How are R^2 and R^4 isomorphic as VS's over Q?

  • Context: Graduate 
  • Thread starter Thread starter joeblow
  • Start date Start date
Click For Summary
SUMMARY

The discussion centers on the isomorphism between the C-tensor product of C and C, and the R-tensor product of C and C as Q-modules. It is established that while the former is isomorphic to R² and the latter to R⁴ over R, both vector spaces are infinite dimensional over Q. The isomorphism holds due to the equality of the cardinality of their bases, which is the cardinality of the Continuum. The tensor product serves to extend the field of scalars, transforming a real vector space of dimension n into a complex vector space of dimension n and a real vector space of dimension 2n.

PREREQUISITES
  • Understanding of tensor products in linear algebra
  • Familiarity with vector spaces over different fields (R, C, Q)
  • Knowledge of cardinality and dimensions of vector spaces
  • Basic concepts of isomorphism in linear algebra
NEXT STEPS
  • Study the properties of tensor products in linear algebra
  • Explore the concept of vector spaces over different fields, focusing on R, C, and Q
  • Learn about cardinality and its implications in vector space theory
  • Investigate isomorphisms in the context of infinite dimensional spaces
USEFUL FOR

Mathematicians, students of linear algebra, and anyone interested in advanced topics related to vector spaces and tensor products.

joeblow
Messages
71
Reaction score
0
I came across a problem asserting that the C-tensor product of C and C and the R-tensor product of C and C are isomorphic as Q-modules. How does this begin to make sense as they do not have the same dimension over R? The first is isomorphic to R2 and the second is isomorphic to R4 over R.

Also, I'm struggling with tensors. Does anyone have a good source I should check out? (I've tried many)
 
Last edited:
Physics news on Phys.org
joeblow said:
I came across a problem asserting that the C-tensor product of C and C and the R-tensor product of C and C are isomorphic as Q-modules. How does this begin to make sense as they do not have the same dimension over R? The first is isomorphic to R2 and the second is isomorphic to R4 over R.

Also, I'm struggling with tensors. Does anyone have a good source I should check out? (I've tried many)

Over Q these vector spaces are infinite dimensional. They will be isomorphic if the cardinality of their bases is the same - which I think is the cardinality of the Continuum.

The tensor product is a way to extend the field of scalars of a vector space. A real vector space of dimension n (n can be infinite) becomes a complex vector space of dimension n when tensored with C. It becomes a real vector space of twice the dimension over R.

If one views R as a 1 dimensional vector space over itself with single basis vector v, the all elements are of the form rV for real numbers,r. Over C the basis is also v and the resulting vector space is 1 dimensional over C. But over R the basis is V and iV and so is 2 dimensional over R.
 
Last edited:
lavinia said:
Over Q these vector spaces are infinite dimensional. They will be isomorphic if the cardinality of their bases is the same - which I think is the cardinality of the Continuum.
Indeed; we discussed this here.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
991
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 2 ·
Replies
2
Views
5K
Replies
1
Views
2K
  • · Replies 18 ·
Replies
18
Views
5K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K