Open string - string junction transitions

Abstract

It is confirmed that geodesic string junctions are necessary to describe the gauge vectors of symmetry groups that arise in the context of IIB superstrings compactified in the presence of nonlocal 7-branes. By examining the moduli space of 7-brane backgrounds for which the dilaton and axion fields are constant, we are able to describe explicitly and geometrically how open string geodesics can fail to be smooth, and how geodesic string junctions then become the relevant BPS representatives of the gauge bosons. The mechanisms that guarantee the existence and uniqueness of the BPS representative of any gauge vector are also shown to generalize to the case where the dilaton and axion fields are not constant. *

Split attractor flows and the spectrum of BPS D-branes on the quintic

“…And more importantly, it cannot be denied that the split flow picture actually works. 17 A natural conjecture would therefore be that this picture should also arise somehow from microscopic considerations, like it does in the description of QFT BPS states as (possible multi-pronged) strings [36,37]. Clearly it would be very interesting if this were indeed the case.…”

“…Support for this possibility is given by the strong analogy with the multi-pronged string picture of BPS states in quantum field theory [37], where similar spurious multi-pronged strings arise, which are discarded on the basis monodromy arguments, or by lifting the strings to M-theory 2-branes. This is the so-called "s-rule".…”

“…An interesting link, useful to give some intuition for the spectrum, can be made between (split) attractor flows and the "7/3/1"-brane picture of BPS states in rigid N = 2 quantum field theories [36,37]. This comes from the observation [25] that attractor flows can be considered to be geodesic "strings" in moduli space.…”

“…18 In a suitable rigid QFT limit of the Calabi-Yau compactification, this reduces precisely to the string action considered in [36,37]. In this case, the strings can be interpreted as genuine IIB strings stretched between certain D-branes in spacetime.…”

Supergravity flows and D-brane stability

“…The appearance of these composite flows is very reminiscent of the appearance of "3-pronged strings" in the "3-1-7 brane picture" of BPS states in N = 2 quantum field theories [20,21]. This is no coincidence.…”