gamma-sky.net: Portal to the Gamma-Ray Sky

Gamma-sky.net is a novel interactive website designed for exploring the gamma-ray sky. The Map View portion of the site is powered by the Aladin Lite sky atlas, providing a scalable survey image tesselated onto a three-dimensional sphere. The map allows for interactive pan and zoom navigation as well as search queries by sky position or object name. The default image overlay shows the gamma-ray sky observed by the Fermi-LAT gamma-ray space telescope. Other survey images (e.g. Planck microwave images in low/high frequency bands, ROSAT X-ray image) are available for comparison with the gamma-ray data. Sources from major gamma-ray source catalogs of interest (Fermi-LAT 2FHL, 3FGL and a TeV source catalog) are overlaid over the sky map as markers. Clicking on a given source shows basic information in a popup, and detailed pages for every source are available via the Catalog View component of the website, including information such as source classification, spectrum and light-curve plots, and literature references. We intend for gamma-sky.net to be applicable for both professional astronomers as well as the general public. The website started in early June 2016 and is being developed as an open-source, open data project on GitHub (https://github.com/gammapy/gamma-sky). We plan to extend it to display more gamma-ray and multi-wavelength data. Feedback and contributions are very welcome!Comment: 6th International Meeting on High Energy Gamma-Ray Astronomy, Heidelberg, 2016. 6 pages, 5 figures. Website: http://gamma-sky.ne

Hochenergetische Gammastrahlung aus dem Galaktischen Zentrum

Beobachtungen bei allen Wellenlängen haben eine Vielzahl von hochenergetischen Prozessen aufgedeckt, die mit dem supermassereichen schwarzen Loch im Zentrum unserer Galaxie zusammenhängen. Die Gammaastronomie steuert Messungen mit satellitenbasierten und erdgebundenen Teleskopen, wie dem Fermi-LAT und HESS, bei. Diese Messungen können wichtige Beiträge zur Beantwortung einiger zentraler Fragen liefern. Die Gammaquelle HESS J1745-290 ist möglicherweise ein Produkt der Beschleunigung von kosmischer Strahlung zu PeV-Energien und wird daher in dieser Arbeit mit dem HESS II-Array untersucht, das das größte existierende Cerenkov-Teleskop enthält. Dabei werden Photonen mit einer Energie von unter 100 GeV gemessen. Außerdem ist das Galaktische Zentrum ein vielversprechendes Ziel für indirekte Suchen nach dunkler Materie. Eine solche Suche wird in dieser Arbeit basierend auf HESS- und Fermi-LAT-Daten durchgeführt. Da die Winkelauflösunge der aktuellen Instrumente in der Gammastronomie limitiert ist, sind Spektralanalysen oft das einzige Werkzeug zur Untersuchung von Gamma-Quellen. Daher werden in dieser Arbeit Studien durchgeführt, um zu klären, welche Analysemethoden zu verzerrten Parameterschätzer führen können

Universal cooling dynamics towards a quantum critical point

We investigate the loss of adiabaticity when cooling a many-body quantum system from an initial thermal state towards a quantum critical point. The excitation density, which quantifies the degree of adiabaticity of the dynamics, is found to obey scaling laws in the cooling velocity as well as in the initial and final temperatures of the cooling protocol. The scaling laws are universal, governed by the critical exponents of the quantum phase transition. The validity of these statements is shown analytically for a Kitaev quantum wire coupled to Markovian baths, and subsequently argued to be valid under rather general conditions. Our results establish that quantum critical properties can be probed dynamically at finite temperature, without even varying the control parameter of the quantum phase transitions.Comment: 5+4 pages, 2+2 figures; companion paper to "Long-range Kitaev chain in a thermal bath: Analytic techniques for time-dependent systems and environments" by the same authors and submitted on the same da

The Ca-activated Cl Channel and its Control in Rat Olfactory Receptor Neurons

Odorants activate sensory transduction in olfactory receptor neurons (ORNs) via a cAMP-signaling cascade, which results in the opening of nonselective, cyclic nucleotide–gated (CNG) channels. The consequent Ca2+ influx through CNG channels activates Cl channels, which serve to amplify the transduction signal. We investigate here some general properties of this Ca-activated Cl channel in rat, as well as its functional interplay with the CNG channel, by using inside-out membrane patches excised from ORN dendritic knobs/cilia. At physiological concentrations of external divalent cations, the maximally activated Cl current was ∼30 times as large as the CNG current. The Cl channels on an excised patch could be activated by Ca2+ flux through the CNG channels opened by cAMP. The magnitude of the Cl current depended on the strength of Ca buffering in the bath solution, suggesting that the CNG and Cl channels were probably not organized as constituents of a local transducisome complex. Likewise, Cl channels and the Na/Ca exchanger, which extrudes Ca2+, appear to be spatially segregated. Based on the theory of buffered Ca2+ diffusion, we determined the Ca2+ diffusion coefficient and calculated that the CNG and Cl channel densities on the membrane were ∼8 and 62 μm−2, respectively. These densities, together with the Ca2+ diffusion coefficient, demonstrate that a given Cl channel is activated by Ca2+ originating from multiple CNG channels, thus allowing low-noise amplification of the olfactory receptor current

Adiabatic quantum trajectories in engineered reservoirs

We analyze the efficiency of protocols for adiabatic quantum state transfer assisted by an engineered reservoir. The target dynamics is a quantum trajectory in the Hilbert space and is the fixed point of a time-dependent master equation. We specialize to quantum state transfer in a qubit and determine the optimal schedule for a class of time-dependent Lindblad equations. The speed limit on state transfer is extracted from a physical model of a qubit coupled to a reservoir, from which the Lindblad equation is derived in the Born-Markov limit. Our analysis shows that the resulting efficiency is comparable to the efficiency of the optimal unitary dynamics. Numerical studies indicate that reservoir-engineered protocols could outperform unitary protocols outside the regime of the Born-Markov master equation, namely, when correlations between the qubit and reservoir become relevant. Our study contributes to the theory of shortcuts to adiabaticity for open quantum systems and to the toolbox of protocols of the NISQ era.Comment: 14+7 pages, 7 figure