Planet formation in Binaries

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions to this apparent paradox are presented. The last part of our review presents a thorough description of the problem of planet habitability, for which the binary environment creates a complex situation because of the presence of two irradation sources of varying distance.Comment: Review chapter to appear in "Planetary Exploration and Science: Recent Advances and Applications", eds. S. Jin, N. Haghighipour, W.-H. Ip, Springer (v2, numerous typos corrected

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

Communication for Peaceful Social Change and Global Citizenry

The adoption of the 17 Sustainable Development Goals (SDGs) by the United Nations (UN) in 2015 represents a universal call to action involving multiple international actors for the purpose of eradicating poverty, improving living conditions and promoting peace. This entry provides a theoretical overview of the contributions of scholars and practitioners who highlight the importance of a transformative, educational and emancipatory communication by different social actors to establish the main lines of action for the 2030 Agenda for Sustainable Development. This communicative model involves the coordination of actors and strategies, both short- and long-term, cross-cutting actions and discourses to build social, cultural and political settings based on the criteria of peace, equality, social justice and human rights. Specifically, this entails a contribution to the objectives set out in SDG 16, “Peace, Justice and Strong Institutions”, given that the proposed theoretical framework is grounded in Communication for Peace and Communication for Social Change, and includes a systematization of different strategies and experiences from a variety of social issuers, mainly institutions, non-governmental organizations (NGOs) or social movements, aimed at promoting peaceful and inclusive societies. Specifically, communication for peaceful social change and global citizenry contributes to the achievement of specific SDG 16 objectives, particularly 16.1: Significantly reduce all forms of violence... [...