Institutskolloquium des IPP 2020

Statistics revealed that people dramatically differ in their capability to resist all sorts of temptations from nicotine and alcohol to food cravings and shopping. Latest research shows that brains of the people who can better resist things which seem pleasant now but are dangerous in the long run, distinctly differ from those of others. These differences include not only physiology but also biochemistry: brain of willpower superheroes literally works in another way when exhibited to cravings. In her lecture Irina Yakutenko will explain what differences are most important in the context of self-control and tell which genes are responsible for the behavior patterns that manage our reactions to tempting things. In the last part of the lecture she will outline some strategies that can help people who bear ‘unfavorable’ gene variants to overcome devastating reactions of their brain that threaten important life plans. [mehr]

Wenn das Raumschiff Enterprise zu fremden Planeten reist, benötigt es dafür eine exorbitante Menge an Energie. Wie wird diese Energie erzeugt bzw. gespeichert? Wie funktionieren die Fusionsreaktoren und der Warp-Reaktor an Bord der Enterprise und wie der Impuls- und der Warp-Antrieb? Welche Visionen hatten die Star Trek-Autoren bzgl. der Energieversorgung von Kleingeräte wie Tricorder, Phaser oder dem Kommunikator? Ein Vergleich zu heutigen Technologien macht deutlich, dass wir noch weit von den Möglichkeiten der Energiespeicherung, wie sie bei Star Trek gezeigt wird, entfernt sind. [mehr]

Wendelstein 7-X is the first large optimized stellarator that was designed with reactor relevant requirements in mind. Its design criteria include reduction of the neoclassical heat transport, minimization of the bootstrap plasma current, improved fast-ion confinement and a suitable divertor concept. The ultimate goal of the project is to validate the viability of this design line as a fusion reactor that could allow a true steady state operation without hazardous disruption events. W7-X came into operation in 2015 after a lengthy construction phase and it has now completed two experimental campaigns, including a short limiter phase and a test divertor phase. This presentation reviews the most prominent experimental results from the point of view of the overall plasma performance. Although the initial experimental time was largely devoted to technical but necessary aspects, such as commissioning of plasma diagnostics, error field correction, first wall conditioning and heating power upgrade; some prominent physics results that are likely to remain relevant in the future were already obtained. In particular, it is found that the plasma performance is well below pure neoclassical predictions in the vast majority of discharges. Typical energy confinement times are at the level at or below the empirical ISS04-scaling. The ion temperature in such discharges is limited below 1.6 keV, with profiles reminiscent of stiffness in tokamaks. Furthermore, almost no dependence on the efficiency of collisional coupling between ions and electrons and on magnetic configuration (effective helical ripple) is observed. But, a significant and serendipitous improvement of the plasma performance is observed after the injection of a series of frozen hydrogen pellets that leads to very peaked density profiles. Ion temperatures above 3 keV and energy confinement times above the ISS04-scaling, were achieved in post-pellet phases. This conditions correspond to the highest triple product realized in stellarators so far. At least two important conclusions can be drawn from the described observations. Firstly, the record parameters obtained with pellet injection strongly suggest that the W7-X transport optimization is effective. Secondly, the findings in non-pellet cases imply that the plasma performance in W7-X is otherwise dominated by anomalous losses. Even though a detailed understanding of turbulent losses still needs to be elaborated with the help of e.g. gyro-kinetic GENE simulations, presently it appears that peaking of the density profile is important for improving the plasma performance. Future experiments to validate this conjecture will benefit from further improved experimental capabilities, such as first wall cooling, active pumping, continuous pellet injection, increased heating power. Apart from that, a truly steady state plasma operation will soon become possible after installation of water cooled targets. [mehr]

Jesús Pérez-Ríos Fritz-Haber-Institute der Max-Planck-Gesellschaft In this talk, we present a novel direct detection concept to search for dark matter with 100 keV to 100 MeV masses. Here, dark matter scatters off molecules, and as a consequence, the molecules are promoted to excited rovibrational stated. These excited states rapidly decay through photon emissions that are recorded as the signal. We discuss in detail carbon monoxide at a temperature of 50K and with high vapor pressure, leading to efficient photon emission. Using different isotopes of the molecule, the target becomes sensitive to spin-dependent dark matter interactions with the neutron. Besides, we consider a target made of halogen halides, which probe spin-dependent dark matter interactions with the proton. The present detection concept can be realized with near-term technology and allows for the exploration of orders of magnitude of new dark matter parameter space. [mehr]

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Since its first meeting devoted to this topic in 1994, discrete tomography has developed into a powerful imaging tool with a remarkably rich theory connecting various mathematical and application fields. Unlike its "continuous" counterpart, computerized tomography (CT) introduced in the 1970s, discrete tomography deals with the reconstruction of discrete objects, which are typically accessible through data that has been acquired from a small number of angles. In this rather general talk, I would like to illustrate several recent developments in this field focusing on problems of revealing structures in numbers, metals, and plasma columns. Among the persons and entities that make an appearance in this talk are the Beatles, the U.S. Census Bureau, Leonhard Euler, and Bavarian farmers. [mehr]

