{
  "abstract": "A scalar field, which oscillates coherently over the space and decays through production of daughter particles, plays an important role in cosmology. It was recently shown that the parametric-resonance and Feynman-diagrammatic approaches give the same decay rate for a Bosonic daughter particle at a large time duration. We study how the parametric-resonance result approaches to this asymptotic value, by numerically following the time evolution of the phase density of the daughter particle. We see a difference among different instability bands in the narrow-resonance regime. The lowest-order instability band approaches to the Feynman-diagrammatic result in tens of scalar oscillation periods, while the high-order instability bands approach dependently also on a coupling between the scalar and daughter particles. This would infer that the total decay width, to which the lowest-order instability band contributes most dominantly in the perturbation theory, approaches to the Feynman-diagrammatic result also independently of the coupling. To confirm it, we consider a simpler and analytically solvable quantum mechanical model: Rabi models. In the Bosonic Rabi model, the parametric-resonance and Feynman-diagrammatic results agree with each other for all the time. On the other hand, in the Fermionic Rabi model, they disagree at a large time duration. This difference would be attributed to Bose enhancement vs Pauli blocking.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.08420",
  "author_total": 2,
  "authors": [
    {
      "name": "Ayuki Kamada"
    },
    {
      "name": "Kodai Sakurai"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/58wbsz4av889n.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.08420",
  "fulltext_url": null,
  "id": "58wbsz4av889n",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.08420",
  "language": null,
  "licence": "CC0-1.0",
  "licence_label": "CC0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/publicdomain/zero/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "hep-ph"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7212071513",
  "pdf_url": "https://arxiv.org/pdf/2609.08420",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/58wbsz4av889n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:49Z",
      "native_id": "2609.08420",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.08420"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Time evolution of scalar condensate decay",
  "title_text": "Time evolution of scalar condensate decay",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:49Z",
  "url": "https://research.draconitic.com/paper/58wbsz4av889n",
  "venue": "arXiv",
  "versions": []
}