Ws2023

Tuesday seminars start at 15:15. Friday seminars start at 14:15.

Unless otherwise stated, the seminars will be held in PHY 5.1.34A.

Tue, 17th Oct

Fri, 20th Oct

Tue, 24th Oct

  • Time: 15:15
  • Speaker: Martin Proebstl (Bachelor Vortrag)
  • Title: Hidden symmetries of the quantum harmonic oscillator
Abstract This work investigates the SU(3) group's root system and irreducible representations for the 3-dimensional isotropic harmonic oscillator. It demonstrates that the ladder operators derived from this analysis are identical to boson creation and annihilation operators. The study reveals that the oscillator's states can belong to a multiplet of the SU(3) group and provides a new lemma to distinguish states within this multiplet. Additionally, the findings extend to the n-dimensional isotropic harmonic oscillator, confirming the SU(n) symmetry group hypothesis proposed by Jauch and Hill in 1940.

Fri, 27th Oct

  • Time: 14:15
  • Speaker: Maria Koller (Master Vortrag)
  • Title: Renormalon contribution to quasi-Generalized Parton Distributions
Abstract In recent years, great progress has been made in lattice calculations for PDFs. One popular method is to calculate the quasi-PDF and then fit it to the standard PDF via a factorization formula. The same approach has also proven useful for GPDs by introducing a quasi-GPD. To arrive at precision calculations, the structure of the power corrections for these quasi-GPDs must be studied. This can be done using the concept of renormalons.

Tue, 31st, Oct

Fri, 3rd Nov

  • Time: 14:15
  • Speaker: Antonin Portelli (CERN, Edinburgh)
  • Invited by: S.C.
  • Title: Radiative corrections to leptonic decays
Abstract The current precision on the determination of CKM matrix elements is below a percent in a number of cases, and tensions between results are present, for example in the Vus/Vud plane. Investigating that problem is essential for searching new physics through weak decays, and at this level of precision a crucial ingredient is the determination of radiative corrections to pseudoscalar meson weak decays. Those have been computed so far mainly through effective field theories, which can have uncontrolled uncertainties. It is therefore important for lattice QCD+QED simulations to provide accurate predictions from first principles. In this talk I will present various results, mainly from the UKQCD collaboration, illustrating a number of challenges faced when performing such calculation. The first calculation at physical quark masses of radiative corrections to kaon and pion was published in [1], after the pioneering work from [2]. A feature of [1] is an uncomfortably large systematic error due to theoretical uncertainties on higher-order finite-size corrections. I will present our result and particularly detail this issue, based on the formalism established in [3]. I will conclude with future possible directions to address this problem.

Tue, 7th Nov

Fri, 10th Nov FOR 2926 meeting in Hamburg

Tue, 14th Nov

Thu, 16th Nov

  • All theory lunch and seminar
  • Lunch: 11:30
  • Time: 14:15
  • Location: the usual seminar room, Room PHY 5.1.34A
  • Speaker: Christoph Lehner
  • Title: Machine learning and lattice gauge theory

Fri, 17th Nov

Tue, 21st Nov

  • Time: 15:15
  • Speaker: Phiala Shanahan (MIT)
  • Note: the online seminar will also be held in the seminar room.
  • Title: Partonic structure of the nucleon from lattice QCD
Abstract I will describe new lattice QCD results for several aspects of the partonic structure of the nucleon. First, I will discuss the gravitational form factors (GFFs), which are defined from matrix elements of the energy-momentum tensor and encode how mass, spin, and internal forces are distributed both spatially and among the hadron's constituents. Second, I will discuss the Collins-Soper kernel which describes the rapidity evolution of transverse momentum dependent parton distribution functions, and show new results for this quantity in the nonperturbative region.

