ERC FUNDED PROJECTS

The goal of this project is to develop a mathematical theory for steady three-dimensional water waves with vorticity. The mathematical model consists of the incompressible Euler equations with a free surface, and vorticity is important for modelling the interaction of surface waves with non-uniform currents. In the two-dimensional case, there has been a lot of progress on water waves with vorticity in the last decade. This progress has mainly been based on the stream function formulation, in which the problem is reformulated as a nonlinear elliptic free boundary problem. An analogue of this formulation is not available in three dimensions, and the theory has therefore so far been restricted to irrotational flow. In this project we seek to go beyond this restriction using two different approaches. In the first approach we will adapt methods which have been used to construct three-dimensional ideal flows with vorticity in domains with a fixed boundary to the free boundary context (for example Beltrami flows). In the second approach we will develop methods which are new even in the case of a fixed boundary, by performing a detailed study of the structure of the equations close to a given shear flow using ideas from infinite-dimensional bifurcation theory. This involves handling infinitely many resonances.

1 203 627 €

Start date: 2016-03-01, End date: 2021-02-28

A hot topic in today's debate on global warming is drag reduction in aeronautics. The most beneficial concept for drag reduction is to maintain the major portion of the airfoil laminar. Estimations show that the potential drag reduction can be as much as 15%, which would give a significant reduction of NOx and CO emissions in the atmosphere considering that the number of aircraft take offs, only in the EU, is over 19 million per year. An important element for successful flow control, which can lead to a reduced aerodynamic drag, is enhanced physical understanding of the transition to turbulence process. In previous wind tunnel measurements we have shown that roughness elements can be used to sensibly delay transition to turbulence. The result is revolutionary, since the common belief has been that surface roughness causes earlier transition and in turn increases the drag, and is a proof of concept of the passive control method per se. The beauty with a passive control technique is that no external energy has to be added to the flow system in order to perform the control, instead one uses the existing energy in the flow. In this project proposal, AFRODITE, we will take this passive control method to the next level by making it twofold, more persistent and more robust. Transition prevention is the goal rather than transition delay and the method will be extended to simultaneously control separation, which is another unwanted flow phenomenon especially during airplane take offs. AFRODITE will be a catalyst for innovative research, which will lead to a cleaner sky.

1 418 399 €

Start date: 2010-11-01, End date: 2015-10-31

Most of the technological materials have been developed by very expensive and cumbersome trial and error methods. On the other hand, computer based theoretical design of advanced materials is an area where rapid and extensive developments are taking place. Within my group new theoretical tools have now been established which are extremely well suited to the study of complex materials. In this approach basic quantum mechanical theories are used to describe fundamental properties of alloys and compounds. The utilization of such calculations to investigate possible optimizations of certain key properties represents a major departure from the traditional design philosophy. The purpose of my project is to build up a new competence in the field of computer-aided simulations of advanced materials. The main goal will be to achieve a deep understanding of the behaviour of complex metallic systems under equilibrium and non-equilibrium conditions at the atomic level by studying their electronic, magnetic and atomic structure using the most modern and advanced computational methods. This will enable us to establish a set of materials parameters and composition-structure-property relations that are needed for materials optimization. The research will be focused on fundamental technological properties related to defects in advanced metallic alloys (high-performance steels, superalloys, and refractory, energy related and geochemical materials) and alloy phases (solid solutions, intermetallic compounds), which will be studied by means of parameter free atomistic simulations combined with continuum modelling. As a first example, we will study the Fe-Cr system, which is of great interest to industry as well as in connection to nuclear waste. The Fe-Cr-Ni system will form another large group of materials under the aegis of this project. Special emphasis will also be placed on those Fe-alloys which exist under extreme conditions and are possible candidates for the Earth core.

