nLab probe brane




In the string theory literature, by “probe branes” authors refer to the idea of “adding” to a configuration of black branes a small number of further branes whose (gravitational, electric, and/or RR-field) backreaction on the given black brane background is neglected. In this sense a probe brane “probes” the (forces exerted by a given) background field configuration without backreacting onto it (up to some approximation), whence the terminology.

This is, of course, the default perspective for Green-Schwarz sigma-model-branes in the given background, but authors tend to speak of “probe branes” when they think of these branes as actually being black branes themselves, just so light (i.e. of such small number compared to the number of background branes) that their backreaction may be neglected not in principle but for practical purposes.

One will not find this as a formal definition in the literature, but it transpires for instance in the following passages:

Polchinski & Strassler (2000), p. 18: “The D3-brane charge of the probe is nn […] This is assumed in this section to be small compared to NN so that the effect of the probe on the background can be ignored.”

Karch & Randall (2001): “4. The Probe Picture […] In this section we will show that when neglecting the backreaction of the D5 branes on the geometry […] Of course this is just the probe approximation. Ultimately, one has to account for the back reaction.”

Bozhilov (2003), p. 1: “The probe branes approach for studying issues in the string/M-theory uses an approximation, in which one neglects the back-reaction of the branes on the background. In this sense, the probe branes are multidimensional dynamical systems, evolving in given, variable in general, external fields.”

One particular use of (the idea of) probe branes is as flavor branes in backgrounds appearing in the AdS/QCD correspondence, see the references below.



Early appearance of the concept of “probe branes”:

Further discussion:

As flavor branes

Interpretation of probe branes as flavor branes in the context of the AdS/QCD correspondence:

Last revised on June 25, 2023 at 12:08:44. See the history of this page for a list of all contributions to it.