\(QS74_{9}^{(1)}\)
Description
Phase Portrait
Topological Invariants
| TCSP | Fin Sep | Inf Sep |
|---|---|---|
| \(74\) | \(421\) | \(311101\) |
Example
The quadratic differential system
\[\begin{cases} \dot{x} = y+4 \, x \, (x+y) \\ \dot{y} = d+e \, y+x^{2}+4 \, x \, y+3 \, y^{2} \end{cases}\]
with parameters: \(d = -0.000001, \quad e = 0.1\)
has the following phase portrait done with P4. If you want, you may download the P4 file here. Since the image is not clear enough, we have added a ZOOM of it.
The phase portrait appears in the following papers
- With name \(V21\) in {J. C. Artés and L. Cairó}, Phase portraits of quadratic differential systems with a weak focus and a (1,1) SN, {Preprint} (2026).
- With name \(U^1_{C26}\) in {J. C. Artés, J. Llibre and A. C. Rezende}, Structurally unstable quadratic vector fields of codimension one, Birkhäuser/Springer, Cham, 2018, vi+267 pp.
Missed in:
- {X. Huang}, Qualitative analysis or certain nonlinear differential equations, {Ph.D. U. Delft}, (1996).
Bifurcations in codimension 0
- Bifurcation interface between the codimension 0 portrait \(QS10_{1}^{(0)}\) and \(QS5_{5}^{(0)}\).
Comments
This phase portrait appears in J. C. Artés and L. Cairó ({Preprint} (2026)) featuring a weak focus of first order. Consequently, a configuration structurally equivalent to \(QS74_{9}^{(1)}\) could potentially exhibit an additional limit cycle bifurcating from the focus.