How Can I Differentiate Various Group Types in Algebra?

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Discussion Overview

The discussion revolves around differentiating various types of groups in algebra, including concepts such as surjective homomorphisms, isomorphic groups, cyclic groups, subgroups, normal groups, symmetric groups, quaternion groups, and quotient groups. Additionally, participants explore the concepts of supremum and infimum in the context of sets.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about distinguishing between various group types and seeks suggestions for better understanding.
  • Another participant defines isomorphism as a bijective homomorphism and describes subgroups as subsets of larger groups, noting that normal groups have specific properties related to cosets.
  • Participants discuss the supremum as the least upper bound and the infimum as the greatest lower bound, providing examples to illustrate these concepts.
  • There is a claim that the supremum of the set (0, 15] is 15 and the infimum is 0, which is affirmed by another participant.
  • One participant questions the definition of bounded sets, leading to a clarification that a set is bounded if it is bounded above and below.
  • There is a discussion about the minimum and infimum of the set A = (-12, 3], with some participants asserting that -12 is the infimum and questioning the closure of the set.
  • Another participant corrects a claim about closure, stating that a number cannot be closed and that the set is not closed since it does not contain all its limit points.

Areas of Agreement / Disagreement

Participants express various definitions and interpretations of group types and mathematical concepts, with some agreement on definitions but also notable confusion and differing perspectives, particularly regarding the closure of sets and the properties of infimum and supremum.

Contextual Notes

Some definitions and properties discussed may depend on specific mathematical contexts or assumptions that are not fully articulated in the discussion.

Charles007
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THese days. I am trying to tidy up with my summary notes.

I got surjective homomophism, isomorphic, and cyclic group, Subgroup, normal group, symmetric group, Quaternion group, and quotient group.

How to distinguish them. Is there any tric to understand and remember these. I am completely mess up with these things. what I should do...!~~ I being revising for 10days.

Any one give me some suggestion.
 
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One more question.

How, the supremum, the least upper bound.

Infimum, , supremum.

what is it mean?

Attempt.

for example,

1,. (0,15]

2, {n/2n+1|n belongs to nautral number (N)}
 


An isomorphism is a bijective homomorphism.
A subgroup is a group that is a subset of some 'larger' group (it is usually studied in relation to the original group)
A group is normal is every left coset is a right coset (rearranging the formula is useful for solving common group theory problems). Quotient groups are related to normal groups and deal with cosets.
The quaternion group is a nonabelian group with interesting properties
The symmetric group is a group of permutations.

The supremum of a set is the least upper bound of the set. That is, out of all the upper bounds of your set, the supremum is the 'smallest'.
The infimum is the opposite and is the greatest lower bound of the set.
for (0, 15], the supremum is 15 and infimum is 0
 


VeeEight said:
An isomorphism is a bijective homomorphism.
A subgroup is a group that is a subset of some 'larger' group (it is usually studied in relation to the original group)
A group is normal is every left coset is a right coset (rearranging the formula is useful for solving common group theory problems). Quotient groups are related to normal groups and deal with cosets.
The quaternion group is a nonabelian group with interesting properties
The symmetric group is a group of permutations.

The supremum of a set is the least upper bound of the set. That is, out of all the upper bounds of your set, the supremum is the 'smallest'.
The infimum is the opposite and is the greatest lower bound of the set.
for (0, 15], the supremum is 15 and infimum is 0

Thank you very much. Now I know what I should do next.

Collect all defination of group and connect them using your collection.

One more question. suppose we have a set A (-12,3]. (-x)------(-12)---------0-------------3----------------------------x

They minum for set A is -12, and infimum is -12. -12 is not closed, and 3 is closed.

The supremum of a set is the least upper bound of the set. So the 3 is supremum, the least upper bound [3,x) . also 3 is the max.

Am I right?
 


Let A and B be non-empty and bounded subsets of R.

What it is mean by bounded?
 


Charles007 said:
They minum for set A is -12, and infimum is -12. -12 is not closed, and 3 is closed.

Am I right?

a number cannot be closed. sets are closed if they contain all their limit points. the set you list is not closed, since 12 is a limit point and 12 is not in the set.
 


One more question. suppose we have a set A (-12,3]. (-x)------(-12)---------0-------------3----------------------------x

They minum for set A is -12, and infimum is -12. -12 is not closed, and 3 is closed.

The supremum of a set is the least upper bound of the set. So the 3 is supremum, the least upper bound [3,x) . also 3 is the max.

Am I right?

Yes 3 is the supremum and -12 is the infimum. The set has no minimum.

Let A and B be non-empty and bounded subsets of R.

What it is mean by bounded?

Set A is bounded above if there is some x in R such that a < x for all a in A. Bounded below is defined similarly and a set is bounded if it is bounded above and below.
 

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