Past activities

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Bethe Colloquium by Richard Neher

May 2017
Richard Neher

May's Bethe Colloquium took place on Thursday, May 4th
(4:15 pm) in Hörsaal I:

  • Richard Neher (Biozentrum, University of Basel)
  • Rapid adaptation and the predictability of next year's flu
  • Hörsaal I, Physikalisches Institut

Abstract: Evolution is simple if adaptive mutations, that is evolutionary innovations, appear and spread one at a time. However, in large microbial populations many mutations arise simultaneously resulting in a complex dynamics of competing variants. I will discuss recent insights into universal properties of such rapidly adapting populations which has surprising parallels to the physics of front propagation and disordered systems. Not only do these models describe observations, but they also allow to predict which variants in the population are likely to be successful. When applied to seasonal influenza virus, such predictions can anticipate virus variants of future seasons and help to optimize the influenza vaccine.  

Bethe Forum "Discrete Symmetries"

03.04.2017 – 07.04.2017
Poster Discrete Symmetries
From 3rd to 7th April, 2017, the bctp hosted the Bethe Forum on "Discrete Symmetries". The Bethe Forum was organized by Steve King (Southampton), Stefan Antusch (Basel), Hans Peter Nilles (Bonn), and Andreas Trautner (Bonn).

More information and the talks are available on the webpage.

XXIX Workshop - Beyond the Standard Model

20.03.2017 – 23.03.2017
Bad Honnef Poster
From March 20th to March 23rd, 2017, the yearly workshop "Beyond the Standard Model" took place at the Physikzentrum Bad Honnef. The workshop focused on recent developments in the theory of fundamental particles, the physics of the early universe, and mathematical physics. There have been four introductory pedagogical lectures as well as shorter talks by the participants.
The topics and speakers of the pedagogical lectures were:
  • G. Arutyunov (Hamburg): Quantum Integrable Models in the AdS/CFT correspondence
  • D. Berman (London): An introduction to double and exceptional field theory
  • A. Nielsen (Hannover): Gravitational Waves and Black Holes
  • J. Wells (Ann Arbor): Particle Physics - Quo Vadis?
For more information and see the webpage.

Bethe Forum Lecture Series on "Neutrinos"

06.03.2017 – 10.03.2017
Alexei Smirnov
The Lecture Series on "Neutrinos" took place from 6th to 10th March, 2017, in the Bethe Center for Theoretical Physics in Bonn. The lectures were held by Alexei Smirnov (Max Planck Institute for Nuclear Physics, Heidelberg, Germany).

Topics included were

  • Masses, mixing and oscillations
  • Flavor transformations in matter
  • Phenomenology of neutrinos from various sources
  • Mass hierarchy and CP-violation
  • Beyond the 3-neutrino paradigm
  • Neutrino masses: towards the underlying physics
For more information see the webpage.

Bethe Colloquium by James Wells

January 2017
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"

28.11.2016 – 02.12.2016
Poster Beyond the standard Higgs-system
The Bethe Forum "Beyond the standard Higgs-system" took place from November 28th to December 2nd, 2016, in the Bethe Center for Theoretical Physics in Bonn. The organizers were Sabine Kraml (Grenoble), Hans Peter Nilles (Bonn), Tilman Plehn (Heidelberg) and Veronica Sanz (Sussex).

More information is available here.

Bethe Colloquium by Joachim Schultze

November 2016
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 2016
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 it 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 2016
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"

10.10.2016 – 14.10.2016
Poster 8th Bethe Center Workshop
We are happy to announce the 8th Bethe Center Workshop "Particle Physics meets Cosmology" on October 10 - 14, 2016 in Physikzentrum Bad Honnef, Hauptstr. 5, 53604 Bad Honnef. The organizers are Hans Peter Nilles (co-chair), Cristiano Porciani (co-chair), Matthias Bartelmann, Wilfried Buchmüller, Arthur Hebecker, Bruno Leibundgut, Thomas Konstandin and Jochen Weller. The workshop is jointly organized by Transregio 33 - The Dark Universe (Bonn, Heidelberg, München) and SFB 676 Particle, Strings and the Early Universe (Hamburg).

