Stability of massive objects in a new scalar-tensor theory

We define a new scalar-tensor theory with an effective gravitational coupling constant depending on a scalar field. The coupling is such that the gravitational interaction decreases with the strength of the scalar field. We show that this is not sufficient to prevent the gravitational collapse of sufficiently massive dense objects

Importance of nuclear viscosity and thermal conductivity and the analysis of the bounce-off effect in high energy heavy ion collisions

We present an analysis of high energy heavy ion collisions at intermediate impact parameters, using a two-dimensional fluid-dynamical model including shear and bulk viscosity, heat conduction, a realistic treatment of the nuclear binding, and an analysis of the final thermal emission of free nucleons. We find large collective momentum transfer to projectile and target residues (the highly inelastic bounce-off effect) and explosion of the hot compressed shock zones formed during the impact. As the calculated azimuthal dependence of energy spectra and angular distributions of emitted nucleons depends strongly on the coefficients of viscosity and thermal conductivity, future exclusive measurements may allow for an experimental determination of these transport coefficients. The importance of 4π measurements with full azimuthal information is pointed out

Kinetic energy flow in Nb(400 A MeV) + Nb: evidence for hydrodynamic compression of nuclear matter

A kinetic-energy—flow analysis of multiplicity-selected collisions of 93Nb(Elab=400A MeV)+93Nb is performed on the basis of the nuclear fluid dynamical model. The effects of finite particle numbers on the flow tensor are explicitly taken into account. Strong sidewards peaks are predicted in dN/dcosθF, the distribution of event by event flow angles. This is in qualitative agreement with recent data from the "Plastic Ball" electronic detection system. Cascade simulations fail to reproduce the data

Viscous fluid dynamical calculation of the reaction 12C(85 MeV/nucleon) + 197Au

Proton spectra have been calculated for the reaction 12C(85 MeV/nucleon) + 197Au using a three-dimensional hydrodynamical model with viscosity and thermal conductivity and final thermal breakup. The theoretical results are compared to recent data. It is shown that the predicted flow effects are not observable as a result of the impact parameter averaging inherent in the inclusive proton spectra. In contrast, angular distributions of medium mass nuclei (A>3) in nearly central collisions can provide signatures for flow effects

Phase transition of the nucleon-antinucleon plasma in a relativistic mean-field theory

Studying Walecka's mean-field theory we find that one can reproduce the observed binding energy and density of nuclear matter within experimental precision in an area characterized by a line in the coupling-constant plane. A part of this line defines systems which exhibit a phase transition around Tc~200 MeV for zero baryon density. The rest corresponds to such systems where the phase transition is absent; in that case a peak appears in the specific heat around T~200 MeV. We interpret these results as indicating that the hadron phase of nuclear matter alone indicates the occurrence of an abrupt change in the bulk properties around ρV~0 and T~200 MeV

Event-by-event analysis : possible testing ground for the nuclear matter equation of state

Intranuclear cascade calculations and fluid dynamical predictions of the kinetic energy flow are compared for collisions of 40Ca + 40Ca and 238U + 238U. The aspect ratio, R13, as obtained from the global analysis, is independent of the bombarding energy for the intranuclear cascade model. Fluid dynamics, on the other hand, predicts a dramatic increase of R13 at medium energies Elab≲200 MeV/nucleon. In fact, R13(Elab) directly reflects the incompressibility of the nuclear matter and can be used to extract the nuclear equation of stat at high densities. Distortions of the flow tensor due to few nucleon scattering are analyzed. Possible procedures to remove this background from experimental data are discussed

