A geometrical instability for ultra-light fields during inflation?

Westudythebehaviourofisocurvatureperturbationsinnon-linearsigmamodels which naturally emerge in supergravity and string inflationary scenarios. We focus on the case of negatively curved field manifolds which can potentially lead to a geometrical destabilisation of isocurvature modes. We find however that heavy fields are stable when their effective mass is computed on the attractor background solution. On the other hand, we show that ultra-light fields can potentially suffer from a geometrical instability when the background trajectory is a geodesic in field space. In this case a full understanding of the system is likely to require the use of non-perturbative methods.Comment: Matches published version, 5 pages, 2 figure

Fish assemblages across the Mediterranean Sea and the effects of protection from fishing = I Popolamenti ittici nel Mediterraneo e gli effetti della protezione dall’impatto della pesca

Several studies have assessed the effectiveness of individual marine protected areas (MPAs) in protecting fish assemblages, but regional assessments of multiple parks are scarce. Here fish surveys using visual census were done in marine parks and fished areas at 31 locations across the Mediterranean Sea. Fish species richness, diversity and biomass (especially of top predators) were higher in MPAs compared to fished areas, and community structure differed significantly between MPAs and fished areas. Results suggest that MPAs are generally effective means to protect and recover fish populations and assemblages

Preoccupano le infestazioni della cimice asiatica

2015-Anno caldo delle cimici. Nel corso dell’estate le infestazioni di Halyomorpha halys hanno investito un territorio sempre più ampio, con gravi percentuali di danno su numerose colture. A esse si sono sovrapposti gli attacchi di altri pentatomidi, accomunati anch’essi dalla caratteristica di pungere e deprezzare i frutti. Il malessere degli agricoltori è crescente e la situazione in alcuni contesti ha assunto le dimensioni di un’autentica emergenza

Halyomorpha halys in Emilia, prime risposte dal monitoraggio

OSSERVAZIONI IN CAMPO CONDOTTE NEL 2013-2014. Dopo la sua comparsa in Italia, accertata nel 2012, è stato attivato nella zona di ritrovamento un programma di monitoraggio teso a studiare l’insetto e il suo comportamento nell’ambiente. La specie desta maggiori preoccupazioni nel settore frutticolo, dove il danno rappresentato dalle tipiche deformazioni può giungere al 100

On the record of the Lessepsian migrant Fistularia commersonii (Rüppell, 1835) from the Adriatic Sea

On 7 November and 15 December 2006, two specimens of the Lessepsian migrant Fistularia commersonni were caught in trammel nets off the coastal waters of Tricase Porto (southwestern Adriatic, Italy) and Sveti Andrija (southeastern Adriatic, Croatia), respectively. These represent the first records of this species in the Adriatic Sea

Large-scale assessment of Mediterranean marine protected areas effects on fish assemblages

Marine protected areas (MPAs) were acknowledged globally as effective tools to mitigate the threats to oceans caused by fishing. Several studies assessed the effectiveness of individual MPAs in protecting fish assemblages, but regional assessments of multiple MPAs are scarce. Moreover, empirical evidence on the role of MPAs in contrasting the propagation of non-indigenous-species (NIS) and thermophilic species (ThS) is missing. We simultaneously investigated here the role of MPAs in reversing the effects of overfishing and in limiting the spread of NIS and ThS. The Mediterranean Sea was selected as study area as it is a region where 1) MPAs are numerous, 2) fishing has affected species and ecosystems, and 3) the arrival of NIS and the northward expansion of ThS took place. Fish surveys were done in well-enforced no-take MPAs (HP), partially-protected MPAs (IP) and fished areas (F) at 30 locations across the Mediterranean. Significantly higher fish biomass was found in HP compared to IP MPAs and F. Along a recovery trajectory from F to HP MPAs, IP were similar to F, showing that just well enforced MPAs triggers an effective recovery. Within HP MPAs, trophic structure of fish assemblages resembled a top-heavy biomass pyramid. Although the functional structure of fish assemblages was consistent among HP MPAs, species driving the recovery in HP MPAs differed among locations: this suggests that the recovery trajectories in HP MPAs are likely to be functionally similar (i.e., represented by predictable changes in trophic groups, especially fish predators), but the specific composition of the resulting assemblages may depend on local conditions. Our study did not show any effect of MPAs on NIS and ThS. These results may help provide more robust expectations, at proper regional scale, about the effects of new MPAs that may be established in the Mediterranean Sea and other ecoregions worldwide