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Zero-dimensional Polish spaces are a particularly convenient setting for descriptive set theory. Examples of such spaces include the Cantor space and Baire space . Hausdorff zero-dimensional spaces are precisely the subspaces of topological powers 2 I {\displaystyle 2^{I}} where 2 = { 0 , 1 } {\displaystyle 2=\{0,1\}} is given the discrete ...
In geometry, a point is an abstract idealization of an exact position, without size, in physical space, [1] or its generalization to other kinds of mathematical spaces.As zero-dimensional objects, points are usually taken to be the fundamental indivisible elements comprising the space, of which one-dimensional curves, two-dimensional surfaces, and higher-dimensional objects consist; conversely ...
For ordinary Euclidean spaces, the Lebesgue covering dimension is just the ordinary Euclidean dimension: zero for points, one for lines, two for planes, and so on.However, not all topological spaces have this kind of "obvious" dimension, and so a precise definition is needed in such cases.
A point particle is an appropriate representation of any object whenever its size, shape, and structure are irrelevant in a given context. For example, from far enough away, any finite-size object will look and behave as a point-like object. Point masses and point charges, discussed below, are two common cases.
In geometry, a point group in three dimensions is an isometry group in three dimensions that leaves the origin fixed, or correspondingly, an isometry group of a sphere.It is a subgroup of the orthogonal group O(3), the group of all isometries that leave the origin fixed, or correspondingly, the group of orthogonal matrices.
A generic point of the topological space X is a point P whose closure is all of X, that is, a point that is dense in X. [1]The terminology arises from the case of the Zariski topology on the set of subvarieties of an algebraic set: the algebraic set is irreducible (that is, it is not the union of two proper algebraic subsets) if and only if the topological space of the subvarieties has a ...
Specifically, let r 0 be the position vector of some point P 0 = (x 0, y 0, z 0), and let n = (a, b, c) be a nonzero vector. The plane determined by the point P 0 and the vector n consists of those points P, with position vector r, such that the vector drawn from P 0 to P is perpendicular to n.
The isometries that fix a given point P form the stabilizer subgroup of the Euclidean group with respect to P. The restriction to this stabilizer of above group homomorphism is an isomorphism. So the isometries that fix a given point form a group isomorphic to the orthogonal group. Let P be a point, f an isometry, and t the translation that ...