Search

While the standard point of view is that the ultimate endpoint of black hole evolution is determined by Hawking evaporation, there is a growing evidence that classical and semi-classical instabilities affect both black holes with inner horizons as well as their ultra-compact counterparts. In this paper we start from this evidence pointing towards extremal black holes as stable endpoints of the gravitational collapse, and develop a general class of spherical and axisymmetric solutions with multiple extremal horizons. Excluding more exotic possibilities, entailing regular cores supporting wormhole throats, we argue that these configurations could be the asymptotic graveyard, the end-point, of dynamical black hole evolution — albeit the timescale of such evolution are still unclear and possibly long and compatible with current astrophysical observations. [ABSTRACT FROM AUTHOR]

Regular black holes represent a conservative model in which the classical singularity is replaced by a non-singular core without necessarily modifying the spacetime outside the trapping horizon. Given the possible lack of phenomenological signatures, it is crucial to study the consistency of the model. In this short work, we review the physical mechanism leading to the instability of the central core, arguing that that non-perturbative backreation is non-negligible and must be taken into account to provide a meaningful description of physical black holes. [ABSTRACT FROM AUTHOR]

Classical black holes shield us from the singularities that inevitably appear in general relativity. Singularity regularization being one of the main landmarks for a successful theory of quantum gravity, quantum black holes are not obliged to hide their inner core from the outside world. Notwithstanding the aforesaid, it is often implicitly assumed that quantum gravity effects must remain confined to black hole interiors. In this essay, we argue in the opposite direction, discussing theoretical evidence for the existence of strong correlations between the physics inside and outside nonsingular black holes. We conclude that astronomical tests of the surroundings of black holes can provide invaluable information about their so-far unexplored interiors. [ABSTRACT FROM AUTHOR]

The evaporation of black holes raises a number of conceptual issues, most of them related to the final stages of evaporation, where the interplay between the central singularity and Hawking radiation cannot be ignored. Regular models of black holes replace the central singularity with a nonsingular spacetime region, in which an effective classical geometric description is available. It has been argued that these models provide an effective, but complete, description of the evaporation of black holes at all times up to their eventual disappearance. However, here we point out that known models fail to be self-consistent: the regular core is exponentially unstable against perturbations with a finite timescale, while the evaporation time is infinite, therefore making the instability impossible to prevent. We also discuss how to overcome these difficulties, highlighting that this can be done only at the price of accepting that these models cannot be fully predictive regarding the final stages of evaporation. [ABSTRACT FROM AUTHOR]

The reconstruction of ancient road systems is undoubtedly one of the main objectives of historical geography. However, tracing ancient routes – which formed pathways of cultural, economic and political interchange – remains often difficult, because of the scarcity of historical and archaeological sources, and of the inherent problems in the identification of ancient toponyms. This is certainly true for the south-eastern region of Anatolia in pre-Classical times: although epigraphic sources of different provenience do provide us with some information on ancient itineraries, many uncertainties and gaps in documentation still prevent an overall comprehension of ancient road systems. As a case study, the present article analyses the ancient site of Melid (Malatya), identified with the Arslantepe mound located in the Malatya plain. Ancient sources will be re-analysed with the help of computational modelling, which may fill in, at least partially, the gaps in the available documentation, simulating the impact of the social interactions and political changes over the evolution of an ancient road system. [ABSTRACT FROM AUTHOR]

The paper provides an overview of the digital tools developed as part of the Ebla Digital Archives Project, which aims to offer a digital edition of roughly 3,000 cuneiform tablets from ancient Ebla (modern Tell Mardikh, in western Syria), dated to the middle of the third millennium BCE. The Ebla archive is the oldest one in the history of mankind, for which extensive information concerning the primary setting of the documents is available. The archaicity of the writing system, combined with the inherent difficulties in reconstructing languages from the remote past (Sumerian, Akkadian, Eblaite), pushes us to rethink the strategies to properly digitally capture the complexity of these sources, of invaluable historical significance: administrative documents, literary texts, vocabularies, letters, etc. We tackled the problem through the development of a PostgreSQL database, which is populated by ad hoc Python scripts that parse input transliteration files, which in turn are encoded using a shallow mark-up language. The individual steps in such workflow are discussed, as well as the benefits in terms of advanced queries for information retrieval that such approach offers. [ABSTRACT FROM AUTHOR]

