Theorie-Seminare WS 21/22

Do. 14.10.2021, 16.30 Uhr

Rebecca Diesing (U Chicago)

A Revised Theory of Cosmic Ray Acceleration: Solving the Problem of Steep Spectra

Abstract:
Galactic cosmic rays (CRs) are accelerated at the forward shocks of supernova remnants (SNRs) via diffusive shock acceleration (DSA), an efficient acceleration mechanism that predicts power-law energy distributions of CRs. However, observations of nonthermal SNR emission imply CR energy distributions that are generally steeper than E−2, the standard DSA prediction. Recent results from kinetic hybrid simulations suggest that such steep spectra may arise from the drift of magnetic structures with respect to the thermal plasma behind the shock. I will discuss how, using a semi-analytic model of non-linear DSA, we can apply this new theory to a wide range of SNRs and other astrophysical shocks. I will further show how, by accounting for the motion of magnetic structures behind the shock, we produce CR energy distributions that are substantially steeper than E−2 and consistent with observations.

Host: P. Mertsch

 

Do. 21.10.2021, 16.30 Uhr

Andrea Shindler (Michigan)

Unravelling matter-antimatter asymmetry in the universe

Abstract:
The observed baryon asymmetry in the universe cannot be reconciled with the current form of the Standard Model (SM) of particle physics. The amount of CP-violation stemming from the Cabibbo-Kobayashi-Maskawa matrix is not sufficient to explain the observed matter-antimatter asymmetry. Historically, one of the first systems to be studied in the search for CP-violation is the electric dipole moment (EDM) of the neutron. The contribution to the neutron EDM coming from the SM is several order of magnitudes smaller than the current experimental bound, thus providing a unique background-free window for potential discovery of physics Beyond the Standard Model (BSM). Beside all the CP-violating effective operators describing the contributions from BSM, the neutron EDM can potentially be induced by the strong CP-violating theta term.
After a brief introduction on baryon asymmetry and a summary of the current status for experimental searches of a neutron EDM, I describe the different CP-violating sources and the challenges that present a calculation of the corresponding hadronic matrix elements. I then proceed detailing recent results obtained, with my collaborators, on the neutron EDM with a specific focus on the the main theoretical and numerical tool used: the gradient flow. I conclude with near-term goals, challenges and an optimistic view into the future.

Host: R. Harlander

 

Do. 28.10.2021, 16.30 Uhr

Andrea Caputo (Weizmann)

TBA

Host: F. Kahlhoefer

 

Do. 11.11.2021, 16.30 Uhr

Cora Uhlemann (Newcastle U)

TBA

Host: J. Lesgourgues

 

Fr. 12.11.2021 11:00 (MBP2 117 and via zoom) (special day and time!)

Maria Schuld (Xanadu and University of KwaZulu-Natal)

Prospects of machine learning with quantum computers

Abstract:
Machine learning is frequently listed among the most promising applications for quantum computing. This is in fact a rather curious choice: Today’s machine learning algorithms are notoriously powerful in practice, but remain theoretically very hard to study. Quantum computing, in contrast, does not offer practical benchmarks on any relevant scales, and theory is often the only tool we have to judge whether it could become relevant. In this talk I discuss this mismatch between commercial expectations and scientific challenges in more detail, and explain why it is so hard to say something about the practical power of quantum computers for machine learning at this stage. On the other hand, I show how quantum computing and machine learning do fit together surprisingly elegantly in a number of ways, such as the natural interpretation of quantum circuits as linear models in high-dimensional data spaces, or the ease with which quantum circuits can be trained by existing deep learning pipelines. Fundamental research that uncovers more of these links could turn out to be an important game changer for the design of future quantum machine learning applications. 

Host: M. Krämer

 

Do. 18.11.2021, 16.30 Uhr

Valentin V. Khoze  (Durham U.)

Searching for QCD Instantons at Hadron Colliders

Host: M. Worek

 

Do. 25.11.2021, 16.30 Uhr

Oleg Lebedev (U Helsinki)

TBA

Host: F. Kahlhoefer

 

Do. 02.12.2021, 9.00 Uhr !!!

Tom Melia (Tokyo U, IPMU)

TBA

Host: R. Harlander

 

Do. 09.12.2021, 16.30 Uhr

Lavinia Heisenberg (ETH Zürich)

TBA

Host: J. Lesgourgues

 

Do. 13.01.2022, 16.30 Uhr

Juan Garcia-Bellido (Universidad Autónoma de Madrid)

TBA

Host: J. Lesgourgues

 

Do. 20.01.2022, 16.30 Uhr

Javier Mazzitelli (MPI Munich)

Next-to-next-to-leading order event generation for top-quark pair production

Host: M. Worek

 

Do. 27.01.2022, 16.30 Uhr

Alexandre Marcowith (U Montpellier)

TBA

Host: P. Mertsch

 

Do. 03.02.2022, 16.30 Uhr

Maximilian Stahlhofen (U. Freiburg)

TBA

Host: M. Czakon