Spectral-phase interferometry for direct electric-field reconstruction applied to seeded extreme-ultraviolet free-electron lasers

We present a setup for complete characterization of femtosecond pulses generated by seeded free-electron lasers (FEL's) in the extreme-ultraviolet spectral region. Two delayed and spectrally shifted replicas are produced and used for spectral phase interferometry for direct electric field reconstruction (SPIDER). We show that it can be achieved by a simple arrangement of the seed laser. Temporal shape and phase obtained in FEL simulations are well retrieved by the SPIDER reconstruction, allowing to foresee the implementation of this diagnostic on existing and future sources. This will be a significant step towards an experimental investigation and control of FEL spectral phase

Rome’s urban history inferred from Pb-contaminated waters trapped in its ancient harbor basins

Heavy metals from urban runoff preserved in sedimentary deposits record long-term economic and industrial development via the expansion and contraction of a city’s infrastructure. Lead concentrations and isotopic compositions measured in the sediments of the harbor of Ostia—Rome’s first harbor—show that lead pipes used in the water supply networks of Rome and Ostia were the only source of radiogenic Pb, which, in geologically young central Italy, is the hallmark of urban pollution. High-resolution geochemical, isotopic, and 14C analyses of a sedimentary core from Ostia harbor have allowed us to date the commissioning of Rome’s lead pipe water distribution system to around the second century BC, considerably later than Rome’s first aqueduct built in the late fourth century BC. Even more significantly, the isotopic record of Pb pollution proves to be an unparalleled proxy for tracking the urban development of ancient Rome over more than a millennium, providing a semiquantitative record of the water system’s initial expansion, its later neglect, probably during the civil wars of the first century BC, and its peaking in extent during the relative stability of the early high Imperial period. This core record fills the gap in the system’s history before the appearance of more detailed literary and inscriptional evidence from the late first century BC onward. It also preserves evidence of the changes in the dynamics of the Tiber River that accompanied the construction of Rome’s artificial port, Portus, during the first and second centuries AD

Solving nonlinear Klein-Gordon equations on unbounded domains via the Finite Element Method

A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents $femtoscope$ $-$ a Python numerical tool based on the Finite Element Method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, $femtoscope$ is showcased with a study of the chameleon fifth force in Earth orbit.Comment: Correction of typography in Table I (p.7

What to expect from scalar-tensor space geodesy

Scalar-tensor theories with screening mechanisms come with non-linearities that make it difficult to study setups of complex geometry without resorting to numerical simulations. In this article, we use the $\textit{femtoscope}$ code that we introduced in a previous work in order to compute the fifth force arising in the chameleon model in the Earth orbit. We go beyond published works by introducing a departure from spherical symmetry \unicode{x2014} embodied by a mountain on an otherwise spherical Earth \unicode{x2014} as well as by implementing several atmospheric models, and quantify their combined effect on the chameleon field. Building on the numerical results thus obtained, we address the question of the detectability of a putative chameleon fifth force by means of space geodesy techniques and, for the first time, quantitatively assess the back-reaction created by the screening of a satellite itself. We find that although the fifth force has a supposedly measurable effect on the dynamics of an orbiting spacecraft, the imprecise knowledge of the mass distribution inside the Earth greatly curtails the constraining power of such space missions. Finally, we show how this degeneracy can be lifted when several measurements are performed at different altitudes.Comment: 32 pages, 19 figure

A lead isotope perspective on urban development in ancient Naples

The influence of a sophisticated water distribution system on urban development in Roman times is tested against the impact of Vesuvius volcanic activity, in particular the great eruption of AD 79, on all of the ancient cities of the Bay of Naples (Neapolis). Written accounts on urbanization outside of Rome are scarce and the archaeological record sketchy, especially during the tumultuous fifth and sixth centuries AD when Neapolis became the dominant city in the region. Here we show that isotopic ratios of lead measured on a well-dated sedimentary sequence from Neapolis’ harbor covering the first six centuries CE have recorded how the AD 79 eruption was followed by a complete overhaul of Neapolis’ water supply network. The Pb isotopic signatures of the sediments further reveal that the previously steady growth of Neapolis’ water distribution system ceased during the collapse of the fifth century AD, although vital repairs to this critical infrastructure were still carried out in the aftermath of invasions and volcanic eruptions

CONTRIBUTION DU SIG A LA RECONSTITUTION DES PROCESSUS DE PROGRADATION DE LA MAJERDA : quels enjeux pour le port d’Utique?

International audienceThe Majerda delta formation has been the subject of many studies since the late XIXe century. The reconstruction of the fluvial palaeo-environments of the lower Majerda valley is significant as it is critical to understand the decline of Utica following the siltation of the harbor, which is presently buried under sediments. The progression of the delta across the corridor separating the Southern and the Northern compartments of the ancient Utica bay is the cornerstone of our research on the delta. On the basis of a GIS we propose to identify hydro- and morpho-sedimentary processes of the deltaic progradation dynamics. They lead to innovative ways of considering the initial implantation site of Utica, the conditions of harbor siltation and the Majerda River itself across the Northern compartment. Observations and analysis from the GIS allowed highlighting a double system of alluvial fans over the whole delta. The first component which may be described as “torrential” is present throughout the delta fringe, while the second category of flat alluvial fans occurs at the Majerda defluviation sites, forming coalescing alluvial lobes. The ancient merging of these two morphological systems close to Utica could reflect a process of harbor silting more complex than previously considered, the Majerda River being considered as the unique factor of change so far

Mario Liverani, La Bible et l’invention de l’histoire. Histoire ancienne d’Israël

Écrire aujourd’hui l’histoire de l’ancien Israël est un défi, dont le livre magistral et passionnant de Mario Liverani (ML) – professeur d’histoire du Proche-Orient ancien à l’Université La Sapienza de Rome depuis 1970 et spécialiste de renommée internationale – montre à la fois la nécessité et la difficulté, voire même l’écueil. La nécessité tient au fait que la critique historique de la Bible a connu une véritable révolution durant les trois dernières décennies. Il suffit de feuilleter en p..

Mario Liverani, La Bible et l’invention de l’histoire. Histoire ancienne d’Israël

Écrire aujourd’hui l’histoire de l’ancien Israël est un défi, dont le livre magistral et passionnant de Mario Liverani (ML) – professeur d’histoire du Proche-Orient ancien à l’Université La Sapienza de Rome depuis 1970 et spécialiste de renommée internationale – montre à la fois la nécessité et la difficulté, voire même l’écueil. La nécessité tient au fait que la critique historique de la Bible a connu une véritable révolution durant les trois dernières décennies. Il suffit de feuilleter en p..

Mario Liverani, La Bible et l’invention de l’histoire. Histoire ancienne d’Israël

Écrire aujourd’hui l’histoire de l’ancien Israël est un défi, dont le livre magistral et passionnant de Mario Liverani (ML) – professeur d’histoire du Proche-Orient ancien à l’Université La Sapienza de Rome depuis 1970 et spécialiste de renommée internationale – montre à la fois la nécessité et la difficulté, voire même l’écueil. La nécessité tient au fait que la critique historique de la Bible a connu une véritable révolution durant les trois dernières décennies. Il suffit de feuilleter en p..