Mass inflation is a well established instability, conventionally associated to Cauchy horizons (which are also inner trapping horizons) of stationary geometries, leading to a divergent exponential buildup of energy. We show here that finite (but often large) exponential buildups of energy are present for dynamical geometries describing accreting black holes with slowly evolving inner trapping horizons, even in the absence of Cauchy horizons. The explicit evaluation of the adiabatic conditions behind these exponential buildups shows that this phenomenon is universally present for physically reasonable accreting conditions. This noneternal mass inflation does not require the introduction of global spacetime concepts. We also show that various known results in the literature are recovered in the limit in which the inner trapping horizon asymptotically approaches a Cauchy horizon. Our results imply that black hole geometries with nonextremal inner horizons, including the Kerr geometry in general relativity, and nonextremal regular black holes in theories beyond general relativity, can describe dynamical transients but not the long-lived end point of gravitational collapse.

Background: Current strategies for prognostic stratification in haemodynamically stable patients with acute pulmonary embolism require improvement. The aims of this study in haemodynamically stable patients with acute pulmonary embolism were (a) to evaluate the prognostic value of a novel respiratory index (oxygen saturation in air to respiratory rate ratio) and (b) to derive a risk model which includes the respiratory index and evaluate its value in predicting 30-day mortality., Methods: Prospective cohorts of haemodynamically stable patients with acute pulmonary embolism were merged to a collaborative database that served to create two subsequent derivation and validation cohorts based on a temporal criterion. The study outcome was 30-day all-cause death., Results: Thirty-day all-cause death occurred in 7.5% and in 6.9% of patients in the derivation and validation cohorts (each composed of 319 patients). In the derivation cohort, the respiratory index (odds ratio 0.66, 95% confidence interval 0.48-0.90) and simplified Pulmonary Embolism Severity Index (odds ratio 9.16, 95% confidence interval 1.22-68.89) were predictors of 30-day mortality. The cut-off value of the respiratory index ⩽3.8 was identified to best predict 30-day all-cause death (15.4% vs 5.0%, odds ratio 2.94, 95% confidence interval 1.22-7.11). The respiratory index ⩽3.8 was combined with the simplified Pulmonary Embolism Severity Index to create the Respiratory Index model that showed a good discriminatory power in the derivation (c-statistic 0.703, 95% confidence interval 0.60-0.80) and in the validation cohort (c-statistic 0.838, 95% confidence interval 0.768-0.907)., Conclusion: In hemodynamically stable patients with acute pulmonary embolism, the respiratory index was an independent predictor of 30-day all-cause death. The Respiratory Index model which includes the simplified Pulmonary Embolism Severity Index and the respiratory index, provides a good risk stratification of haemodynamically stable patients with acute pulmonary embolism.

Early identification of causative pathogen in sepsis patients is pivotal to improve clinical outcome. SeptiFast (SF), a commercially available system for molecular diagnosis of sepsis based on PCR, has been mostly used in patients hospitalized in hematology and intensive care units. We evaluated the diagnostic accuracy and clinical usefulness of SF, compared to blood culture (BC), in 391 patients with suspected sepsis, hospitalized in a department of internal medicine. A causative pathogen was identified in 85 patients (22%). Sixty pathogens were detected by SF and 57 by BC. No significant differences were found between the two methods in the rates of pathogen detection (P = 0.74), even after excluding 9 pathogens which were isolated by BC and were not included in the SF master list (P = 0.096). The combination of SF and BC significantly improved the diagnostic yield in comparison to BC alone (P < 0.001). Compared to BC, SF showed a significantly lower contamination rate (0 versus 19 cases; P < 0.001) with a higher specificity for pathogen identification (1.00, 95% confidence interval [CI] of 0.99 to 1.00, versus 0.94, 95% CI of 0.90 to 0.96; P = 0.005) and a higher positive predictive value (1.00, 95% CI of 1.00 to 0.92%, versus 0.75, 95% CI of 0.63 to 0.83; P = 0.005). In the subgroup of patients (n = 191) who had been receiving antibiotic treatment for ≥24 h, SF identified more pathogens (16 versus 6; P = 0.049) compared to BC. These results suggest that, in patients with suspected sepsis, hospitalized in an internal medicine ward, SF could be a highly valuable adjunct to conventional BC, particularly in patients under antibiotic treatment.