Low temperature plasmas represent a unique state of matter composed of neutral atoms and molecules, radicals, excited states, ions and electrons. These plasmas have characteristic electron energies of a few eV and can produce a chemically rich environment at close to ambient temperatures. These unique non-equilibrium condition enables the delivery of highly reactive plasma species even to heat sensitive surfaces and enabled major advances in the microelectronics industry. Recent developments at atmospheric pressure led to several emerging applications including wound healing, food decontamination, and water purification. In addition to the unique highly non-equilibrium plasma conditions in a highly collisional environment, the complex interactions of plasmas with matter which includes self-organization phenomena provide ample of opportunities for interesting fundamental research. In this talk, I will present an overview of the-state-of-the-art in the field of low temperature plasmas. I will particularly emphasize some scientific advances in the understanding of non-equilibrium plasma kinetics and the interaction of plasmas with liquids and living matter that enabled above-mentioned promising innovative applications emerging from the field. [mehr]

Nowadays, we are witnessing a series of scientific and technological breakthroughs in an area of research where Information Theory and Quantum Physics are combined and give rise to new and powerful ways of processing and transmitting information. In particular, quantum computers will be able to solve problems that are beyond the capabilities of existing supercomputers.In this talk I will explain how those devices work, review the current efforts to build them, and give some examples of their potential impact. I will mainly concentrate in quantum simulators, capable of solving quantum many-body problems where conventional computers require resources (time and memory) typically growing exponentially with system size. Both quantum computers or analog quantum simulators may perform that task in a much more efficient way. I will review some of the quantum algorithms that have been proposed for this task and then explain the advantages and disadvantages of analog quantum simulators. [mehr]

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Cuneiform tablets from Ancient Mesopotamia number in the hundreds of thousands. They offer astonishingly detailed pictures of the lives and doings of the societies which invented writing and urbanisation, pioneered astronomy, and gave us 360 degrees in a circle. Everything we know about them has had to be worked out – a huge endeavour of the last 150 years, which is still ongoing. This talk, which assumes no prior knowledge, will show something of the methods we use in grappling with Babylonian and Assyrian – from working out the grammar, to navigating problems of meaning and textual logic, to reconstructing pronunciation. It is designed for those who are curious about ancient languages, and would like to have an idea of what goes on 'behind the scenes'. [mehr]

Review of the main theoretical and experimental achivements of modern cosmology happened during last 40 years. [mehr]

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New Frontiers in Superconductivity: Superhydrides at High Pressures Superconductivity has been one of the most profound quantum phases in condensed matter physics. Efforts to identify and develop room temperature superconducting materials are an intensive area of research, motivated by both fundamental science and the prospects for applications. More than a century of rigorous research has led physicists to believe that the highest Tc that can be achieved is 40K for conventional superconductors. However, the recent discovery of superconductivity in hydrogen sulfide at 203K changed the notion of what might be possible for phonon–mediated superconductors. In this talk, I will discuss recent developments on high pressure superconductivity. One of the long-standing challenges in experimental physics is the observation of room-temperature superconductivity. An important discovery leading to room-temperature superconductivity is the pressure-driven disproportionation of hydrogen sulfide (H2S) to H3S, with a confirmed transition temperature of 203 kelvin at 155 gigapascals. Both H2S and CH4 readily mix with hydrogen to form guest–host structures at lower pressures, and are of comparable size at 4 gigapascals. By introducing methane at low pressures into the H2S + H2 precursor mixture for H3S, molecular exchange is allowed within a large assemblage of van der Waals solids that are hydrogen-rich with H2 inclusions; these guest–host structures become the building blocks of superconducting compounds at extreme conditions. I shall present our most recent results on superconductivity in a photochemically transformed carbonaceous sulfur hydride system, starting from elemental precursors, with a maximum superconducting transition temperature of 287.7 ± 1.2 kelvin (about 15 degrees Celsius) achieved at 267 ± 10 gigapascals. Superconductivity is established by the observation of zero resistance, a magnetic susceptibility of up to 190 gigapascals, and reduction of the transition temperature under an external magnetic field of up to 9 tesla, with an upper critical magnetic field of about 62 tesla according to the Ginzburg–Landau model at zero temperature. The Raman spectroscopy is used to probe the chemical and structural transformations before metallization. The discovery achieves the more than a century long quest to find room temperature superconductivity, a phenomenon that was first observed by Kamerlingh Onnes in 1911. Finally, I shall discuss future research directions in probing room temperature superconductivity by introduction of chemical tuning within our ternary system at much lower pressures. 1. Elliot Snider, Nathan Dasenbrock-Gammon, Raymond McBride, Mathew Debessai, Hiranya Vindana, Kevin Vencatasamy, Keith Lawler, Ashkan Salamat, Ranga P. Dias “Room Temperature Superconductivity in a Carbonaceous Sulfur Hydride” Nature 586, 373-377 (2020) 2. Elliot Snider, Nathan Dasenbrock-Gammon, Raymond McBride, Noah Meyers, Keith Lawler, Ashkan Salamat, Ranga P. Dias “Superconductivity to 262 kelvin via catalyzed hydrogenation of yttrium at high pressures” (In press) [mehr]

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