Exact solutions of a full causal bulk viscous FRW cosmological model with variable <i>G</i> and Λ through factorization
Bibliographic record
Abstract
We study the classical flat full causal bulk viscous Friedmann–Robertson–Walker cosmological model with variable gravitational and cosmological constants through the factorization method. The method allows us to find some new exact parametric solutions. The assumptions made lead us to study two approaches. We find, in the studied cases, that the Universe ends in an accelerating era except in the case of a particular solution where the Universe could be noninflationary for all times. In both approaches the cosmological constant is a decreasing function of time, while the gravitational constant behaves as a growing or decreasing time function depending on the sign of Λ. By taking into account recent observations that indicate that Λ must be positive, we conclude that G increases with time except in the first solution where both “constants” tend asymptotically in the large time limit to a constant value. We also present a new factorization scheme that allows us to generate new solutions to a kind of variable-coefficient, nonlinear, second-order, ordinary differential equation.
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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) | 0.000 | 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".