# Past activities

« previous | page 1 of 7 | next »#### Bethe Colloquium by James Wells

The first Bethe Colloquium in 2017 took place on Thursday, January 19th

(4:15 pm) in Hörsaal I:

- James Wells (University of Michigan, Ann Arbor / DESY, Hamburg)
- The theoretical physics ecosystem behind the Higgs boson discovery
- Hörsaal I, Physikalisches Institut

**Abstract:** A simplified history of the Higgs boson has Peter Higgs positing it in the mid-1960s followed by a long wait while experimentalists progressively turned up collider
energies until it appeared several decades later. However, in order for both the hypothesis and the experimental discovery to occur, a vast and complex theory ecosystem, across
multiple subfields, had to thrive in the years before Higgs's hypothesis and in the years that followed, builing up to its discovery. In the process I describe how important the
discovery of the Higgs boson has been to particle physics and what it means for the future. I also provide a response to Anderson's recent statement in Nature: "Maybe the Higgs boson
(of particle physics) is fictitious!"

#### Bethe Forum "Beyond the standard Higgs-system"

More information is available here.

#### Bethe Colloquium by Joachim Schultze

November's 2nd Bethe Colloquium took place on November 21th

(2:15 pm) in Hörsaal I:

- Joachim Schultze (LIMES Institut, Bonn)
- Genomic Research goes Computational
- Hörsaal I, Physikalisches Institut

**Abstract:** The life and medical sciences have seen a revolution in the last decade. Initiated in the 1990s with the Human Genome Project, genomic research has significantly
accelerated since 2007 when next generation sequencing (NGS) technologies were introduced. NGS is seen as the single most important driver of innovation in the life sciences in the
next 10 to 25 years. The number of human genomes sequenced by 2015 already reached 300,000 and in the same year US-president Barack Obama announced a US-based project sequencing 1
million American citizens. A few weeks ago, the pharma company Astra Zeneca announced to sequence even 2 million human beings. At the same time the Beijing Genome Center is on its way
sequencing all species existing in China. All these advances have triggered three main developments: first, biology becomes more and more computational. Mathematics and informatics
play an ever-increasing role in genomic research and therefore in the life sciences. This biological data avalanche without computation and meaningful algorithms - even including deep
learning algorithms - would be meaningless. Second, biology becomes quantitative. Indeed, genomic technologies allow the generation of truly quantitative data. And third, data-driven
hypothesis generation and machine learning-based decision making slowly but steadily replaces classical approaches based on thoughts, postulates and speculation. I will give an
overview of these developments and will also bring them into the perspective of our own goals applying genomics to questions in neurodegeneration and immunology.

#### Bethe Colloquium by Markus Gabriel

November's Bethe Colloquium took place on November 14th

(2:15 pm) in Hörsaal I:

- Markus Gabriel (Institut für Philosophie, Bonn)
- What is Metaphysics and Why Does ist Matter?
- Hörsaal I, Physikalisches Institut

**Abstract:** As a first approximation metaphysics is a discipline which deals with absolutely everything which exists. There are many names for this extraordinary totality: the
world as a whole, reality, cosmos, nature, the universe. Yet, how could we possibly ever know enough in order to figure out what the fundamental structure of such an extraordinary
object or domain of objects is? In my presentation, I will introduce some contemporary philosophical arguments in central fields of theoretical philosophy such as metaphysics,
metametaphysics and epistemology. In particular, my aim is to raise questions concerning the limits of both science and metaphysics. In this context, I will also deal with the
recently much-discussed question whether the universe is or could be a simulation and how anyone could ever come to believe that it might be.

#### Bethe Colloquium by Peter Scholze

October's Bethe Colloquium took place on October 27th

(4:15 pm) in Hörsaal I:

- Peter Scholze (Mathematical Institute Bonn)
- Hyperbolic 3-manifolds and Galois representations
- Hörsaal I, Physikalisches Institut

**Abstract:** A large part of modern number theory deals with the relation between algebraic objects and analytic objects, as in the famous Shimura-Taniyama-Weil conjecture
relating elliptic curves with modular forms, whose proof by Wiles, completed by Taylor, et. al., lead to the solution of Fermat's Last Theorem. I will try to explain the general
Langlands conjectures underlying this picture, and describe some recent results, in particular in the situation mentioned in the title.

#### 8th Bethe Center Workshop "Particle Physics meets Cosmology"

More information and the application form are available here.

