Coarsen

Coarsen is a verb meaning to make something coarser or rougher. In everyday language it can describe roughening a texture, dulling a surface, or leading to less refined behavior. In technical contexts, coarsening often refers to increasing the characteristic size of features or reducing detail by using a coarser scale.

In materials science and metallurgy, coarsening describes the growth of microstructural features such as grains or precipitates, especially during high-temperature exposure. Grain coarsening or Ostwald ripening reduces the total grain boundary area, which can alter mechanical properties such as strength and toughness. The rate and pattern of coarsening depend on temperature, composition, and diffusion processes within the material.

In sedimentology and geology, coarsening can refer to a sedimentary sequence in which grain size increases upward, known as a coarsening-upward sequence. This pattern often reflects changes in energy conditions or sediment supply during deposition.

In image processing and numerical methods, coarsening means producing a coarser representation of data. This can involve downsampling an image, aggregating data over larger cells, or creating a coarser computational grid for multigrid or hierarchical modeling. The purpose is typically to reduce computational cost or to enable analysis at multiple scales.

In everyday use, to coarsen can also describe a decline in refinement or courtesy, such as behavior that becomes rougher or less polished.

See also: Ostwald ripening, grain growth, downsampling, multigrid methods, coarsening-upward sequence.