Filtering gravity: Modification at large distances

G. Dvali

    Research output: Contribution to journalConference articlepeer-review


    In this lecture I address the issue of possible large distance modification of gravity and its observational consequences. Although, for the illustrative purposes we focus on a particular simple generally-covariant example, our conclusions are rather general and apply to large class of theories in which, already at the Newtonian level, gravity changes the regime at a certain very large crossover distance rc. In such theories the cosmological evolution gets dramatically modified at the crossover scale, usually exhibiting a 'self-accelerated' expansion, which can be differentiated from more conventional 'dark energy' scenarios by precision cosmology. However, unlike the latter scenarios, theories of modified-gravity are extremely constrained (and potentially testable) by the precision gravitational measurements at much shorter scales. The reason is that modification implies the new propagating light degrees of freedom (additional polarizations of graviton) which penetrate at short distances in a rather profound way, and lead to the deviations from Einstein's gravity at the source-dependent scales, that for the light sources are way below rc. At the level of the straightforward perturbative expansion in Newtonian coupling, new polarizations exhibit a 'strong coupling' behavior, which invalidates the linearized approximation at short distances and is essential for the observational viability of the theory. We clarify some physical aspects of this phenomenon and the role of the resummed solutions.

    Original languageEnglish (US)
    Pages (from-to)92-98
    Number of pages7
    JournalPhysica Scripta T
    StatePublished - 2005
    EventNobel Symposium 127 on String Theory and Cosmology - Sigtuna, Sweden
    Duration: Aug 14 2003Aug 19 2003

    ASJC Scopus subject areas

    • Atomic and Molecular Physics, and Optics
    • Mathematical Physics
    • Condensed Matter Physics


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