Two new arXiv preprints study how “cosmological collider” signals appear in multifield inflation when curvature and isocurvature modes mix strongly. One paper examines a two-field inflationary setup with constant-turn derivative mixing between the curvature fluctuation and a massive isocurvature field. It treats the quadratic mixing nonperturbatively using exact hypergeometric solutions to build mixed propagators and the late-time branches associated with a heavy field. With an isocurvature cubic self-interaction, the authors derive contributions to the squeezed-limit bispectrum that show a power-law envelope together with logarithmic oscillations. They relate the oscillation frequency to the heavy mass and keep the full dependence on mixing strength in the amplitude and phase. The second paper develops an analytic, nonperturbative-in-mixing formalism for primordial non-Gaussianity, resumming curvature–isocurvature transfer to all orders in the mixing strength. It constructs dressed propagators and derives exact tree-level bispectra from interactions such as \(\dot\zeta^2\sigma\), \(\dot\zeta\sigma^2\), and \(\sigma^3\). It finds that in the strong-mixing regime the power spectrum and bispectrum can be substantially enhanced, producing distinctive scaling laws, while the weak-mixing limit reproduces known cosmological-collider and quasi-single-field results.
arXiv papers analyze cosmological collider signatures from strongly mixed multifield inflation
Two new arXiv preprints study how “cosmological collider” signals appear in multifield inflation when curvature and isocurvature modes mix strongly. One paper examines a two-field inflationary setup w...
- Both papers analyze multifield inflation with curvature–isocurvature mixing that is treated nonperturbatively in the mixing strength.
- One work attributes oscillatory squeezed-bispectrum features to heavy-field “nonanalytic” late-time branches, with oscillation frequency encoding the heavy mass.
- The other paper derives exact integral representations and closed-form leading squeezed-limit expressions for bispectrum contributions from specific interaction terms (e.g., \(\dot\zeta^2\sigma\), \(\dot\zeta\sigma^2\), \(\sigma^3\)).
- In the strong-mixing regime, both works report enhanced primordial correlators (power spectrum and/or bispectrum) compared with weak-mixing expectations.
- The frameworks recover established cosmological-collider/quasi-single-field behavior in the weak-mixing limit and aim to extend analytic access beyond the weak-coupling approximation.
arXiv:2607.14891v1 Announce Type: cross Abstract: We study cosmological collider signatures in a two-field inflationary system with constant-turn derivative mixing between the canonically normalized curvature fluctuation and a massive isocurvature field. Building on recently derived exact hypergeometric solutions that treat the quadratic mixing nonperturbatively, we construct the mixed propagators constituting the cosmological correlators. A Mellin-Barnes approach helps isolate the pair of nonanalytic late-time branches carried by a heavy field. For a cubic isocurvature self-interaction, these branches contribute towards a squeezed bispectrum with a power-law envelope and logarithmic oscillations. The oscillation frequency encodes the heavy mass, while the amplitude and phase retain the full mixing dependence rather than a perturbative expansion. We perform the squeezed limit integral analytically and compare it with numerical results across representative masses and mixing strengths. At fixed mixing we derive the large-mass JWKB expansion of the squeezed correlator and its phase. We also give integral representations for the isocurvature Wightman function. The research idea was suggested by ARC, the calculation was performed by GPT, and the results were checked by the authors.
2 hours agoarXiv:2607.14529v1 Announce Type: new Abstract: We develop an analytic treatment of primordial non-Gaussianity in multifield inflation that is nonperturbative in the constant curvature--isocurvature mixing strength $\lambda$. Using exact linear solutions for the coupled curvature perturbation $\zeta$ and isocurvature perturbation $\sigma$, we construct dressed propagators and derive exact integral representations for the tree-level bispectra generated by the interactions $\dot\zeta^2\sigma$, $\dot\zeta\,\sigma^2$, and $\sigma^3$. This formalism resums curvature--isocurvature transfer to all orders in $\lambda$ and applies for arbitrary values of the entropy mass $\mu$. We obtain closed-form expressions for the leading squeezed limit of the bispectrum contributions and recover the well-known cosmological-collider and quasi-single-field results in the weak-mixing limit. In the strong-mixing regime, where conventional transfer perturbation theory breaks down, we find that both the power spectrum and the bispectrum can be dramatically enhanced, giving rise to distinctive nonperturbative scaling laws for the reduced non-Gaussian amplitude. Together, these results open a new analytic window onto multifield inflation beyond the weak-coupling approximation and establish a framework for studying cosmological-collider signals, primordial-black-hole production, and loop corrections in strongly mixed inflationary dynamics.
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