Modified Friedmann equation and inflation in a warped codimension-two braneworld
Bibliographic record
Abstract
We study the Friedmann equation for the warped codimension-two braneworld background which most closely resembles the Randall-Sundrum model. Extra matter on the (Planck) 4-brane, with equation of state ${p}_{\ensuremath{\theta}}=(\ensuremath{\alpha}\ensuremath{-}1)\ensuremath{\rho}$ for the azimuthal pressure, is required to satisfy the junction conditions. For $1<\ensuremath{\alpha}<5$, we show that there are two static solutions to the Einstein equations for given values of the brane stress-energies. Close to the static solutions, the relation between Hubble expansion rate $H$ and brane tension reproduces the standard 4D result for small $H$, but exhibits unusual deviations when $H$ is of order of the anti-de Sitter (AdS) curvature scale. The two static branches for $1<\ensuremath{\alpha}<5$ are shown to come together smoothly at a maximum value of $H$; however the radion is shown to be unstable in the branch with higher $H$. This remains true even with a mechanism for stabilization of the radion, i.e., the Goldberger-Wise (GW) mechanism, since large enough $H$ overcomes the force of stabilization. Even in the unstabilized case, cosmological constraints on the time and spatial variation of Newton's constant are typically satisfied; only fifth-force constraints require the stabilization. For $\ensuremath{\alpha}>5$ the model is intrinsically stable, without the need for a GW field, and in this case we show that inflationary predictions can be modified by the nonstandard Friedmann equation; in particular, it is possible to get an upper limit on the spectral index, large deviations from the consistency condition between the tensor spectrum and ratio $r$, and large running of the spectral index even though the slow-roll parameters remain small.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".