Department of Physics

Physics Friday Colloquia

– Spring 2015

Department of Physics organizes a series of colloquia. Friday's colloquium is open to everyone. It will be served tea/coffee and biscuits from 14:00. Talk starts at 14:15.

Time: Friday at 14:15 - 15:00

Location: R10 Realfagbygget NTNU (Natural Science Building)

This year we have tried to put together a broad program of great speakers, so we do hope that you will join us regularly throughout this semester. Topics will include material science, nanoscience, life sciences and biophysics, atmospheric physics and more.

The Friday Colloquia are meant for a broad physics audience, so the speakers have been encouraged to make their talks accessible for groups varying from undergraduate students to professors of the various sections. We hope that you will find all of the colloquia interesting!

Coordinators: Michael Kachelriess and Robert Hibbins

Friday colloquia for the spring 2015

January 23

Peter Berg, Department of Physics (NTNU)
«The Industrial Revolution: A Phase Transition?»

January 23

Peter Berg, Department of Physics (NTNU)
«The Industrial Revolution: A Phase Transition?»

Abstract

The Industrial Revolution: A Phase Transition?

To understand the future of energy and the economy, we need to understand the past. As scientists and engineers strive towards a renewable energy future, it is not clear how this transition would impact future economic growth. In this context, energy-economic models may help assess possible scenarios, based on past events.

This talk will provide an insight into classical macro-economic models and how they are applied to understand economic history. Special focus will lie on the Industrial Revolution as the main historical event against which any macro-economic model should be validated. To this day, it remains a challenge to capture the transition from an agricultural to an industrial society by use of an appropriate model that reproduces various growth rates correctly.

The presentation is divided into three parts: i) a general discussion of economic models and their shortfalls from a physicists perspective, ii) a macro-economic model for the Industrial Revolution and iii) a brief note on why oil prices have fallen so dramatically over the last six months.

Note: The material presented under ii) is based on joint research with Mark Staley at TD Bank in Toronto, Canada.

Mon, 19 Jan 2015 08:33:05 +0100

January 30

Roos De Wit, Department of Physics (NTNU)
«Small scale wave coupling of the atmosphere»

January 30

Roos De Wit, Department of Physics (NTNU)
«Small scale wave coupling of the atmosphere»

Abstract

Small scale wave coupling of the atmosphere

Although the atmospheric layer between 70 and 100 km is far above the Earth’s surface, it is important to better understand the processes that drive the weather in this region, as the inclusion of it in weather and climate models has been shown to improve forecast and prediction capabilities.

Small scale atmospheric waves couple this region, known as the ‘mesosphere and lower thermosphere (MLT)’, to the lower atmosphere, as changes in lower atmospheric winds modify the upward propagation of the waves: the wind direction and strength determines which waves can travel upward. It is these small scale waves that are the main driver of change in the MLT, and force the flow of air.

In this talk I will discuss direct observations of these small scale waves in the MLT over Trondheim, Norway. Data recorded over a full seasonal cycle were used to determine how changes in the winds below the MLT change the force these small waves exerted on the airflow in the MLT. This work demonstrated that the wind field gives a good indication of the direction and strength of the wave forcing on the MLT. These results can be used in the future to constrain weather and climate models so that they more accurately reflect the processes occurring in the whole atmosphere.

Mon, 19 Jan 2015 08:33:35 +0100

February 6

Matthias Eschrig, University of London and NTNU
«The complex life at the border between competing quantum condensates»

February 6

Matthias Eschrig, University of London and NTNU
«The complex life at the border between competing quantum condensates»

Abstract

The complex life at the border between competing quantum condensates

Much of the complexity of Nature results from the combined action of three concepts: symmetry breaking, topological stability, and emergence.

Symmetry breaking and emergence of new symmetries are counteracting principles, the result of which is complexity, ultimately a precondition for the existence of life. Two major fields within condensed-matter physics that reflect these principles are magnetism and superconductivity. Both phenomena are essentially many-body quantum effects, the study of which is one of the grand challenges of modern science. The combination of superconducting quantum coherence with spin-ordered or spin-correlated states is one of the promising new developments in condensed matter physics. I will discuss examples of physical phenomena emerging from the competition between and coexistence of superconductivity and magnetism.

 

Tue, 03 Feb 2015 13:47:02 +0100

February 13

Jörn Kersten, University of Bergen (UiB)
«Latest News from Neutrinos»

February 13

Jörn Kersten, University of Bergen (UiB)
«Latest News from Neutrinos»

Abstract

Latest News from Neutrinos

The discovery of neutrino oscillations established that neutrinos are massive particles, providing the first unambiguous evidence for physics beyond the Standard Model. 

I will give an overview of the current knowledge on neutrino oscillations, including the recent measurement of the last unknown mixing angle theta13 and prospects for the future. I will also discuss attempts to measure the absolute neutrino mass scale as well as the role of neutrinos in cosmology and astrophysics.

