Introduction to the mathematics of general relativity: Difference between revisions

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===Tensors===

[[Image:Components stress tensor cartesian.svg|300px|right|thumb|Stress, is a second-order tensor. Stressthat isrepresents herethe shownresponse asof a seriesmaterial ofto vectorsforce onapplied eachat sidean angle. The two directions of the boxtensor represent the "normal" (at right angles to the surface) force, and "shear" (parallel to the surface) force.]]

A tensor extends the concept of a vector to additional directions. A [[scalar (mathematics)|scalar]], that is, a simple number without a direction, would be shown on a graph as a point, a zero-dimensional object. A vector, which has a magnitude and direction, would appear on a graph as a line, which is a one-dimensional object. A vector is a first-order tensor, since it holds one direction.