Spectral features of Earth-like planets and their detectability at different orbital distances around F, G, and K-type stars

We investigate the spectral appearance of Earth-like exoplanets in the HZ of different main sequence stars at different orbital distances. We furthermore discuss for which of these scenarios biomarker absorption bands may be detected during primary or secondary transit with near-future telescopes and instruments.We analyze the spectra taking into account different filter bandpasses of two photometric instruments planned to be mounted to the JWST. We analyze in which filters and for which scenarios molecular absorption bands are detectable when using the space-borne JWST or the ground-based telescope E-ELT. Absorption bands of CO2, H2O, CH4 and O3 are clearly visible in high-resolution spectra as well as in the filters of photometric instruments. However, only during primary eclipse bands of CO2, H2O and O3 are detectable for all scenarios when using photometric instruments and an E-ELT telescope setup. CH4 is only detectable at the outer HZ of the K star since here the atmospheric modeling results in very high abundances. Since the detectable CO2 and H2O bands overlap, separate bands need to be observed to prove their existence in the atmosphere. In order to detect H2O in a separate band, a S/N>7 needs to be achieved for E-ELT observations, e.g. by co-adding at least 10 transit observations. Using a spaceborne telescope like the JWST enables the detection of CO2 at 4.3mu, which is not possible for ground-based observations due to the Earth's atmospheric absorption. Hence combining observations of spaceborne and groundbased telescopes might allow to detect the presence of the biomarker molecule O3 and the related compounds H2O and CO2 in a planetary atmosphere. Other absorption bands using the JWST can only be detected for much higher S/Ns, which is not achievable by just co-adding transit observations since this would be far beyond the planned mission time of JWST.(abridged)Comment: 15 pages, 8 figure

Spatially tunable spin interactions in neutral atom arrays

Analog quantum simulations with Rydberg atoms in optical tweezers routinely address strongly correlated many-body problems due to the hardware-efficient implementation of the Hamiltonian. Yet, their generality is limited, and flexible Hamiltonian-design techniques are needed to widen the scope of these simulators. Here we report on the realization of spatially tunable interactions for XYZ models implemented by two-color near-resonant coupling to Rydberg pair states. Our results demonstrate the unique opportunities of Rydberg dressing for Hamiltonian design in analog quantum simulators

Warming the early Earth - CO2 reconsidered

Despite a fainter Sun, the surface of the early Earth was mostly ice-free. Proposed solutions to this so-called "faint young Sun problem" have usually involved higher amounts of greenhouse gases than present in the modern-day atmosphere. However, geological evidence seemed to indicate that the atmospheric CO2 concentrations during the Archaean and Proterozoic were far too low to keep the surface from freezing. With a radiative-convective model including new, updated thermal absorption coefficients, we found that the amount of CO2 necessary to obtain 273 K at the surface is reduced up to an order of magnitude compared to previous studies. For the late Archaean and early Proterozoic period of the Earth, we calculate that CO2 partial pressures of only about 2.9 mb are required to keep its surface from freezing which is compatible with the amount inferred from sediment studies. This conclusion was not significantly changed when we varied model parameters such as relative humidity or surface albedo, obtaining CO2 partial pressures for the late Archaean between 1.5 and 5.5 mb. Thus, the contradiction between sediment data and model results disappears for the late Archaean and early Proterozoic.Comment: 53 pages, 4 tables, 11 figures, published in Planetary and Space Scienc

Nanoscale Structuring in Confined Geometries using Atomic Layer Deposition: Conformal Coating and Nanocavity Formation

Nanoscale structuring in confined geometries using atomic layer deposition (ALD) is demonstrated for surfaces of nanochannels in track-etched polymer membranes and in mesoporous silica (SBA-15). Suitable process conditions for conformal ALD coating of polymer membranes and SBA-15 with inorganic oxides (SiO₂, TiO₂, Al₂O₃) were developed. On the basis of the oxide-coated layers, nanochannels were further structured by a molecular-templated ALD approach, where calixarene macromolecules are covalently attached to the surface and then embedded into an Al₂O₃ layer. The removal of calixarene by ozone treatment results in 1–2 nm wide surface nanocavities. Surfaces exposed to different process steps are analyzed by small angle X-ray scattering (SAXS) as well as by X-ray photoelectron and infrared spectroscopy. The proposed nanostructuring process increases the overall surface area, allows controlling the hydrophilicity of the channel surface, and is of interest for studying water and ion transport in confinement

