Renyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

We discuss the Renyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories in the scaling limit. We unify the previous conformal-field-theory approaches to describe primary and descendant states in systems with both open and closed boundaries. We provide universal expressions for the first two descendants in the identity family. We apply our technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and find excellent agreement with numerical results obtained for finite spin chains. We also demonstrate that entanglement entropies are a powerful tool to resolve degeneracy of higher excited states in critical lattice models

Modern Ethiopia and Colonial Eritrea

The article develops some reflections on present-day Eritrea in the light of the colonial past and in the context of modern Ethiopia. If we consider Eritrea and its path towards independence, some differences and analogies emerge in comparison with other African colonies. The Eritrean independence is taking place today in a very specific context in post-colonial Africa. It is not a simple case of delayed decolonization, postponed by 30 years with respect to other former African colonies. The history of Eritrea must be studied within the colonial context: colonialism created a national identity, but Eritrea is a colony that did not become an independent state. This phenomenon can be attributed to various causes which I will try to underline. The process of state formation in Eritrea raises some problems for historians. The construction of a new political legitimacy is strictly connected to the birth of a national historiography in the country. I would like to examine in a critical way the process of writing history in contemporary Eritrea. Reconstructing the history of the past goes beyond the reconstruction of the history of the Eritrean state today. We have to consider the entire area – the Horn of Africa – in the pre-colonial period. The paper discusses the interrelation between the creation of the state and the national historiography

James De Lorenzi, Guardians of the Tradition: History and Historical Writings in Ethiopia and Eritrea

Revie

In memoriam Fratel Ezio Tonini (1939–2016)

Obituar

Bairu Tafla: Troubles and Travels of an Eritrean Aristocrat: A Presentation of Käntiba Gilamikaʾél’s Memoirs

Revie

Dynamics of entanglement entropy and entanglement spectrum crossing a quantum phase transition

We study the time evolution of entanglement entropy and entanglement spectrum in a finite-size system which crosses a quantum phase transition at different speeds. We focus on the Ising model with a time-dependent magnetic field, which is linearly tuned on a time scale $\tau$ . The time evolution of the entanglement entropy displays different regimes depending on the value of $\tau$, showing also oscillations which depend on the instantaneous energy spectrum. The entanglement spectrum is characterized by a rich dynamics where multiple crossings take place with a gap-dependent frequency. Moreover, we investigate the Kibble-Zurek scaling of entanglement entropy and Schmidt gap.Comment: Accepted for publication in Phys. Rev.

The nebular spectra of SN 2012aw and constraints on stellar nucleosynthesis from oxygen emission lines

We present nebular phase optical and near-infrared spectroscopy of the Type IIP supernova SN 2012aw combined with NLTE radiative transfer calculations applied to ejecta from stellar evolution/explosion models. Our spectral synthesis models generally show good agreement with the ejecta from a MZAMS = 15 Msun progenitor star. The emission lines of oxygen, sodium, and magnesium are all consistent with the nucleosynthesis in a progenitor in the 14 - 18 Msun range. We also demonstrate how the evolution of the oxygen cooling lines of [O I] 5577 A, [O I] 6300 A, and [O I] 6364 A can be used to constrain the mass of oxygen in the non-molecularly cooled ashes to < 1 Msun, independent of the mixing in the ejecta. This constraint implies that any progenitor model of initial mass greater than 20 Msun would be difficult to reconcile with the observed line strengths. A stellar progenitor of around MZAMS = 15 Msun can consistently explain the directly measured luminosity of the progenitor star, the observed nebular spectra, and the inferred pre-supernova mass-loss rate. We conclude that there is still no convincing example of a Type IIP explosion showing the nucleosynthesis expected from a MZAMS > 20 Msun progenitor.Comment: Accepted for publication in MNRA

A Preliminary Analysis for Understanding Variations in Mountain Springs’ Water Availability under Climate Change in Aosta Valley

The availability of freshwater resources in alpine mountain areas has been affected by the impacts of climate change on groundwater storage mechanisms. A web of complex interactions characterizes climate systems, and several potential effects of climate change in such areas remain largely unknown. Therefore, examining how groundwater storage mechanisms are changing in response to climate-driven agents is becoming increasingly crucial. To comprehend the existing relationship between changes in weather conditions and water availability in the Aosta Valley region (Northwestern Italy) and how their trends have changed over the last decade, a 7-year discharge series of different Aosta Valley springs (Promise, Alpe Perrot, Promiod, Cheserod) and precipitation data of the related meteorological stations (Aymaville-Viayes, La Thuile-Villaret, Champdepraz, Sant Vincent) were analyzed. The extent of the correlations between springs discharge measurements and hydrometeorological data was investigated. Besides, precipitation and flow rate trend analyses using the Mann–Kendall and Sen’s slope trend detection tests were performed. The Aymaville-Viayes, La Thuile-Villaret, Champdepraz, and Sant Vincent meteorological stations revealed an overall decreasing trend in annual rainfall (mm), with a slight increase in intensity (mm/day) as a result of the reduction in rainfall events (number of rainy days). Nonetheless, based on the analysis of flow rate data relating to the associated springs, Alpe Perrot, Cheserod, and Promise show an overall increasing trend of discharge over time. Although the Cheserod and Promise springs were not found to be highly correlated with rainfall, their aquifers appear to positively respond to the modified climate conditions, increasing the amount of groundwater stored. The moderate correlation values of these two springs can be a consequence of several factors such as aquifer features, distance from the weather station, and solid precipitation amounts that supply water in the following hydrogeological year. Being able to continuously monitor the effects induced by changed climatic conditions on water reserves through simplified analysis approaches such as those presented in this paper is increasingly necessary. Moreover, implementing future studies through in-depth analyses of soil infiltration, groundwater recharge and storage mechanisms are required to predict the mountain aquifers’ behavior in changing climatic conditions

Estimating Quasi-long-range Order via Renyi Entropies

We show how entanglement entropies allow for the estimation of quasi-long-range order in one dimensional systems whose low-energy physics is well captured by the Tomonaga-Luttinger liquid universality class. First, we check our procedure in the exactly solvable XXZ spin-1/2 chain in its entire critical region, finding very good agreement with Bethe ansatz results. Then, we show how phase transitions between different dominant orders may be efficiently estimated by considering the superfluid-charge density wave transition in a system of dipolar bosons. Finally, we discuss the application of this method to multispecies systems such as the one dimensional Hubbard model. Our work represent the first proof of a direct relationship between the Luttinger parameter and R\'enyi entropies in both bosonics and fermionic lattice models.Comment: v2: minimal changes, 6 pages, 7 figures, accepted for publication in Phys. Rev.