Convergence of the Magnus series

The Magnus series is an infinite series which arises in the study of linear ordinary differential equations. If the series converges, then the matrix exponential of the sum equals the fundamental solution of the differential equation. The question considered in this paper is: When does the series converge? The main result establishes a sufficient condition for convergence, which improves on several earlier results.Comment: 11 pages; v2: added justification for conjecture, minor clarifications and correction

O ministério da injustiça e sem direitos humanos em Angola

Angola is one of the few countries in the world that boasts a dedicated Ministry of Justice and Human Rights. But does this translate into a wider implementation of these rights? This article provides a historical overview of the trajectory of Human Rights in Angola through the analysis of different moments and iterations of the performance of (in)justice since the country’s independence in November 1975 – from the political trials of the mercenaries in 1976-1977 and the events surrounding 27 May 1977 to the post-electoral massacres and persecutions in 1992 and 1993, the persecution of human rights activists in the post-Arab Spring period and, since 2019, the implementation of a public reconciliation commission (CIVICOP). Through this longitudinal approach, which highlights continuities in the trajectory of Human Rights in Angola in the transition from the 20th to the 21st centuries, I argue that the case of Angola illustrates the paradox of how a governance-based implementation of a Human Rights agenda can actually prevent its enactment and implementation. This is explained through the incorporation and subsumption of Human Rights into political agendas as a performative display.info:eu-repo/semantics/publishedVersio

O ministério da injustiça e sem direitos humanos em Angola

Angola is one of the few countries in the world that boasts a dedicated Ministry of Justice and Human Rights. But does this translate into a wider implementation of these rights? This article provides a historical overview of the trajectory of Human Rights in Angola through the analysis of different moments and iterations of the performance of (in)justice since the country’s independence in November 1975 – from the political trials of the mercenaries in 1976-1977 and the events surrounding 27 May 1977 to the post-electoral massacres and persecutions in 1992 and 1993, the persecution of human rights activists in the post-Arab Spring period and, since 2019, the implementation of a public reconciliation commission (CIVICOP). Through this longitudinal approach, which highlights continuities in the trajectory of Human Rights in Angola in the transition from the 20th to the 21st centuries, I argue that the case of Angola illustrates the paradox of how a governance-based implementation of a Human Rights agenda can actually prevent its enactment and implementation. This is explained through the incorporation and subsumption of Human Rights into political agendas as a performative display.info:eu-repo/semantics/publishedVersio

Micromotion-enabled improvement of quantum logic gates with trapped ions

The micromotion of ion crystals confined in Paul traps is usually considered an inconvenient nuisance, and is thus typically minimised in high-precision experiments such as high-fidelity quantum gates for quantum infor- mation processing. In this work, we introduce a particular scheme where this behavior can be reversed, making micromotion beneficial for quantum information processing. We show that using laser-driven micromotion side- bands, it is possible to engineer state-dependent dipole forces with a reduced effect of off-resonant couplings to the carrier transition. This allows one, in a certain parameter regime, to devise entangling gate schemes based on geometric phase gates with both a higher speed and a lower error, which is attractive in light of current efforts towards fault-tolerant quantum information processing. We discuss the prospects of reaching the parameters required to observe this micromotion-enabled improvement in experiments with current and future trap designs

Processos revolucionários em discurso: Descentralizando e desconstruindo os impactos do 25 de Abril em Angola

É já um lugar-comum afirmar o papel fulcral que o 25 de Abril de 1974 teve no processo de descolonização das colónias portuguesas em África, nomeadamente no que diz respeito à incorporação da descolonização como desígnio do programa do MFA e subsequente criação de itinerários políticos e jurídicos para as respetivas declarações de independência (ver Coutinho 1984; Marques 2013; Correia 2019). No caso de Angola, esse processo plasmou-se no âmbito do Acordo de Alvor de janeiro de 1975, que mapeava um itinerário para a independência do país através de uma negociação multilateral entre o governo português e os três principais movimentos de libertação – o MPLA, a UNITA e a FNLA –, que por sua vez estabeleceria um governo de transição tripartido, com pastas distribuídas entre os três movimentos até à realização de umas eleições que nunca se chegaram a materializar.info:eu-repo/semantics/publishedVersio

On an asymptotic method for computing the modified energy for symplectic methods

We revisit an algorithm by Skeel et al. [5,16] for computing the modified, or shadow, energy associated with symplectic discretizations of Hamiltonian systems. We amend the algorithm to use Richardson extrapolation in order to obtain arbitrarily high order of accuracy. Error estimates show that the new method captures the exponentially small drift associated with such discretizations. Several numerical examples illustrate the theory

Mercaderes, productos y embarcaciones, en las relaciones comerciales marítimas entre dos ciudades mediterraneas: Orán - Valencia (1600-1703)

Este trabajo nos introduce en lo que debió ser el comercio marítimo exportador oraní destinado a Valencia a lo largo del seiscientos y los tres primeros años del setecientos (1600-1703); teniendo como base documental la Serie Petge de Mar (perteneciente a la sección Maestre Racional; custodiada en el Archivo del Reino de Valencia), pudiendo conjeturar con relativa sencillez particularidades y asuntos heterogéneos de la actividad mercantil que se construyó entre ambas ciudades; Orán como remitente de productos de diversa índole y, Valencia, como destinataria y consumidora de ellos. Un mundo visto desde el observatorio que es el puerto-playa del Grao de Valencia, donde, a modo de calidoscopio, nos pondrá en contacto con un universo formado por diferentes modelos de embarcaciones y los patrones que las dirigían; artículos (tan importantes en este comercio como el trigo, los esclavos, las pieles o la cera) o a los hombres vinculados en este intercambio mercantil, tanto desde la vertiente exportadora como importadora; teniendo, siempre, como testigo el mar Mediterráne