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A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. [1] Concretions are often ovoid or spherical in shape, although irregular shapes also occur.
To the definition of an ovoid: t tangent, s secant line. In projective geometry an ovoid is a sphere like pointset (surface) in a projective space of dimension d ≥ 3. Simple examples in a real projective space are hyperspheres . The essential geometric properties of an ovoid are:
Spontaneous symmetry breaking is a promising mechanism, which could be used to give mass to the vector gauge particles. A significant difficulty which one encounters, however, is Goldstone's theorem, which states that in any quantum field theory which has a spontaneously broken symmetry there must occur a zero-mass particle. So the problem ...
To the definition of an oval in a projective plane To the definition of an ovoid. In a projective plane a set Ω of points is called an oval, if: Any line l meets Ω in at most two points, and; For any point P ∈ Ω there exists exactly one tangent line t through P, i.e., t ∩ Ω = {P}.
Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography (i.e. coastal geomorphology, geology, and oceanography) and the human geography of the coast.
This produces a variation on the definition, namely the projective plane is defined as the set of lines in that pass through the origin and the coordinates of a non-zero element (,,) of a line are taken to be homogeneous coordinates of the line. These lines are now interpreted as points in the projective plane.
Analogously, a mass deficit will weaken the gravity pull but will increase the geopotential at a given distance, causing the geoid to move towards the mass deficit. The presence of a localized inclusion in the background medium will rotate the gravity acceleration vectors slightly towards or away from a denser or lighter body, respectively ...
The ellipsoid is a mathematically defined regular surface with specific dimensions. The geoid, on the other hand, coincides with that surface to which the oceans would conform over the entire Earth if free to adjust to the combined effect of the Earth's mass attraction (gravitation) and the centrifugal force of the Earth's rotation.