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Ali Seidabadi

Publications and source records attributed to Ali Seidabadi.

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Effective reheating in Gauss--Bonnet inflation with $\mu(\phi,X)$ coupling

We study effective reheating in a scalar--Gauss--Bonnet inflationary model with a phase-space-dependent coupling $\mu(\phi,X)$, 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 $N_{\rm re}$ and temperature $T_{\rm re}$ through the thermal-history matching relation. We first perform two fixed-pivot reference scans by varying the overall Gauss--Bonnet strength $\lambda_{\rm GB}$ and the kinetic parameter $g_{_X}$ separately. For the reference parameter choices, increasing either parameter increases $N_{\rm re}$ and decreases $T_{\rm re}$ for the selected reheating equations of state. Additional benchmark calculations clarify how these variations depend on the dynamical regime of the model. In the $\lambda_{\rm GB}$ scan, the increase in $N_{\rm re}$ and the decrease in $T_{\rm re}$ 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 $g_{_X}$ scan, stronger field-space localization and kinetic saturation can instead lead to a slight decrease in $N_{\rm re}$ and an increase in $T_{\rm re}$ as $g_{_X}$ 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, $\overline{w}_{\rm re}=-1/3,0,2/3,$ and $1$.

astro-ph.CO

Beyond $f(\phi)\mathcal{G}$: Gauss--Bonnet inflation with $\mu(\phi,X)$

Gauss--Bonnet inflation typically affects the dynamics over an extended portion of the trajectory, making it difficult to isolate a controlled imprint at CMB scales. We consider a trajectory-selective coupling \(\mu(\phi,X)\) that gates the Gauss--Bonnet sector in phase space, enabling the higher-curvature contribution to be localized within a finite e-fold window while remaining negligible elsewhere. We identify stable inflationary solutions consistent with this localization and enforce standard ghost and gradient stability conditions for both scalar and tensor perturbations. For these viable backgrounds we compute pivot-scale observables and examine their dependence on the overall Gauss--Bonnet strength and on the kinetic gating. The framework offers a controlled route for realizing localized higher-curvature effects with predictable consequences for CMB-scale measurements.

astro-ph.CO