Multiple kinetic k-essence, phantom barrier crossing and stability
Bibliographic record
Abstract
We investigate models of dark energy with purely kinetic multiple k-essence sources that allow for the crossing of the phantom divide line, without violating the conditions of stability.It is known that with more than one kinetic k-field one can possibly construct dark energy models whose equation of state parameter w X crosses -1 (the phantom barrier) at recent red-shifts, as indicated by the Supernova Ia and other observational probes.However, such models may suffer from cosmological instabilities, as the effective speed of propagation c X of the dark energy density perturbations may become imaginary while the w X = -1 barrier is crossed.Working out the expression for c X we show that multiple kinetic k-essence fields do indeed lead to a w X = -1 crossing dark energy model, satisfying the stability criterion c 2 X 0 as well as the condition c X 1 (in natural units), which implies that the dark energy is not super-luminal.As a specific example, we construct a phantom barrier crossing model involving three k-fields for which c X is a constant, lying between 0 and 1.The model fits well with the latest Supernova Ia Union data, and the best fit shows that w X crosses -1 at red-shift z 0.2, whereas the dark energy density nearly tracks the matter density at higher red-shifts.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".