ERC FUNDED PROJECTS

"During the last decade, a strikingly successful cosmological concordance model has been established. With only six free parameters, nearly all observables, comprising millions of data points, may be fitted with outstanding precision. However, in this beautiful picture a few ""blemishes"" have turned up, apparently not consistent with the standard model: While the model predicts that the universe is isotropic (i.e., looks the same in all directions) and homogeneous (i.e., the statistical properties are the same everywhere), subtle hints of the contrary are now seen. For instance, peculiar preferred directions and correlations are observed in the cosmic microwave background; some studies considering nearby galaxies suggest the existence of anomalous large-scale cosmic flows; a study of distant quasars hints towards unexpected large-scale correlations. All of these reports are individually highly intriguing, and together they hint toward a more complicated and interesting universe than previously imagined -- but none of the reports can be considered decisive. One major obstacle in many cases has been the relatively poor data quality. This is currently about to change, as the next generation of new and far more powerful experiments are coming online. Of special interest to me are Planck, an ESA-funded CMB satellite currently taking data; QUIET, a ground-based CMB polarization experiment located in Chile; and various large-scale structure (LSS) data sets, such as the SDSS and 2dF surveys, and in the future Euclid, a proposed galaxy survey satellite also funded by ESA. By combining the world s best data from both CMB and LSS measurements, I will in the proposed project attempt to settle this question: Is our universe really anisotropic? Or are these recent claims only the results of systematic errors or statistical flukes? If the claims turn out to hold against this tide of new and high-quality data, then cosmology as a whole may need to be re-written."

1 500 000 €

Start date: 2011-01-01, End date: 2015-12-31

The detection of primordial gravity waves created during the Big Bang ranks among the greatest potential intellectual achievements in modern science. During the last few decades, the instrumental progress necessary to achieve this has been nothing short of breathtaking, and we today are able to measure the microwave sky with better than one-in-a-million precision. However, from the latest ultra-sensitive experiments such as BICEP2 and Planck, it is clear that instrumental sensitivity alone will not be sufficient to make a robust detection of gravitational waves. Contamination in the form of astrophysical radiation from the Milky Way, for instance thermal dust and synchrotron radiation, obscures the cosmological signal by orders of magnitude. Even more critically, though, are second-order interactions between this radiation and the instrument characterization itself that lead to a highly non-linear and complicated problem. I propose a ground-breaking solution to this problem that allows for joint estimation of cosmological parameters, astrophysical components, and instrument specifications. The engine of this method is called Gibbs sampling, which I have already applied extremely successfully to basic CMB component separation. The new and ciritical step is to apply this method to raw time-ordered observations observed directly by the instrument, as opposed to pre-processed frequency maps. While representing a ~100-fold increase in input data volume, this step is unavoidable in order to break through the current foreground-induced systematics floor. I will apply this method to the best currently available and future data sets (WMAP, Planck, SPIDER and LiteBIRD), and thereby derive the world's tightest constraint on the amplitude of inflationary gravitational waves. Additionally, the resulting ancillary science in the form of robust cosmological parameters and astrophysical component maps will represent the state-of-the-art in observational cosmology in years to come.

1 999 205 €

Start date: 2018-04-01, End date: 2023-03-31

CHROMPHYS aims at a breakthrough in our understanding of the solar chromosphere by combining the development of sophisticated radiation-magnetohydrodynamic simulations with observations from the upcoming NASA SMEX mission Interface Region Imaging Spectrograph (IRIS). The enigmatic chromosphere is the transition between the solar surface and the eruptive outer solar atmosphere. The chromosphere harbours and constrains the mass and energy loading processes that define the heating of the corona, the acceleration and the composition of the solar wind, and the energetics and triggering of solar outbursts (filament eruptions, flares, coronal mass ejections) that govern near-Earth space weather and affect mankind's technological environment. CHROMPHYS targets the following fundamental physics questions about the chromospheric role in the mass and energy loading of the corona: - Which types of non-thermal energy dominate in the chromosphere and beyond? - How does the chromosphere regulate mass and energy supply to the corona and the solar wind? - How do magnetic flux and matter rise through the chromosphere? - How does the chromosphere affect the free magnetic energy loading that leads to solar eruptions? CHROMPHYS proposes to answer these by producing a new, physics based vista of the chromosphere through a three-fold effort: - develop the techniques of high-resolution numerical MHD physics to the level needed to realistically predict and analyse small-scale chromospheric structure and dynamics, - optimise and calibrate diverse observational diagnostics by synthesizing these in detail from the simulations, and - obtain and analyse data from IRIS using these diagnostics complemented by data from other space missions and the best solar telescopes on the ground.

2 487 600 €

Start date: 2012-01-01, End date: 2016-12-31

How are the outer layers of the Sun heated to temperatures in excess of a million kelvin? A large number of heating mechanisms have been proposed to explain this so-called coronal heating problem, one of the fundamental questions in contemporary solar physics. It is clear that the required energy is transported from the solar interior through the chromosphere into the outer layers but it remains open by which physical mechanisms and how the provided energy is eventually dissipated. The key to solving the chromospheric/coronal heating problem lies in accurate observations at high spatial, temporal and spectral resolution, facilitating the identification of the mechanisms responsible for the transport and dissipation of energy. This has so far been impeded by the small number of accessible diagnostics and the challenges with their interpretation. The interferometric Atacama Large Millimeter/submillimeter Array (ALMA) now offers impressive capabilities. Due to the properties of the solar radiation at millimeter wavelengths, ALMA serves as a linear thermometer, mapping narrow layers at different heights. It can measure the thermal structure and dynamics of the solar chromosphere and thus sources and sinks of atmospheric heating. Radio recombination and molecular lines (e.g., CO) potentially provide complementary kinetic and thermal diagnostics, while the polarisation of the continuum intensity and the Zeeman effect can be exploited for valuable chromospheric magnetic field measurements. I will develop the necessary diagnostic tools and use them for solar observations with ALMA. The preparation, optimisation and interpretation of these observations will be supported by state-of-the-art numerical simulations. A key objective is the identification of the dominant physical processes and their contributions to the transport and dissipation of energy. The results will be a major step towards solving the coronal heating problem with general implications for stellar activity.

1 995 964 €

Start date: 2016-09-01, End date: 2021-08-31