Skip to content
DraconiticResearch
Search Sources API
203,234 studies31 sourcesUpdated 40 min ago
PreprintarXiv licencearXiv

Revisiting the Lyth bound constraints on inflation from ACT DR6 results

  • Rui Yang
  • Jun Tao
  • Peng Wang
  • Mian Zhu
Open at sourcePDFDOICite

Abstract

The Lyth bound asserts that the field excursion of inflaton must be sub-Planckian, thereby imposing an upper bound on the amplitude of the tensor power spectrum in inflationary scenario. This bound is conventionally derived assuming a scale-invariant curvature power spectrum, i.e., ns = 1. However, astrophysical observations confirm a red-tilted spectrum with ns < 1. In light of recent results from the Atacama Cosmology Telescope (ACT) DR6, we revisit these constraints using the newly implied scalar spectral index of ns ≃ 0.9743. Incorporating the ACT data yields a different upper bound on the tensor-to-scalar ratio r, which can potentially exclude inflationary scenarios previously robust under the original Lyth bound with ns = 1. Our result highlights the urgent need to combine theoretical Lyth bound considerations with the most up-to-date astrophysical data.

Versions

Related

  1. Symmetry-protected α-attractor hybrid inflation in supergravity and constraints from ACT DR6 and DESI DR2
    Swapnil Kumar Singh
    Physics of the Dark UniversePeer-reviewedLicence not statedFull text7 citedCosmologyOpenAlex
  2. Analytic results for slow-roll curved-space inflation and exponential potentials
    Dimitrios Tsimpis, Govind Venugopal
    arXivPreprintCC BY 4.0Full textCosmologyGravitation & general relativityarXiv
  3. General Spin-1 Dynamics During Inflation: Microcausality Constraints and Cosmological Collider Signals
    Trevor Cheung, Carlos Duaso-Pueyo, David Stefanyszyn +1
    arXivPreprintCC BY 4.0Full textCosmologyGravitation & general relativityarXiv
  4. Primordial Tensor Signatures and Gravitational Wave Constraints in Lorentz Violating Inflation with Non-Canonical Kinetics
    Dibash Plaban Kalita, Shreya Banerjee
    arXivPreprintCC0Full textCosmologyGravitation & general relativityarXiv
  5. Cosmological constraints on single-field inflation models from ACT/SPT data and observations at sub-Mpc scales
    Qing-Yang Wang, Jing-Zhi Zhou, Fei-Yu Chen +1
    arXivPreprintarXiv licenceFull textCosmologyGravitation & general relativityarXiv

Cite

BibTeXRIS
BibTeX
@misc{yang2026revisiting,
  title = {{Revisiting the Lyth bound constraints on inflation from ACT DR6 results}},
  author = {Rui Yang and Jun Tao and Peng Wang and Mian Zhu},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2606.16711},
  eprint = {2606.16711},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.16711},
}
RIS
TY  - UNPB
TI  - Revisiting the Lyth bound constraints on inflation from ACT DR6 results
AU  - Rui Yang
AU  - Jun Tao
AU  - Peng Wang
AU  - Mian Zhu
PY  - 2026
DA  - 2026/11/04
PB  - arXiv
DO  - 10.48550/arxiv.2606.16711
UR  - https://arxiv.org/abs/2606.16711
AB  - The Lyth bound asserts that the field excursion of inflaton must be sub-Planckian, thereby imposing an upper bound on the amplitude of the tensor power spectrum in inflationary scenario. This bound is conventionally derived assuming a scale-invariant curvature power spectrum, i.e., n_s = 1. However, astrophysical observations confirm a red-tilted spectrum with n_s < 1. In light of recent results from the Atacama Cosmology Telescope (ACT) DR6, we revisit these constraints using the newly implied scalar spectral index of n_s ≃ 0.9743. Incorporating the ACT data yields a different upper bound on the tensor-to-scalar ratio r, which can potentially exclude inflationary scenarios previously robust under the original Lyth bound with n_s = 1. Our result highlights the urgent need to combine theoretical Lyth bound considerations with the most up-to-date astrophysical data.
ER  -