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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2604.18641 |
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| _version_ | 1866917423575203840 |
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| author | Arshad, Malaika Zafar, Jehanzad Althukair, Ahdab Ahmad, Bilal |
| author_facet | Arshad, Malaika Zafar, Jehanzad Althukair, Ahdab Ahmad, Bilal |
| contents | We show that a Weyl-flat null origin of inflation need not be in tension with present observations. For canonical single-field inflation, any background with $ε(N)\to ε_\infty\in(0,1)$ as $N\to\infty$ is asymptotically power-law, inherits the same Weyl-flat null past boundary, and reconstructs an exponential tail in field space. This identifies the origin as an asymptotic universality class rather than a rigid exact solution. We study a minimal deformation, $ε(N)=ε_\infty+(1-ε_\infty)\left(\frac{N_0}{N+N_0}\right)^p$ with $p>1$, which preserves the asymptotic geometry, yields a smooth exit, and produces realistic finite-$N$ phenomenology. Solving the scalar and tensor mode equations directly in e-fold time, we find a viable corridor with $n_s$ in the Planck-preferred range and $r\sim10^{-3}-10^{-2}$, including reheating-compatible benchmarks. The result is a calculable single-field framework in which a Penrose-compatible Weyl-flat inflationary origin survives as a realistic and testable possibility. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_18641 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Inflation from a Weyl-flat null origin Arshad, Malaika Zafar, Jehanzad Althukair, Ahdab Ahmad, Bilal High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We show that a Weyl-flat null origin of inflation need not be in tension with present observations. For canonical single-field inflation, any background with $ε(N)\to ε_\infty\in(0,1)$ as $N\to\infty$ is asymptotically power-law, inherits the same Weyl-flat null past boundary, and reconstructs an exponential tail in field space. This identifies the origin as an asymptotic universality class rather than a rigid exact solution. We study a minimal deformation, $ε(N)=ε_\infty+(1-ε_\infty)\left(\frac{N_0}{N+N_0}\right)^p$ with $p>1$, which preserves the asymptotic geometry, yields a smooth exit, and produces realistic finite-$N$ phenomenology. Solving the scalar and tensor mode equations directly in e-fold time, we find a viable corridor with $n_s$ in the Planck-preferred range and $r\sim10^{-3}-10^{-2}$, including reheating-compatible benchmarks. The result is a calculable single-field framework in which a Penrose-compatible Weyl-flat inflationary origin survives as a realistic and testable possibility. |
| title | Inflation from a Weyl-flat null origin |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2604.18641 |