# Dispersion

The term “dispersion” takes on different meanings depending on the context and branch of its intended use. In common usage it can take on the meaning of distribution without order.

## Economics and finance

• Dispersion [finance]: a measure for the statistical distribution of portfolio returns.
• Price dispersion: a variation in prices across sellers of the same item.
• Wage dispersion: the amount of variation in wages encountered in an economy.
• Dispersed knowledge: in economics is the notion that no single agent has information as to all of the factors which influence prices and production throughout the system.

## Science and mathematics

### Mathematics

• Statistical dispersion: a quantifiable variation of measurements of differing members of a population.
• Index of dispersion: a normalized measure of the dispersion of a probability distribution.
• Dispersion point: a point in a topological space the removal of which leaves the space highly disconnected.

### Physics

• The dependence of wave velocity on frequency or wavelength:
• Dispersion [optics] for light waves.
• Dispersion (water waves): for water waves.
• Acoustic dispersion: for sound waves.
• Dispersion relation: the mathematical description of dispersion in a system.
• Modal dispersion, spreading of signals in multimode fibers and waveguides by a distortion mechanism.
• Polarization mode dispersion: a form of modal dispersion.
• Dielectric dispersion: the dependence of the permittivity of a dielectric material on the frequency of an applied electric field.
• Dispersive mass transfer: in fluid dynamics, the spreading of mass from areas of high to low concentration.
• Atmospheric dispersion modeling: mathematical simulation of how air pollutants disperse in the ambient atmosphere.
• London dispersion force: an instantaneous induced dipole-induced dipole.
• Dispersed particle resistance: a measured parameter to characterize battery active materials.

### Other sciences

• Dispersion [chemistry]: a system in which particles are dispersed in a continuous phase of a different composition.
• Dispersion [electrical engineering]: phenomenon that can occur, for example, through insulating supports of inadequate characteristics, aged or faulty, or along their surface exposed to humidity and atmospheric impurities, through the air (corona effect in high voltage lines), in the ground around underground cables if their insulating sheaths have failed. In this case, the dispersion can be considerable and give rise to stray currents of considerable intensity. The dispersion, as well as being an anomalous and parasitic phenomenon, is in many cases used and favored, for example, to disperse in the ground lightning that have hit a lightning rod, or maintain the ground potential, through connection with appropriate earth electrodes, external metal parts, normally not live, of plants, machines, appliances, etc.. with which it comes into common contact and which, in the absence of grounding, could give rise to electrocution for failure of an electrical insulation.
• Dispersion [ecology]: a widespread phenomenon affecting all living organisms, which, however, is opposed by barriers of various kinds. Dispersal is active if it is carried out by its own means, passive if it is due to causes independent of the animal’s activity. The distance of active dispersal is not directly related to the movement capabilities of the animals; many species of birds and insects with good flight capabilities, in fact, are relatively filopatric. Passive dispersal can be achieved by various systems: some animals are dispersed by wind (anemochoric dispersal); water currents can disperse nonaquatic organisms clinging to floating material (hydrochoric dispersal) and aquatic organisms; the animals themselves can be dispersal agents for other animals (biochoric dispersal); for example, hosts spread their parasites; wading birds, with mud adhering to their legs, a quantity of small aquatic organisms; humans have voluntarily and involuntarily (through their means of transport) spread a great many animals. Dispersal is called short-range if it involves movements that do not exceed the boundaries of the species’ range; long-range if it takes animals outside the range. The first, which can be implemented spontaneously or as a result of intraspecific competition (see territoriality), is an important mechanism that maintains gene flow within populations, the second can lead to the expansion of the range or the colonization of new biotopes.
• Dispersion [geology]: a process whereby sodic soil disperses when exposed to water.
• Dispersion [materials science]: the fraction of atoms of a material exposed to the surface.
• Dispersion polymerization: a polymerization process.
• Velocity dispersion: the statistical variation of velocities about the mean velocity for a group of astronomical objects.

## Synonyms

• (of elements of a group, of a whole) dissemination, disintegration, scattering, scattering, fragmentation
• (figurative sense) (of time, energies) waste, wastefulness, dissipation, squandering
• (physical) loss, decomposition
• consumption

## Antonyms

• (of elements of a group, of a whole) accumulation, collection
• (figurative) (of time, energy) saving, recovery
• (physical) concentration

## Derived words

• Thermodispersion
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