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A **power law** in statistics is a relationship between
quantities where one is proportional to the power of the other.
Often such relations only hold over a given range.
Template:

y=ax^{k}

Subtypes include "square law" and "inverse-square law". Some physics examples:

- Stefan-Boltzmann law (black-body radiation power versus temperature).
- Newtonian gravity.
- Electrostatics.
- Kepler's third law.
- initial mass function of stars.

A **power law spectrum** is a spectrum such that the flux at each
frequency (or energy as per the energy-per-photon)
is related to that frequency by a power law.
A spectrum may be classified as basically power law,
as opposed to, for example, a **black-body spectrum**.
Cosmic rays' spectrum is basically power law.

Compton reflection

cosmic rays (CR)

dense core mass function (DCMF)

luminosity function (LF)

radio relics

spectral index (α)

synchrotron radiation