More information and the application form are available here.

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

14.09.2016
Logo Forschergruppe
The goal of the DFG Research Unit 2239 is to provide theoretical calculations, numerical tools and analyses for the systematic study of new physics phenomena in the context of the LHC. Results are being discussed in regular meetings. This upcoming meeting will be focusing on Higgs physics and dark matter at the LHC as well as on the interpretation of exciting new data.

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 2016
Xenia de la Ossa and Eric Zaslow

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"

04.07.2016 – 08.07.2016
Mirror Symmetry Poster
The Bethe Forum on "Mirror Symmetry" took place from 4th to 8th July, 2016, in the Bethe Center for Theoretical Physics. The organizers were Daniel Huybrechts (Bonn), Hans Jockers (Bonn) and Albrecht Klemm (Bonn).

Further information can be found here.

Bonner Schülerakademie 2016

July 2016
Bonner Schülerakademie 2016
As in the previous years, the Bonner Schüerakademie Physik/Astronomie took place from 11th to 15th July, 2016, in the Bethe Center for Theoretical Physics.
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"

13.06.2016 – 17.06.2016
Dark matter beyond Supersymmetry Poster
The Bethe Forum on "Dark matter beyond Supersymmetry" took place from 13th to 17th June, 2016, in the Bethe Center for Theoretical Physics. The organizers are Oleg Lebedev (Helsinki), Lars Bergström (Stockholm), Manuel Drees (Bonn) and Alejandro Ibarra (TUM, Munich).

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

Bethe Colloquium by Gabrijela Zaharijas

June 2016
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"

30.05.2016 – 03.06.2016
Dark matter beyond supersymmetry Poster
The Bethe Forum on "Model Building in the 13 TeV Era" took place from May 30th to to June 3rd, 2016, in the Bethe Center for Theoretical Physics. The organizers are Rolf Kappl (Bonn), Herbert K. Dreiner (Bonn), Christophe Grojean (DESY, Hamburg) and Martin Winkler (Bonn).

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

Bethe Colloquium by Gilad Perez

June 2016
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"

22.04.2016
Logo Forschergruppe
The goal of the DFG Research Unit 2239 is to provide theoretical calculations, numerical tools and analyses for the systematic study of new physics phenomena in the context of the LHC. Results are being discussed in regular meetings. This upcoming meeting will be focusing on Higgs physics and dark matter at the LHC as well as on the interpretation of exciting new data.

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 2016
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

04.04.2016 – 08.04.2016
Dark matter beyond supersymmetry Poster
The lecture course will start with a discussion of the Brout-Englert-Higgs mechanism of electroweak symmetry breaking and its relation to the quantum structure of the vacuum. Possible realisations of electroweak symmetry breaking within the Standard Model of particle physics, extended Higgs sectors and composite Higgs models will be presented, and their phenomenology will be highlighted. Our present knowledge about the signal that has been discovered at about 125 GeV will be summarised, and possible interpretations will be discussed. Prospects for the upcoming runs of the LHC and possible future colliders will be sketched. In this context also possible implications of the excess that was recently observed by ATLAS and CMS at about 750 GeV in searches in the two-photon channel will be discussed.
You will find further information here.

Bethe Forum on "Axions and the Low Energy Frontier"

07.03.2016 – 18.03.2016
Axions and the Low Energy Frontier Poster
The Bethe Forum on "Axions and the Low Energy Frontier" took place from 7th to 18th March, 2016, in the Bethe Center for Theoretical Physics. The organizers are Klaus Desch (Bonn), Axel Lindner (DESY, Hamburg), Hans Peter Nilles (Bonn), Georg Raffelt (MPI, Munich). You will find further information here.

Bethe Forum Lecture Series on Supersymmetric Grand Unified Theories

15.02.2016 – 19.02.2016
Stuart Raby
We are happy to announce the Lecture Series on "Supersymmetric Grand Unified Theories" from 15th to 19th February, 2016, in the Bethe Center for Theoretical Physics in Bonn. The lectures will be held by Stuart Raby (Ohio State University, Columbus, Ohio, USA).

