Programm Sommersemester 2017
Montag, 24.04.2017 , 16:15 Uhr, Hörsaal 28 D 001
Dr. Gerda Horneck (DLR, Institute of Aerospace Medicine)
Astrobiology, the Quest for the Conditions of Life in the Universe
The over-riding objective of astrobiological research is to attain a better understanding of the principles leading to the emergence of life from inanimate matter, its evolution, and its distribution, not only on Earth, but within the context of comic evolution. This requires a coordinated approach of scientists from different disciplines, ranging from cosmology, astronomy, planetary sciences, physics, chemistry, geology, paleontology to biology. Assuming water in liquid phase as universal prerequisite for habitability, the neighbor planet Mars, the moons Europa and Enceladus of the giant planets as well as the growing number of extrasolar planets are now favored targets of astrobiological research.
Montag, 08.05.2017 , 16:15 Uhr, Hörsaal 28 D 001
Prof. Dr. Sandor Varro (Wigner Research Center for Physics, Hungarian Academy of Sciences)
Hundred twelve years of the photon: from Einstein's light quanta to extreme light
We review the historical background and variants of the notion of light quanta since Einstein’s “heuristic viewpoint” on the photoelectric effect was published in 1905. The conceptual development will be analysed, on the basis of discussing the interaction of extremely low-intensity and extremely large-intensity light (e.g. lasers) with matter. At some points, we shall also attempt to interrelate the physical interpretations of the photon with light-related measurement techniques, frontiers research, and with the technological development.
Montag, 22.05.2017 , 16:15 Uhr, Hörsaal 28 D 001
Prof. Dr. Joachim Burgdörfer (TU Wien)
Attosecond physics: Opportunities and challenges
Recent advances in the generation of well characterized sub-femtosecond laser pulses have opened up unpredicted opportunities for the real-time observation of electronic dynamics in atoms, molecules, and solids.
Such attosecond chronoscopy allows a novel look at a wide range of fundamental photophysical and photochemical
processes in the time domain, including Auger and autoionization processes, photoemission from atoms, molecules, and surfaces, complementing conventional energy-domain spectroscopy. Attosecond chronoscopy raises fundamental conceptual and theoretical questions as to which novel information becomes accessible and which dynamical processes can be controlled and steered. I will give a few examples for the recent progress of our understanding of time-resolved photoemission from atoms, molecules, and solids.
Montag, 12.06.2017 , 16:15 Uhr, Hörsaal 28 D 001
Prof. Dr. Mikhail Katsnelson (Radboud University of Nijmegen)
Electronic structure and properties of a few-layer black phosphorus
I will review theoretical issues related to a newly discovered two-dimensional material, few-layer black phosphorus (for the case of single layer, also known as phosphorene). This is a direct-gap semiconductor with a gap in Γ point changing from roughly 2 eV in single layer to 0.3 eV in the bulk, with anisotropic and essentially non-parabolic energy spectrum. I will present tight-binding parametrization of electron energy spectrum and its application to large-scale simulations of optical and plasmonic properties. At strong interlayer electric field (or potassium doping) electronic phase transition happens to semimetallic phase with anisotropic Dirac cones. I will discuss consequences of this transition for plasmon spectra and quantum Hall effect. I will also consider single- and two-phonon scattering processes and intrinsic limits on charge carrier mobility in single-layer black phosphorus which turn out to be much
more restrictive than for graphene.
Montag, 26.06.2017 , 16:15 Uhr, Hörsaal 28 D 001
Dr. Daniela Huppenkothen (New York University)
Wrong but Useful: Cutting-Edge Statistical and Machine Learning Applications for the Next Generation of High-Energy Astrophysics
In recent years, instruments across scientific domains have started collecting extraordinarily large data sets of previously unknown complexity, motivating the necessity for new software tools and statistical methods. In astronomy, the telescopes currently starting operations or coming online in the next years will open up the sky to
searches for transient sources and monitoring campaigns with an unprecedented spatial, spectral and temporal coverage and resolution. These data sets will allow us to probe physical regimes inaccessible to us on Earth: for example, accretion of matter onto black holes can help us understand general relativity in strong gravitational fields, while neutron stars probe the dense matter equation of state. However, because of the data’s complexity and size,
answering key questions in astrophysics will only be possible with new statistical approaches. Using examples from high-energy astrophysics, I will discuss how recent developments in machine learning and statistics allows us study both black holes and other sources in ever greater detail. I will show possible future directions of research that will help us address the flood of complex new data sets to come.
Montag, 24.07.2017 , 16:15 Uhr, Hörsaal 28 D 001
Dr. Mikhail Pletyukhov (RWTH Aachen University)
Many-body physics with light
Coulomb interaction between electrons is important for the formation of
different states of matter and manifests itself in a broad variety of
phenomena. In turn, photons do not directly interact with each other, as
it follows from the linearity of the Maxwell's equations. Nevertheless,
an effective interaction between photons can be induced via the
light-matter coupling, and the study of this phenomenon lies in the core
of nonlinear optics. Promoting this paradigm to the quantum realm, one
faces new interesting effects arising from interaction of individual
photons and atoms. In my talk I review the recent studies of exotic
quantum states of light arising due to the interplay between effective
nonlinearities of photons and their bosonic statistics. Modern prospects
in a description of open driven-dissipative systems are also discussed.