Jets of nuclear matter from high energy heavy ion collisions

The fluid dynamical model is used to study the reactions 20Ne+238U and 40Ar+40Ca at Elab=390 MeV/nucleon. The calculated double differential cross sections d²ð​/dΩdE exhibit sidewards maxima in agreement with recent experimental data. The azimuthal dependence of the triple differential distributions, to be obtained from an event-by-event analysis of 4π; exclusive experiments, can yield deeper insight into the collision process: Jets of nuclear matter are predicted with a strongly impact-parameter-dependent thrust angle θ​jet(b). NUCLEAR REACTIONS Ar+Ca, Ne+U, Elab=393 MeV/nucleon, fluid dynamics with thermal breakup, double differential cross sections, azimuthal dependence of triple differential cross sections, event-by-event thrust analysis of 4π exclusive experiments

Fragment emission in high-energy heavy-ion reactions

We present a theoretical description of nuclear collisions which consists of a three-dimensional fluid-dynamical model, a chemical equilibrium breakup calculation for local light fragment (i.e., p, n, d, t, 3He, and 4He) production, and a final thermal evaporation of these particles. The light fragment cross sections and some properties of the heavy target residues are calculated for the asymmetric system Ne+U at 400 MeV/N. The results of the model calculations are compared with recent experimental data. Several observable signatures of the collective hydrodynamical processes are consistent with the present data. An event-by-event analysis of the flow patterns of the various clusters is proposed which can yield deeper insight into the collision dynamics

Virtual Exploration of Urban Spatial Changes due to Regional Tramway Line Construction

For most large infrastructure projects, it is mandatory to assess their impact on the urban and rural environment before they are started. Many shareholders want to involve the public or even are obliged to do so due to legal provisions. For interactive exploration, a 3D viewer is needed that supports very complex scenes. They should be realistically rendered for sufficient credibility. Applied research on this topic (in close cooperation with industrial partners) resulted in GEARViewer, a geospatial rendering framework. It supports huge geospatial scenes consisting of large-scale terrain models, buildings, roads, tramways, railways, tunnels, vegetation and a skylight model. Everything is georeferenced. It can import GIS data and turn this into 3D objects. In the future, it will also support Building Information Modeling (BIM) standards. Furthermore, it also simulates traffic in a simplified way including cars, trams, trains and pedestrians. It was used for many planned projects in Austria and Germany. In this paper, we describe one of the projects for the city centre of Innsbruck, created with the GEARViewer. It supported several stages of the segment wise planning and realization of a new regional tramway line over multiple years. Depending on progress, the project visualization incorporated varying levels of details into the existing city model, from graphic planning concepts during route optimization to detailed depictions of stops and road design shortly before constructional implementation. In this way, shareholders and citizens can experience the geospatial transformation and changes of the street network and traffic flow in the affected regions of the city. The system allows the regular creation of videos, screenshots, interactive online panorama tours and live demonstrations for publications and citizen information events. In order to fit the current state of planning, the system and model were constantly extended and updated. It supported the project progress and associated votes and discussions by supplying the display of variants, flexible viewpoints and realistic visualization

Genotypic variability enhances the reproducibility of an ecological study

Many scientific disciplines are currently experiencing a “reproducibility crisis” because numerous scientific findings cannot be repeated consistently. A novel but controversial hypothesis postulates that stringent levels of environmental and biotic standardization in experimental studies reduces reproducibility by amplifying impacts of lab-specific environmental factors not accounted for in study designs. A corollary to this hypothesis is that a deliberate introduction of controlled systematic variability (CSV) in experimental designs may lead to increased reproducibility. We tested this hypothesis using a multi-laboratory microcosm study in which the same ecological experiment was repeated in 14 laboratories across Europe. Each laboratory introduced environmental and genotypic CSV within and among replicated microcosms established in either growth chambers (with stringent control of environmental conditions) or glasshouses (with more variable environmental conditions). The introduction of genotypic CSV led to lower among-laboratory variability in growth chambers, indicating increased reproducibility, but had no significant effect in glasshouses where reproducibility was generally lower. Environmental CSV had little effect on reproducibility. Although there are multiple causes for the “reproducibility crisis”, deliberately including genetic variation may be a simple solution for increasing the reproducibility of ecological studies performed in controlled environments