hystereseja

Hystereseja is the Finnish plural form of hysteresis and is used in scientific contexts to describe systems whose present state depends on their past history of inputs. In general, hysteresis denotes a memory of past conditions, so the relationship between cause and effect is not single-valued: for a given input, the output can follow different paths depending on how the input was changed to reach that point.

The phenomenon is observed in many domains. In magnetism, magnetic hysteresis occurs when the magnetic flux density B depends on the magnetic field H, producing a loop when H is cycled. In mechanics and materials science, stress–strain hysteresis appears in viscoelastic and plastically deforming materials as energy is dissipated during loading and unloading. In electronics, ferroelectric and other nonlinear systems show hysteresis, and in control engineering hysteresis can serve as a threshold-based nonlinearity, as in bang–bang or hysteresis controllers.

Mathematically, hysteresis is modeled using history-dependent operators such as the Preisach model or Prandtl–Ishlinskii model, which capture how outputs depend on the entire input history. Experiments often quantify hysteresis by the area of the loop formed in input–output plots, which relates to energy dissipation and memory strength. Major and minor loops describe the system’s response to different cycling patterns of input.

Beyond physics, hysteresis concepts appear in economics and biology, where historical shocks can have lasting effects on current states. Hystereseja thus covers a broad class of history-dependent phenomena across disciplines.