7 research outputs found
Fivebrane instantons and higher derivative couplings in type I theory
We express the infinite sum of D-fivebrane instanton corrections to couplings in type I string vacua, in terms of an elliptic
index counting 1/2-BPS excitations in the effective brane theory. We
compute the index explicitly in the infrared, where the effective theory is
argued to flow to an orbifold CFT. The form of the instanton sum agrees
completely with the predicted formula from a dual one-loop computation in type
IIA theory on . The proposed CFT provides a proper description of
the whole spectrum of masses, charges and multiplicities for 1/2- and 1/4- BPS
states, associated to bound states of D5-branes and KK momenta. These results
are applied to show how fivebrane instanton sums, entering higher derivative
couplings which are sensitive to 1/4-BPS contributions, also match the
perturbative results in the dual type IIA theory.Comment: 14 pages, corrected some typos. Version to appear in Nucl. Phys.
One Loop Partition Function in Plane Waves R-R Background
We compute the one loop partition function of type IIB string in plane wave
R-R 5-form background using both path integral and operator formalisms
and show that the two results agree perfectly. The result turns out to be equal
to the partition function in the flat background. We also study the Tadpole
cancellation for the unoriented closed and open string model in plane wave R-R
5-form background studied in hep-th/0203249 and find that the cancellation of
the Tadpole requires the gauge group to be SO(8).Comment: 12 pages, no figures, latex, misprint corrected and reference added;
to appear in JHE
Generalized Continuity Equation for Quasi-Hermitian Hamiltonians
The continuity relation is generalized to quasi-Hermitian one-dimensional Hamiltonians. As an application we show that the reflection and transmission coefficients computed with the generalized current obey the conventional unitarity relation for the continuous double delta function potential