Contents
Some notes.
We want to check that the the -isomorphism sends IIA cocycles to IIB cocycles.
Contents
Conventions
The following computation uses the spinor conventions of CDF, II.8.1.
In particular we take and .
Using we get
As a consequence, the following expressions are real
Given a choice of Clifford matrices in we choose Clifford matrices in dimension 10 and 11 as discussed at Majorana spinors – In dimension 11, 10 and 9:
Notice that for is the same for both chiralities, except if . Therefore if we write
then the IIB spin representation is given by elements . Hence we set
Definition
hence
Double dimensional reduction
For an extension we decompose any element in
into a piece of the same degree and a piece of one degree lower, by the identification
Here is the “dimensional reduction”, while is the “double dimensional reduction”.
Notice the prefactor of here, which is crucial in the following.
The M-brane cocycles
Let’s be careful and go back to the source: from DAuria-Fre 82, equation (3.27) we have (with our convention that ) that
Hence if we set
for any then
Now for T-duality to come out right, below it turns out that we need
for some global prefactor
So we should solve for and .
Matching them on gives that
Then matching that on gives
hence
hence there is a unique solution:
The IIA D-brane cocycles
We get the IIA cocycle for F1, D0, D2 and D4 from double dimensional reduction of the above M-brane cocycles.
In all of the following the global prefactor is being suppressed.
Problem: For the (unique!) solution from above, then is , hence half of what it needs to be to give the IIA-extension. This breaks the dd-reduction. Needs a fix. But what?
Deriving the IIB D-brane cocycles
Now let’s check that a IIB cocycle like will come out as it should under sending the above data through the -T-duality construction.
The D1-brane
So we write
and need to match this to the corresponding 1-forms that we get from the IIA data above. This gives
where in the third line we inserted from def. .
This matches the expression in (Sakaguchi 00, equation (2.10)) if we identify our with his (which makes sense).
The D3-brane
Similarly:
where in the third line we inserted from def. .
This matches with Sakaguchi 00, equation (2.11).
References
The IIA -brane cocycles are in section 6.1 of
- C. Chryssomalakos, José de Azcárraga, J. M. Izquierdo and C. Pérez Bueno, The geometry of branes and extended superspaces, Nuclear Physics B Volume 567, Issues 1–2, 14 February 2000, Pages 293–330 (arXiv:hep-th/9904137)
The IIB -brane cocycles are in section 2 of
- Makoto Sakaguchi, section 2 of IIB-Branes and New Spacetime Superalgebras, JHEP 0004 (2000) 019 (arXiv:hep-th/9909143)