#### Meeting of the Research Unit "New Physics at the LHC"

Further information about the Research Unit and the program of the meeting can be found here:

http://web.physik.rwth-aachen.de/service/wiki/bin/view/Kraemer/NewPhysicsattheLHC

#### Bethe Colloquium by Xenia de la Ossa (Oxford) and Eric Zaslow (Evanston)

July's Bethe Colloquium took place on July 17th

(2:30 pm) in Hörsaal I:

- Xenia de la Ossa (Oxford) and Eric Zaslow (Evanston)
- 25 Years of Mirror Symmetry, 20 Years of Homological Mirror Symmetry
- Hörsaal I, Physikalisches Institut
- Part 1 by Xenia de la Ossa at 2:30pm, part 2 by Eric Zaslow at 4:15pm
- Coffee break at 3:45pm

**Part 1: Reflections on Mirror Symmetry (Xenia de la Ossa, Oxford)**

I will give a review of the history of mirror symmetry. This has had many ramifications, but its prime utility in physics is that it permits the evaluation of path integrals without
recourse to perturbation theory. I will make reference also to a possible impact on arithmetic, and return to the origins of the subject with a consideration of the moduli space of
the vacuum state of the heterotic string.

**Part 2: HMS, Hopefully Made Simple (Eric Zaslow, Evanston)**

I will try to explain a few ideas which make Homological Mirror Symmetry tractable and intuitive in a few simple examples.

#### Bethe Forum on "Mirror Symmetry"

Further information can be found here.

#### Bonner Schülerakademie 2016

Students from upper secondary schools and future university students took part in this event. The 19 participants enjoyed a varied program of scientific talks, guided laboratory tours, visits and experiments.

Further information can be found here.

#### Bethe Forum on "Dark matter beyond Supersymmetry"

Further information, the registration form and updates on the program can be found here.

#### Bethe Colloquium by Gabrijela Zaharijas

June's 2nd Bethe Colloquium took place on June 16nd

(4:15 pm) in Hörsaal I:

- Gabrijela Zaharijas (Nova Gorica)
- Dark Matter search with the Fermi Large Area Telescope
- Hörsaal I, Physikalisches Institut

**Abstract:** High energy gamma-rays are one of the most promising tools to constrain or reveal the nature of dark matter. During the almost eight years of the Fermi satellite
mission, the data from its Large Area Telescope (LAT) were used to set constraints on the dark matter cross section to various particle channels which now cut well into the
theoretically motivated region of the parameter space. In this talk I will describe methods used to search for evidence of dark matter with the LAT, and review the status of the
searches. Special attention will be given to the latest indications of the origin of the unaccounted gamma-ray excess at few GeV in the Fermi-LAT data in the region around the
Galactic Center, which steered lots of attention as it was shown to be consistent with putative signals of WIMP dark matter particles. Finally I will discuss projections of the
expected sensitivities with continued LAT data taking.

#### Bethe Forum on "Model Building in the 13 TeV Era"

Further information, the registration form and updates on the program can be found here.

#### Bethe Colloquium by Gilad Perez

June's Bethe Colloquium took place on June 2nd

(4:15 pm) in Hörsaal I:

- Gilad Perez (Weizmann Institute, Rehovot)
- Probing the atomic Higgs force
- Hörsaal I, Physikalisches Institut

**Abstract:** After the discovery of the Higgs particle at the LHC, the Higgs mechanism is expected to account for the masses of the fundamental particles. We argue that, while
this is true for the electroweak gauge bosons, we are still in the dark regarding the origin of the charged fermions masses, in particular those of electron, up and down quark. It
motivates us to propose a non-collider approach to probe Higgs boson couplings to these matter constituents via precision measurement of isotope shifts in atomic clock transitions. We
present an experimental method which competes with and potentially surpasses the LHC in bounding the Higgs-to-light-fermion couplings. Better knowledge of the latter is an important
test of the Standard Model and could lead to an alternative understanding of the flavor puzzle (the fact that the fermion masses span five orders of magnitude in scale). We will then
discuss how to translate the above (potential) fantastic sensitivity to constrain the presence of heavy new particles that are well beyond the reach of near future accelerators.

