Exploring the Limits of Integral Inequalities in Measure Spaces

In summary, an integral inequality is a mathematical statement that compares an integral to another quantity and is typically written as an inequality. It differs from a regular inequality in that it involves a more complex operation and can hold for a range of values. Real-world applications include physics, engineering, and economics. Solving an integral inequality involves finding the value or range of values that satisfy the inequality. Integral inequalities can also be used in multiple dimensions by using multiple integrals.
  • #1
jostpuur
2,116
19
Let X be a measure space, and [itex]f:X\times X\to [0,\infty[[/itex] some integrable function. Is the following inequality always true,

[tex]
\int\limits_{X} dx\;f(x,x)\; \leq\; \sup_{x_1\in X} \int\limits_{X} dx_2\; f(x_1,x_2) ?
[/tex]
 
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  • #2
No. Let f(x,y)=sinxsiny for 0<=x,y,<=2pi and zeo otherwise. The left integral is pi, while the right integral is 0.
 
  • #3
I see.

[tex]
f:[0,2\pi]\times [0,2\pi]\to [0,\infty[,\quad f(x,y) = \sin(x)\sin(y) + 1
[/tex]

gives a counter example that satisfies the original conditions.
 

1. What is an integral inequality?

An integral inequality is a mathematical statement that compares the value of an integral (a type of mathematical operation used to find the area under a curve) to another quantity. It is typically written as an inequality, such as f(x) ≤ g(x), where f(x) and g(x) are functions and the inequality holds for all values of x.

2. How is an integral inequality different from a regular inequality?

An integral inequality involves an integral, which is a more complex mathematical operation compared to simple arithmetic operations used in regular inequalities. This means that the variables in an integral inequality can represent a range of values instead of just single numbers, and the inequality may hold for a range of values instead of just one specific value.

3. What are some real-world applications of integral inequalities?

Integral inequalities are commonly used in physics, engineering, and economics to model and solve problems involving rates of change, optimization, and area/volume calculations. For example, they can be used to determine the optimal design for a bridge or the most efficient way to allocate resources in a production process.

4. How are integral inequalities solved?

Solving an integral inequality involves finding the value or range of values for the variable that satisfies the inequality. This can be done through various methods such as using the properties of integrals, graphing, or using numerical methods. The specific approach depends on the complexity of the inequality and the available tools.

5. Can integral inequalities be used in multiple dimensions?

Yes, integral inequalities can be extended to multiple dimensions, such as for calculating volume or surface area in three-dimensional space. This involves using multiple integrals, which are similar to single integrals but with additional variables representing the different dimensions.

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