# Is Supergravity just Super String Theory without open strings?

I'm trying to understand the elements of the AdS-CFT correspondence. The definition I have in mind is a correspondence between:

• (A) a Super String Theory of $$D_p$$-branes and closed strings in a $$10$$d flat bulk, with open strings living on the branes
• (B) a $$II$$B Supergravity Theory where closed strings live in a $$10$$d bulk that is asymptotically flat and tends to $$AdS_5 \times S^5$$ near the origin

and the two are linked because the curved spacetime of theory (B) is the effect that the $$D_p$$-branes of theory (A) would have on a flat spacetime. Then if one chooses $$p=3$$ fun things happen in the low-energy limit.
My question is, why is (A) called a SST and (B) is called a SUGRA? I mean, they both have closed strings. Is the only difference between the two theories (in general, not necessarily applied to the AdS-CFT correspondence) the absence of open strings in SUGRA?

• Well Type IIA and IIB supergravity are low-energy effective actions of the respective string theories, and conversely the string theories are supposedly their UV completions. I don't think there are "strings" in SUGRA as such. – Nihar Karve May 18 at 10:21
• @NiharKarve I did not have in mind the clear concept of SUGRA being the low-energy effective theory of SST, but this makes perfect sense: closed strings are decoupled in (A), so they are in (B) also, therefore the SUGRA of (B) is the low-energy theory of the open+brane sector of (A). – Mauro Giliberti May 18 at 10:49