Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
The Set of Controls with Values in a Compact Convex Set is Weakly Metrizable and Compact
theoremthm:l2-control-set-weak-metrizable-compact-2026aAnalysisLet be a real number and a natural number, write and adopt the pairing , the norm and the metric of the Lebesgue space in the case . Let be a n…Weak Lower Semicontinuity of the Running-Cost Integral along a State Path
lemmalem:running-cost-integral-weak-lsc-2026bAnalysisProbabilityLet and be natural numbers with and , let be population cost data on states with control dimension , and let be the probability simplex. Let be a real number, adopt the notation of…The Set of Controls with Values in a Closed Bounded Set is Nonempty, Bounded, Convex and Closed
lemmalem:l2-control-set-properties-2026aAnalysisLet , and be as in the definition of the set of -valued controls, write , and adopt the norm and the metric of the Lebesgue space in the case…Bounded Sequences in the Lebesgue Space of Square-Integrable Vector-Valued Functions Have Weakly Convergent Subsequences
theoremthm:l2-weak-compactness-2026aAnalysisLet and be as in the definition of the Lebesgue space , write , and adopt the pairing , the norm and the metric of that definition. Le…The Set of Controls with Values in a Prescribed Subset of Euclidean Space
definitiondef:l2-control-set-2026aAnalysisLet be a real number and let be a natural number. Adopt the notation of the Lebesgue space in the case : the set of square-integrable maps, the class of such a map, the space…Closed Convex Subsets of the Lebesgue Space of Square-Integrable Vector-Valued Functions are Weakly Sequentially Closed
lemmalem:l2-mazur-weak-closed-2026aAnalysisLet and be as in the definition of the Lebesgue space , write , and adopt the pairing , the norm and the metric of that definition. Le…Riesz-Frechet Representation of Bounded Linear Functionals on the Lebesgue Space of Square-Integrable Vector-Valued Functions
theoremthm:l2-riesz-frechet-2026aAnalysisLet and be as in the definition of the Lebesgue space , write , and adopt the pairing and the norm of that definition. Let…Rational Intervals and Rays Generate the Borel Sigma-Algebra of the Real Line
lemmalem:borel-real-generators-2026aAnalysisTopologyLet be the set of rational numbers and let be the Borel -algebra on the real line. Write for the family of open intervals with and , and for the family of rays…Generator Criterion for Measurability
lemmalem:measurability-generator-criterion-2026aAnalysisProbabilityLet and be measurable spaces and let be a function. 1. (Pullback -algebra) The family of all subsets of with is a -algebra on . 2. (Generator criterion) Let be a fa…The Integers and the Rational Numbers are Countable
lemmalem:rationals-countable-2026aAnalysisSet TheoryLet be the set of integers and let be the set of rational numbers, both regarded as subsets of the real numbers. Then the following hold. 1. is countable. 2. is countable. 3. For every natural number , the set…- Let be the real numbers with the order of its ordered field structure, let be the set of rational numbers, and let denote the absolute value of . For write to mean and . Then the follo…
Existence and Uniqueness of the Integer Part of a Real Number
theoremthm:floor-integer-part-2026aAnalysisAdopt the notation of the definition of the integers: is the real numbers with the order of its ordered field structure, is the set of natural numbers, is the canonical map, and is the set of integers. For wr…Arithmetic, Order, Discreteness and Intervals of the Integers
lemmalem:integers-arithmetic-order-2026bAnalysisAlgebraThe integers split into zero, the positive and the negative naturals, are closed under the ring operations, have no element strictly between 0 and 1, and the integers from a to b form a finite set with b-a+1 elements.The Rational Numbers as a Subset of the Real Numbers
definitiondef:rational-numbers-2026aAnalysisAlgebraLet be the real numbers, a field in which denotes the multiplicative inverse of a nonzero element , and let be the set of integers. The set of rational numbers is…- Let be the real numbers, an ordered field whose additive identity is and in which denotes the additive inverse of , let be the set of natural numbers, and let be the canonical map of . The set of…
Nearest-Point Projection onto a Nonempty Closed Convex Subset of the Lebesgue Space of Square-Integrable Vector-Valued Functions
theoremthm:l2-convex-projection-2026aAnalysisLet and be as in the definition of the Lebesgue space , write , and adopt the pairing , the norm and the metric of that definition. Le…Basic Properties of Weak Convergence in the Lebesgue Space of Square-Integrable Vector-Valued Functions
lemmalem:weak-convergence-l2-basics-2026aAnalysisLet and be as in the definition of the Lebesgue space , write , and adopt the pairing , the norm and the metric of that definition, tog…Convex Subset of the Lebesgue Space of Square-Integrable Vector-Valued Functions
definitiondef:convex-subset-l2-2026aAnalysisLet and be as in the definition of the Lebesgue space , whose vector operations are those of that definition. A subset of is convex if for all and every real number with…Separability of the Lebesgue Space of Square-Integrable Vector-Valued Functions
lemmalem:l2-interval-separable-2026aAnalysisLet and be as in the definition of the Lebesgue space , and adopt the notation of that definition, of the inner-product lemma, and the level- dyadic atoms of the dyadic averaging lemma. Write for the function eq…Completeness of the Lebesgue Space of Square-Integrable Vector-Valued Functions
lemmalem:l2-interval-complete-2026aAnalysisLet and be as in the definition of the Lebesgue space , and adopt the notation of that definition together with that of the inner-product lemma for . Then the following hold. 1. (Completeness.) The metric space…