On the Scattering of Gravitons on Two Parallel D-Branes

I discuss the scattering of a graviton (or a dilaton, or an anti-symmetric tensor) on two parallel static Dp-branes. The graviton belongs to a type II string in 10D.Comment: 1+9 pages, TeX with macros include

A note on the Zakharov-Shabat topological model

In this note I discuss some features of the topological theory obtained from the Zakharov-Shabat (or general sl(2,C)) hierarchy, and comment on some possible physical and/or mathematical interpretations of it.Comment: 9 page

Bosonization of World-Sheet Fermions in Minkowski Space-Time

We propose a way of bosonizing free world-sheet fermions for $4$-dimensional heterotic string theory formulated in Minkowski space-time. We discuss the differences as compared to the standard bosonization performed in Euclidean space-time.Comment: 1+9 pages, TeX macros include

Incoherent and Coherent Eavesdropping in the 6-state Protocol of Quantum Cryptography

All incoherent as well as 2- and 3-qubit coherent eavesdropping strategies on the 6 state protocol of quantum cryptography are classified. For a disturbance of 1/6, the optimal incoherent eavesdropping strategy reduces to the universal quantum cloning machine. Coherent eavesdropping cannot increase Eve's Shannon information, neither on the entire string of bits, nor on the set of bits received undisturbed by Bob. However, coherent eavesdropping can increase as well Eve's Renyi information as her probability of guessing correctly all bits. The case that Eve delays the measurement of her probe until after the public discussion on error correction and privacy amplification is also considered. It is argued that by doing so, Eve gains only a negligibly small additional information.Comment: 17 pages, 4 figures: Updated version, discussion on error correction and privacy amplification adde