Magnetic substructure in the northern Fermi Bubble revealed by polarized WMAP emission

We report a correspondence between giant, polarized microwave structures emerging north from the Galactic plane near the Galactic center and a number of GeV gamma-ray features, including the eastern edge of the recently-discovered northern Fermi Bubble. The polarized microwave features also correspond to structures seen in the all-sky 408 MHz total intensity data, including the Galactic center spur. The magnetic field structure revealed by the polarization data at 23 GHz suggests that neither the emission coincident with the Bubble edge nor the Galactic center spur are likely to be features of the local ISM. On the basis of the observed morphological correspondences, similar inferred spectra, and the similar energetics of all sources, we suggest a direct connection between the Galactic center spur and the northern Fermi Bubble.Comment: Accepted for publication in The Astrophysical Journal Letters after minor change

General Relativistic Three-Dimensional Multi-Group Neutrino Radiation-Hydrodynamics Simulations of Core-Collapse Supernovae

We report on a set of long-term general-relativistic three-dimensional (3D) multi-group (energy-dependent) neutrino-radiation hydrodynamics simulations of core-collapse supernovae. We employ a full 3D two-moment scheme with the local M1 closure, three neutrino species, and 12 energy groups per species. With this, we follow the post-core-bounce evolution of the core of a nonrotating $27$-$M_\odot$ progenitor in full unconstrained 3D and in octant symmetry for $\gtrsim$$380\,\mathrm{ms}$. We find the development of an asymmetric runaway explosion in our unconstrained simulation. We test the resolution dependence of our results and, in agreement with previous work, find that low resolution artificially aids explosion and leads to an earlier runaway expansion of the shock. At low resolution, the octant and full 3D dynamics are qualitatively very similar, but at high resolution, only the full 3D simulation exhibits the onset of explosion.Comment: Accepted to Ap

Lineare und nichtlineare dielektrische Eigenschaften abstimmbarer SrTiO3-Schichten bei hohen Frequenzen

Due to the dependence of their dielectric properties on an external electrical field, ferroelectric materials proof to be of interest for a number of modern radio-frequency (rf) applications. Especially for their integration into frequency-tunable rf-devices (i.e. for mobile communications) the linear and nonlinear dielectric properties of thin ferroelectric SrTiO$_{3}$-films are of interest. Therefore, in this work the structural as well as the dielectric properties of thin SrTiO$_{3}$-films are being examined. The lattice strain of the epitaxial deposited SrTiO$_{3}$ films is proven to strongly effect the dielectric properties. Correlations of the dielectric constant, the rf loss, the dielectric tunability and the structural properties are demonstrated. The results are explained in ternis of a thermodynamic model that describes the influence of lattice strain on the polarization of the SrTiO$_{3}$ films. Experimental determination of the intermodulation distortion (IMD) proofs to be an ideal tool for the examination of the nonlinear dielectric properties of the films. IMDs are generated by applying two fundamental rf-signals of slightly différent frequencies to systems with nonlinear properties. Two different origins of IMD-signals are being verified for our SrTiO$_{3}$-films : the nonlinear behaviour of the dielectric constant and the onset of conductivity at extremely high fundamental rf-powers. The coaction of both mechanisms leads to a rather unusual dependence of the IMD signals on the power of the fundamental signals. Furthermore, the nonlinear dielectric constant generates IMD signals of higher orders i, i.e. i = 3, 5, 7, 9. Finally, the influence ofthe geometry of integrated ferroelectric elements upon the performance of any device is examined. Different varactor designs are analyzed theoretically and experimentally. It turns out that the properties of complex varactors with structured dimensions down to 4$\mu$m can be described in terms of an improved model of parallel capacitors. Via this analysis, novel varactor geometry for the integration in tunable rf-devices is presented. In comparison with the standard planar capacitor, the tunability of the device is improved by about 300% and the rf losses are reduced by about 50%. The quality factor of exceeds K $\geq$ 50 (i.e. sufficient for most applications) already at extremely low operating voltages of U$_{dc}$ < 20V. The standard planar capacitor and the new vertical capacitor are well described by the model of parallel capacitors

R-process Nucleosynthesis from Three-Dimensional Magnetorotational Core-Collapse Supernovae

