Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)

[no abstract available

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Sustainable Design of Multiscale CO2 Electrochemical Conversion

The storage of renewable electricity in chemical bonds is a compelling technological option that combines flexibility with the synthesis of high energy-dense fuels and chemicals and may use CO2 as raw material. The electrochemical conversion of CO2 is not yet a mature technology. Both fields, electrochemical conversion and carbon dioxide utilisation (CDU), have their own trade-offs; CO2 electrochemical reduction (CO2ER) environmental and economic performance is highly context-dependent. The successful deployment of CO2 electrochemical conversion will depend not only on the further development and scaling of the technology but also on finding appropriate combinations of technologies, business models, and socioeconomic strategies. The current project aims to create critical knowledge on the sustainable implementation of CO2 electrochemical devices for a variety of contexts. The research approach presented in the current work will develop a multidisciplinary framework to assess the contributions and trade-offs of CO2 electrochemical systems, including centralised and decentralised configurations, which are evaluated under realistic conditions. This is a crucial step in understanding the role and contribution of CO2ER within the different CO2 mitigation options in place in the upcoming years. To achieve the project’s goal, we propose a multidisciplinary methodology that includes process systems engineering (PSE) and operations research (OR) tools, and humanistic and social sciences methodologies. Modelling and optimisation techniques, value-sensitive design, and identification of government and market-based governance interventions will help identifying potential areas of improvement and bottlenecks to successfully bring CO2ER to the market. The assessment will be performed at several levels: unit (reaction pathways), process (scheduling and operation, plant layout optimisation), supply chain (optimisation under deterministic and stochastic conditions), and system (social, governance and markets perspectives) of CO2ER. The project results will (i) propose optimal CO2ER-based plants and (ii) supply chains under different contexts; (iii) translate stakeholders’ sustainability value into design requirements for CO2ER; (iv) propose a list of government interventions and market mechanisms that will allow CO2ER market penetration, and (v) identify, quantify and mitigate the influence of the most relevant sources of uncertainty.Energy and IndustryOrganisation & GovernanceChemE/Chemical Engineerin