Big Bang Nucleosynthesis constraints on Barrow entropy

We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on the exponent of Barrow entropy. The latter is an extended entropy relation arising from the incorporation of quantum-gravitational effects on the black-hole structure, parameterized effectively by the new parameter Delta. When considered in a cosmological framework and under the light of the gravity-thermodynamics conjecture, Barrow entropy leads to modified cosmological scenarios whose Friedmann equations contain extra terms. We perform a detailed analysis of the BBN era and we calculate the deviation of the freeze-out temperature comparing to the result of standard cosmology. We use the observationally determined bound on vertical bar delta T-f/T-f vertical bar in order to extract the upper bound on Delta. As we find, the Barrow exponent should be inside the bound Delta less than or similar to 1.4 x 10(-4) in order not to spoil the BBN epoch, which shows that the deformation from standard Bekenstein-Hawking expression should be small as expected. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

By utilizing Big Bang Nucleosynthesis (BBN) data, constraints were imposed on the exponent of Barrow entropy, finding that it should be within a certain range to avoid affecting the BBN epoch.