The Bonn-Cologne Graduate School of Physics and Astronomy is organizing a weekend seminar at the Physikzentrum Bad Honnef. As in the previous two events (in 2011 and 2013) we will have a mixture of workshops, evening talks, science quiz, excursions, etc.

Registration

Student registration is closed; non-student participants, please contact Ralf Bulla.

Program

Here is a sketch of the program ...

schedule

... and the list of workshops:

Friday, Apr 17
A1 Andreas Eckart, Nastaran Fazeli, Gerold Busch
Supermassive black holes and their host galaxies
A2 Michael Lässig
Predicting the evolution of the flu
A3 Toby Opferkuch
Supersymmetry, and physics beyond the Standard Model

Saturday, Apr 18
B1 Peter Schneider
Cosmology with (weak) gravitational lensing
B2 Jan Klaers, Philipp Strack
Introduction to cavity QED
B3 Jochen Dingfelder
Tetraquarks and their detection by the Belle experiment

Sunday, Apr 19
C1 Branislav Nikolic, Jens Boos, Arezu Dehghanfar, Pranjal Dhole, Patrick J. Wong
Quantum gravity and aspects of relativity
C2 Maria Hermanns
Bosons, Fermions, Anyons
C3 Philipp Bechtle
The Search for Physics Beyond the SM at the LHC

Abstracts

A1 Andreas Eckart, Nastaran Fazeli, Gerold Busch
Supermassive black holes and their host galaxies


Most galaxies are thought to host a supermassive black hole, having masses from millions to billions of the mass of the sun, in their center.
The first half of the workshop will focus on the supermassive black hole in the center of our Galaxy, the Milky Way. By measuring the orbits of the stars surrounding the center of our Galaxy with highest angular resolution, we can be quite confident that the Galaxy contains a supermassive black hole of mass 4*106 Msun in its center. It is associated with the compact radio source Sagittarius A* that shows flare emission from the millimeter to the X-ray domain. Due to its proximity, the Galactic Center is an ideal laboratory to study the vicinity of these extreme objects and to test the laws of physics in the presence of highly compact masses. Several dusty objects are found in the neighborhood of the central black hole. One of them, the dusty object G2/DSO, has been monitored during the last years. Its nature is still unclear: Depending on its nature, its close passage might produce enhanced accretion activity and will allow further conclusions on the nature of the circumnuclear environment.
In the second part of the workshop, we will go out to more distant galaxies: Active galaxies (at higher redshifts also known as Quasars) belong to the most extreme objects in our cosmos. They show point source emission in their centers that can outshine the light of the host galaxy, that contains many billions of stars, by a factor of up to thousand. The emission is thought to come from accretion of mass onto the central supermassive black hole. A crucial point in black hole feeding is that gas has to lose angular momentum. Here, galaxy-galaxy interaction but also internal processes like stellar bars or spiral arms etc. come into play. Furthermore, strong correlations between the mass of the central black hole and the host galaxies show that the central black hole plays an essential role in the evolution of galaxies. We will discuss how observations with state-of-the-art telescopes as the Very Large Telescope in the Chilean desert allow us to analyze the centers of galaxies that are hundreds of millions of lightyears away from us.

A2 Michael Lässig
Predicting the evolution of the flu
What statistical physics can do for the life sciences


The human flu virus undergoes rapid evolution, which is driven by interactions with its host immune system. We take this system as an example of rapid adaptation processes, which can be described in terms of non-equilibrium statistical mechanics models. For influenza, such models successfully predict the evolution of influenza one year into the future. This has important consequences for public health: evolutionary predictions can inform the selection of influenza vaccine strains. Based on this example, we discuss a fundamental question: what is, what may become, and what is not predictable in evolution? And what does this have to do with cooperative phenomena and universality? We argue that stattistical mechanics will play a key role in making evolutionary biology a predictive science.

A3 Toby Opferkuch
Supersymmetry, and physics beyond the Standard Model


The Standard Model (SM) of particle physics has so far provided an exceptional description of observed experimental phenomena. As the Large Hadron Collider continues to push the energy barrier there remains to date no convincing signals of physics Beyond the Standard Model (BSM). Nevertheless, there exists compelling theoretical and experimental justifications as to why we expect BSM physics. In this workshop we will explore these justifications and give an introduction into BSM physics, with a focus on supersymmetry. Supersymmetry alone provides not only an elegant solution to a number of problems in the SM but also creates a framework whereby physical observables remain easily calculable. Here we shall also give an introduction into some of the computer tools necessary for reconciling experimental observations with the numerous theoretical models that exist today. Finally we will look at possible particle physics interpretations of dark matter within supersymmetric theories, as well as the addition of axions both with and without supersymmetry.

