**Connection (mathematics)**

In geometry, the notion of a **connection** makes precise the idea of transporting data along a curve or family of curves in a *parallel* and consistent manner. There are a variety of kinds of connections in modern geometry, depending on what sort of data one wants to transport. For instance, an affine connection, the most elementary type of connection, gives a means for transporting tangent vectors to a manifold from one point to another along a curve. An affine connection is typically given in the form of a covariant derivative, which gives a means for taking directional derivatives of vector fields: the infinitesimal transport of a vector field in a given direction.

Connections are of central importance in modern geometry in large part because they allow a comparison between the local geometry at one point and the local geometry at another point. Differential geometry embraces several variations on the connection theme, which fall into two major groups: the infinitesimal and the local theory. The local theory concerns itself primarily with notions of parallel transport and holonomy. The infinitesimal theory concerns itself with the differentiation of geometric data. Thus a covariant derivative is a way of specifying a derivative of a vector field along another vector field on a manifold. A Cartan connection is a way of formulating some aspects of connection theory using differential forms and Lie groups. An Ehresmann connection is a connection in a fibre bundle or a principal bundle by specifying the allowed directions of motion of the field. A Koszul connection is a connection generalizing the derivative in a vector bundle.

Connections also lead to convenient formulations of *geometric invariants*, such as the curvature (see also curvature tensor and curvature form), and torsion tensor.

Read more about Connection (mathematics): Motivation: The Unsuitability of Coordinates, Historical Survey of Connections, Possible Approaches

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### Famous quotes containing the word connection:

“Parents have railed against shelters near schools, but no one has made any *connection* between the crazed consumerism of our kids and their elders’ cold unconcern toward others. Maybe the homeless are not the only ones who need to spend time in these places to thaw out.”

—Anna Quindlen (b. 1952)