Fri, 24th Nov

  • Time: 14:15
  • Speaker: Daniel Mohler (Darmstadt)
  • Invited by: S.C.
  • Title: Quark-model puzzles and Lattice QCD : From the Λ(1405) to heavy-light mesons
Abstract While explicitly exotic states such as some of the tetraquark and the pentaquark candidates seen in recent years are striking examples of hadrons not falling into the naive quark-model picture, there are also many states which could be simple quark-antiquark or three-quark states, yet traditionally pose a challenge to both model calculations and Lattice QCD determinations of the hadron spectrum alike. I will discuss two such examples. The first is the $\Lambda(1405)$, a strangeness $S=-1$ baryon with quantum numbers $I(J^P)=0(\frac{1}{2}^-)$. Here I present results from a recent Lattice QCD calculation of the coupled-channel $\Sigma\pi$ and $N\bar{K}$-scattering amplitude. Our results in the $\Lambda(1405)$ channel support the picture of a two-pole structure suggested by theoretical approaches based on $SU(3)$ chiral symmetry and unitarity. As a second example I will discuss Lattice QCD predictions for the positive parity $B_{s0}^*$ and $B_{s1}$ bottom-strange states. These are the b-quark cousins of charm-strange states whose discovery at the b-factories in the early 2000s helped spark a renewed interest in hadron spectroscopy in the last two decades

Tue, 28th Nov

  • Time: 15:15
  • Speaker: Konstantin Asteriadis
  • Title: Higgs boson production in weak boson fusion at high precision
Abstract Precise measurements of Higgs boson production in weak-boson fusion at the HL-LHC necessitate revisiting many theoretical studies of this process. I present first steps in this direction. In contrast to earlier computations at NNLO QCD, decays of the Higgs boson at leading order are included. For the first time we also include contributions from non-factorizable corrections and study effects of anomalous weak couplings of the Higgs boson at this order.

Fri, 1st Dec

  • Time: 14:15
  • Speaker: Gurtej Kanwar (Bern)
  • Invited by: C.L.
  • Title: Generative AI and contour deformations for lattice field theory
Abstract Lattice calculations are typically limited by the large computational cost required to perform Monte Carlo integration with controlled statistical noise. I will discuss recent progress in applying generative models and learned contour deformations to solve statistical noise problems without compromising exactness. In particular, I will detail how these tools are being developed to target lattice gauge theories, such as lattice QCD, where specific challenges associated with the gauge manifold and large gauge symmetry group must be addressed.

Mon, 4th Dec

  • Time: 16:00
  • Location: H34
  • Speaker: Giovanni Chirilli (Habilitationsvortrag)
  • Title: Exploring the Proton's innermost structure at the Electron-ion Collider

Tue, 5th Dec

  • Time: 15:15
  • Speaker: Matteo Marcoli (Durham)
  • Invited by: A.v.M.
  • Title: The Colourful Antenna Subtraction Method for NNLO calculations in QCD
Abstract In this talk I will present the colourful antenna subtraction method for NNLO calculations in QCD. It is a reformulation of the well established antenna subtraction technique, aimed at overcoming intrinsic limitations present in the original formulation. The central aspect of the colourful approach consists in inferring structures needed to locally subtract the infrared-divergent behaviour of real emission corrections from virtual subtraction terms, relying on the cancellation of infrared singularities and on the correspondence between integrated and unintegrated antenna functions. As I will explain, this method is particularly well-suited to address high-multiplicity processes and is prone to be fully automated. As an application, I will discuss the construction of the subtraction infrastructure for the calculation of the NNLO correction to hadronic three-jet production.
  • Literature 10.1007/JHEP10(2022)099 (all gluons case), hep-ph/2310.19757 (general case)

Fri, 8th Dec

  • Time: 14:15
  • Speaker: Alessandro Cotellucci (HU-Berlin)
  • Invited by: C. L.
  • Title: Sea-Quark Isospin-Breaking Effects
Abstract The quest for sub-percentage precision in hadronic observables requires the inclusion of isospin-breaking effects (IBE) in Lattice QCD simulations. The sources of IBE are two: the up and down mass splitting and QED. These two effects have the same order or magnitude and a consistent evaluation needs to take both of them into account. From the practical point of view, there are two ways to include IBE in the simulations: the dynamical generation of QCD+QED configurations and the perturbative expansion of the IBE around isosymmetric QCD (the so-called RM123 method). The latter is widely established in literature but is usually performed in the electro-quenched approximation, neglecting contributions from sea quarks. In this talk, I present an attempt to include sea quark effects focussing on disconnected diagrams.

