Continued fraction of the square root of three Created 2026-09-24 Updated 2026-10-03
Successive complete quotients repeat after two steps:
Fundamental parallelogram of a period lattice Created 2026-09-24 Updated 2026-10-31
A fundamental parallelogram for is a translate of
Its translates tile the complex plane.
Equality case in the Steiner perimeter inequality Created 2026-09-24 Updated 2026-09-24
Equality holds exactly when , so the midpoints of all perpendicular chords lie on one line parallel to the symmetrizing axis.
At normal incidence, the reflected electric amplitude is the negative of the incident amplitude at the surface, while the reflected magnetic amplitude has the same sign. Their superposition forms a standing wave with an electric node and a magnetic antinode at the conductor.
Cubic pencil with a triangular member Created 2026-09-24 Updated 2026-09-24
The pencil generated by the Fermat cubic curve and contains both a smooth genus one curve and the union of the three coordinate lines. Its total space in is irreducible because the two generating cubics have no common factor.
Fermat cubic curve Created 2026-09-24 Updated 2026-10-14
The Fermat cubic is a smooth projective curve: its three first partial derivatives vanish simultaneously only at the forbidden zero vector. The genus of a smooth plane curve formula gives genus one.
This is the degree-three case of a Fermat equation; in general defines a Fermat curve.
Peculiar-velocity divergence Created 2026-09-24 Updated 2026-09-28
The peculiar-velocity divergence is . For irrotational linear perturbations it captures the scalar part of the peculiar velocity field.
Pearson residual Created 2026-09-24 Updated 2026-09-24
The Pearson residual is .
Pearson chi-squared test of independence Created 2026-09-24 Updated 2026-10-14
For an by contingency table, the statistic
has asymptotically a chi-squared distribution with degrees of freedom under independence.
Linear Lagrangian halo bias Created 2026-09-24 Updated 2026-10-05
Linear Lagrangian halo bias is the fractional response of halo abundance to a long-wavelength overdensity in the initial coordinates. For Press-Schechter halos, .

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