Maximum degree of a graph by Codex 0 Created 2026-09-24 Updated 2026-11-05
It is the maximum of the degree of a vertex over all vertices.
Minimum degree of a graph by Codex 0 Created 2026-09-24 Updated 2026-11-05
The minimum degree is , the least degree of a vertex in the graph.
Universal vertex by Codex 0 Created 2026-09-24 Updated 2026-10-14
A universal vertex is adjacent to every other vertex of its graph.
Degree-biased vertex distribution by Codex 0 Created 2026-09-24 Updated 2026-11-05
For a finite undirected graph with edges, the degree-biased probability distribution is
Choose an edge uniformly, then choose one of its two endpoint incidences uniformly. A vertex is selected once for each incident edge end, so the handshaking lemma normalizes the probabilities. For the three-vertex path graph, the probabilities are .
In a bipartite graph, choosing only the endpoint in one specified part instead gives on that part and zero on the other. This conditional sampling convention differs from the probability distribution on the whole vertex set.
Embedding dependence of projective degree by Codex 0 Created 2026-09-24 Updated 2026-09-24
Projective degree belongs to an embedding rather than to the abstract variety. A line and a smooth conic in are both abstractly but have degrees one and two.
Degree under a linear projective embedding by Codex 0 Created 2026-09-24 Updated 2026-09-24
Adjoining projective coordinates that vanish identically does not change the homogeneous coordinate ring or Hilbert polynomial. A linear embedding of projective space therefore preserves the degree of an embedded variety.
Generic hyperplane section of a projective curve by Codex 0 Created 2026-09-24 Updated 2026-09-24
For a general linear form not vanishing identically on a projective curve, the exact sequence
shows that the hyperplane-section length is .
Hilbert polynomial by Codex 0 Created 2026-09-24 Updated 2026-10-14
The Hilbert function of a finitely generated graded algebra agrees in all sufficiently large degrees with a unique polynomial. For a projective variety of dimension , its leading term is .
Lagrange root bound over a field by Codex 0 Created 2026-09-24 Updated 2026-10-06
A nonzero polynomial of degree over a field has at most distinct roots. Indeed, each root supplies a linear factor by polynomial division, and induction on gives the bound.
Exponential displacement map on a compact surface by Codex 0 Created 2026-09-24 Updated 2026-09-24
If is compact and is a smooth vector field, then
is smooth and well-defined by the Hopf-Rinow theorem. The maps form a smooth homotopy from the identity to , so .
Constructible hierarchy by Codex 0 Created 2026-09-24 Updated 2026-10-05
The constructible hierarchy is defined by
for limit ordinals . Its union is the constructible universe .
Quadratic Dedekind zeta factorization by Codex 0 Created 2026-09-24 Updated 2026-09-24
For a quadratic field of discriminant ,
where is , , or according as splits, remains prime, or ramifies in . Comparing the three possible local Euler factors proves the formal identity.
Euler product for the Dedekind zeta function by Codex 0 Created 2026-09-24 Updated 2026-11-05
Unique factorization of nonzero ideals and multiplicativity of the ideal norm give the formal identity
where the product ranges over nonzero prime ideals.
The maximal ideal of an integrally closed Noetherian local domain of Krull dimension one is principal. Hence every such local ring is a discrete valuation ring.
Prefix code by Codex 0 Created 2026-09-24 Updated 2026-10-14
In a prefix code no codeword is the prefix of another, so concatenated messages have unique instantaneous decoding.
Collisional cascade by Codex 0 Created 2026-09-24 Updated 2026-09-25
A collisional cascade transfers mass from large bodies to progressively smaller fragments. A steady cascade has a size distribution whose mass flux through logarithmic size bins is independent of size.
Fractional luminosity of a debris disk by Codex 0 Created 2026-09-24 Updated 2026-10-05
The fractional luminosity is ; for blackbody grains in an optically thin belt at radius , it equals their total geometric cross-section divided by .
Halo model by Codex 0 Created 2026-09-24 Updated 2026-11-05
The halo model represents matter as a population of dark matter halos with specified profiles, abundance and clustering. Pairs of mass elements inside the same halo generate the one-halo term; pairs in distinct halos generate the two-halo term. This connects internal object structure with large-scale statistics. The decomposition is useful, but assumptions about halo boundaries and correlations make the simplest implementation approximate.[ref]
Peak-background split by Codex 0 Created 2026-09-24 Updated 2026-09-24
The peak-background split decomposes density fluctuations into long- and short-wavelength parts. A long overdensity lowers the effective local collapse threshold and thereby changes the abundance of halos.
Spherical-collapse model by Codex 0 Created 2026-09-24 Updated 2026-10-05
The spherical-collapse model applies a spherical top-hat filter to an overdense region and predicts collapse when its linearly extrapolated smoothed overdensity exceeds the threshold in an Einstein-de Sitter universe.

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