B1 Peter Schneider
Cosmology with (weak) gravitational lensing


Gravitational light deflection was the first crucial test of General Relativity and provides a versatile tool in astrophysics and cosmology. It probes the total mass distribution of isolated cosmic objects (such as galaxies and clusters) as well as the large-scale matter distribution in the Universe and its evolution. Gravitational lensing allows us to probe predictions of the cosmological model, the relation between luminous objects and the underlying dark matter distribution, and is seen as (one of) the most promising tool for empirically studying the properties of `dark energy'.
Within this workshop, the basic concepts and some of the key cosmological applications of gravitational lensing will be discussed.

B2 Jan Klaers, Philipp Strack
Introduction to cavity QED


In this workshop, we will introduce the basic systems and principles of cavity quantum electrodynamics (cavity QED). We will first explain the cavity system in the Weitz group at the University of Bonn and then survey some of the theoretical ideas that may lead to the fabrication of new states of matter with such systems.

C1 Branislav Nikolic, Jens Boos, Arezu Dehghanfar, Pranjal Dhole, Patrick J. Wong
Quantum gravity and aspects of relativity


Quantum gravity is still elusive. Several candidate theories do exist, among them string theory, loop quantum gravity, covariant approaches, and canonical quantization. However, the lack of experimental data in the regime of relevant energy scales of 1019 GeV makes it difficult to rule out or confirm theories. Nevertheless, during the quest for the ultimate theory, interesting insights have been gained, regarding both classical relativity and quantum theories thereof. In this workshop, several student members of the Cologne group of Gravitation and Relativity will present their fields of interest.
Our first example is quantum cosmology: Canonical quantization of the Friedmann universe leads to the Wheeler–De Witt equation on a symmetry-reduced minisuperspace, which in turn can be expanded in terms of the Planck mass to yield effective correction terms to the equations of General Relativity. Applying this to fluctuations in the cosmic microwave background (CMB) then yields a prediction of corrections to the (classically) scale-invariant power spectrum.
Yet another application in quantum cosmology is singularity avoidance by considering the vanishing and/or tunneling of the wave function of the Universe. It can be shown, under quite general assumptions, that cosmological singularities can be avoided by taking quantum aspects into account.
In the framework of classical relativity, the gauge approach is interesting because it manages to describe gravity in the framework of Yang–Mills-type gauge theories encountered in particle physics. The price to pay is accepting that Einstein’s geometry has to be given up, and be replaced by a wider class of geometries including not only curvature but also torsion.
Loop quantum gravity (LQG) in vacuum traditionally does not include torsion. It shows up naturally, however, if fermions are included into the theory by means of the Holst action. Furthermore, the Barbero–Immirzi parameter of LQG may be treated as a conformal field with interesting implications for our understanding of microscopic structure of spacetime.
Last but not least, there is a growing interest in the paradigm of emergent gravity. There, so-called horizon thermodynamics is considered to be fundamental, and the emergent nature of the gravitational field equations can be shown from first principles. How this approach might be helpful for a quantization of gravitation is still under debate.

C2 Maria Hermanns
Bosons, Fermions, Anyons


The physical world we are familiar with is made up of two kinds of particles - bosons and fermions - that are defined by their exchange properties. Under exchange of two identical bosons or fermions, the wave function remains unchanged or acquires a minus sign, respectively. In fact, these are the only two possibilities that are allowed in three spatial dimensions. However, considering two spatial dimensions instead offers much more freedom. In particular, one can interpolate between bosons and fermions, i.e. an exchange of two identical particles changes the wave function by a phase exp[i a], with arbitrary value for a. Consequently, such particles are called anyons. In this lecture, we will discuss why this is possible in two but not three spatial dimensions, and introduce some physical systems, where such anyonic particles occur.

C3 Philip Bechtle
The Search for Physics Beyond the SM at the LHC


In this contribution we will focus on physics beyond the SM at the LHC, which is motivated by a number of different phenomena: The light Higgs boson mass literally asks for New Physics right around the corner, and the dark matter in the universe point towards phenomena beyond the SM in the kinematically accessible energy range. Supersymmetry is still the best motivated model, but a number of alternatives will be discussed. In addition to an overview of the experimental searches, the seminar will also include a discussion of the statistical methods used to discriminate signals from the background and to set limits on properties of new phenomena.

Excursions

Saturday afternoon is free for excursions. There are various options (note that E1 and E2 are different tours):

Last update: Mar 25, 2015. For more information please contact Ralf Bulla.