Friday colloquia - Department of Physics
The physics colloquia of the Department of physics are open to all. An important goal for the colloquia is to be a meeting place between faculty and students to learn about interesting developments in physics. Students are especially encouraged to attend. Speakers are asked to keep the talks at a level targeting a master student in physics but even bachelor students should be able to appreciate the content of the talks.
The presentations start at 14.15 but everyone is encourage to arrive at 14.00 for some coffee, pastries and mingeling with faculty and students.
In the spring semester 2020 all colloquia are in Realfagbygget R10.
If you have any suggestions for colloquia speakers, contact the coordinator.
7 February 2020 - The Impacts of Energetic Particle Precipitation into the Atmosphere
Title: The Impacts of Energetic Particle Precipitation into the Atmosphere
Speaker: Yvan Orsolini
Abstract: The sun influences the climate of the earth not only through its radiative forcing but also -at least potentially- through energetic particle precipitation (EPP). EPP refers to the precipitation into the upper atmosphere of protons originating from the sun during relatively rare and sporadic solar proton events, or else of electrons originating from the earth radiation belts. The latter give rise to phenomenon of aurora borealis. During geomagnetic storms, the electrons can be more energetic and penetrate into the mesosphere, the atmospheric layer between 50 and 90 km.
EPP generates nitrogen and hydrogen oxides through a complex chemistry involving neutral and ionic trace species. While the broad aspects of the EPP impact on middle atmosphere chemistry is captured by state-of-the-art models and largely supported by satellite observations, its potential feedback on the general atmospheric circulation -hence on climate- is still debated. We present the basic modelling tools currently used to address this challenging question at the interface of dynamic meteorology and space sciences.
14 February 2020 - Fluid Mechanics
Title: Fluid Mechanics
Speaker: Simen Ådnøy Ellingsen
Abstract: When a depth-varying current is present beneath the water surface it can affect surface waves profoundly. The interaction of water waves and sub-surface shear currents has been studied for 7 decades, yet their importance to a wide array of applications has only been widely recognised in relatively recent times. Waves and shear currents co-exist, e.g., in river deltas with strong surface jets, surface shear layers in the wind-swept ocean, and flow over shallows where the bottom boundary layer becomes important to wave motion.
The talk has two parts: the first concerns how shear affects waves, to wit ring waves and ship waves, the second takes the inverse view of inferring the sub-surface current from measurements of surface waves.
Lord Kelvin famously showed in 1887 that waves behind a ship in deep water always forms the same angle, approximately 39 degrees. We showed theoretically, that in the presence of vertical shear this no longer holds, and different angles, and even asymmetric ship waves can result. Likewise, ring waves from a localised disturbance can become strikingly asymmetric. In a recent experiment these effects were observed for the first time. Applying the theory to realistic ships on a real, measured current shows that ship fuel consumption can be drastically mispredicted if the depth-structure of the current is not correctly accounted for.
A method is then presented for remote-sensing of surface currents by observing ambient water waves from above. Significant improvement over state-of-the-art methods is demonstrated for strongly sheared profiles. The method is ideal for current measurements using radar or optical video, from ships, drones or in the future even satellites, and unlike in-situ single-point measurements can cover large areas quickly.
A brief overview of opportunities for advanced fluid mechanics courses and Masters thesis projects in the Thermo-Fluids group at the Dept of Energy & Process Engineering NTNU will be given.
21 February 2020 - Flight of synthetic whirling fruits
Title: Flight of synthetic whirling fruits
Speaker: Andreas Carlson
Abstract: Wind dispersion of seeds is a widespread evolutionary adaptation found in plants, which allows them to multiply in numbers and to colonize new geographical areas. Appendages of seeds, fruits and other diaspores (dispersal units) are essential for their wind dispersal, as they act as wings and enable them to fly. Whirling fruits generate an auto-gyrating motion from their sepals, a leaf like structure, which curve upwards and outwards, creating a lift force that counteracts gravitational force. In this talk, I will present how we have combined a simple theoretical model and experiments to understand how the shape of the wings of whirling fruits may have evolved into a form optimal for its wind dispersion potential, i.e., a maximal flight time/minimal terminal descent velocity. Similar shapes are found for a wide range of whirling fruits collected in the wild, highlighting that wing curvature (fold angle) can aid wind dispersal of whirling fruits and may improve the fitness of their producers in the context of an ecological strategy.
