PHYS08200604018 Shamik Banerjee - Homi Bhabha National ...
PHYS08200604018 Shamik Banerjee - Homi Bhabha National ...
PHYS08200604018 Shamik Banerjee - Homi Bhabha National ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
82 CHAPTER 4. GENERALITIES OF QUARTER BPS DYON PARTITION FUNCTION<br />
the quarter BPS partition function near the pole that controls the jump in the index at this<br />
particular wall.<br />
As an example we can consider the Z 2 CHL model of §4.5.4. The decay (Q, P ) →<br />
(Q, 0) + (0, P ) is controlled by the behaviour of ̂Φ near ˇv = 0. Thus if we did not know the<br />
spectrum of magnetically charged half BPS states in this theory, we could study the behaviour<br />
of ̂Φ near ˇv = 0 to get this information. In this case since all the other walls are related to this<br />
one by S-duality transformation, this is the only independent information we can get. However<br />
for more complicated models there can be more information.<br />
To illustrate this we shall consider the example of the Z 6 CHL model [69,70] mentioned<br />
in footnote 9. Our set A consists of charge vectors of the form<br />
⎛ ⎞ ⎛ ⎞<br />
0<br />
K<br />
Q = ⎜ m/6<br />
⎟<br />
⎝ 0 ⎠ , P = ⎜ J<br />
⎟<br />
⎝ 1 ⎠ , m, K, J ∈ Z , (4.7.1)<br />
−1<br />
0<br />
as in (4.5.4.1). We now consider the decay associated with the matrix<br />
( )<br />
a0 b 0<br />
=<br />
c 0 d 0<br />
From (4.3.1) we see that this corresponds to the decay<br />
( )<br />
1 1<br />
. (4.7.2)<br />
2 3<br />
(Q, P ) → (M 0 , 2M 0 ) + (N 0 , 3N 0 ) , M 0 ≡ 3Q − P, N 0 ≡ −2Q + P . (4.7.3)<br />
The charge vectors M 0 and N 0 are not related to Q or P by a T-duality transformation since<br />
they correspond to charges that are triple and double twisted respectively. Furthermore the<br />
dyon charges (M 0 , 2M 0 ) and (N 0 , 3N 0 ) cannot be related by S-duality group Γ 1 (6) to either<br />
a purely electric or a purely magnetic state whose index is known. On the other hand the<br />
partition function of quarter BPS states of the type given in (4.7.3) is known [17, 24]. Thus<br />
the latter can be used to extract information about the partition function of these half BPS<br />
states.<br />
From (4.3.2) it follows that the relevant zero of ̂Φ we need to examine is at<br />
6ˇρ + ˇσ + 5ˇv = 0 . (4.7.4)<br />
The zeroes of ̂Φ have been classified in [15, 24]. For a generic Z N model ̂Φ has double zeroes<br />
at<br />
n 2 (ˇσˇρ − ˇv 2 ) + jˇv + n 1ˇσ − ˇρm 1 + m 2 = 0<br />
m 1 ∈ N Z, n 1 , m 2 , n 2 ∈ Z, j ∈ 2 Z + 1, m 1 n 1 + m 2 n 2 + j2<br />
4 = 1 4 . (4.7.5)