Semikoherent

Semikoherent is an adjective used in several scientific fields to describe a partial or intermittent degree of coherence or registry between systems, typically crystalline lattices or time-frequency components. It sits between coherent, in which structures are in near-perfect alignment or phase, and incoherent, in which alignment is absent. The exact meaning varies by field but generally implies a pattern of partial coupling, regularity, or partial phase coherence.

In materials science, semicoherent interfaces occur when two crystalline lattices have a lattice mismatch that cannot be eliminated completely. The interface accommodates strain with periodic arrays of misfit dislocations, leading to partial registry along directions parallel to the interface. The density and spacing of dislocations depend on misfit, material pair, and temperature. Semicoherent interfaces can reduce overall interfacial energy compared with fully incoherent boundaries, while still permitting limited diffusion or mechanical interaction across the boundary. They are relevant in epitaxial thin-film growth and in the design of alloys and composite materials.

In astronomical data analysis and gravitational wave science, a semicoherent (or semi-coherent) search refers to a hybrid method that combines short coherent analyses of data segments with an incoherent combination of their results. This approach reduces computational cost relative to a fully coherent analysis while retaining much of the sensitivity to long-duration signals, such as continuous gravitational waves from rotating neutron stars or pulsars. The technique involves segmenting data, computing a coherent statistic on each segment, and summing or statistically combining the results across segments.

Terminology and applications vary by discipline, and "semicoherent" is not a fixed technical term in all contexts.