SPACE seminar: Mariam Abdelaziz - "Inflation without an Inflaton"

Tuesday 5 May 2026, 12:00 → 13:00 Europe/Rome

San Marcellino (Aula 4)

Speaker:  Mariam Abdelaziz  (SSM)

Abstract: Inflation is remarkably successful at addressing the main shortcomings of the Big Bang picture, explaining the observed large-scale homogeneity and isotropy of the Universe, and generating the primordial seeds from which cosmic structure later formed. In the standard picture, these seeds arise from quantum vacuum fluctuations of a scalar inflaton field. Yet this success comes with a price: different choices of the inflaton potential lead to many possible realizations of inflation, making the framework highly model dependent. This naturally motivates a broader question: can inflation be realized without introducing an inflaton at all? In this talk, I will discuss the “Inflation without an Inflaton (IWI)” scenario, in which accelerated expansion takes place in an exact de Sitter background and scalar perturbations are generated instead as second-order effects of tensor metric fluctuations, namely primordial gravitational waves. I will introduce the basic idea behind this framework, present its prediction for the scalar power spectrum, and discuss recent progress in understanding the intrinsic primordial non-Gaussianity of the scalar fluctuations it produces.

References:

1. %\cite{Bertacca:2024zfb} \bibitem{Bertacca:2024zfb} D.~Bertacca, R.~Jimenez, S.~Matarrese and A.~Ricciardone, %``Inflation without an inflaton,'' Phys. Rev. Res. \textbf{7}, no.3, L032010 (2025) doi:10.1103/vfny-pgc2 [arXiv:2412.14265 [astro-ph.CO]]. %6 citations counted in INSPIRE as of 20 Apr 2026D.~Bertacca, R.~Jimenez, S.~Matarrese and A.~Ricciardone,
   %``Inflation without an inflaton,''
   Phys. Rev. Res. \textbf{7}, no.3, L032010 (2025)
   doi:10.1103/vfny-pgc2
   [arXiv:2412.14265 [astro-ph.CO]].%\cite{Bertacca:2024zfb} \bibitem{Bertacca:2024zfb} D.~Bertacca, R.~Jimenez, S.~Matarrese and A.~Ricciardone, %``Inflation without an inflaton,'' Phys. Rev. Res. \textbf{7}, no.3, L032010 (2025) doi:10.1103/vfny-pgc2 [arXiv:2412.14265 [astro-ph.CO]]. %6 citations counted in INSPIRE as of 20 Apr 2026%\cite{Bertacca:2024zfb} \bibitem{Bertacca:2024zfb} D.~Bertacca, R.~Jimenez, S.~Matarrese and A.~Ricciardone, %``Inflation without an inflaton,'' Phys. Rev. Res. \textbf{7}, no.3, L032010 (2025) doi:10.1103/vfny-pgc2 [arXiv:2412.14265 [astro-ph.CO]]. %6 citations counted in INSPIRE as of 20 Apr 2026Bertacca, R. Jimenez, S. Matarrese and A. Ricciardone, Inflation without an inflaton, Phys. Rev. Res. 7, L032010 (2025) [arXiv:2412.14265 [astro-ph.CO]].
2. M. Traforetti, M. Abdelaziz, D. Bertacca, R. Jimenez, S. Matarrese and A. Ricciardone, Inflation without an inflaton. II. Observational predictions, Phys. Rev. D 113, 023553 (2026) [arXiv:2511.11808 [astro-ph.CO]].
3. M. Abdelaziz, M. Traforetti, D. Bertacca, R. Jimenez, S. Matarrese and A. Ricciardone, Inflation without an Inflaton III: non-Gaussian signatures, [arXiv:2603.15036 [astro-ph.CO]].

 

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