Cosmological Hydrodynamics with Multi-Species Chemistry and Nonequilibrium Ionization and Cooling

We have developed a method of solving for multi-species chemical reaction flows in non--equilibrium and self--consistently with the hydrodynamic equations in an expanding FLRW universe. The method is based on a backward differencing scheme for the required stability when solving stiff sets of equations and is designed to be efficient for three-dimensional calculations without sacrificing accuracy. In all, 28 kinetic reactions are solved including both collisional and radiative processes for the following nine separate species: H, H+, He, He+, He++, H-, H2+, H2, and e-. The method identifies those reactions (involving H- and H2+) ocurring on the shortest time scales, decoupling them from the rest of the network and imposing equilibrium concentrations to good accuracy over typical cosmological dynamical times. Several tests of our code are presented, including radiative shock waves, cosmological sheets, conservation constraints, and fully three-dimensional simulations of CDM cosmological evolutions in which we compare our method to results obtained when the packaged routine LSODAR is substituted for our algorithms.Comment: Latex and postscript, 24 pages, with 6 figures. The paper is also available at http://zeus.ncsa.uiuc.edu:8080/~abel/PGas/bib.html Submitted to New Astronom

Edith Abbott Was Right: Designing Fieldwork Experiences for Contemporary Health Care Practice

Successful social work practice in the contemporary, economically driven, health care environment demands unprecedented levels of technical competence, initiative, creativity and conceptual sophistication. Fieldwork plays a critical role in social work education for such demanding practice by providing interns initial opportunities to apply their newly acquired knowledge, skills and abilities. This article discusses the contribution of fieldwork to the preparation of social work practitioners and presents two programs that may serve as alternative models of fieldwork. Observations of the impact of these models, including a summary of two evaluations of one model are presented. We contend that a fieldwork structure using rotations may increase the value of fieldwork for students both academically and in the employment process. Correct citation for final version of manuscript is: Spitzer, W., Holden, G., Cuzzi, L. C., Rutter, S., Chernack, P., & Rosenberg, G. (2001). Edith Abbott was right: Designing fieldwork experiences for contemporary health care practice. Journal of Social Work Education, 37, 79-90

Lattice Bosonization

A free lattice fermion field theory in 1+1 dimensions can be interpreted as SOS-type model, whose spins are integer-valued. We point out that the relation between these spins and the fermion field is similar to the abelian bosonization relation between bosons and fermions in the continuum. Though on the lattice the connected $2n$-point correlation functions of the integer-valued spins are not zero for any $n \ge 1$, the two-point correlation function of these spins is that of free bosons in the infrared. We also conjecture the form of the Wess-Zumino-Witten chiral field operator in a nonabelian lattice fermion model. These constructions are similar in spirit to the ``twistable string" idea of Krammer and Nielsen.Comment: 8 pages, latex, no figure

Causation of traffic accidents with children from the perspective of all involved participants

In the year 2014 about 2,800 children between zero and 14 years got injured due to traffic accidents in Austria. More than 50% were taking part in traffic as active road users like cyclists or pedestrians. Within this study 46 real world traffic accidents between vehicles and children as pedestrians were analysed. In 39 cases, car drivers hit the crossing children. In the other cases, the collision opponents were busses, trucks or motorcycles. Most of the children got hit while crossing a road at urban sites. By analysing the traffic accidents from the perspectives of all involved participants, vehicle drivers and injured children, it is possible to identify factors for each participant, which led to the accident and factors that contributed the accident. The main task is to find patterns in the behaviour of crash victims (children and driver) before the collision. One important fact is that in more than 50% of the analysed cases sight obstructions were an important contributing factor for both, the driver and the child. From drivers view situations in which the child moved unexpected into the driven road lane were often found. For the injured child, factors like: no attention to the road traffic or no sufficient traffic observation were found to be relevant. Further it- possible to sensitise children and adults to possible source of critical traffic situations according to the findings of this study

Theory of self-resonance after inflation. II. Quantum mechanics and particle-antiparticle asymmetry

We further develop a theory of self-resonance after inflation in a large class of models involving multiple scalar fields. We concentrate on inflaton potentials that carry an internal symmetry, but also analyze weak breaking of this symmetry. This is the second part of a two-part series of papers. Here in Part 2 we develop an understanding of the resonance structure from the underlying many-particle quantum mechanics. We begin with a small-amplitude analysis, which obtains the central resonant wave numbers, and relate it to perturbative processes. We show that the dominant resonance structure is determined by (i) the nonrelativistic scattering of many quantum particles and (ii) the application of Bose-Einstein statistics to the adiabatic and isocurvature modes, as introduced in Part 1 [M. P. Hertzberg et al., Phys. Rev. D 90, 123528 (2014)]. Other resonance structures are understood in terms of annihilations and decays. We set up Bunch-Davies vacuum initial conditions during inflation and track the evolution of modes including Hubble expansion. In the case of a complex inflaton carrying an internal U(1) symmetry, we show that when the isocurvature instability is active, the inflaton fragments into separate regions of ϕ-particles and anti-ϕ-particles. We then introduce a weak breaking of the U(1) symmetry; this can lead to baryogenesis, as shown by some of us recently [M. P. Hertzberg and J. Karouby, Phys. Lett. B 737, 34 (2014); Phys. Rev. D 89, 063523 (2014)]. Then using our results, we compute corrections to the particle-antiparticle asymmetry from this preheating era.Massachusetts Institute of Technology. Center for Theoretical PhysicsMassachusetts Institute of Technology. Undergraduate Research Opportunities ProgramUnited States. Dept. of Energy (Cooperative Research Agreement Contract DE-FG02-05ER41360)Natural Sciences and Engineering Research Council of Canada (Postdoctoral Fellowship

A supersymmetric model for triggering Supernova Ia in isolated white dwarfs

We propose a model for supernovae Ia explosions based on a phase transition to a supersymmetric state which becomes the active trigger for the deflagration starting the explosion in an isolated sub-Chandrasekhar white dwarf star. With two free parameters we fit the rate and several properties of type Ia supernovae and address the gap in the supermassive black hole mass distribution. One parameter is a critical density fit to about $3 \cdot 10^7$ g/cc while the other has the units of a space time volume and is found to be of order $0.05\,$ Gyr $R_E^3$ where $R_E$ is the earth radius. The model involves a phase transition to an exact supersymmetry in a small core of a dense star.Comment: 20 pages, 5 figures, expanded version to be published in Physical Review