{
  "abstract": "Starting from the constant-roll condition, which involves the constant-roll parameter $β$, which is a fundamental constant in the constant-roll inflationary models, we derive the scalar power spectrum and obtain an analytic expression for the scalar spectral index $n_s$ in terms of $β$ and the number of remaining e-folds $\\tilde N$. The resulting relation is non-monotonic in $β$, allowing two distinct constant-roll branches, one with $β<0$ and one with $β>0$, to reproduce nearly the same observed scalar tilt. We constrain $β$ using Planck 2018 CMB data, and further using the combined Planck 2018 + ACT DR6 data. For Planck 2018, the posterior distribution of $β$ exhibits a bimodal structure associated with the two analytical branches, while the combined Planck+ACT analysis tightens the allowed range of $β$ and shows continued consistency with the $β=0$ slow-roll-like spectral point. The data constrain $β$ to be small, but do not require it to vanish exactly. We also estimate the inflationary mass scale $M$ by using the observed scalar-amplitude normalization at the pivot scale. Both the negative and positive $β$ branches give a high-scale inflationary normalization of order $M\\sim10^{-5}M_{\\rm Pl}$. We show that the $β\\to 0$ limit is only spectrally slow-roll like, but does not reproduce standard slow-roll dynamics. Our results show that constant-roll inflation is observationally competitive with the usual slow-roll inflationary paradigm. The constant roll inflation model is supported by the latest CMB observations equally well or marginally better when compared with the slow roll inflation model.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.32865",
  "author_total": 3,
  "authors": [
    {
      "name": "Sandip Biswas"
    },
    {
      "name": "Rajib Saha"
    },
    {
      "name": "Kaushik Bhattacharya"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/b5tyn24csgrh0.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.32865",
  "fulltext_url": null,
  "id": "b5tyn24csgrh0",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.32865",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.CO"
    ],
    [
      "arxiv",
      "gr-qc"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7214798318",
  "pdf_url": "https://arxiv.org/pdf/2609.32865",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-26",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/b5tyn24csgrh0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2609.32865",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.32865"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Constant-Roll Inflation as a Competitive Alternative to Slow-Roll Inflation",
  "title_text": "Constant-Roll Inflation as a Competitive Alternative to Slow-Roll Inflation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/b5tyn24csgrh0",
  "venue": "arXiv",
  "versions": []
}