Critical phenomena at the threshold of black hole formation for collisionless matter in spherical symmetry

We perform a numerical study of the critical regime at the threshold of black hole formation in the spherically symmetric, general relativistic collapse of collisionless matter. The coupled Einstein-Vlasov equations are solved using a particle-mesh method in which the evolution of the phase-space distribution function is approximated by a set of particles (or, more precisely, infinitesimally thin shells) moving along geodesics of the spacetime. Individual particles may have non-zero angular momenta, but spherical symmetry dictates that the total angular momentum of the matter distribution vanish. In accord with previous work by Rein et al, our results indicate that the critical behavior in this model is Type I; that is, the smallest black hole in each parametrized family has a finite mass. We present evidence that the critical solutions are characterized by unstable, static spacetimes, with non-trivial distributions of radial momenta for the particles. As expected for Type I solutions, we also find power-law scaling relations for the lifetimes of near-critical configurations as a function of parameter-space distance from criticality.Comment: 32 pages, 10 figure

The 1.23 Ga Fjellhovdane rhyolite, Grøssæ-Totak; a new age within the Telemark supracrustals, southern Norway

The Grøssæ-Totak supracrustal belt is part of the several-kilometre thick Telemark supracrustal sequences that are exposed in southern Norway. Deposition of the Telemark supracrustals spans the period between Telemarkian continental growth at ~1.52-1.48 Ga and Sveconorwegian orogenesis associated with continental collision at ~1.1-0.9 Ga. The timing of deposition is largely constrained by U-Pb geochronology of detrital zircons in sedimentary units, and igneous zircons within felsic volcanics. A younger Supergroup that has been referred to as the Sveconorwegian Supergroup comprises depositional ages younger than 1.16 Ga; units of the Grøssae-Totak belt have been mapped as part of this Supergroup. This study presents a new U-Pb age of 1233 ± 29 Ma for the Fjellhovdane rhyolite, one of the lowermost units within the Grøssæ-Totak belt; this age suggests that at least the lower part of this sequence is not part of the Sveconorwegian Supergroup, but formed in an earlier volcano-sedimentary basin that is correlative in age to the Sæsvatn-Valldal and Setesdal supracrustal belts that occur to the west and south respectively. The geochemistry of the Fjellhovdane rhyolite is compatible with crustal melting of previously-formed supra-subduction rocks, as has been advocated for the Sæsvatn-Valldal rhyolites

Critical Collapse of the Massless Scalar Field in Axisymmetry

We present results from a numerical study of critical gravitational collapse of axisymmetric distributions of massless scalar field energy. We find threshold behavior that can be described by the spherically symmetric critical solution with axisymmetric perturbations. However, we see indications of a growing, non-spherical mode about the spherically symmetric critical solution. The effect of this instability is that the small asymmetry present in what would otherwise be a spherically symmetric self-similar solution grows. This growth continues until a bifurcation occurs and two distinct regions form on the axis, each resembling the spherically symmetric self-similar solution. The existence of a non-spherical unstable mode is in conflict with previous perturbative results, and we therefore discuss whether such a mode exists in the continuum limit, or whether we are instead seeing a marginally stable mode that is rendered unstable by numerical approximation.Comment: 11 pages, 8 figure

New Critical Behavior in Einstein-Yang-Mills Collapse

We extend the investigation of the gravitational collapse of a spherically symmetric Yang-Mills field in Einstein gravity and show that, within the black hole regime, a new kind of critical behavior arises which separates black holes formed via Type I collapse from black holes formed through Type II collapse. Further, we provide evidence that these new attracting critical solutions are in fact the previously discovered colored black holes with a single unstable mode.Comment: 13 pages, 4 figure

Government effectiveness and the COVID-19 pandemic

The COVID-19 pandemic threatens to derail progress achieved in sustainable development. This study investigates the effectiveness of government policy responses to the COVID-19 pandemic, namely the number of deaths. Using the Oxford COVID-19 Government Response Tracker (OxCGRT) dataset for a global sample of countries between March and September 2020, we find a non-linear association between government response indices and the number of deaths. Less stringent interventions increase the number of deaths, whereas more severe responses to the pandemic can lower fatalities. The outcomes are similar for a sample of countries disaggregated by regions. These findings can be informative for policymakers in their efforts to mitigate the spread of the virus and save lives.Data Availability Statement: COVID-19 data were obtained from https://github.com/CSSEGISandData/COVID-19, accessed on 2 September 2020.https://www.mdpi.com/journal/sustainabilityEconomic

Geochronology and structure of the eastern margin of the Tanzania Craton east of Dodoma