#### Meeting of the Research Unit "New Physics at the LHC"

Further information about the Research Unit and the program of the meeting can be found here:

http://web.physik.rwth-aachen.de/service/wiki/bin/view/Kraemer/NewPhysicsattheLHC

#### Bethe Colloquium by Dr. Hans-Thomas Janka

April's Bethe Colloquium took place on April 21st

(4:15 pm) in Hörsaal I:

- Hans-Thomas Janka (MPI for Astrophysics, Garching)
- Supernova Simulations in Three Dimensions: Models Confronting Observations
- Hörsaal I, Physikalisches Institut

**Abstract:** Recently the first self-consistent three-dimensional computer simulations of supernova explosions of massive stars have become possible and reveal new, stunning
phenomena like a dipolar emission asymmetry of electron neutrinos and antineutrinos. They lend support to the viability of the neutrino-driven explosion mechanism in principle,
although stars above ten solar masses are hard to explode and might suggest still missing physics. The violent hydrodynamical instabilities that facilitate the onset of the explosion
lead to kicks and spins of the newly formed neutron stars and to supernova asymmetries whose observations can help to decipher the physics of the central engine.

#### Bethe Forum Lecture Series on "Higgs Physics" by Georg Weiglein

You will find further information here.

#### Bethe Forum on "Axions and the Low Energy Frontier"

#### Bethe Forum Lecture Series on Supersymmetric Grand Unified Theories

Topics included

- GUT model building in space-time dimensions
- Examples of complete 4D SUSY GUTs
- Orbifold GUTs
- Embedding orbifold GUTs into the heterotic string
- Testing SUSY GUTs at the LHC

Further information and the registration can be found here.

#### Bethe Colloquium by Prof. Marc Vanderhaeghen

January's Bethe Colloquium took place on January 28th

(4:15 pm) in Hörsaal I:

- Marc Vanderhaeghen (Johannes Gutenberg University Mainz)
- Precision hadron physics
- Hörsaal I, Physikalisches Institut

**Abstract:** To answer physics questions at both the highest and lowest energy scales, hadron physics plays a central and connecting role. In many questions at the forefront of
particle physics, atomic physics, and nuclear astrophysics, the progress is limited by a missing quantitative knowledge of the strong interaction in the non-perturbative domain of
Quantum Chromo Dynamics (QCD). On the other hand, precision measurement e.g. in atomic and particle physics lead to new insights on the structure of hadrons, as well as to the
question how hadrons emerge out of their constituent quarks and gluons.

In this talk, I will survey several examples of this fruitful interplay. In the field of particle physics, the most precise measurement worldwide of the weak mixing angle in
electron-proton scattering will open a window on searches for new physics. Furthermore, I will illustrate how measurements and theoretical calculations will lead to an improved
knowledge of the anomalous magnetic moment of the muon. In the interplay with atomic physics, new measurement campaigns of nucleon form factors and polarizabilities, combined with
more refined theoretical analyses, will allow to importantly improve on the limiting factors in the interpretation of high precision tests of the Lamb shift in muonic atoms and to
shed light on the proton radius puzzle. In the interplay with nuclear astrophysics, measurements in nuclear systems will allow to study the nuclear equation of state, and address
important questions in astrophysics, such as the detailed structure of neutron stars.

#### Bethe Colloquium by Prof. Andreas Weiler

December's Bethe Colloquium took place on December 3rd

(4:15 pm) in Hörsaal I:

- Andreas Weiler (Technische Universität München)
- Naturalness' last stand
- Hörsaal I, Physikalisches Institut

**Abstract:** With the discovery of the Higgs boson, the Standard Model of particle physics celebrated a great triumph. It also brought the naturalness puzzle sharper into focus:
What keeps the Higgs mass so light? Will supersymmetry soon be found or should we consider a cosmological solution? Run 2 of the LHC is about to tackle this and a multitude of urgent
questions. We will review what I consider as the most interesting lessons learned and open issues, and outline the main directions for future progress.

