Open string pair creation from worldsheet instantons

We revisit the problem of charged string pair creation in a constant external electric field. The string states are massive and creation of pairs from the vacuum is a tunnelling process, analogous to the Schwinger process where charged particle-anti-particle pairs are created by an electric field. We find the instantons in the worldsheet sigma model which are responsible for the tunnelling events. We evaluate the sigma model partition function in the multi-instanton sector in the WKB approximation which keeps the classical action and integrates the quadratic fluctuations about the solution. We find that the summation of the result over all multi-instanton sectors reproduces the known amplitude. This suggests that corrections to the WKB limit must cancel. To show that they indeed cancel, we identify a fermionic symmetry of the sigma model which occurs in the instanton sectors and which is associated with collective coordinates. We demonstrate that the action is symmetric and that the interaction action is an exact form. These conditions are sufficient for localization of the worldsheet functional integral onto its WKB limit.

Section: Worldsheet Instantonsmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Semiclassical Evaluation Of the Cylinder Amplitudementioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Worldsheet instantons and the amplitude for string pair production in an external field as a WKB exact functional integral

Gordon

Semenoff

2018

“…In those cases we cannnot use the instanton technique as we did in the present paper. A generalization of this method for constant electric field has been proposed in [21] and it may be suitable for the discussion of non-homogeneous backgrounds. We have not gone in this work beyond the semiclassical approximation and have not studied this in the direct manner in which it was possible to study it in string theory for the case of constant electric [6] and magnetic fields [22].…”

Section: Conclusion and Open Issuesmentioning

confidence: 99%

String pair production in non homogeneous backgrounds

Bolognesi

Rabinovici

Tallarita

2016

We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.

D-brane scattering and annihilation

D’Amico

Gobbetti

Kleban

et al. 2015

Abstract:We study the dynamics of parallel brane-brane and brane-antibrane scattering in string theory in flat spacetime, focusing on the pair production of open strings that stretch between the branes. We are particularly interested in the case of scattering at small impact parameter b < l s , where there is a tachyon in the spectrum when a brane and an antibrane approach within a string length. Our conclusion is that despite the tachyon, branes and antibranes can pass through each other with only a very small probability of annihilating, so long as g s is small and the relative velocity v is neither too small nor too close to 1. Our analysis is relevant also to the case of charged open string production in world-volume electric fields, and we make use of this T-dual scenario in our analysis. We briefly discuss the application of our results to a stringy model of inflation involving moving branes.