We investigate r-process nucleosynthesis in three-dimensional (3D) general-relativistic magnetohydrodynamic simulations of rapidly rotating strongly magnetized core collapse. The simulations include a microphysical finite-temperature equation of state and a leakage scheme that captures the overall energetics and lepton number exchange due to postbounce neutrino emission and absorption. We track the composition of the ejected material using the nuclear reaction network SkyNet. Our results show that the 3D dynamics of magnetorotational core-collapse supernovae (CCSN) are important for their nucleosynthetic signature. We find that production of r-process material beyond the second peak is reduced by a factor of 100 when the magnetorotational jets produced by the rapidly rotating core undergo a kink instability. Our results indicate that 3D magnetorotationally powered CCSNe are a robust r-process source only if they are obtained by the collapse of cores with unrealistically large precollapse magnetic fields of order $10^{13}$G. Additionally, a comparison simulation that we restrict to axisymmetry, results in overly optimistic r-process production for lower magnetic field strengths.Comment: 10 pages, 9 figures, 2 tables. submitted to Ap

Directed Chaotic Transport in Hamiltonian Ratchets

We present a comprehensive account of directed transport in one-dimensional Hamiltonian systems with spatial and temporal periodicity. They can be considered as Hamiltonian ratchets in the sense that ensembles of particles can show directed ballistic transport in the absence of an average force. We discuss general conditions for such directed transport, like a mixed classical phase space, and elucidate a sum rule that relates the contributions of different phase-space components to transport with each other. We show that regular ratchet transport can be directed against an external potential gradient while chaotic ballistic transport is restricted to unbiased systems. For quantized Hamiltonian ratchets we study transport in terms of the evolution of wave packets and derive a semiclassical expression for the distribution of level velocities which encode the quantum transport in the Floquet band spectra. We discuss the role of dynamical tunneling between transporting islands and the chaotic sea and the breakdown of transport in quantum ratchets with broken spatial periodicity.Comment: 22 page

Wild at Heart:-The Particle Astrophysics of the Galactic Centre

We treat of the high-energy astrophysics of the inner ~200 pc of the Galaxy. Our modelling of this region shows that the supernovae exploding here every few thousand years inject enough power to i) sustain the steady-state, in situ population of cosmic rays (CRs) required to generate the region's non-thermal radio and TeV {\gamma}-ray emis-sion; ii) drive a powerful wind that advects non-thermal particles out of the inner GC; iii) supply the low-energy CRs whose Coulombic collisions sustain the temperature and ionization rate of the anomalously warm, envelope H2 detected throughout the Cen-tral Molecular Zone; iv) accelerate the primary electrons which provide the extended, non-thermal radio emission seen over ~150 pc scales above and below the plane (the Galactic centre lobe); and v) accelerate the primary protons and heavier ions which, advected to very large scales (up to ~10 kpc), generate the recently-identified WMAP haze and corresponding Fermi haze/bubbles. Our modelling bounds the average magnetic field amplitude in the inner few degrees of the Galaxy to the range 60 < B/microG < 400 (at 2 sigma confidence) and shows that even TeV CRs likely do not have time to penetrate into the cores of the region's dense molecular clouds before the wind removes them from the region. This latter finding apparently disfavours scenarios in which CRs - in this star-burst-like environment - act to substantially modify the conditions of star-formation. We speculate that the wind we identify plays a crucial role in advecting low-energy positrons from the Galactic nucleus into the bulge, thereby explaining the extended morphology of the 511 keV line emission. (abridged)Comment: One figure corrected. Accepted for publication in MNRAS. 29 pages, 14 figure

Efficient volumetric mapping of multi-scale environments using wavelet-based compression

Volumetric maps are widely used in robotics due to their desirable properties in applications such as path planning, exploration, and manipulation. Constant advances in mapping technologies are needed to keep up with the improvements in sensor technology, generating increasingly vast amounts of precise measurements. Handling this data in a computationally and memory-efficient manner is paramount to representing the environment at the desired scales and resolutions. In this work, we express the desirable properties of a volumetric mapping framework through the lens of multi-resolution analysis. This shows that wavelets are a natural foundation for hierarchical and multi-resolution volumetric mapping. Based on this insight we design an efficient mapping system that uses wavelet decomposition. The efficiency of the system enables the use of uncertainty-aware sensor models, improving the quality of the maps. Experiments on both synthetic and real-world data provide mapping accuracy and runtime performance comparisons with state-of-the-art methods on both RGB-D and 3D LiDAR data. The framework is open-sourced to allow the robotics community at large to explore this approach.Comment: 11 pages, 6 figures, 2 tables, accepted to RSS 2023, code is open-source: https://github.com/ethz-asl/wavema