Kvasiperiode

Kvasiperiode (quasi-period) is a pattern or signal that repeats with approximate regularity but not with exact repetition. It arises in systems where cycles persist but are not perfectly uniform, due to slight changes in frequency, amplitude, or phase, or due to the superposition of multiple oscillations.

In mathematics, a quasi-periodic function is formed by a finite sum of periodic components whose frequencies are incommensurate, producing motion on a higher-dimensional torus. As a result, the overall pattern never exactly repeats, though it displays regular structure and near-repetition over finite intervals.

In signal processing, physics and biology, quasi-periodic phenomena show recurring features such as peaks in an autocorrelation function, but timing or amplitude may slowly vary. They differ from strictly periodic signals, which have a fixed period, and from aperiodic signals, which lack any regular recurrence. Quasi-periodicity is often associated with beating patterns or slowly modulated cycles.

Examples include the beating of two close frequencies, circadian or seasonal rhythms with variability, and quasiperiodic tilings in materials science. The concept is used to model persistent but imperfect cycles in time-series analysis, astrophysics, acoustics, and complex dynamical systems, providing a framework for understanding phenomena that are repeating yet not precisely locked to a single period.