The precise position, nature and U-Pb zircon geochronology of the eastern margin of the Tanzania Craton has been studied in the Mpwapwa area, some 60 km east of Dodoma, central Tanzania, in a number of field transects over a ca. 45 km strike length of the craton margin. The rocks to the east of the Tanzania Craton in this area either belong to the Palaeoproterozoic Usagaran belt, or the “Western Granulite” terrane of the Neoproterozoic East African Orogen, according to different authors. The eastern part of the craton is underlain by typical Neoarchaean migmatitic grey granodioritic orthogneisses dated by ICP-MS at 2674 ± 73 Ma. There is a gradual increase in strain eastwards in these rocks, culminating in a 1 to 2 km wide, locally imbricated, ductile thrust/shear zone with mylonites indicating an oblique top-to-the-NW, transpressional sense of movement. East of the craton-edge shear zone, a series of high-grade supracrustal rocks are termed the “Mpwapwa Group”, in view of uncertain age and regional lithostratigraphic correlations. There is an apparent east-west lithological zonation of Mpwapwa Group parallel to the craton margin shear zone. In the west, immediately adjacent to the craton, the group consists of typical “shelf facies” metasediments (marbles, calc-silicates, quartzites etc.). U-Pb dating of detrital zircons from two Mpwapwa Group quartzite samples from this marginal zone contain only Archaean detritus, constraining their maximum depositional age to > ca. 2.6 Ga and suggesting that the group is Neoarchaean in age. The shelf rocks pass eastwards into garnet and kyanite-bearing semi-pelitic gneisses interlayered with bimodal mafic-felsic gneisses, where the mafic amphibolite gneisses may represent meta-basalts and the felsic rocks may have meta-rhyolite, -granite or –psammite protoliths. Massive garnet-clinopyroxene amphibolite layers in the Mpwapwa Group gneisses may have been intrusive mafic sills and possibly correlate with the Palaeoproterozoic Isimani Suite, which outcrops south of the study area and includes 2 Ga eclogites. Zircons from a quartzo-feldsapthic gneiss sample from the bimodal gneisses were dated and showed it to be a probable Neoarchaean rock which underwent metamorphism during the Palaeoproterozoic Usagaran event at ca. 1950 Ma. This event was broadly coeval with subduction, closure of an ocean basin and eclogite formation further south and led to the initial juxtaposition of the two Archaean blocks. The metamorphism probably dates the tectonic event when the Archaean Mpwapwa Group rocks were juxtaposed against the orthogneissic Tanzania Craton. The Mpwapwa Group was intruded by weakly foliated biotite granite at 1871 ± 35 Ma. Zircons in the granite have metamorphic rims dated between 550 and 650 Ma that grew during the East African orogenic event

Geopolitical risks and recessions in a panel of advanced economies : evidence from over a century of data

This paper uses a panel of 17 advanced countries over the annual period of 1899–2013, to analyze for the first time, the role played by geopolitical risks in predicting recessions. After controlling for other standard predictors based on a logit model, we find that while aggregate geopolitical risks do not have any predictive ability, geopolitical acts enhance the probability of future recessions, with geopolitical threats reducing the same.http://www.tandfonline.com/loi/rael202020-06-15hj2019Economic

The effectiveness of monetary and fiscal policy shocks on U.S. inequality : the role of uncertainty

The study examines the effect of monetary and fiscal policy on inequality conditioned on low and high uncertainty. We use U.S. quarterly time series data on different measures of income, labour earnings, consumption and total expenditure inequality as well as economic uncertainty. Our analysis is based on the impulse responses from the local projection methods that enable us to recover a smoothed average of the underlying impulse response functions. The results show that both contractionary monetary and fiscal policies increase inequality, and in the presence of relatively higher levels of uncertainty, the effectiveness of both policies is weakened. Thus, pointing to the need for policy-makers to be aware of the level of uncertainty while conducting economic policies in the U.S.http://link.springer.com/journal/111352019-04-04hj2018Economic

Embryonic expression and cloning of the murine GATA-3 gene.

We describe the embryonic expression pattern as well as the cloning and initial transcriptional regulatory analysis of the murine (m) GATA-3 gene. In situ hybridization shows that mGATA-3 mRNA accumulation is temporally and spatially regulated during early development: although found most abundantly in the placenta prior to 10 days of embryogenesis, mGATA-3 expression becomes restricted to specific cells within the embryonic central nervous system (in the mesencephalon, diencephalon, pons and inner ear) later in gestation. GATA-3 also shows a restricted expression pattern in the peripheral nervous system, including terminally differentiating cells in the cranial and sympathetic ganglia. In addition to this distinct pattern in the nervous system, mGATA-3 is also expressed in the embryonic kidney and the thymic rudiment, and further analysis showed that it is expressed throughout T lymphocyte differentiation. To begin to investigate how this complex gene expression pattern is elicited, cloning and transcriptional regulatory analyses of the mGATA-3 gene were initiated. At least two regulatory elements (one positive and one negative) appear to be required for appropriate tissue-restricted regulation after transfection of mGATA-3-directed reporter genes into cells that naturally express GATA-3 (T lymphocytes and neuroblastoma cells). Furthermore, this same region of the locus confers developmentally appropriate expression in transgenic mice, but only in a subset of the tissues that naturally express the gene