In string theory, specifically in type IIA string theory, the brane intersection of a D2-brane with an O8-plane is called an E-string.

graphics grabbed from KKLPV 14, p. 4

Hence under the S-duality between type I and heterotic string theory the E-string is dual to the heterotic string.

The M-theory lift of the E-string is the brane intersection of an M2-brane with an M9-brane which wraps the M-theory circle fiber, hence an M9 IM9_I-brane of Horava-Witten theory (KKLPV 14, p. 4/5), hence a D8-brane from the dual perspective of type I' string theory.

The other end of the M2-brane-lift of the E-string is on an M5-brane:

graphics grabbed from GHKKLV 15

graphics grabbed from HLV 14

In contrast, if both ends of the M2-brane are on an M5-brane, some authors speak of “M-strings”:

graphics grabbed from HLV 14

KK-compactification of M-theory


  • Babak Haghighat, Guglielmo Lockhart, Cumrun Vafa, Fusing E-string to heterotic string: E+EHE + E \to H, Phys. Rev. D 90, 126012 (2014) (arXiv:1406.0850)

  • Joonho Kim, Seok Kim, Kimyeong Lee, Jaemo Park, Cumrun Vafa, Elliptic Genus of E-strings, JHEP 1709 (2017) 098 (arXiv:1411.2324)

  • Abhijit Gadde, Babak Haghighat, Joonho Kim, Seok Kim, Guglielmo Lockhart, Cumrun Vafa, 6d String Chains, JHEP 1802 (2018) 143 (arXiv:1504.04614)

Last revised on October 13, 2019 at 14:18:05. See the history of this page for a list of all contributions to it.