English

Effective reheating in Gauss--Bonnet inflation with $μ(φ,X)$ coupling

Cosmology and Nongalactic Astrophysics 2026-08-03 v1

Abstract

We study effective reheating in a scalar--Gauss--Bonnet inflationary model with a phase-space-dependent coupling μ(ϕ,X)\mu(\phi,X), in which a compact field-space feature is combined with a bounded kinetic gate. The modified inflationary background determines the pivot-scale quantities and the effective energy density at the end of inflation. These quantities are then used to derive the reheating duration NreN_{\rm re} and temperature TreT_{\rm re} through the thermal-history matching relation. We first perform two fixed-pivot reference scans by varying the overall Gauss--Bonnet strength λGB\lambda_{\rm GB} and the kinetic parameter gXg_{_X} separately. For the reference parameter choices, increasing either parameter increases NreN_{\rm re} and decreases TreT_{\rm re} for the selected reheating equations of state. Additional benchmark calculations clarify how these variations depend on the dynamical regime of the model. In the λGB\lambda_{\rm GB} scan, the increase in NreN_{\rm re} and the decrease in TreT_{\rm re} persist, although both variations become strongly suppressed when the coupling is more localized or when the end of inflation is controlled more strongly by the E-model potential. In the gXg_{_X} scan, stronger field-space localization and kinetic saturation can instead lead to a slight decrease in NreN_{\rm re} and an increase in TreT_{\rm re} as gXg_{_X} is increased. When the bounded kinetic contribution is considered together with a weaker overall Gauss--Bonnet interaction, the resulting changes in the reheating quantities become nearly negligible. The fixed-pivot predictions of the representative and alternative benchmarks are compared with CMB constraints.These reheating constraints are then discussed for four representative values of the effective equation-of-state parameter, wre=1/3,0,2/3,\overline{w}_{\rm re}=-1/3,0,2/3, and 11.

Keywords

Cite

@article{arxiv.2608.02506,
  title  = {Effective reheating in Gauss--Bonnet inflation with $μ(φ,X)$ coupling},
  author = {Ali Seidabadi and Sara Saghafi and Kourosh Nozari},
  journal= {arXiv preprint arXiv:2608.02506},
  year   = {2026}
}

Comments

25 pages, 7 figures, 9 tables