A bound on the effective gravitational coupling from semiclassical black holes

R. Brustein, G. Dvali, G. Veneziano

    Research output: Contribution to journalArticlepeer-review


    We show that the existence of semiclassical black holes of size as small as a minimal length scale l UV implies a bound on a gravitational analogue of 't-Hooft's coupling λ G(l)≡N(l)G N/l 2 at all scales l l UV. The proof is valid for any metric theory of gravity that consistently extends Einstein's gravity and is based on two assumptions about semiclassical black holes: i) that they emit as black bodies, and ii) that they are perfect quantum emitters. The examples of higher dimensional gravity and of weakly coupled string theory are used to explicitly check our assumptions and to verify that the proposed bound holds. Finally, we discuss some consequences of the bound for theories of quantum gravity in general and for string theory in particular.

    Original languageEnglish (US)
    Article number085
    JournalJournal of High Energy Physics
    Issue number10
    StatePublished - 2009


    • Black Holes
    • Black Holes in String Theory
    • Models of Quantum Gravity

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics


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