Measurable functions and division by zero

Click For Summary
SUMMARY

The discussion centers on the measurability of the function g(t) = f(t)/t on the interval [0,1], where f is a measurable function. It is established that g is undefined at t=0 due to division by zero, but this occurs on a set of measure zero. The conclusion drawn is that g is measurable on [0,1] since it agrees with the measurable function g_0 = g|_{(0,1]} almost everywhere. The key point is that the definition of measurable functions does not exclude functions that take infinite values, allowing g to be defined on the entire interval [0,1] with g(0) = ∞.

PREREQUISITES
  • Understanding of measurable functions in real analysis
  • Knowledge of measure theory, particularly concepts of measure zero sets
  • Familiarity with limits and continuity in mathematical functions
  • Basic understanding of the extended real number line, including the concept of infinity
NEXT STEPS
  • Study the properties of measurable functions in real analysis
  • Explore measure theory, focusing on measure zero sets and their implications
  • Investigate the concept of functions defined almost everywhere and their applications
  • Learn about the extended real number line and its role in defining limits and continuity
USEFUL FOR

Mathematicians, students of real analysis, and anyone interested in the properties of measurable functions and their implications in measure theory.

AxiomOfChoice
Messages
531
Reaction score
1
Consider the function [itex]g(t) = f(t)/t[/itex] on [itex][0,1][/itex], where [itex]f[/itex] is measurable on [itex][0,1][/itex]. Does it follow that [itex]g[/itex] is measurable on [itex][0,1][/itex]? I know there's a problem -- namely, division by zero -- only on a set of measure zero -- namely, [itex]\{0\}[/itex] -- and that [itex]g[/itex] agrees with the measurable function [itex]g_0 = g|_{(0,1]}[/itex] almost everywhere. So I'd think the answer is "yes," since I was under the impression that if two functions agreed almost everywhere, then if one was measurable, the other was too...but I thought that was only if the functions were defined on the same set, and [itex]g[/itex] and [itex]g_0[/itex] clearly are not.
 
Physics news on Phys.org
There is nothing in the definition of measurable functions to prevent a function from being infinite.
 
In other words, g is defined on the whole interval [0,1]:
[tex]g:[0,1]\to\overline{\mathbb{R}}[/tex]

taking the value [itex]\infty[/itex] at t=0.
(well, I don't know how f is defined, but at least if f if is everywhere finite this makes sense)
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K