Charge Conjugation from Space-Time Inversion

We show that the CPT group of the Dirac field emerges naturally from the PT and P (or T) subgroups of the Lorentz group.Comment: 4 pages, no figure

Environmental, economic, and social sustainability in aquaculture: the aquaculture performance indicators

Aquaculture is a rapidly growing food production technology, but there are significant concerns related to its environmental impact and adverse social effects. We examine aquaculture outcomes in a three pillars of sustainability framework by analyzing data collected using the Aquaculture Performance Indicators. Using this approach, comparable data has been collected for 57 aquaculture systems worldwide on 88 metrics that measure social, economic, or environmental outcomes. We first examine the relationships among the three pillars of sustainability and then analyze performance in the three pillars by technology and species. The results show that economic, social, and environmental outcomes are, on average, mutually reinforced in global aquaculture systems. However, the analysis also shows significant variation in the degree of sustainability in different aquaculture systems, and weak performance of some production systems in some dimensions provides opportunity for innovative policy measures and investment to further align sustainability objectives.Taryn Garlock has received financial support from NIFA Hatch Project #7006413, and Frank Asche has received financial support from NIFA Hatch Project #7004716. Håkan Eggert, Carlos Chávez, Nnaemeka Chukwuone, and Byela Tibesigwa acknowledge financial support from The Swedish International Development Cooperation Agency (Sida) through the Environment for Development Initiative (61050402). Frank Asche and Ragnar Tveteras acknowledge funding from the Norwegian Research Council (CT299404, CT320612, and CT328724). Carlos Chávez acknowledges funding from the project FONDAP 1523A0007. Madan Dey acknowledges funding from USAID (7200AA18CA00030) and Mississippi State University (No. 193900.312455.03C). Ganesh Kumar acknowledges funding from NOAA (NA21OAR4170091). Rasmus Nielsen acknowledges funding from the University of Copenhagen. The views expressed are those of the authors, and not our respective employers or funding agencies. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank

Impacts of Covid-19 on Norwegian salmon exports: A firm-level analysis

A rapidly growing literature investigates how the recent Covid-19 pandemic has affected international seafood trade along multiple dimensions, creating opportunities as well as challenges. This suggests that many of the impacts of the Covid measures are subtle and require disaggregated data to allow the impacts in different supply chains to be teased out. In aggregate, Norwegian salmon exports have not been significantly impacted by Covid-related measures. Using firm-level data to all export destinations to examine the effects of lockdowns in different destination countries in 2020, we show that the Covid-related lockdown measures significantly impacted trade patterns for four product forms of salmon. The results also illustrate how the Covid measures create opportunities, as increased stringency of the measures increased trade for two of the product forms. We also find significant differences among firms' responses, with large firms with larger trade networks reacting more strongly to the Covid measures. The limited overall impacts and the significant dynamics at the firm level clearly show the resiliency of the salmon supply chains.publishedVersio

Challenges and opportunities: impacts of COVID-19 on Norwegian seafood exports

A rapidly growing literature shows that COVID-19 and the measures to contain the spread of the virus can have significant market impacts for seafood. These can be interruptions of production, or reductions in demand directly or indirectly due to supply chain challenges. In this paper we investigate the potential impacts of COVID-19 on seafood exports from Norway, the world's second largest seafood exporter, using highly detailed data from 2016 through May 2021. These data allow us to assess upstream impacts in the seafood supply chain close to the producer level in aggregate and by main sector, impacts on the largest products, and the extent to which export firm structure and export markets served have changed. We find very few impacts in aggregate as well as for individual products, suggesting that the markets and supply chains used by Norwegian seafood exports were sufficiently robust and flexible to accommodate the shocks created by COVID-19. Given Norway's size as a seafood exporter, the impact of COVID-19 has likely been moderate upstreams for a number of seafood sectors around the world, especially those in wealthy nations, with opportunities balancing out challenges, and that the supply chains have been highly resilient.publishedVersio