From topological to geometric equivalence in the classification of singularities at infinity for quadratic vector fields
Bibliographic record
Abstract
In the topological classification of phase portraits no distinctions are made between a focus and a node and neither are they made between a strong and a weak focus or between foci of different orders. These distinctions are however important in the production of limit cycles close to the foci in perturbations of the systems. The distinction between the one direction node and the two directions node, which plays a role in understanding the behavior of solution curves around the singularities at infinity, is also missing in the topological classification. In this work we introduce the notion of \textit{geometric equivalence relation of singularities} which incorporates these important purely algebraic features. The \textit{geometric} equivalence relation is finer than the \textit{topological} one and also finer than the \textit{qualitative equivalence relation} introduced in \cite{J_L}. We also list all possibilities we have for finite and infinite singularities, taking into consideration these finer distinctions, and introduce notation for each one of them. %Our %long term goal is to use this finer and deeper equivalence relation to classify %the quadratic family according to their different \textit{geometric %configurations of singularities}, finite and infinite. In this work we give the classification theorem and bifurcation diagram in the 12-dimensional parameter space, using the \textit{geometric equivalence relation}, of the class of quadratic systems according to the configuration of singularities at infinity of the systems. Our classification theorem, stated in terms of invariant polynomials, is an algorithm for computing the \textit{geometric configurations} of infinite singularities for any family of quadratic systems, in any normal form. %The theorem we give also %contains a bifurcation diagram, done in the 12-parameter space, of %the \textit{geometric configurations} of singularities at infinity, %and this bifurcation set is algebraic in the parameter space. To %determine the bifurcation diagram of configurations of singularities %at infinity for any family of quadratic systems, given in any normal %form, becomes thus a simple task using computer algebra %calculations.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.003 | 0.005 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
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".