Torsten Enßlin

Cosmologist, Astrophysicist, Scientist

I am a scientist at the Max-Planck-Institut für Astrophysik (MPA), Garching (near Munich), and lecturer at the Ludwig Maximilians University, Munich in Germany. I am interested in Information Theory, especially Information Field Theory (IFT), Cosmology and High Energy Astrophysics.

Recent Research Highlights

Relics of the Big Bang

In the first fractions of a second after the birth of our universe, not only elementary particles and radiation, but also magnetic fields were generated. A team led by the Max Planck Institute for Astrophysics in Garching has now calculated what these magnetic fields should look like today in the universe – in great detail and in 3D.

LOFAR radio observations document rejuvenation in space

In observations of galaxy clusters, astronomers in collaboration with the MPA discovered a new class of cosmic radio sources. With the digital radio telescope Low Frequency Array (LOFAR) they received the longest radio waves that can be measured on Earth. They identified a remarkable "tail"behind a galaxy in the radio light, which must have been re-energized after it had faded away. In the journal Science Advances, the team describes this discovery, which either confirms a theoretical prediction on the interaction between shock waves and radio plasma or represents a novel phenomenon.

Wanted: the rotating radio emission of the Milky Way

The magnetic fields of the Milky Way cause electrons with nearly the speed of light to rotate and to emit radio waves. As consequence, this radiation should also "rotate" in some way, i.e. the polarization of the radiation will be circularly polarized. This very weak circular polarization of the Milky Way, however, has not been observed so far. Researchers at the Max Planck Institute for Astrophysics and colleagues have now predicted some properties of this polarization and created a "wanted poster" to allow targeted searches. A measurement of the circular polarization would provide important insights into the structure of the galactic magnetic fields and confirm that electrons - and not positrons - are the source of this radio emission in the Milky Way.

The embarrassment of false predictions -
How to best communicate probabilities?

Complex predictions such as election forecasts or the weather reports often have to be simplified before communication. But how should one best simplify these predictions without facing embarrassment? In astronomical data analysis, researchers are also confronted with the problem of simplifying probabilities. Two researchers at the Max Planck Institute for Astrophysics now show that there is only one mathematically correct way to measure how embarrassing a simplified prediction can be. According to this, the recipient of a prediction should be deprived of the smallest possible amount of information.

Information Field Theory

Information field theory (IFT) is information theory, the logic of reasoning under uncertainty, applied to fields. A field can be any quantity defined over some space, e.g. the air temperature over Europe, the magnetic field strength in the Milky Way, or the matter density in the Universe. IFT describes how data and knowledge can be used to infer field properties. Mathematically it is a statistical field theory and exploits many of the tools developed for such. Practically, it is a framework for signal processing and image reconstruction.

Cosmology

The temperature fluctuations in the cosmic microwave background (CMB) and the cosmic matter distribution in the large-scale structure (LSS) are both tracers of the primordial quantum fluctuations. Those are believed to have happened during the very first moments of the Universe in the inflationary epoch. CMB and LSS are therefore our primary information sources on cosmology. Their detailed studies provide us insight into the history, geometry and composition of the Universe. IFT permits us to construct optimal methods to analyse and interpret CMB and LSS data, and to image with high fidelity the cosmic structures imprinted in those data sets.

High Energy Astrophysics

The Universe is permeated by high-energy particles and magnetic fields. Charged particles with nearly the speed of light spiraling around in the magnetic fields, which themselves are bound to the cosmic plasma. The particles and fields are important ingredients of the interstellar and intergalactic media. They transport energy, they push and heat the thermal gas, and they trace violent processes in cosmic plasmas. A number of observational windows in basically all electromagnetic wavebands, ranging from the radio to the gamma ray regime, provide us with direct and indirect vision into the high energy Universe. The IFT group develops special purpose methods to better imagine relativistic particles, magnetic fields, and even to tomographically reconstruct their distributions within the Milkey Way.

Lecture on Information Theory & Information Field Theory

Imaging in astronomy, geology and medicine require intelligent methods to obtain high fidelity images from noisy, incomplete data. The theoretical and mathematical framework in which imaging and data analysis methods are derived should be information theory to which these lectures will introduce first (first 1/3 semester, suited for Bachelor and Master students, 3 ETCS). Based on this, information theory for fields will be developed, which can be used to reconstruct signals from data (remaining 2/3 semester, more targeted at Master students, 6 ETCS).

Seminar Information Theory & Information Field Theory

The seminar is intended for participants of the lecture on Information Theory (1/3 semester) & Information Field Theory (2/3 semester), the content of which will be assumed to be known by all participants. The main seminar goal is to extend the participants' knowledge beyond the material covered in the lecture, especially with respect to concrete measurement situations, imaging, and existing algorithms. A second goal is to practice presentations and open discussions.

Past & current Software Projects

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Contact

  • Address

    MPA
    Karl-Schwarzschild-Str. 1
    85748 Garching
    Germany
    Office: 010

  • Email

    ensslin@mpa-garching.mpg.de

  • Phone

    +49 (0) 89 30000 2243