Spinors in d dimensions and Clifford algebra

Click For Summary
SUMMARY

The discussion centers on understanding spinors in d-dimensional vector spaces and the associated Clifford algebra C(Q) defined by a quadratic form Q. The participants clarify that the basis e_μ is orthogonal with respect to the symmetric scalar product φ rather than Q, leading to the equation 3.1, which expresses the relationship between the basis elements. The dimension of the Clifford algebra C(Q) is established as 2^d, confirming its significance in the study of spinors.

PREREQUISITES
  • Understanding of d-dimensional vector spaces
  • Familiarity with quadratic forms and scalar products
  • Knowledge of Clifford algebra concepts
  • Basic grasp of mathematical notation and symbols used in algebra
NEXT STEPS
  • Study the properties of Clifford algebra C(Q) in detail
  • Explore the relationship between quadratic forms and orthogonality
  • Learn about the applications of spinors in physics and mathematics
  • Investigate the differences between real (R) and complex (C) fields in vector spaces
USEFUL FOR

Mathematicians, physicists, and students interested in advanced algebraic structures, particularly those studying spinors and their applications in theoretical physics.

nrqed
Science Advisor
Messages
3,762
Reaction score
297
I bought a book on susy and there is a chapter on spinors in d-dimensions.
Now, maybe I am extremely dumb but I just can't understand the first few lines!

EDIT: I was being very dumb except that I think there is a typo...See below...


BEGINNING OF QUOTE

Consider a d-dimensional vector space V over the field F for which we shall choose two alternatives F=R or F=C. Let Q be a quadratic form on V:

Q:x \in V \rightarrow Q(x) \in F

This defines a symmetric scalar product

\phi(x,y) \equiv xy + yx = Q(x+y) - Q(x) - Q(y)

In particular, for e_\mu , \mu = 1 \ldots d, a basis of V, orthogonal with respect to Q, we then have

<br /> e_\mu e_\nu + e_\nu e_\mu = 2 \delta_{\mu \nu} Q(e_\mu) \cdot 1 ~~~(3.1)

The associative algebra with unit element generated by the e_\mu with the defining relation (3.1) is called the Clifford algebra C(Q) of the quadratic form Q. The dimension of C(Q) is 2^d


END OF QUOTE

Questions:



1) What does it mean to say that the basis is orthogonal with respect to Q? Does that mean Q(e_\mu + e_\nu) = 0 unless mu = nu? Or is that a typo an dhe meant to write orthogonal with respect to \phi, not Q?

2) No matter what I try I don't see how to get from the definition of phi to equation 3.1!


EDIT: I THINK I GOT IT

Just as I posted I think that I finally understood.

First, I think the author really meant that the basis is orthogonal with respect to phi and not Q. In that case, we get

\delta_{\mu \nu} (Q(2 e_\mu) - Q(e_\mu) - Q(e_\mu))

since the form is quadratic, this gives

\delta_{\mu \nu} (4 Q( e_\mu) - Q(e_\mu) - Q(e_\mu)) = 2 \delta_{\mu \nu} Q(e_\mu)


For some reason it just clicked after I posted my question!
 
Last edited:
Physics news on Phys.org
I think i like the book...Who is the author of that book?? How can i buy it too??
 

Similar threads

Replies
1
Views
1K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 13 ·
Replies
13
Views
5K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K