#### Meeting of the Research Unit "New Physics at the LHC"

Further information about the Research Unit and the program of the meeting can be found here:

http://web.physik.rwth-aachen.de/service/wiki/bin/view/Kraemer/NewPhysicsattheLHC

#### Bethe Colloquium by Prof. Christof Wetterich

November's Bethe Colloquium took place on November 19th (4:15 pm) in Hörsaal I:

- Christof Wetterich (Universität Heidelberg)
- Big Bang or freeze?
- Hörsaal I, Physikalisches Institut

**Abstract:** If the sizes of atoms are allowed to vary, the geometry of our Universe can be described by different pictures, with distances between galaxies shrinking, expanding
or static. Motivated by quantum gravity we discuss a unified picture where both inflation and a present dynamical dark energy arise from the same scalar field. The history of the
Universe undergoes a crossover from a „past fixed point“ where all particles are massless, to a „future fixed point“ where spontaneous breaking of the exact scale invariance generates
the particle masses. The cosmological solution can be extrapolated to the infinite past in physical time - the Universe has no beginning and no physical singularity. This is seen most
easily in a frame where particle masses and the Planck mass are field-dependent and increase with time. In this „freeze frame“ the Universe shrinks and heats up during radiation and
matter domination. In the equivalent, but singular Einstein frame cosmic history finds the familiar big bang description. The big-bang-singularity turns out to be an artifact of an
unsuitable choice of „field-coordinates“. We discuss a simple model which is compatible with all present cosmological observations. It could be tested by the observation of huge lumps
in the cosmic neutrino background, the detection of early dark energy , or rather large primordial graviton fluctuations generated during inflation.

#### Meeting of the Research Unit "New Physics at the LHC"

A meeting of the Research Unit took place on Wednesday, 28th October, in the bctp. A further meeting in the bctp is scheduled for Wednesday, 25th November.

Details about the work of the Research Unit and the program of the meeting can be found here.

#### Bethe Colloquium by Prof. Jan Louis

October's Bethe Colloquium took place on October 22nd (4:15 pm) in Hörsaal I:

- Jan Louis (Universität Hamburg)
- String Theory - Status and Perspectives
- Hörsaal I, Physikalisches Institut

**Abstract:** After a brief introduction to string theory we discuss its relevance for particle physics, cosmology and mathematics.

#### Inaugural meeting of jDPG Bonn

Read more about the jDPG meeting here.

#### Annual meeting of the SFB/TR 16 "Subnuclear Structure of Matter"

More information about the SFB/TR 16 can be found here.

####
7th Bethe Center Workshop 2015

Challenges in Strong Interaction Physics

We were happy to organize this year’s Bethe Center Workshop from September 29th to October 2nd, 2015, in the Physikzentrum Bad Honnef, Germany. The topic was **Challenges in Strong Interaction Physics** with foci on nuclear and
hadron physics. The four workshop days will had the following themes:

- Non-perturbative Hadron-Hadron Interactions: few-particle systems
- Strongly interacting many-body systems
- Hadronic transitions form factors and (g-2)
- Hunting for physics beyond the SM

**Local Organising Committee**

Christoph Hanhart, Ulf-G. Meißner, Bastian Kubis, Evgeny Epelbaum, Hans-Werner Hammer, Carsten Urbach

#### Bethe Colloquium by Prof. Peter Koepke

July's Bethe Colloquium took place on July 2nd (3:15 pm) in Hörsaal I:

- Peter Koepke (Mathematical Institute, University of Bonn)
- Turing Machines: Exploring the Limits of Computability
- Hörsaal I, Physikalisches Institut

**Abstract:** To demonstrate the computability of a function it suffices to exhibit a concrete computational procedure like some algorithm for decimal arithmetic or a computer
program. Proofs of incomputability, however, require a general notion of computability and an argument that each of those computable functions disagrees with the given function.

In 1936, Alan Turing proposed a mathematical model of computation by abstract machines, and he used it to give a negative answer to the Entscheidungsproblem of David Hilbert: there is
no general procedure which decides the truth or falsity of every mathematical statement within some finite time. Turing machines soon became universally recognized as the correct
model of intuitive computability: they are mathematically simple, correspond to idealized digital computers, and they are equivalent to notions of computability based on other
paradigms.

In my talk I shall survey the origins of computability theory and illuminate some aspects of Turing's biography and his general views on computability and (artificial) intelligence. I
shall also mention research intended to overcome the limitations of Turing computability by allowing infinitary computations. There are investigations and speculations whether such
computations can be physically "realized" by letting a classical Turing machine work in an orbit around a black hole.

#### Bethe Forum on String Cosmology

#### Bethe Colloquium by Prof. Henry S.-H. Tye

June's Bethe Colloquium took place on June 18th (3:15 pm) in Hörsaal I:

- Henry S.-H. Tye (Cornell University)
- Sphaleron and Baryon Number Violating Processes
- Hörsaal I, Physikalisches Institut

**Abstract:** It is known that baryon number violating processes are allowed in elecrotroweak theory, but they are believed to be exponentially suppressed. I like to argue
otherwise. The reasoning is based on the periodicity property of the sphaleron potential in the electroweak theory, where we write down the one-dimensional time-independent
Schr\"{o}dinger equation with the Chern-Simons number as the coordinate. The baryon-lepton number violating processes may even take place at LHC soon.

