Cosmic crystallography is a technique used in physics and astronomy to determine the possible
topology
In mathematics, topology (from the Greek language, Greek words , and ) is concerned with the properties of a mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformations, such ...
of the universe (e.g. a torus, 3-sphere, etc.). Astronomers observe sources of high
redshift
In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...
and look for repeating patterns that may indicate the connection of edges.
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Pair separation histograms
Cosmic crystallographers use cosmic separation histograms to infer characteristics of the universe. Large spikes are expected to appear if the universe is not simply connected
In topology, a topological space is called simply connected (or 1-connected, or 1-simply connected) if it is path-connected and every path between two points can be continuously transformed (intuitively for embedded spaces, staying within the spac ...
.
References
Physical cosmology
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