Thermal-acoustic fermionic dynamics and primordial perturbations in warm Yukawa inflation

@misc{li2026thermalacoustic,
  title = {{Thermal-acoustic fermionic dynamics and primordial perturbations in warm Yukawa inflation}},
  author = {Xi-Bin Li and Ke Fu and Ya-Ting Wang and De-Tian Zhao and Xiao-Min Zhang},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.23029},
  eprint = {2609.23029},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.23029},
  note = {CC0},
}

TY  - UNPB
TI  - Thermal-acoustic fermionic dynamics and primordial perturbations in warm Yukawa inflation
AU  - Xi-Bin Li
AU  - Ke Fu
AU  - Ya-Ting Wang
AU  - De-Tian Zhao
AU  - Xiao-Min Zhang
PY  - 2026
DA  - 2026/09/19
PB  - arXiv
DO  - 10.48550/arxiv.2609.23029
UR  - https://arxiv.org/abs/2609.23029
AB  - We investigate fermion production and its cosmological consequences in a warm inflationary scenario with a Yukawa interaction between the inflaton field and Dirac fermions. Treating the produced fermions as a thermalized relativistic fluid, we derive the coupled perturbation equations incorporating dissipative effects and thermal fluctuations. By solving the resulting system through Green's function methods, we identify distinct contributions from thermal noise, thermal-acoustic propagation, and higher-order scattering processes to the scalar perturbations. We show that acoustic propagation of fermionic fluctuations becomes significant in the relativistic regime, where the competition between gravitational attraction and Pauli degeneracy pressure allows collective fermionic modes to influence the primordial spectrum. Furthermore, we calculate the fermion number density and acoustic velocity, revealing that strong Yukawa interactions enhance non-adiabatic fermion production and modify the thermodynamic properties of the fermion bath. The sourced scalar and tensor perturbations are calculated, indicating that fermion production can substantially amplify primordial fluctuations, particularly in the strong-coupling regime. Since scalar perturbations receive more efficient enhancement than tensor modes, the tensor-to-scalar ratio is suppressed relative to the standard single-field warm inflation prediction. Our results show that thermalized fermions provide an additional mechanism for modifying primordial perturbations and offer new insights into the role of particle production in warm inflationary cosmology.
ER  -