If the Worst Comes to the Worst. Dictator Giving When Recipient's Endowments are Risky

Donors may often not be sure whether a recipient really deserves their help. Does this uncertainty deter generosity? In an experiment we find that, to the contrary, under most specifications of uncertainty, dictators give more, compared with the donation the same dictator makes to a recipient they know to have the expected value of the endowment with certainty. They are particularly concerned about the possibility that a recipient leaves the lab with no payoff from the game

Sparse measure-valued optimal control problems governed by wave equations

In dieser Arbeit werden Optimalsteuerungsprobleme für die lineare Wellengleichung und die nicht lineare KdV-Burger's Gleichung untersucht. Das Hauptaugenmerk liegt auf Kontrollen, deren örtliche Träger sehr lokalisiert sind und deren zeitliche Träger verteilt sind. Wir verwenden die Kontrollräume L 2(I,M(Omega)) und M(Omega,L 2(I)) und ein nicht glattes Kontrollkosten-Funktional, das für die Lokalisierung des Trägers der Kontrolle sorgt. Diese Wahl beinhaltet punktweise Kontrollen mit zeitabhängigen Intensitäten und zeitabhängigen (-unabhängigen) Positionen, welche in Aktuator-Platzierungs-Problemen und in inversen Problem Verwendung finden. Die maßwertigen Optimalsteuerungsprobleme werden vorerst von einem theoretischen Standpunkt untersucht. Dies beinhaltet einen Existenzbeweis von optimalen Kontrollen, die Herleitung von Optimalitätsbedingungen und die Untersuchung der strukturellen Eigenschaften der optimalen Steuerung (Struktur des Trägers). Die Hauptschwierigkeit in der Analysis ist die geringe Regularität des Zustandes, verursacht von der geringen Regularität der Kontrollen, und die Nichtglattheit des Zielfunktionals. Weiterhin wird ein semiglattes Newton Verfahren für das L 2(IxOmega) regularisierte Problem im Hinblick auf superlineare Konvergenz im Funktionenraum analysiert. Ferner wird eine Orts-Zeit-Finite-Elemente-Methode für maßwertige Optimalsteuerungsprobleme mit der linearen Wellengleichung als Zustandsgleichung untersucht, insbesondere werden a-priori Fehlerschranken für den Zustand und das Zielfunktional hergeleitet. Die erwähnte semiglatte Newton Methode wird für die Lösung des diskreten Optimalsteuerungsproblems verwendet.In this work optimal control problems governed by the linear wave equation and the non-linear KdV-Burger's equation are analyzed. The main focus lies on controls which are sparse in space and distributed in time. We utilize the control spaces L 2(I,M(Omega)) and M(Omega,L 2(I)) and a non-smooth control cost functional which enhances sparsity of the optimal control. This particularily includes pointwise controls with time-dependent intensities and time-dependent (time-independent) positions which have applications in optimal actuator placement problems and inverse problems. These measure-valued optimal control problems are investigated from a theoretical point view which includes the proof of existence of optimal controls, the derivation of optimality conditions and the investigation of the structure of the optimal control (sparsity pattern). The main difficulty in the analysis is the lack of regularity of the state caused by the low regularity of controls and the non-smoothness of the objective functional. Moreover, a semismooth Newton method for the L 2(IxOmega) regularized problem is analyzed with regard to superlinear convergence in function space. Furthermore, a space-time finite element discretization for the measure-valued optimal control problem governed by the linear wave equation is investigated. In particular, a priori error estimates for the state and the functional are derived. The mentioned semismooth Newton method is used for the numerical solution of the discrete optimal control problem.vorgelegt von Carl Philip TrautmannAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassungen in dt. und in engl. SpracheGraz, Univ., Diss., 2015OeBB(VLID)76749