stabilitet

Stabilitet, or stability, is the property of a system to resist changes or to return to a reference state after disturbances. The concept is used across science and engineering to describe whether a system remains near its desired configuration under fluctuations in environment, inputs, or internal conditions.

In mechanics and physics, a system in stable equilibrium sits at a local minimum of potential energy. A small displacement leads to restoring forces that drive the state back toward equilibrium; damping reduces oscillations. Unstable equilibrium occurs at a maximum or saddle point, where small perturbations grow.

In control theory and engineering, stability concerns whether feedback systems produce bounded, predictable responses. Techniques include Lyapunov stability analysis, which uses a function that always decreases along trajectories, and BIBO stability, which ensures bounded inputs lead to bounded outputs. Asymptotic stability implies convergence to an equilibrium over time.

In chemistry and thermodynamics, stability refers to whether a composition or phase minimizes free energy under given conditions. Thermodynamically stable substances resist transformation, while metastable states persist for long times despite being non-equilibrium; kinetic factors can block the thermodynamic path.

In economics, ecology, and politics, stability means low volatility and resilience to shocks. Economic stability involves inflation control, steady growth, and durable financial conditions; ecological stability refers to persistent community structure; political stability means sustained governance with low risk of abrupt disruption.

Assessment depends on the context: eigenvalues of linearized models indicate local stability, energy or Lyapunov functions can certify stability, and simulations explore responses to disturbances. Stability is often a design objective as well as an intrinsic property of natural systems.