Tue, 12th Dec

  • Time: 15:15
  • Speaker: Aaron Holmer (Master Vortrag)
  • Title: Tensor Networks for 3-dimensional strong coupling QCD
Abstract TBD

Wed, 13th Dec

  • Christmas workshop

Fri, 15th Dec

  • Time: 14:15
  • Speaker: Matthias Weisswange
  • Title: Renormalisation of chiral Gauge Theories with non-anticommuting γ5 in the BMHV Scheme at the 3-Loop Level
Abstract The dimensional renormalisation of chiral gauge theories, such as the electroweak Stan- dard Model, inevitably leads to the problem of accommodating the manifestly 4-dimensional nature of γ5 in D dimensions. In order to avoid inconsistencies at the multi-loop level, γ5 can be treated rigorously as a non-anticommuting object using the Breitenlohner- Maison/’t Hooft-Veltman (BMHV) scheme within dimensional regularisation (DReg). Employing the BMHV scheme, however, violates gauge invariance, which subsequently needs to be restored using symmetry-restoring counterterms guaranteed to exist by the methods of algebraic renormalisation. Employing the regularised quantum action prin- ciple of DReg a possible symmetry-breaking can be rewritten as a composite operator insertion into the effective quantum action. Thus, these symmetry-restoring counter- terms can efficiently be calculated via ∆ = b∆ + ∆ct operator inserted Green functions. The UV-divergences are extracted utilizing an infrared rearrangement via the so called all massive tadpoles method, where all occurring Feynman diagrams are mapped to fully massive single-scale vacuum bubbles. Ultimately, this renormalisation procedure will be needed for high-precision calculations of e.g. electroweak observables. We have success- fully performed this renormalisation procedure up to the 3-loop level in an abelian chiral gauge theory, serving as a toy model for the investigation of new theoretical concepts, obtaining a consistently renormalised theory with ultimately restored BRST invariance. The obtained results will soon be published.
  • Literature [arXiv: 2109.11042] [arXiv: 2303.09120]

Tue, 19th Dec

  • Time: 15:15
  • Speaker: Simon Kuberski (CERN)
  • Invited by: S.C.
  • Title: B-physics in the continuum from static and relativistic heavy quarks
Abstract We present our strategy and first results for calculating B-physics observables on the lattice with a controlled continuum extrapolation by combining static and relativistic heavy quarks. Computations in large volumes below the scale of the bottom quark and in the static limit are combined with results for relativistic bottom quarks in physically small volumes. This allows us to trace the mass-dependence of the observables from the charm region up to the static limit and to obtain results for B-physics by interpolation. We employ 2+1 flavors of O(a) improved Wilson quarks at five values of the lattice spacing down to 0.039 fm. Interpolations are performed in the continuum and thus independent of the lattice regularization.
  • Literature [arXiv:2312.09811] [arXiv:2312.10017]

Fri, 22nd Dec

Winter break: 24th Dec 2023 - 7th Jan 2024

Happy Holidays and New Year 2024!!!

Tue, 9th Jan

  • Time: 15:15
  • Speaker: Sebastian Lahrtz
  • Title: Lattice calculation of the Pion Boer-Mulders function via the LaMET approach.
Abstract I will present the first lattice calculation of the Boer-Mulders function from the Pion. Those calculations were done on a single CLS ensemble by using the framework of LaMET. I will talk about the lattice setup as well as the analysis leading to our result. I will also discuss possible improvements and future work in this direction.

Fri, 12th Jan

  • Time: 14:15
  • Speaker: Valentin Moos
  • Title: Status of TMD distribution extractions and related MCEG preparation for the EIC
Abstract I present our TMDPDF extraction with N4LL accuracy, discuss current limitations in the area of TMD extractions and present current follow up research projects. I present our research project of using Monte Carlo Event Generators to make predictions for TMD physics relevant results from the Electron Ion Collider, by tuning the encoded partons transverse momentum treatment.

Tue, 16th Jan

  • Time: 15:15
  • Speaker: Simon Pfahler
  • Title: Tensor Train Methods for Mutual Hazard Networks in High Dimensions
Abstract I present the Mutual Hazard Network, a cancer progression model for inferring influences between mutations from patient data. As the space of possible tumors grows exponentially with the number of possible mutations, classical methods for learning MHNs are limited to fewer than 25 events. I present a method to avoid this runtime explosion, and discuss the new problems that arise with this method. In order to mitigate these problems, I introduce a new divergence measure for probability distributions, and investigate its properties.

