Quantum Corrections in Massive Gravity

We compute the one-loop quantum corrections to the potential of ghost-free massive gravity. We show how the mass of external matter fields contribute to the running of the cosmological constant, but do not change the ghost-free structure of the massive gravity potential at one-loop. When considering gravitons running in the loops, we show how the structure of the potential gets destabilized at the quantum level, but in a way which would never involve a ghost with a mass smaller than the Planck scale. This is done by explicitly computing the one-loop effective action and supplementing it with the Vainshtein mechanism. We conclude that to one-loop order the special mass structure of ghost-free massive gravity is technically natural.Comment: v2: References added, 29 pages, 7 figure

The meaning of internationalism in Angola:Were the Cubans “exporting” the revolution or becoming “the good colonizers”?

Between 1975 and 1991, Cuba deployed to Angola more than 300 000 military personnel (of which some 2 000 lost their lives), and around 50 000 civilians worked as doctors, nurses, teachers or engineers. The cultural impact of the presence of Cubans in the first half of the civil war in post-independence Angola marked deeply a whole generation of men and women and is still pretty much under-researched. In this article, I discuss the meaning of internationalism in Angola for Cuban society, resorting to sources (literature, poetry, testimony and political speeches) that have been addressing the Angolan conflict and analysing the meaning of Cuba’s internationalist policy stemming from both Cuba and abroad. By showing the mobilizing and activist character of the Cuban experience in Angola, through accounts on internationalism, my argument is that, rather than imposing themselves in a foreign nation, the Cubans were attempting to incorporate Angola in their own national narrative, in the sense of Eric Hobsbawm’s ‘‘ invention of tradition’’.«Exporter » la révolution ou devenir de «bons colonisateurs » ? Le sens de l’internationalisme cubain en Angola. Entre 1975 et 1991, Cuba a déployé en Angola plus de 300 000 soldats (dont 2 000 ont perdu la vie), et envoyé 50 000 civils environ comme médecins, infirmières, enseignants ou ingénieurs. Cette présence cubaine dans la guerre civile postérieure à l’indépendance en Angola a eu un impact culturel profond sur toute une génération d’hommes et de femmes. Elle est restée très peu étudiée. Cet article interroge le sens qu’a eu l’engagement internationaliste en Angola pour la société cubaine, en s’appuyant sur des sources diverses (littérature, poésie, témoignages et discours politiques) qui ont évoqué le conflit en Angola et ont analysé l’internationalisme cubain. En mettant en évidence à partir de témoignages la mobilisation et le militantisme qui caractérisent l’expérience cubaine en Angola, je montre que les Cubains n’ont pas tant cherché à s’imposer à une autre nation qu’à intégrer l’Angola dans leur propre récit national ¢ au sens de «l’invention de la tradition » d’Eric Hobsbawm.Ribeiro Raquel. The meaning of internationalism when the Cubans ‘‘exporting’’ the revolution or becoming ‘‘the good colonizers’’?. In: Outre-mers, tome 101, n°384-385,2014. Coopérants et coopération en Afrique : circulations d'acteurs et recompostitions culturelles (des années 1950 à nos jours) pp. 267-286

Preheating in Dirac-Born-Infeld inflation

We study how the universe reheats following an era of chaotic Dirac-Born-Infeld inflation, and compare the rate of particle production with that in models based on canonical kinetic terms. Particle production occurs through non-perturbative resonances whose structure is modified by the nonlinearities of the Dirac-Born-Infeld action. We investigate these modifications and show that the reheating process may be efficient. We estimate the initial temperature of the subsequent hot, radiation-dominated phase.Comment: 23 page