Covariant constraints for generic massive gravity and analysis of its characteristics

We perform a covariant constraint analysis of massive gravity valid for its entire parameter space, demonstrating that the model generically propagates five degrees of freedom; this is also verified by a new and streamlined Hamiltonian description. The constraint's covariant expression permits computation of the model's caustics. Although new features such as the dynamical Riemann tensor appear in the characteristic matrix, the model still exhibits the pathologies uncovered in earlier work: superluminality and likely acausalities.Comment: 26 pages LaTeX, references added, version to appear in Phys. Rev.

Generalizing Galileons

The Galileons are a set of terms within four-dimensional effective field theories, obeying symmetries that can be derived from the dynamics of a 3+1-dimensional flat brane embedded in a 5-dimensional Minkowski Bulk. These theories have some intriguing properties, including freedom from ghosts and a non-renormalization theorem that hints at possible applications in both particle physics and cosmology. In this brief review article, we will summarize our attempts over the last year to extend the Galileon idea in two important ways. We will discuss the effective field theory construction arising from co-dimension greater than one flat branes embedded in a flat background - the multiGalileons - and we will then describe symmetric covariant versions of the Galileons, more suitable for general cosmological applications. While all these Galileons can be thought of as interesting four-dimensional field theories in their own rights, the work described here may also make it easier to embed them into string theory, with its multiple extra dimensions and more general gravitational backgrounds.Comment: 16 pages; invited brief review article for a special issue of Classical and Quantum Gravity. Submitted to CQ

Self-calibration: an efficient method to control systematic effects in bolometric interferometry

International audienc

Halmyris: Geoarchaeology of a fluvial harbour on the Danube Delta (Dobrogea, Romania)

In Northern Dobrogea, north of the Dunavăţ promontory, the Roman fortress of Halmyris was founded in the late 1st century AD on a Getic settlement dating to the middle of the 1st millennium BC, probably associated with a Greek emporium of the Classical and Hellenistic periods. At the time of the foundation of Halmyris, the Danube delta had already prograded several kilometres to the east leading to the progressive retreat of the sea and the formation of a deltaic plain characterised by numerous lakes and river channels. Here, we present the results of a multiproxy study combining sedimentology and palaeoecology to (1) understand the evolution of fluvial landscapes around Halmyris since ca. 8000 years BP and (2) identify the fluvial palaeoenvironments close to the city in Getic/Greek and Roman times, in order to locate and characterise the waterfront and the harbour. Our overriding objective was to improve understanding of human–environment relations in river delta settings. We demonstrate that Halmyris, protected by the Danubian floods due to its location on a palaeo-cliff top, had direct access to the river. A secondary channel of the Saint George, flowing north of the site, has been elucidated between the 7th century BC and the 7th century AD and could have been used as a natural harbour