# Index Concordia

## Relativity – Week 04

Posted in Relativity by Index Guy on September 29, 2007

[For all the details look at sections IIA7, IIIA1, IIIA4 and IIIB1 of part 1 of Fields.]

This week saw the conclusion of spinor notation and the beginning of action principles. On Monday we wrote Maxwell’s equation in spinor notation. Then me mentioned briefly chirality and duality.

## Quantum field theory – Week 04

Posted in Quantum Field Theory by Index Guy on September 29, 2007

This week was slow in quantum field theoretical aspects. At least to my taste.

We finished the discussion on Lie groups and algebras. Then we considered the Lorentz group and an infinitesimal transformation. From this we derived expressions for the generators of the group, and their algebra. Next week, Poincaré and hopefully canonical quantization.

## Group theory – Week 04

Posted in Group theory by Index Guy on September 28, 2007

During this week we study the Dirac group and its representations. Recall that the order $g$ of the Dirac group is

$g = 2^{n+1},$

with $n$ being the number of spacetime dimensions. We will consider separate cases when $n$ is either even or odd. The number of classes $r$ depends on $n$:

• for $n$ even, $r = 2^{n} + 1$ and
• for $n$ odd, $r = 2^{n} + 2$.

## Relativity – Week 03

Posted in Relativity by Index Guy on September 25, 2007

During the third week we discussed spinor notation.

## Group theory – Week 03

Posted in Group theory by Index Guy on September 21, 2007

We started the week by defining what a semi-direct product is:

• A group $G$ is the semi-direct product of two subgroups if one of those subgroups is normal and only shares the identity with the other.

An example is the Poincaré group, which is a semi-direct product of translations (the invariant subgroup) and Lorentz transformations (not an invariant subgroup of Poincaré).

## Quantum field theory – Week 03

Posted in Quantum Field Theory by Index Guy on September 20, 2007

During this week we derived Noether’s theorem from requiring form-invariance of the Lagrange density under a general transformation of the coordinates and the fields. This transformation was written in terms of $N$ parameters. Then Noether’s theorem claims the existence of conserved vectors.