Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
The Computational Basis and the State Vectors of a Qubit
lemmalem:qubit-basis-and-states-2026aAnalysisLinear AlgebraLet the qubit state space be as in that definition, with computational basis vectors and , standard inner product and induced norm . Let be an element of , and let denote the…- Let be the complex coordinate space with , which is a complex vector space by The Complex Coordinate Space is a Complex Vector Space, equipped with the standard inner product, which is an inner product on it by…
- Let together with be a complex inner product space and let be the norm induced by the inner product. A vector is a unit vector if .
The Standard Inner Product Makes the Complex Coordinate Space an Inner Product Space
lemmalem:standard-inner-product-cn-2026aAnalysisLinear AlgebraLet be a natural number, let be the complex coordinate space, which is a complex vector space by The Complex Coordinate Space is a Complex Vector Space, and let be the standard inner product on it. Then the following hold.…Standard Inner Product on the Complex Coordinate Space
definitiondef:standard-inner-product-cn-2026aAnalysisLinear AlgebraLet be a natural number, let be the complex coordinate space, and for a complex number let denote its complex conjugate. The standard inner product on assigns to each pair the complex number…The Complex Coordinate Space is a Complex Vector Space
lemmalem:cn-vector-space-2026aAlgebraLinear AlgebraLet be a natural number and let be the complex coordinate space, with the componentwise operations of that definition. Then with these operations is a complex vector space. Its zero vector is the -tuple al…- Let be a natural number and let be the field of complex numbers. The complex coordinate space is the set of all ordered -tuples of complex numbers, together with the operations defined componentwise by…
The Induced Norm is a Norm, and Induces a Metric
lemmalem:inner-product-norm-is-norm-2026aAnalysisLinear AlgebraLet together with be a complex inner product space, let be the norm induced by the inner product, and write with the additive inverse of Elementary Identities in a Vector Space. Then the following hold.…- Let together with be a complex inner product space and let . By condition 4 of Complex Inner Product Space the number is a real number with . The norm induced by the inner product assigns to …
- Let be a complex vector space with zero vector , and for a complex number let denote its modulus. A norm on is a map assigning to each a real number , subject to the following conditions for all and all com…
Cauchy-Schwarz Inequality in a Complex Inner Product Space
theoremthm:cauchy-schwarz-complex-2026aAnalysisLinear AlgebraLet together with be a complex inner product space and let . Then, with the modulus of a complex number, an inequality between real numbers, the two facto…Elementary Properties of a Complex Inner Product
lemmalem:inner-product-elementary-properties-2026aAnalysisLinear AlgebraLet together with be a complex inner product space, let be its zero vector, let , and let be a complex number with conjugate . Then the following hold. 1. (Additivity in the first argument)…- Let be the field of complex numbers, let be a complex vector space, let be its zero vector, and for let denote its complex conjugate. An inner product on is a map assigning to each pair of elements of…
- Let be a field and let and be vector spaces over . A map is linear if 1. for all ; 2. for all and , where on the left-hand sides the operations are those of and on th…
- Let be a field, let be a vector space over , and let be its zero vector. A subset of is a linear subspace of if 1. ; 2. for all ; 3. for all and .
Elementary Identities in a Vector Space
lemmalem:vector-space-basic-identities-2026aAlgebraLinear AlgebraLet be a field and let be a vector space over , with the conditions 1-8 of that definition. Then the following hold. 1. (Uniqueness of the zero vector) There is exactly one element with for every . 2. (Uniqueness of additive inverses)…- Let be a field, with additive identity and multiplicative identity . A vector space over is a set together with two operations: an addition, assigning to each pair of elements of an element of , and a scalar multiplication, assigning to each…
Global Existence for the Backward Riccati Equation under Convexity Conditions
corollarycor:backward-riccati-convex-existence-2026aAnalysisLinear AlgebraLet be a real number and natural numbers. Let (), (), (), (), and () assign real matrices to each , all entries being continuous functions of , such that every and ever…- Let be a natural number and let be a symmetric positive definite real matrix. Then is invertible, and its inverse is symmetric positive definite.
- Let be natural numbers. Products below are matrix products, is the transpose, and is the trace. 1. (Linearity) For real matrices and real numbers , where denotes the entrywise linear combination:…