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Warm Inflation in a Braneworld Scenario

Sabina Yeasmin, Atri Deshamukhya

TL;DR

This work investigates warm inflation on a brane-world cosmology with a natural axion-like potential, incorporating both constant and temperature-dependent dissipation and analyzing weak ($Q\ll1$) and strong ($Q\gg1$) regimes. The authors derive the brane-modified background dynamics, slow-roll conditions, and a perturbation framework that includes thermal noise via a G(Q) factor in the scalar spectrum and a tensor spectrum P_T, with the tensor-to-scalar ratio r and spectral index n_s defined accordingly. They constrain the model using Planck 2018 and BK18 data, finding viable parameter spaces in both dissipation regimes for the constants Γ0 and C_Γ as well as for the five-dimensional Planck mass M5, and they show that the axion decay constant f remains sub-Planckian, improving theoretical consistency. Overall, the results demonstrate that warm inflation with a brane-world correction and axion-like potential can be compatible with current cosmological observations across a wide range of dissipation scenarios, highlighting the viability of brane-based warm inflation models.

Abstract

In the literature, many warm inflationary models are formulated. In this piece of work, a warm inflationary model in the braneworld scenario is studied, considering constant and variable dissipation coefficients. Performance of the model has been considered in both strong and weak dissipative regimes. We study the dynamics of this scenario under slow-roll approximation and estimate cosmological observables, viz., the spectral index and tensor-to-scalar ratio. In order to constrain the parameters in our model, we consider data from Planck 2018 and BICEP.

Warm Inflation in a Braneworld Scenario

TL;DR

This work investigates warm inflation on a brane-world cosmology with a natural axion-like potential, incorporating both constant and temperature-dependent dissipation and analyzing weak () and strong () regimes. The authors derive the brane-modified background dynamics, slow-roll conditions, and a perturbation framework that includes thermal noise via a G(Q) factor in the scalar spectrum and a tensor spectrum P_T, with the tensor-to-scalar ratio r and spectral index n_s defined accordingly. They constrain the model using Planck 2018 and BK18 data, finding viable parameter spaces in both dissipation regimes for the constants Γ0 and C_Γ as well as for the five-dimensional Planck mass M5, and they show that the axion decay constant f remains sub-Planckian, improving theoretical consistency. Overall, the results demonstrate that warm inflation with a brane-world correction and axion-like potential can be compatible with current cosmological observations across a wide range of dissipation scenarios, highlighting the viability of brane-based warm inflation models.

Abstract

In the literature, many warm inflationary models are formulated. In this piece of work, a warm inflationary model in the braneworld scenario is studied, considering constant and variable dissipation coefficients. Performance of the model has been considered in both strong and weak dissipative regimes. We study the dynamics of this scenario under slow-roll approximation and estimate cosmological observables, viz., the spectral index and tensor-to-scalar ratio. In order to constrain the parameters in our model, we consider data from Planck 2018 and BICEP.

Paper Structure

This paper contains 11 sections, 64 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Warm inflation dynamics in the braneworld scenario
  3. Perturbation calculation
  4. Dynamics of axion-like particles
  5. Numerical results in high energy ($V\gg \lambda$) and weak dissipation ($Q\ll 1$) regime
  6. Case-1: $\Gamma=\Gamma_0$
  7. Case-2: $\Gamma(T)=C_\Gamma\frac{\tau^3}{f^{2}}$
  8. Numerical results high energy ($V\gg \lambda$) and strong dissipation ($Q\gg 1$) regime
  9. Case-1: $\Gamma=\Gamma_0$
  10. Case-2: $\Gamma(T)=C_\Gamma\frac{\tau^3}{f^{2}}$
  11. Conclusion

Figures (6)

  • Figure 1: Spectral index $n_s$ and tensor-to-scalar ratio $r$ as a function of $M_5$ (in units of $M_4$) for $\Gamma_0=4\times 10^{-7} M_4$.
  • Figure 2: Spectral index $n_s$ and tensor-to-scalar ratio $r$ as a function of $M_5$ (in units of $M_4$) for $C_\Gamma=6\times 10^{6}$.
  • Figure 3: The spectral index $n_s$, and the tensor-to-scalar ratio $r$ predicted by warm natural inflationary model in the braneworld scenario for $N=60$ in strong dissipative regime (red solid line). The marginalized joint $95\%$ CL regions for the spectral index $n_s$, and the tensor-to-scalar ratio $r$, obtained from Planck 2018 and lensing data alone, and their combinations with BICEP3/Keck Array (BK18) and BAO data are shown in blue and yellow respectively.
  • Figure 4: Spectral index $n_s$ and tensor-to-scalar ratio $r$ as a function of $M_5$ (in units of $M_4$) for $\Gamma_0=1.6\times 10^{-3} M_4$ (blue), $\Gamma_0=2\times 10^{-3} M_4$ (orange) and $\Gamma_0=2.6\times 10^{-3} M_4$ (green).
  • Figure 5: The spectral index $n_s$, and the tensor-to-scalar ratio $r$ predicted by warm natural inflationary model in the braneworld scenario for $N=60$ in strong dissipative regime (red solid line). The marginalized joint $95\%$ CL regions for the spectral index $n_s$, and the tensor-to-scalar ratio $r$, obtained from Planck 2018 and lensing data alone, and their combinations with BICEP3/Keck Array (BK18) and BAO data are shown in blue and yellow respectively.
  • ...and 1 more figures