Koaleszció

Koaleszció, or coalescence, is the process by which two or more separate entities merge to form a single entity. The term, derived from Latin coalescere, is used across disciplines to describe a merging event that reduces the number of distinct units.

In fluid dynamics, coalescence refers to the merging of droplets or bubbles when they come into contact and the intervening liquid film drains under capillary forces, leading to a larger drop or bubble. This mechanism strongly influences the stability of emulsions and foams, and it can be affected by viscosity, interfacial tension, and external flows.

In materials science and metallurgy, coalescence describes the merging of particles, grains, or voids during processes such as annealing, diffusion, or sintering. Through coalescence, the average size of grains or clusters increases and the total interfacial area decreases, affecting mechanical properties and transport phenomena.

In astrophysics and cosmology, coalescence denotes mergers of celestial objects, such as black holes or neutron stars, often accompanied by the emission of gravitational waves. Such events are key sources for gravitational-wave observatories and provide insights into extreme gravity, stellar evolution, and cosmology.

In population genetics, coalescent theory models the genealogical relationships of gene copies by tracing their lineages backward in time until they converge at common ancestors. Coalescent events help infer historical population sizes, migration, and evolutionary processes.

Applications of coalescence concepts span theory and practice, from predicting the stability of emulsions to interpreting the history of populations and detecting gravitational-wave signals from cosmic mergers.