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Numbers

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  Numbers [ edit ] Many number systems, such as the integers and the  rationals , enjoy a naturally given group structure. In some cases, such as with the rationals, both addition and multiplication operations give rise to group structures. Such number systems are predecessors to more general algebraic structures known as  rings  and fields. Further abstract algebraic concepts such as  modules ,  vector spaces  and  algebras  also form groups. Integers [ edit ] The group of integers  �  under addition, denoted  ( � , + ) , has been described above. The integers, with the operation of multiplication instead of addition,  ( � , ⋅ )  do  not  form a group. The associativity and identity axioms are satisfied, but inverses do not exist: for example,  � = 2  is an integer, but the only solution to the equation  � ⋅ � = 1  in this case is  � = 1 2 , which is a rational number, but not an in...

HILBERT SPACES

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  Hilbert spaces [ edit ] Main article:  Hilbert space The succeeding snapshots show summation of 1 to 5 terms in approximating a periodic function (blue) by finite sum of sine functions (red). Complete inner product spaces are known as  Hilbert spaces , in honor of  David Hilbert . [51]  The Hilbert space  � 2 ( Ω ) ,  with inner product given by ⟨ �   ,   � ⟩ = ∫ Ω � ( � ) � ( � ) ¯ � � , where  � ( � ) ¯  denotes the  complex conjugate  of  � ( � ) , [52] [nb 11]  is a key case. By definition, in a Hilbert space any Cauchy sequence converges to a limit. Conversely, finding a sequence of functions  � �  with desirable properties that approximates a given limit function, is equally crucial. Early analysis, in the guise of the  Taylor approximation , established an approximation of  differentiable functions   �  by polynomials. [53]  By the  Stone–Weierstrass theorem , ever...

LINEAR ALGEBRA

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Linear algebra 90 languages Article Talk Read Edit View history From Wikipedia, the free encyclopedia In three-dimensional  Euclidean space , these three planes represent solutions to linear equations, and their intersection represents the set of common solutions: in this case, a unique point. The blue line is the common solution to two of these equations. Linear algebra  is the branch of  mathematics  concerning  linear equations  such as: � 1 � 1 + ⋯ + � � � � = � , linear maps  such as: ( � 1 , … , � � ) ↦ � 1 � 1 + ⋯ + � � � � , and their representations in  vector spaces  and through  matrices . [1] [2] [3] Linear algebra is central to almost all areas of mathematics. For instance, linear algebra is fundamental in modern presentations of  geometry , including for defining basic objects such as  lines ,  planes  and  rotations . Also,  functional analysis , a branch of mathematical analysis, may be viewe...