2 000 000 €

Start date: 2009-03-01, End date: 2014-02-28

Today, much interest in several fields of physics is devoted to the study of small, open quantum systems, whose properties are profoundly affected by the environment; i.e., the continuum of decay channels. In nuclear physics, these problems were originally studied in the context of nuclear reactions but their importance has been reestablished with the advent of radioactive-beam physics and the resulting interest in exotic nuclei. In particular, strong theory initiatives in this area of research will be instrumental for the success of the experimental program at the Facility for Antiproton and Ion Research (FAIR) in Germany. In addition, many of the aspects of open quantum systems are also being explored in the rapidly evolving research on ultracold atomic gases, quantum dots, and other nanodevices. A first-principles description of open quantum systems presents a substantial theoretical and computational challenge. However, the current availability of enormous computing power has allowed theorists to make spectacular progress on problems that were previously thought intractable. The importance of computational methods to study quantum many-body systems is stressed in this proposal. Our approach is based on the ab initio no-core shell model (NCSM), which is a well-established theoretical framework aimed originally at an exact description of nuclear structure starting from realistic inter-nucleon forces. A successful completion of this project requires extensions of the NCSM mathematical framework and the development of highly advanced computer codes. The '++' in the project title indicates the interdisciplinary aspects of the present research proposal and the ambition to make a significant impact on connected fields of many-body physics.

1 304 800 €

Start date: 2009-12-01, End date: 2014-11-30

The proposed project aims to create a center of excellence that aims at understanding the approximability of NP-hard optimization problems. In particular, for central problems like vertex cover, coloring of graphs, and various constraint satisfaction problems we want to study upper and lower bounds on how well they can be approximated in polynomial time. Many existing strong results are based on what is known as the Unique Games Conjecture (UGC) and a significant part of the project will be devoted to studying this conjecture. We expect that a major step needed to be taken in this process is to further develop the understanding of Boolean functions on the Boolean hypercube. We anticipate that the tools needed for this will come in the form of harmonic analysis which in its turn will rely on the corresponding results in the analysis of functions over the domain of real numbers.

2 376 000 €

Start date: 2009-01-01, End date: 2014-12-31

Magnetic fields in stars, planets, accretion discs, and galaxies are believed to be the result of a dynamo process converting kinetic energy into magnetic energy. This work focuses on the solar dynamo, but dynamos in other astrophysical systems will also be addressed. In particular, direct high-resolution three-dimensional simulations are used to understand particular aspects of the solar dynamo and ultimately to simulate the solar dynamo as a whole. Phenomenological approaches will be avoided in favor of obtaining rigorous results. A major problem is catastrophic quenching, i.e. the decline of dynamo effects in inverse proportion to the magnetic Reynolds number, which is huge. Tremendous advances have been made in the last few years since the cause of catastrophic quenching in dynamos has been understood in terms of magnetic helicity evolution. The numerical tools are now in place to allow for magnetic helicity fluxes via coronal mass ejections, thus alleviating catastrophic quenching. This work employs simulations in spherical shells, augmented by Cartesian simulations in special cases. The roles of the near-surface shear layer, the tachocline, as well as pumping in the bulk of the convection zone are to be clarified. The Pencil Code will be used for most applications. The code is third order in time and sixth order in space and is used for solving the hydromagnetic equations. It is a public domain code developed by roughly 20 scientists world wide and maintained under an a central versioning system at Nordita. Automatic nightly tests of currently 30 applications ensure the integrity of the code. It is used for a wide range of applications and may include the effects of radiation, self-gravity, dust, chemistry, variable ionization, cosmic rays, in addition to those of magnetohydrodynamics. The code with its infrastructure offers a good opportunity for individuals within a broad group of people to develop new tools that may automatically be useful to others.

