{"work":{"id":"50d0254f-bf80-4d3c-84a9-e99783b23b2e","openalex_id":null,"doi":null,"arxiv_id":"2505.10534","raw_key":null,"title":"ACT-ing on inflation: Implications of non Bunch-Davies initial condition and reheating on single-field slow roll models","authors":null,"authors_text":null,"year":2025,"venue":"astro-ph.CO","abstract":"We investigate a class of slow roll inflationary models in the light of the recent Cosmic Microwave Background constraints from Planck 2018, ACT DR6, DESI DR1, and BICEP/\\textit{Keck} 2018. The combined dataset favors a higher value of the scalar spectral index $n_{_\\mathrm{S}}=0.9743 \\pm 0.0034$, which places increased pressure on several conventional inflationary scenarios. In this study, we analyze the observational viability of various well-motivated models, including the $\\alpha$-attractor E- and T-models, chaotic inflation, hilltop inflation, and natural inflation. We incorporate the effects of a post-inflationary phase of reheating and examine how the dynamics of reheating influence the predictions in the $n_{_\\mathrm{S}}-r$ plane. We also impose a lower bound on the reheating temperature based on the constraint from the effective number of relativistic species ($\\Delta{N}_{\\mathrm{eff}}$) arising from primordial gravitational waves. While reheating improves agreement with observations for some models, significant regions of parameter space remain disfavored. Finally, we explore the impact of a non Bunch-Davies initial state and demonstrate that it can substantially improve the fit to the $n_{_\\mathrm{S}}-r$ data across a broader class of inflationary models, thereby offering a potentially viable mechanism for reconciling theory with the latest observations.","external_url":"https://arxiv.org/abs/2505.10534","cited_by_count":null,"metadata_source":"pith","metadata_fetched_at":"2026-07-04T14:09:53.942369+00:00","pith_arxiv_id":"2505.10534","created_at":"2026-05-10T05:51:09.823541+00:00","updated_at":"2026-07-04T14:09:53.942369+00:00","title_quality_ok":true,"display_title":"ACT-ing on inflation: Implications of non Bunch-Davies initial condition and reheating on single-field slow roll models","render_title":"ACT-ing on inflation: Implications of non Bunch-Davies initial condition and reheating on single-field slow roll models"},"hub":{"state":{"work_id":"50d0254f-bf80-4d3c-84a9-e99783b23b2e","tier":"hub","tier_reason":"10+ Pith inbound or 1,000+ external citations","pith_inbound_count":11,"external_cited_by_count":null,"distinct_field_count":2,"first_pith_cited_at":"2025-06-25T18:00:00+00:00","last_pith_cited_at":"2026-05-09T13:05:58+00:00","author_build_status":"not_needed","summary_status":"needed","contexts_status":"needed","graph_status":"needed","ask_index_status":"not_needed","reader_status":"not_needed","recognition_status":"not_needed","updated_at":"2026-06-29T11:48:46.765010+00:00","tier_text":"hub"},"tier":"hub","role_counts":[{"context_role":"background","n":8}],"polarity_counts":[{"context_polarity":"background","n":7},{"context_polarity":"unclear","n":1}],"runs":{},"summary":{},"graph":{},"authors":[]}}