#### Bethe Colloquium by Prof. Urs Achim Wiedemann

May's Bethe Colloquium took place on May 7th (3:15 pm) in Hörsaal I:

- Urs Achim Wiedemann (CERN-PH/TH)
- Heavy-ion collisions at the LHC
- Hörsaal I, Physikalisches Institut

**Abstract:** The “standard model” of ultra-relativistic heavy ion collisions is based on the picture that viscous relativistic fluid dynamics can account for the time evolution of
dense QCD matter produced in the nuclear overlap area, and that this transient QCD fluid attenuates the production of high momentum-transfer processes. My talk will review the
experimental evidence supporting this picture, as well as the questions for a theory of heavy ion collisions arising from it. One recurrent theme will be that the little bangs
produced in heavy ion collisions and the Big Bang are the smallest and largest physical systems respectively, for which fluctuation analysis can inform us about material properties. I
shall discuss recent efforts that raise this observation beyond the level of a mere analogy by exploiting techniques of modern cosmology in heavy ion physics and vice versa.

#### Bethe Colloquium by Prof. Andreas Ringwald

April's Bethe Colloquium took place on April 16th (3:15 pm) in Hörsaal I:

- Andreas Ringwald (DESY)
- The Hunt for Axions and other WISPs
- Hörsaal I, Physikalisches Institut

**Abstract:** Many theoretically well-motivated extensions of the standard model of particle physics predict the existence of very weakly interacting slim (in the sense of
ultralight) particles (WISPs), such as the axion. WISPs may constitute the mysterious dark matter in the universe and solve some puzzles in stellar and high-energy astrophysics. There
are new, relatively small experiments around the globe, which started to hunt for these elusive particles and complement the search for physics beyond the standard model at the Large
Hadron Collider.

#### Bethe Forum on Methods in lattice field theory

Topics included:

- Finite volume methods on the lattice
- Scattering observables
- Exotic bound states and resonances
- All mode averaging and distillation
- Analysis methods for time series of large correlator matrices
- Algorithms for nuclear correlation functions
- Nuclear lattice simulations

#### XVII Workshop - Beyond the Standard Model

The topics and speakers of the pedagogical lectures were:

- Daniel Baumann (Cambridge University): Recent Developments in (String) Cosmology
- Stefano Cremonesi (King's College London): New exact Results in Supersymmetric Field Theories
- Henning Samtleben (ENS Lyon): Introduction to Exceptional Field Theory
- Eran Palti (Heidelberg University): Prospects in String Phenomenology

#### Bethe Forum Lecture Series on Axions

Topics included

- Basics of the Strong CP Problem and Axion Solution
- Axion Models and Low Energy Couplings
- Axion-like-Particles and Other Light States
- Axions in Cosmology
- Axions in String Theory

The homepage of the program can be found here.

#### Bethe Forum on Constructive Methods in Number Theory

Recently there have been several attempts to attack this difficult problem with some success. However we are still far from understanding what Grothendieck called the tower of Teichmüller groupoids. The goal of the workshop is to bring together experts from different fields of mathematics to share their insights and enlighten the connections between the algebraic, geometric and number theoretic aspects of the problem.

The homepage of the program can be found here.

#### Bethe Colloquium by Prof. Arthur Hebecker

Janurary's Bethe Colloquium will take place on January 15th (3:15 pm) in Hörsaal I:

- Arthur Hebecker (Heidelberg University)
- String Theory Landscape and Cosmological Inflation
- Hörsaal I, Physikalisches Institut

**Abstract:** The talk will start by motivating string theory as a theory of quantum gravity. Then the resulting 10-dimensional effective field theory and its compactification to 4
space-time dimensions will be discussed. It turns out that this leads to a very large number of possibilities - the "string theory landscape". This landscape is populated through
eternal inflation, creating the so-called multiverse. To describe our observed cosmology, eternal inflation has to be supplemented by slow-roll inflation which leaves its imprint on
the cosmological microwave background, measured e.g. by the Planck satellite. Recent progress in the string-theoretical understanding of this inflationary period of our universe will
be briefly discussed at the end.