Very Light Gravitino Dark Matter * * *

It is certainly very attractive that two longstanding open questions -the origin of electroweak symmetry breaking -and the nature of the non-baryonic dark matter in the Universeseem to be on the verge of being answered simultaneously and presumably in a unified framework. LHC will give us the opportunity to start scratching the surface of this issue and, if we are lucky enough, to hint more clearly at the correct unified framework. Direct and indirect searches for dark matter will also bring in a very interesting complementarity with the LHC and Tevatron searches. On the theoretical side, several avenues for physics beyond the Standard Model offer particle candidates for non baryonic dark matter. Among these candidates, the (lightest) neutralino in the minimal supergravity (mSUGRA) scenario has been so extensively studied that it deserves the status of “benchmark scenario” [1]. It should be clear, though, that this scenario is just a possibility among other equally compelling ones. Actually, one of its main advantages is its relative model-independence regarding early Universe issues, making such a scenario “simpler” to study (not more “natural”!) for that matter. Let us recall briefly these early Universe issues, as they will be important for the subsequent discussion: i) the particle content of the Universe at the end of inflation is assumed to be described by the MSSM plus the graviton