28 February 2020 - Nano comes to life
Title: Nano comes to life
Speaker: Sonia Contera
Abstract: Drawing on her perspective as one of today’s leading researchers in the field, Contera describes the exciting ways in which nanotechnology makes it possible to understand, interact with, and manipulate biology—such as by designing and building artificial structures and even machines at the nanoscale using DNA, proteins, and other biological molecules as materials. In turn, nanotechnology is revolutionizing medicine in ways that will have profound effects on our health and longevity, from nanoscale machines that can target individual cancer cells and deliver drugs more effectively, to nanoantibiotics that can fight resistant bacteria, to the engineering of tissues and organs for research, drug discovery, and transplantation.
The future will bring about the continued fusion of nanotechnology with biology, physics, medicine, and cutting-edge fields like robotics and artificial intelligence, ushering us into a new “transmaterial era.” As we contemplate the power, advantages, and risks of accessing and manipulating our own biology, Contera offers insight and hope that we may all share in the benefits of this revolutionary research.
6 March 2020 - Molecular Beam Epitaxy at the QuSpin MBE lab
Title: Molecular Beam Epitaxy at the QuSpin MBE lab
Speaker: Christoph Brune
Abstract: The MBE lab is a new addition to the lab activities at IFY and we are still in the build-up process. In this talk I will give an overview on molecular beam epitaxy and the current status of our new lab. I will also briefly present our research plans for the near future.
13 March 2020 - Disciplining effects of physics jokes - CANCELLED
Title: Disciplining effects of physics jokes
Speaker: Maria Berge
Q: Who was the first electric detective?
A: Sherlock Ohms
Get it? This joke’s humour relies on the hearer’s previous knowledge of two usually unrelated facts: that Sherlock Holmes is a fictional detective and that Ohm’s law describes a fundamental relationship between electric current and potential difference. Did you laugh? The primary function of a joke is to make people laugh, but another function can be to create or support intimacy through acknowledging the shared knowledge of an in-group. Physicists have a certain kind of humour and humour has many positive effects: it brings people together and is useful when we interact with each other as tension release. However, we must also carefully consider why we find jokes funny. In this presentation are I will give you several examples of physics jokes but also how humour and jokes may have disciplining effects on an audience.
20 March 2020 - Quantum heat engines - CANCELLED
Title: Quantum heat engines
Speaker: Rosario Fazio
Abstract: Small quantum systems connected to several different thermal reservoirs probably constitute the smallest heat engines one can imagine. Their operating mode may be quite different from their macroscopic counterpart, intimately linked to the dynamics of quantum open systems. Fluctuations and quantum effects, for example, are essential in the characterisation of the performance of the thermal machines. I will try to give an overview of the field with an emphasis on some fundamental questions that can be addressed through the study of quantum heat engines. I will further provide some examples where collective phenomena or adiabatic dynamics play a deisive role.
27 March 2020 - Motivation for physics - CANCELLED
Title: Motivation for physics
Speaker: Maria Vetleseter Bøe
Abstract: Why do our students choose physics? How does their motivation to learn physics interact with our teaching? The talk discusses these questions in light of international and national research, and presents preliminary results from the IMPEL project, which studies motivation among physics students at five Norwegian universities, including NTNU.
3 April 2020 - Cosmological viscosity - CANCELLED
Title: Iver Håkon Brevik
Abstract: I intend first to deal with the fundamental aspects of general relativity (GR), then move on to the Einstein equations in which the viscosity coefficients are plugged in “by hand” in the energy-momentum tensor. Some comparison with observations is given. Perhaps surprisingly, the shear and bulk viscosity coefficients so well known from ordinary fluid mechanics can be incorporated also in GR in a natural way. Especially, this holds for the bulk viscosity. In the analogous more modern theories of QCD matter, the viscosity coefficients similarly turn up. The viscosity concept is ubiquitous.
The talk will be relatively simple, mathematically. It should be easy to follow for physics students in their 3rd or fourth year.
17 April 2020 - Student project presentations - CANCELLED
Title: Student project presentations
24 April 2020 - Superconductivity - the universe in a droplet of Mercury - CANCELLED
Title: Superconductivity - the universe in a droplet of Mercury
Speaker: Asle Sudbø
Abstract: Superconductivity, first discovered upon cooling droplets of Mercury, is the astonishing phenomenon that a metal looses all of its electrical resistance at a sharply defined temperature when it is cooled down. Perhaps even more remarkably, the metal drastically changes its electromagnetic properties at the same sharply defined temperature, in that the metal completely expuls a magnetic field in the superconducting state. Both the loss of electrical resistance and the expulsion of magnetic field are results of a phase-transition taking place among the electrons of the system. I will explain what this phase- transition is, and how it leads to the loss of resistance. The most profound aspect of the phenomenon, the expulsion of magnetic field, has a close analog in phase-transitions in the early universe predicted by the Standard Model. I will explain this analog, and will also explain how the search for the Higgs-particle at the Large Hadron Collider at CERN has a table-top analog in superconductors.