String Thresholds, Dynamical Gauss--Bonnet Couplings, and Starobinsky Attractors
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| Format: | Preprint |
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2018
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| _version_ | 1866917482183262208 |
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| author | Guleryuz, Omer |
| author_facet | Guleryuz, Omer |
| contents | We develop a string-motivated dynamical Gauss--Bonnet completion of Starobinsky inflation. Since a constant Gauss--Bonnet term is topological in four dimensions, observable effects must arise from a modulus, dilaton, or compactification threshold whose value changes during inflation. We formulate the system as a scalar--Gauss--Bonnet effective theory, derive an invariant matching between the threshold-corrected plateau and the leading CMB observables $n_s$, $r$, and the running $α_s \equiv \mathrm d n_s / \mathrm d \ln k$, and impose explicit string and Kaluza--Klein cutoff bounds. Calabi--Yau topology and string threshold amplitudes are used only as microscopic priors for the threshold function; the observable deformation is fixed only after stabilization, trajectory selection, and single-clock matching. In the controlled heavy-modulus regime, a positive matched deformation raises the scalar tilt, lowers the tensor signal, and makes the running mildly less negative. A representative $X_{24}(1,1,2,8,12)$ example illustrates how topological data and an effective threshold response define a quantitative compactification target for the range $κ_G \simeq 7 \text{--} 17$, while emphasizing that this is not a direct prediction from a fully stabilized compactification. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_1808_06404 |
| institution | arXiv |
| publishDate | 2018 |
| record_format | arxiv |
| spellingShingle | String Thresholds, Dynamical Gauss--Bonnet Couplings, and Starobinsky Attractors Guleryuz, Omer General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena High Energy Physics - Theory We develop a string-motivated dynamical Gauss--Bonnet completion of Starobinsky inflation. Since a constant Gauss--Bonnet term is topological in four dimensions, observable effects must arise from a modulus, dilaton, or compactification threshold whose value changes during inflation. We formulate the system as a scalar--Gauss--Bonnet effective theory, derive an invariant matching between the threshold-corrected plateau and the leading CMB observables $n_s$, $r$, and the running $α_s \equiv \mathrm d n_s / \mathrm d \ln k$, and impose explicit string and Kaluza--Klein cutoff bounds. Calabi--Yau topology and string threshold amplitudes are used only as microscopic priors for the threshold function; the observable deformation is fixed only after stabilization, trajectory selection, and single-clock matching. In the controlled heavy-modulus regime, a positive matched deformation raises the scalar tilt, lowers the tensor signal, and makes the running mildly less negative. A representative $X_{24}(1,1,2,8,12)$ example illustrates how topological data and an effective threshold response define a quantitative compactification target for the range $κ_G \simeq 7 \text{--} 17$, while emphasizing that this is not a direct prediction from a fully stabilized compactification. |
| title | String Thresholds, Dynamical Gauss--Bonnet Couplings, and Starobinsky Attractors |
| topic | General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena High Energy Physics - Theory |
| url | https://arxiv.org/abs/1808.06404 |