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Inflation with a Growing Fifth Dimension

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arxiv 2512.04177 v2 pith:RMFD3UFS submitted 2025-12-03 hep-th astro-ph.COgr-qchep-ph

Inflation with a Growing Fifth Dimension

classification hep-th astro-ph.COgr-qchep-ph
keywords inflationbraneinflatonbackgroundadiabaticmodelpotentialpower
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Inflation generally assumes a field with nonzero potential that leads to inflationary expansion happening at arbitrarily early times. We demonstrate potentially observable consequences of inflation with a finite initial time in a model in five-dimensional warped anti-de Sitter space, with both a UV and an IR brane present during inflation. Considering an inflaton with an approximately flat potential localized on the UV brane, we derive the resulting brane motion in the bulk and the 4D effective action describing the dynamics. A concrete model allows us to evaluate possible consequences of a starting point of inflation. The background evolution is driven by the fast roll of the radion at early times and the slow roll of the inflaton at late times. We find that the action has the form of a two-field hyperbolic inflation model, the two fields being the radion and the inflaton, both of which have a time-dependent background solution. This setup is holographically dual to an inflaton coupled to a strongly coupled confining sector in which the ratio of the confinement scale to the 4D Planck scale evolves cosmologically. Focusing on the period when the equation of state becomes that of inflation, we find that the presence of the IR brane leads to deviations from the approximate de Sitter background in addition to those from the slow-roll parameters of the inflaton potential. We quantify the effect of the presence of the IR brane on the two point function of the adiabatic scalar perturbations and tensor perturbations. The dominant deviations occur at large scales: the adiabatic power spectrum has a blue tilt, while the tensor power spectrum shows oscillatory features. We present numerical fits to the shape of the adiabatic power spectrum, and discuss the implications for cosmic microwave background (CMB) analysis.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Strongly Coupled Sectors in Inflation: Gapped Theories of Unparticles

    hep-th 2025-12 unverdicted novelty 7.0

    Compactified 5D unparticle theories generate gapped excitations whose exchange in inflationary correlators yields oscillations modulated by anomalous dimensions and possible interference patterns under brane-localized...

  2. Massive Graviton Dark Matter from a Gapped Continuum

    hep-th 2026-07 conditional novelty 6.0

    Radiative corrections in a 5D linear dilaton brane-world produce a long-lived massive graviton resonance and a holographic fluid, either or both of which can account for dark matter.

  3. Curvature-Assisted Dynamical Compactification in a Pre-Inflationary Higher-Dimensional Universe

    hep-th 2026-04 unverdicted novelty 6.0

    Negative curvature sustains tracker-like radion evolution in a 5D open FRW universe, enabling trapping into a compactified vacuum via Casimir and Kaluza-Klein thermal effects before 4D inflation dilutes curvature remnants.

  4. Confinement in Holographic Theories at Finite Theta

    hep-th 2026-03 unverdicted novelty 6.0

    Holographic 5D model shows confinement critical temperature falls quadratically with vacuum angle, matches lattice QCD, and allows time-dependent theta to trigger supercooling and altered gravitational-wave spectra.

  5. Cosmological history after higher dimensional inflation

    hep-th 2026-06 unverdicted novelty 4.0

    Proposes a post-inflation cosmological evolution in large-extra-dimension models that prevents bulk graviton overproduction up to reheating while preserving scale-invariant perturbations for 1-2 micron-sized dimensions.

  6. Curvature-Assisted Dynamical Compactification in a Pre-Inflationary Higher-Dimensional Universe

    hep-th 2026-04 unverdicted novelty 4.0

    In a 5D open FRW model, negative curvature sustains tracker-like radion evolution that enables dynamical compactification via Casimir stabilization before 4D inflation dilutes curvature remnants.