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A closely related notion of curvature comes from gauge theory in physics, where the curvature represents a field and a vector potential for the field is a quantity that is in general path-dependent: it may change if an observer moves around a loop. Two more generalizations of curvature are the scalar curvature and Ricci curvature. In a curved ...
Radius of curvature and center of curvature. In differential geometry, the radius of curvature, R, is the reciprocal of the curvature. For a curve, it equals the radius of the circular arc which best approximates the curve at that point. For surfaces, the radius of curvature is the radius of a circle that best fits a normal section or ...
The product k 1 k 2 of the two principal curvatures is the Gaussian curvature, K, and the average (k 1 + k 2)/2 is the mean curvature, H. If at least one of the principal curvatures is zero at every point, then the Gaussian curvature will be 0 and the surface is a developable surface. For a minimal surface, the mean curvature is zero at every ...
In 3 dimensions the curl of a vector field is a vector field as is familiar (in 1 and 0 dimensions the curl of a vector field is 0, because there are no non-trivial 2-vectors), while in 4 dimensions the curl of a vector field is, geometrically, at each point an element of the 6-dimensional Lie algebra ().
The Berry curvature per solid angle is given by ¯ = / = /. In this case, the Berry phase corresponding to any given path on the unit sphere S 2 {\displaystyle {\mathcal {S}}^{2}} in magnetic-field space is just half the solid angle subtended by the path.
The equivalence classes are called C r-curves and are central objects studied in the differential geometry of curves. Two parametric C r-curves, : and :, are said to be equivalent if and only if there exists a bijective C r-map φ : I 1 → I 2 such that : ′ and : (()) = (). γ 2 is then said to be a re-parametrization of γ 1.
A normal vector of length one is called a unit normal vector. A curvature vector is a normal vector whose length is the curvature of the object. Multiplying a normal vector by −1 results in the opposite vector, which may be used for indicating sides (e.g., interior or exterior).
Developing the equation for , and grouping the terms in and , we obtain ˙ + ˙ = ¨ + ¨ = ˙ + ˙ Denoting =, the first equation means that is orthogonal to the unit tangent vector at : = The second relation means that = where = = ˙ + ˙ [¨ ¨] is the curvature vector.