6,052 articles
Square-free integer
A square-free integer, also called a squarefree number, is an integer not divisible by any perfect square greater than 1; examples include 6 and 30, while 12 is not.
Square-root information filter
The square-root information filter (SRIF) is a state-estimation algorithm equivalent to the Kalman filter but numerically more stable, developed by Gerald J. Bierman at JPL.
Square–cube law
The square–cube law states that when an object is scaled up, surface area grows as k² and volume as k³, first described by Galileo in 1638.
Squarefree word
A squarefree word is a string of symbols containing no immediately repeated block, such as cocoa; Thue showed in 1906 that arbitrarily long ones exist over three letters.
Squaring the circle
Squaring the circle, also called quadrature of the circle, is the classical problem of constructing a square equal in area to a circle with compass and straightedge.
Squeeze theorem
The squeeze theorem, also called the sandwich theorem or pinching theorem, states that a function trapped between two functions with the same limit has that limit.
Squircle
A squircle is a closed plane curve between a square and a circle, with continuously varying corner curvature, defined as a superellipse with exponent 4.
Srinivasa Ramanujan (ஸ்ரீனிவாஸ் ராமானுஜன்)
Srinivasa Ramanujan Aiyangar (ஸ்ரீனிவாஸ் ராமானுஜன்) was an Indian mathematician, born 1887 and died 1920, known for work on partitions, infinite series, and his collaboration with G. H. Hardy at Cambridge.
Stability (probability)
Stability in probability theory, also called stable convergence, is a strengthening of convergence in distribution, introduced by Alfred Rényi in 1963, in which the limit holds jointly with every event.
Stability selection
Stability selection is a statistical variable selection method, introduced by Meinshausen and Bühlmann in 2010, that runs the lasso on many random subsamples and keeps variables selected consistently.
Stability study statistics
Stability study statistics is the branch of pharmaceutical statistics that designs drug stability protocols and estimates shelf life, chiefly by regressing a quality attribute against time under ICH Q1E guidance.
Stability theory
Stability theory is the branch of model theory, founded on Saharon Shelah's classification program, that sorts first-order theories into dividing lines such as stable, simple, and NIP.
Stabilizer subgroup
The stabilizer subgroup, also called the isotropy group or little group, consists of the elements of a group action that leave a given point fixed.
Stable distribution
The stable distribution, or Lévy alpha-stable distribution, is a probability distribution whose shape is preserved under addition; it includes the normal, Cauchy, and Lévy distributions as closed-form cases.
Stable group
A stable group is a group definable in a model of a stable first-order theory; examples include abelian groups, algebraic groups over algebraically closed fields, and free groups.
Stable Lévy process
Stable Lévy process is a continuous-time Lévy process characterized by $\alpha$-stable increments for $0 < \alpha \leq 2$. It generalizes Brownian motion and exhibits power-law-tailed increments.
Stable manifold theorem
The stable manifold theorem, also known as the Hadamard–Perron theorem, states that orbits near a hyperbolic equilibrium that approach it form a smooth manifold tangent to the stable eigenspace.
Stable matching problem
The stable matching problem, also called the stable marriage problem, asks how to pair two sets of participants so no two would both prefer each other over their assigned partners.
Stable matrix
A stable matrix, also called a Hurwitz matrix, is a square matrix whose eigenvalues all have strictly negative real parts, meaning a continuous linear system governed by it decays to zero.
Stable rank
Stable rank, or topological stable rank, is a numerical invariant of a C-algebra, introduced by Marc Rieffel in 1983 as the first noncommutative generalization of covering dimension.
Stable theory
A stable theory is a complete first-order theory that forbids the combinatorial pattern called the order property, a tameness condition central to Shelah's classification program in model theory.
Stack (mathematics)
In algebraic geometry, a stack is a category fibred in groupoids over schemes that behaves like a sheaf of geometric objects, introduced by Deligne and Mumford in 1969 to solve moduli problems with automorphisms.
Stack machine
A stack machine, also called a stack computer, is a computer or virtual machine whose instructions take operands from a last-in, first-out stack rather than named registers.
Stackelberg game
A Stackelberg game is a game-theoretic model of hierarchical decision-making in which a leader commits to a strategy first and the follower best-responds, applied in economics and security.
Staggered difference-in-differences
Staggered difference-in-differences is a family of econometric designs estimating causal effects when units adopt treatment at different times, using adoption-timing variation and avoiding biased two-way fixed effects comparisons.
Standard Borel space
A standard Borel space, also called a standard measurable space, is a measurable space isomorphic to a Borel subset of a separable complete metric space, central to probability theory.
Standard conjectures on algebraic cycles
The standard conjectures on algebraic cycles are open conjectures in algebraic geometry, formulated by Alexander Grothendieck in the mid 1960s and motivated by the Weil conjectures.
Standard deviation
The standard deviation, named by Karl Pearson in 1893, is a statistical measure of how widely values are dispersed from their mean, calculated as the square root of the variance.
Standard error
The standard error, also called the standard error of estimation, is the standard deviation of a statistic's sampling distribution over repeated samples from a population.
Standard form of a von Neumann algebra
The standard form of a von Neumann algebra is a canonical Hilbert-space representation with a self-dual cone, proved to exist and be unique by Haagerup in 1975.