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 2016
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 2015
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"

25.11.2015
Logo Forschergruppe
The goal of the DFG Research Unit 2239 is to provide theoretical calculations, numerical tools and analyses for the systematic study of new physics phenomena in the context of the LHC. Results are being discussed in regular meetings. This upcoming meeting will be focusing on Higgs physics and dark matter at the LHC as well as on the interpretation of exciting new data.

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 2015
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"

28.10.2015
Logo Forschergruppe
The members of the Research Unit "New Physics at the LHC" pursue theoretical calculations and analyses of new physics scenarios at the LHC which address the hierarchy problem, the origin of dark matter, or both.
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 2015
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

10.10.2015
Inaugural meeting of jDPG Bonn
On Saturday, 10th October, 2015, the seminar room on the Bethe Center for Theoretical Physics was filled to the rafters with young DPG members for the re-inauguration of the jDPG Bonn. The inaugural event exceeded the expectations of the organizing team. After a meeting with an interesting talk by Dr. Michael Geffert (AIfA, Bonn), lively discussion and the exchange of ideas about future events of the Bonn group, the organizers are looking forward to a range of excursions, discussions and presentations in future.

Read more about the jDPG meeting here.

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

07.10.2015 – 09.10.2015
Logo SFB TR 16
From 7th to 9th October, 2015, the collaborators of the SFB/TR 16 "Subnuclear Structure of Matter" held their annual meeting in the BCTP. The collaborators from the University of Bonn, Ruhr University Bochum, and Justus Liebig University Giessen exchanged results and discussed further development of the project.

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

7th Bethe Center Workshop 2015
Challenges in Strong Interaction Physics

29.09.2015 – 02.10.2015
Poster Workshop 2014

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
There were three topical sessions each day. Further information and updates on the program can be found here.

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

Bethe Colloquium by Prof. Peter Koepke

July 2015
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.

(Photo: Creative Commons License Attribution-Share Alike 2.0 Germany)

Bethe Forum on String Cosmology

15.06.2015 – 19.06.2015
String Cosmology Poster
The Bethe Forum on String Cosmology was a one week program which brought together experts in cosmology and string theory. Among other topics, the advances and challenges in embedding inflation in string theory were discussed. The workshop took place from June 15th to June 19th. More information about the program and the registration can be found here.

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

June 2015
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 2015
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 2015
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

23.03.2015 – 02.04.2015
Lattice Field Theory Poster
Lattice field theories have become important tools to study non-perturbative phenomena in Quantum Chromodynamics and nuclear physics. In both fields, the lattice regularisation allows investigation of phenomenologically important observables from first principles. In order to further reduce systematic uncertatinties and to tackle more observables, advanced methods need to be deviced and applied. The aim of the program was to bring together world leading experts for methods in lattice field theory and trigger discussions and future developments in this research area.

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
For more informations and registration see the webpage.

XVII Workshop - Beyond the Standard Model

16.03.2015 – 19.03.2015
Bad Honnef Poster
From March 16th to March 19th, 2015, the yearly workshop "Beyond the Standard Model" took place at the Physikzentrum Bad Honnef. The workshop focused on recent developments in the theory of fundamental particles, the physics of the early universe, and mathematical physics. The deadline for registration was February 6th, 2015.
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
For more information and registration see the webpage.

Bethe Forum Lecture Series on Axions

09.03.2015 – 13.03.2015
Axions Poster

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

02.03.2015 – 06.03.2015
Not on the photograph are Noam Elkies and Fernando Villegas.
Dessins d'enfants and their realization as Belyi maps of compact Riemann surfaces were originally discovered by Felix Klein. Their importance and relevance was finally understood by Alexander Grothendieck who rediscovered and named them in his "Esquisse d'un programme" in 1984. The most important aspect of dessins is the operation of the absolute Galois group on them. Accordingly, dessins d'enfants provide fascinating insights and fundamental links between different fields of mathematics like inverse Galois theory, Teichmüller spaces, hypermaps, algebraic number theory and mathematical physics. The related problem of the construction of Riemann surfaces with given automorphism group turns out to be rather challenging.

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

January 2015
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.

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