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- In the mathematical theory of Riemannian geometry, there are two uses of the term Fermi coordinates.In one use they are local coordinates that are adapted to a geodesic. In a second, more general one, they are local coordinates that are adapted to any world line, even not geodesical. Take a future-directed timelike curve , being the proper time along in the spacetime . Assume that is the initial point of . Fermi coordinates adapted to are constructed this way. Consider an orthonormal basis of with parallel to . Transport the basis along making use of Fermi-Walker's transport. The basis at each point is still orthonormal with parallel to and is non-rotated (in a precise sense related to the decomposition of Lorentz transformations into pure transformations and rotations) with respect to the initial basis, this is the physical meaning of Fermi-Walker's transport. Finally construct a coordinate system in an open tube , a neighbourhood of , emitting all spacelike geodesics through with initial tangent vector , for every . A point has coordinates where is the only vector whose associated geodesic reaches for the value of its parameter and is the only time along for that this geodesic reaching exists. If itself is a geodesic, then Fermi-Walker's transport becomes the standard parallel transport and Fermi's coordinates become standard Riemannian coordinates adapted to . In this case, using these coordinates in a neighbourhood of , we have , all Christoffel symbols vanish exactly on . This property is not valid for Fermi's coordinates however when is not a geodesic.Such coordinates are called Fermi coordinates and are named after the Italian physicist Enrico Fermi. The above properties are only valid on the geodesic. The Fermi-Coordinates adapted to a null geodesic is provided by Mattias Blau, Denis Frank, and Sebastian Weiss. Notice that, if all Christoffel symbols vanish near , then the manifold is flat near . (en)
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- In the mathematical theory of Riemannian geometry, there are two uses of the term Fermi coordinates.In one use they are local coordinates that are adapted to a geodesic. In a second, more general one, they are local coordinates that are adapted to any world line, even not geodesical. Take a future-directed timelike curve , being the proper time along in the spacetime . Assume that is the initial point of . Fermi coordinates adapted to are constructed this way. Consider an orthonormal basis of with parallel to . (en)
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