What Does One-to-One Correspondence Mean in Mathematics?

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Discussion Overview

The discussion centers on the concept of one-to-one correspondence in mathematics, particularly in the context of set theory and linear algebra. Participants explore the definitions, distinctions, and implications of one-to-one correspondence and one-to-one mapping, as well as their relevance in mathematical contexts.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks clarification on the terms "one-to-one correspondence" and "one-to-one mapping," questioning whether they are synonymous or distinct.
  • Another participant explains that a one-to-one correspondence (bijection) involves a pairing between two sets where each element in one set corresponds uniquely to an element in the other set.
  • A further contribution illustrates the concept using an example of associating letters of the alphabet with integers from 1 to 26, emphasizing the mutual exclusivity of the correspondence.
  • One participant notes the distinction between one-to-one correspondence and one-to-one mapping, stating that while both involve unique pairings, a one-to-one correspondence ensures every element in the range is paired with an element from the domain.
  • This participant suggests that the terminology can be confusing and advocates for using the terms injection (for one-to-one mapping) and bijection (for one-to-one correspondence) for clarity.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and definitions related to one-to-one correspondence and one-to-one mapping. There is no consensus on the best terms to use or the clarity of the definitions.

Contextual Notes

Some participants indicate that understanding these concepts may depend on prior exposure to set theory and functions, which could limit the discussion's accessibility to those unfamiliar with these foundational topics.

rethipher
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What is a one-to-one correspondence or one to one mapping? I have heard the later term used plenty of times in linear algebra classes I've taken, i.e. there is a one to one mapping from a subspace to another. But I've never really understood what that meant entirely. Are the two above phrasees the same, or different? And if they are different how are they different? Quick sidenote: this is not homework of any kind, no problems/grades or any such thing. I do self study in my down time when I'm not in school, and this came up in a math book I'm looking at and I think I need to fully understand what it means so I get the full understanding and not just a superficial understanding that I can confuse for real understanding. Thanks for your time and any answer!
 
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The wiki article on Bijection should cover it pretty thoroughly. The premise is as follows: Given two sets (collections of objects), a one-to-one correspondence (bijection) describes a construction where every element in one set is associated with one and only one element of the other set, and vice-versa. It's difficult to explain properly without the concept of a function, but I'm not sure how much set theory you've been exposed to.
 
if you think of a space as a collection of points then a one to one mapping from one space to another is a means of associating a pt in one space with a pt in another for all pts and vice versa.

A simple set example would be to associate the letters of the alphabet with the range of integers from 1 to 26. there is no letter without a corresponding number and there is no number without a corresponding letter.

wikipedia describes it in more detail:

http://en.wikipedia.org/wiki/One-to-one_correspondence
 
It's worth noting that 1-1 correspondence is not the same as 1-1 mapping.

In a 1-1 mapping, different elements of the domain go to different elements of the range.

A 1-1 correspondence is a 1-1 mapping in which every element of the range gets hit by some element of the domain.

This is a confusing bit of terminology, which is why it's better to use the terms injection and bijection. An injection is what I just defined as a 1-1 mapping. A bijection is a 1-1 correspondence.
 

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