Stiffness and A-stability
A problem is called stiff when stability, rather than desired accuracy, forces severely small steps for a method.
Key knowledge
A problem is called stiff when stability, rather than desired accuracy, forces severely small steps for a method. A method is A-stable when its scalar stability region contains the left half-plane. Backward Euler is A-stable; a frozen nonlinear Jacobian eigenvalue test is a diagnostic, not a universal nonlinear stability theorem.
Conditions and scope
- Stiffness depends on the problem, method and accuracy scale; it is not a binary property of every equation.
- A-stability concerns the linear scalar test and does not remove accuracy or implicit-solve requirements.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Opening stiffness discussion, section11.4.2 Observation11.4.1 explicitly qualified as a rule of thumb, section11.4.4 Definition11.4.2.
2026-10-10 · Independent AI editorial review: All241 compact claims, hypotheses, displayed equations/conventions and all596 origin semantic links read; entire241-entry author exact-source inspection matrix and declared limitations reviewed. Prior105 actual inherited Mathematics/Information records read for whole-inventory breadth. Targeted independent primary sections are listed below; this does NOT claim every cited source body or every proof was independently re-read. This is AI reference-content review, not human disciplinary certification, exhaustive textbook reproduction or experimental replication. Receipt: mathematics-information-independent-content-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- math-stiffness-a-stability
- Revision
- university-core.1
- Structured reference record
- University core expansion