2 220 000 €

Start date: 2009-02-01, End date: 2014-01-31

Atmospheric aerosol particles are a major player in the earth system: they impact the climate by scattering and absorbing solar radiation, as well as regulating the properties of clouds. On regional scales aerosol particles are among the main pollutants deteriorating air quality. Capturing the impact of aerosols is one of the main challenges in understanding the driving forces behind changing climate and air quality. Atmospheric aerosol numbers are governed by the ultrafine (< 100 nm in diameter) particles. Most of these particles have been formed from atmospheric vapours, and their fate and impacts are governed by the mass transport processes between the gas and particulate phases. These transport processes are currently poorly understood. Correct representation of the aerosol growth/shrinkage by condensation/evaporation of atmospheric vapours is thus a prerequisite for capturing the evolution and impacts of aerosols. I propose to start a research group that will address the major current unknowns in atmospheric ultrafine particle growth and evaporation. First, we will develop a unified theoretical framework to describe the mass accommodation processes at aerosol surfaces, aiming to resolve the current ambiguity with respect to the uptake of atmospheric vapours by aerosols. Second, we will study the condensational properties of selected organic compounds and their mixtures. Organic compounds are known to contribute significantly to atmospheric aerosol growth, but the properties that govern their condensation, such as saturation vapour pressures and activities, are largely unknown. Third, we aim to resolve the gas and particulate phase processes that govern the growth of realistic atmospheric aerosol. Fourth, we will parameterize ultrafine aerosol growth, implement the parameterizations to chemical transport models, and quantify the impact of these condensation and evaporation processes on global and regional aerosol budgets.

1 498 099 €

Start date: 2011-09-01, End date: 2016-08-31

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are common in elderly and the prevalence of these is increasing. AD and PD have distinct pathogenesis, which precede the overt clinical symptoms by 10-15 years, opening a window for early diagnosis and treatment. New disease-modifying therapies are likely to be most efficient if initiated before the patients exhibit overt symptoms, making biomarkers for early diagnosis crucial for future clinical trials. Validated biomarkers would speed up initiation of treatment, avoid unnecessary investigations, and reduce patient insecurity. AIMS: (1) identify and validate accurate and cost-effective blood-based biomarkers for early identification of those at high risk to develop AD and PD, (2) develop algorithms using advanced imaging and cerebrospinal fluid biomarkers for earlier more accurate diagnoses, and (3) better understand the underlying pathology and early progression of AD and PD, aiming at finding new relevant drug targets. We will assess well-characterized and clinically relevant populations of patients and healthy elderly. We will use population- and clinic-based cohorts and follow them prospectively for 4 year. Participants will undergo neurocognitive evaluation, provide blood and cerebrospinal fluid, and have brain imaging using advanced MRI protocols and a newly developed PET-tracer visualizing brain amyloid. Sample will be analyzed with quantitative mass spectrometry and high sensitivity immunoassays. New biomarkers and brain imaging techniques will aid early diagnosis and facilitate the development of disease-modifying therapies, since treatment can start earlier in the disease process. New methods to quantify relevant drug targets, such as oligomers of β-amyloid and α-synuclein, will be vital when selecting drug candidates for large-scale clinical trials. By improving both diagnosis and therapies the social and economic burden of dementia might be reduced by expanding the period of healthy and active aging

1 500 000 €

Start date: 2013-06-01, End date: 2018-05-31

Spectroscopic binary stars (SB2s) and in particular spectroscopic eclipsing binaries are one of the most useful objects in astrophysics. Their photometric and spectroscopic observations allow one to determine basic parameters of stars and carry out a wide range of tests of stellar structure, evolution and dynamics. Perhaps somewhat surprisingly, they can also contribute to our understanding of the formation and evolution of (extrasolar) planets. We will study eclipsing binary stars by combining the classic - stellar astronomy - and the modern - extrasolar planets - subjects into a cutting edge project. We propose to search for and subsequently characterize circumbinary planets around ~350 eclipsing SB2s using our own novel cutting edge radial velocity technique for binary stars and a modern version of the photometry based eclipse timing of eclipsing binary stars employing 0.5-m robotic telescopes. We will also derive basic parameters of up to ~700 stars (~350 binaries) with an unprecedented precision. In particular for about 50% of our sample we expect to deliver masses of the components with an accuracy ~10-100 times better than the current state of the art. Our project will provide unique constraints for the theories of planet formation and evolution and an unprecedented in quality set of the basic parameters of stars to test the theories of the stellar structure and evolution.

1 500 000 €

Start date: 2010-12-01, End date: 2016-11-30