Is Pointwise Multiplication a Valid Inner Product for Continuous Functions?

The dot product is an inner product. In summary, the space of continuous functions with the innerproduct being the usual product is an inner product space because pointwise multiplication results in another function. However, we often use the space of functions with the norm defined by an integral instead of a simple product because the integral norm gives us a notion of orthogonality, while the simple product does not. This is similar to how the dot product in ℝ3 has a summation to give us a notion of orthogonality.
  • #1
aaaa202
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Is the space of continuous functions with the innerproduct being the usual product an inner product space? And if so, why is it we always want to use the space of functions with the norm defined by an integral and not just a simple product? Is it because this IP gives us no notion of orthogonality?
 
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  • #2
aaaa202 said:
Is the space of continuous functions with the innerproduct being the usual product an inner product space?

Inner products are scalar valued. Pointwise multiplication results in another function.

And if so, why is it we always want to use the space of functions with the norm defined by an integral and not just a simple product? Is it because this IP gives us no notion of orthogonality?

Consider ℝ3 and think about why the dot product has a summation.
 

FAQ: Is Pointwise Multiplication a Valid Inner Product for Continuous Functions?

What is meant by the "space of continuous functions"?

The space of continuous functions refers to a mathematical concept in which all possible continuous functions in a given domain are considered together as a single entity. This space is often denoted by C(X), where X is the domain of the functions. It is a fundamental concept in the field of functional analysis and is widely used in various branches of mathematics and physics.

2. How is the space of continuous functions different from other function spaces?

The main difference between the space of continuous functions and other function spaces is that all the functions in this space are continuous, meaning that they have no abrupt changes or breaks in their values. This is in contrast to other function spaces, such as the space of differentiable functions, which only include functions that have a well-defined derivative at every point in their domain.

3. What are some practical applications of the space of continuous functions?

The space of continuous functions has numerous practical applications in various fields. In mathematics, it is used in the study of differential equations, Fourier analysis, and approximation theory. In physics, it is used in the study of wave phenomena, such as sound and light waves. It is also used in engineering for modeling and analyzing continuous systems, such as electrical circuits and fluid dynamics.

4. What are the important properties of the space of continuous functions?

Some of the important properties of the space of continuous functions include its closure under addition, scalar multiplication, and composition. It is also a complete space, meaning that all Cauchy sequences in this space converge to a function in the same space. Additionally, it is a Banach space, which means it is a complete normed vector space, equipped with a norm that measures the size of a function.

5. How is the space of continuous functions related to the concept of continuity?

The space of continuous functions is closely related to the concept of continuity, as it consists of all the functions that are continuous in a given domain. In fact, the space of continuous functions is often used to define the concept of continuity in a more general setting, such as in topology. Furthermore, the properties of continuity, such as the intermediate value theorem and the extreme value theorem, hold true for all functions in this space.

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