it possible to relate {\it ad hoc} changes in the energy of the Hoyle state to changes in the fundamental parameters of the nuclear Hamiltonian, which are the light quark mass $m_q$ and the electromagnetic fine-structure constant. Here, we update the effective field theory calculation of the sensitivity of the triple-alpha process to small changes in the fundamental parameters. In particular, we consider recent high-precision lattice QCD calculations of the nucleon axial coupling $g_A$, as well as new and more comprehensive results from stellar simulations of the production of carbon and oxygen. While the updated stellar simulations allow for much larger {\it ad hoc} shifts in the Hoyle state energy than previously thought, recent lattice QCD results for the nucleon S-wave singlet and triplet scattering lengths now disfavor the scenario of no fine-tuning in the light quark mass $m_q$.

9 pages, 2 figures, contribution to the EPJA topical issue on "The tower of effective (field) theories and the emergence of nuclear phenomena"

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Cited by in corpus (6)

• 50 Years of Quantum Chromodynamics
• Nuclear Currents in Chiral Effective Field Theory
• $\theta$-dependence of light nuclei and nucleosynthesis
• Alpha-alpha scattering in the Multiverse
• Subleading contributions to the nuclear scalar isoscalar currents
• Improved Constraints on the Variation of the Weak Scale from Big Bang Nucleosynthesis