Fri, 13 Feb 2015 11:17:31 +0100

February 20

Jacob Linder, Department of Physics (NTNU)
«Superconducting Spintronics»

February 20

Jacob Linder, Department of Physics (NTNU)
«Superconducting Spintronics»

Abstract

Superconducting Spintronics

The interaction between superconducting and spin-polarized order has emerged as a major research field following a series of breakthroughs in charge transport in superconductor-ferromagnet heterodevices which could lead to new device functionality. A complete synergy between superconducting and magnetic orders turns out to be possible through the creation of spin-triplet Cooper pairs which are generated at carefully engineered superconductor interfaces with ferromagnetic materials. Currently, there is intense activity focused on identifying materials combinations which merge superconductivity and spintronics in order to enhance device performance. The results look promising: it has been shown, for example, that superconducting order can greatly enhance central effects in spintronics such as spin injection and magnetoresistance. Here, I will present some of the most recent experimental and theoretical advances in this field and provide an outlook for upcoming challenges related to the concept of superconducting spintronics.
Mon, 19 Jan 2015 08:33:57 +0100

February 27

Katherine Freese, University of Michigan and Nordita
«The Dark Side of the Universe»

This Friday colloquium has been cancelled!

February 27

Katherine Freese, University of Michigan and Nordita
«The Dark Side of the Universe»

This Friday colloquium has been cancelled!

Abstract

The Dark Side of the Universe

What is the Universe made of?

This question is the longest outstanding problem in all of modern physics, and it is the most important research topic in cosmology and particle physics today. The reason for the excitement is clear: the bulk of the mass in the Universe consists of a new kind of dark matter particle, and most of us believe its discovery is imminent.

I'll start by discussing the evidence for the existence of dark matter in galaxies, and then show how it fits into a big picture of the Universe containing 5% atoms, 25% dark matter, and 70% dark energy. Probably the best dark matter candidates are WIMPs (Weakly Interacting Massive Particles).

There are three approaches to experimental searches for WIMPS:

  • at the Large Hadron Collider at CERN in Geneva
  • in underground laboratory experiments
  • with astrophysical searches for dark matter annihilation products

Currently there are claimed detections in multiple experiments --- but they cannot possibly all be right. Excitement is building but the answer is still unclear. At the end of the talk I'll turn to dark energy and its effect on the fate of the Universe.

Wed, 25 Feb 2015 16:12:59 +0100

March 6

Rita de Sousa Dias, Department of Physics (NTNU)
«DNA condensation in bacterial model cells»

March 6

Rita de Sousa Dias, Department of Physics (NTNU)
«DNA condensation in bacterial model cells»

Abstract

DNA condensation in bacterial model cells

The folding of DNA has attracted a considerable interest ever since DNA was found to be the storage of genetic information. Chromosomal DNAs are often many orders of magnitude larger than their biological packages (cells or viruses) and, in eukaryotic cells, packing is achieved by the wrapping of DNA around small, basic proteins, called histones. Bacterial cells are very different from eukaryotic cells; they present no nuclear membrane that confines the DNA and there is no compelling evidence for the existence of histone-like proteins that condense and organize the genome. Instead, there is a range of DNA-binding proteins that modulate DNA via bending or bridging. One such type of proteins, H-NS, is a dimer that can self-associate into oligomers and induce bridging between different tracts of DNA.

The fact that the cytoplasm has a very large concentration of macromolecules (RNA and proteins) is believed to favor DNA condensation due to molecular crowding effects. In this respect, it has been shown that cell lysis is accompanied by DNA decompaction.

The presentation will start with a general introduction on DNA condensation, which emphasizes the role of electrostatic interactions in this process. Afterwards,  I will present some results of an on-going project that aims to probe the effect of crowding and protein self-assembly on DNA condensation using simple model systems, studied using fluorescence techniques and Monte Carlo simulations.

Fri, 27 Feb 2015 13:13:21 +0100

March 13

Jan Nordbotten, University of Bergen (UiB)
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March 13

Jan Nordbotten, University of Bergen (UiB)
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Abstract

 

Tue, 03 Feb 2015 13:45:04 +0100

April 10

Philip Hofmann, Aarhus University
«Electronic structure and electron dynamics in two-dimensional materials»

April 10

Philip Hofmann, Aarhus University
«Electronic structure and electron dynamics in two-dimensional materials»

Abstract

Electronic structure and electron dynamics in two-dimensional materials

Two-dimensional materials can be grown epitaxially and in high quality on different substrates, and this can be exploited to study their fundamental electronic structure and many-body effects. In this talk I will discuss the growth and electronic properties of epitaxial graphene, bilayer graphene and single-layer molybdenum disulphide. Specifically, I will focus on the electronic structure of these materials as studied by angle-resolved photoelectron spectroscopy. This technique does not only give access to the materials’ band structure but also to many-body effects such as the electron-electron and electron-phonon interaction. This is particularly so for the time-resolved variety of the technique in which the carrier dynamics can be followed in real time.

Thu, 12 Feb 2015 16:20:05 +0100

April 24

David Fonseca Mota, Institute of Theoretical Astrophysics (UiO)
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April 24

David Fonseca Mota, Institute of Theoretical Astrophysics (UiO)
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Abstract

Thu, 12 Feb 2015 16:15:12 +0100