Functionals->functions of infinite variables?

In summary, a functional can be seen as a normal function that maps between a set of real numbers to another set of real numbers, but it may not have a Taylor expansion or may not hold for certain types of functions such as discontinuous or non-differentiable functions.
  • #1
HomogenousCow
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If we think of a functional as a function of the infinite number of taylor coefficients of the variable function, aren't they then just normal functions, a map between a set of reals to another set of reals.
 
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  • #2
HomogenousCow said:
If we think of a functional as a function of the infinite number of taylor coefficients of the variable function, aren't they then just normal functions, a map between a set of reals to another set of reals.

The "variable function" may not have a Taylor expansion, or if it does for part of its domain, the expansion may not hold for the rest. Simple example, L2 includes discontinuous functions, functions without derivatives, etc.
 

1. What are functionals and how are they different from functions?

Functionals are mathematical operators that take in a function as an input and output a numerical value. They are different from functions because functions take in specific values as inputs and output specific values as outputs, while functionals take in a whole function as an input and output a single value.

2. What is the purpose of using functionals in mathematics?

Functionals are commonly used in mathematics to study and analyze functions with infinite variables, such as in calculus and functional analysis. They allow for a more general and abstract approach to understanding functions and their properties.

3. How are functionals applied in real-world problems?

Functionals are applied in a variety of real-world problems, such as optimization, control theory, and physics. In optimization, functionals are used to find the best possible solution to a problem. In control theory, they are used to design optimal control systems. In physics, functionals are used to study the behavior of physical systems.

4. What are some common examples of functionals?

Some common examples of functionals include the integral, derivative, and expectation functionals. The integral functional takes in a function and outputs the area under the curve. The derivative functional takes in a function and outputs the rate of change of that function. The expectation functional takes in a probability distribution and outputs the expected value of a random variable.

5. What are some key properties of functionals?

Functionals have several important properties, including linearity, continuity, and boundedness. Linearity means that a functional satisfies the properties of additivity and scalability. Continuity means that a small change in the input function results in a small change in the output value. Boundedness means that the output value of a functional is limited within a certain range.

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