From Strangeness Enhancement to Quark-Gluon Plasma Discovery

This is a short survey of signatures and characteristics of the quark-gluon plasma in the light of experimental results that have been obtained over the past three decades. In particular, we present an in-depth discussion of the strangeness observable, including a chronology of the experimental effort to detect QGP at CERN-SPS, BNL-RHIC, and CERN-LHC.Comment: 30 pages, about 20 figures; Dedicated to our mentor Walter Greiner; to be published in the memorial volume edited by Peter O. Hes

Solution of the Dirac equation for strong external fields

The 1s bound state of superheavy atoms and molecules reaches a binding energy of -2mc2 at Z≈169. It is shown that the K shell is still localized in r space even beyond this critical proton number and that it has a width Γ (several keV large) which is a positron escape width for ionized K shells. The suggestion is made that this effect can be observed in the collision of very heavy ions (superheavy molecules) during the collision

Self-Perception Versus Objective Driving Behavior: Subject Study of Lateral Vehicle Guidance

Advancements in technology are steering attention toward creating comfortable and acceptable driving characteristics in autonomous vehicles. Ensuring a safe and comfortable ride experience is vital for the widespread adoption of autonomous vehicles, as mismatches in driving styles between humans and autonomous systems can impact passenger confidence. Current driving functions have fixed parameters, and there is no universally agreed-upon driving style for autonomous vehicles. Integrating driving style preferences into automated vehicles may enhance acceptance and reduce uncertainty, expediting their adoption. A controlled vehicle study (N = 62) was conducted with a variety of German participants to identify the individual lateral driving behavior of human drivers, specifically emphasizing rural roads. We introduce novel indicators for assessing stationary and transient curve negotiation, directly applicable in developing personalized lateral driving functions. To assess the predictability of these indicators using self-reports, we introduce the MDSI-DE, the German version of the Multidimensional Driving Style Inventory. The correlation analysis between MDSI factor scores and proposed indicators showed modest but significant associations, primarily with acceleration and jerk statistics while the in-depth lateral driving behavior turned out to be highly driver-heterogeneous. The dataset including the anonymized socio-demographics and questionnaire responses, the raw vehicle measurements including labels, and the derived driving behavior indicators are publicly available at https://www.kaggle.com/datasets/jhaselberger/spodb-subject-study-of-lateral-vehicle-guidance.Comment: 33 pages, 6 figures, under revie

Phosphorkreislauf, marine Primärproduktion und Redoxbedingungen während Massenaussterbeereignissen

A decrease in marine primary productivity and in the dissolved oxygen inventory due to the effects of anthropogenic global warming, in particular enhanced water column stratification, has been observed over the last five decades. Moreover, modeling studies predict that these trends will continue under scenarios of ongoing greenhouse gas emissions. In the geological past, multiple episodes of climate change occurred, and investigating the associated biogeochemical changes in the sedimentary records of the ancient oceans can give important insights. Some of the warming phases and one cooling phase led to mass extinction events through a cascade of environmental perturbations. While global warming due to greenhouse gas emissions from the Siberian Trap Large Igneous Province is well established for the end-Permian mass extinction, the concomitant chain of effects is a matter of debate. In particular, there are two controversial questions: 1. Did marine primary productivity increase due to enhanced phosphorus input from the continents or decrease (or even collapse) due to inefficient phosphorus recycling in a stratified water column? 2. What was the driver of the observed ocean deoxygenation during the latest Permian? In principle, marine primary productivity and water column redox conditions are closely related through two mechanisms. One is that enhanced primary productivity results in a large organic matter sinking flux and therefore high rates of respiratory oxygen consumption. The other is that both depend on ocean circulation strength, upwelling intensity, mixing efficiency, and the degree of water column stratification. In a stagnant ocean, ventilation of the water column is weak, and nutrient recycling in upwelling regions becomes inefficient. Since the latest Permian warming is thought to have resulted in a stagnating ocean, the following hypothesis was developed: “In distal regions of the Tethys Ocean, primary productivity decreased from the latest Permian into the Early Triassic due to inefficient phosphorus recycling, and the water column was deoxygenated due to weak ventilation of deep waters and reduced oxygen solubility in warm surface waters.” In order to test this, productivity and redox proxies were measured on samples collected from two Tethyan, distal, low-latitude carbonate sections spanning the Permian-Triassic transition. These are the Chibi section (China) and Chanakhchi section (Armenia), the former representing a deep slope setting on the northern margin of the South China craton in the eastern Tethys and the latter a carbonate ramp far from land in the western equatorial Tethys. Both sections exhibit a decrease in total organic carbon contents, reactive phosphorus, and nickel concentrations in the latest Permian, suggesting a productivity decline. At Chibi, C/Porg and C/Preact ratios indicate a switch from inefficient P-burial with high P-regeneration in the late Permian to efficient burial in the Early Triassic. In parallel to the productivity decline, cerium-anomalies, measured on the carbonate fraction, shift from negative to positive values indicative of water column deoxygenation. In the Early Triassic interval of both sections, the proxies consistently signal weak productivity under low-oxygen conditions. Hence, a eutrophication scenario can be confidently ruled out for the study sites, and the presented hypothesis is verified. Distal regions of the Tethys Ocean probably switched to an oligotrophic-anoxic state in the course of latest Permian global warming due to a stably stratified water column with high sea surface temperatures. In this scenario, food shortage for higher trophic levels and anoxia are both potential killing mechanism with a common trigger. The late-Ordovician mass extinction is in stark contrast to the end-Permian mass extinction. It is preceded by a long-term cooling trend through the Ordovician and is commonly seen in the context of the large-scale glaciation of Gondwana in the Hirnantian. A major sea level drop occurred at the base of the M. persculptus graptolite zone, leading to the exposure of epeiric and shelf seas. Published local and global redox proxy records point towards an expansion of anoxic conditions in the open ocean at that time, while shallow settings remained oxygenated. During times of high sea level, shelf environments host the bulk of marine primary productivity. For the modern ocean, it is estimated that about 70% of the delivered phosphorus is retained in shelf sediments through the deposition of organic matter and the diagenetic stabilization of phosphorus into authigenic apatite minerals. Based on this, the following hypothesis was developed to explain the open ocean anoxia in the Hirnantian: “Due to the sea level fall during the glacial maximum in the Hirnantian shelf environments lost their function as a nutrient filter and the open ocean received a large excess in bioavailable phosphorus which fueled primary productivity and led to a high organic matter sinking flux and enhanced respiratory oxygen consumption.” The hypothesis was tested by measuring reactive phosphorus on samples from two tropical shallow-water carbonate sections covering the Ordovician-Silurian transition. These are the Ruisseau aux Algues section on Anticosti Island (Canada) and the Valga-10 core section from Estonia. Decreasing concentrations towards and a minimum at the Hirnantian glacial maximum were found. Using an estimate for the global shelf area and its reduction due to the sea level fall, phosphorus burial fluxes were calculated. According to this, the burial flux in shelf environments was approximately halved, and the open ocean would have received the excess phosphorus. The resulting high primary productivity led to an elevated organic matter sinking flux and strong respiratory oxygen consumption. This scenario is able to explain widespread open ocean anoxia during a cold climatic state, with sea level being the overarching control