Fri, 19th Jan

  • Time: 14:15
  • Speaker: Yasumichi Aoki (RIKEN R-CCS Kobe)
  • Invited by: T.W
  • Title: Chiral fermion simulations on Fugaku and QCD thermodynamics
Abstract Fugaku is the Japanese flagship supercomputer operated by RIKEN Center for Computational Science. Fugaku started its test operation in 2020 and the full service from 2021. We have been using Fugaku for Lattice QCD computations, using Wilson Fermions mainly in PACS collaboration and domain wall fermions (DWF) mainly in JLQCD collaboration for past three years. In this talk a status report on the DWF simulations especially on QCD thermodynamics are given. We have several projects in this category, in which, studies of thermodynamics near the physical point using a line of constant physics and phase structure in three degenerate flavors are discussed in detail, emphasizing how to control the residual chiral symmetry breaking at coarse lattices, which is important for these simulations.

Tue, 23rd Jan

  • Time: 15:15
  • Speaker: Gaia Fontana (Zurich)
  • Invited by: A.v.M.
  • Title: Intersection numbers & polynomial expansions
Abstract I will present recent developments in the intersection-theory approach for the reduction to master integrals. In particular, I will focus on the novel method of p(z)-adic expansion which avoids the explicit appearance of non-rational poles in intermediate steps of the calculation. I will describe the implementation of a purely rational algorithm for computing intersection numbers over finite-fields using the framework FiniteFlow. Based on arXiv:2304.14336.

Fri, 26th Jan

  • Time: 14:15
  • Speaker: Michele della Morte (CP3-Origins)
  • Invited by: S.C.
  • Title: Massive QED on the lattice
Abstract The current precision reached by lattice QCD calculations of low-energy hadronic observables, requires not only the inclusion of electromagnetic corrections, but also control over all the potential systematic uncertainties introduced by the lattice version of QED. We introduce a massive photon as an infrared regulator in lattice QED. That produces a well defined theory, dubbed QEDM, amenable to numerical evaluation. The photon mass is removed through extrapolation. In this talk we present aspects of QEDM such as the presence and fate of the zero modes contributions and we describe how such modes produce finite volume effects. We demonstrate that the required extrapolations are well controlled using numerical data obtained (mostly) on two ensembles which only differ in volume.

Tue, 30th Jan

  • Time: 15:15
  • Speaker: Ferdinand Tölkes (Master Vortrag)
  • Title: Lymphoma classification on whole slide images
Abstract This is the abstract.

Fri, 2nd Feb

  • Time: 14:15
  • Speaker: Sandro Uccirati (Turino)
  • Invited by: A.v.M.
  • Title: Analytic subtraction at NNLO in massless QCD
Abstract I present a novel subtraction scheme designed for the systematic and universal cancellation of higher-order infrared singularities in massless QCD, paving the way for a general analytic solution to the NNLO infrared problem. I explain the key features of the method that allowed us to construct a fully local infrared subtraction at NNLO, applicable to generic coloured massless final states, resulting in a completely analytic subtraction formula which can be readily implemented in any numerical framework containing the relevant matrix elements up to NNLO.

Tue, 6th Feb

  • Time: 15:15
  • Speaker: Thomas Samberger
  • Title: Grassmann tensor approach for two-dimensional QCD in the strong-coupling expansion
Abstract For non-zero chemical potential, the sign problem prohibits calculating the partition function of lattice QCD using usual Monte-Carlo methods. I will present a tensor-network approach for computing the partition function of 2d lattice QCD in the strong-coupling expansion for general orders of the coupling parameter β and show results for observables including O(β^3).

Wed, 7th Feb

  • Time: 15:15
  • Speaker: Clemens Seidl
  • Title: Eigenstate Thermalization and Entanglement Entropy in SU(2) Lattice Gauge Theory
Abstract We present preliminary numerical evidence for the hypothesis that the Hamiltonian SU(2) gauge theory discretized on a lattice obeys the Eigenstate Thermalization Hypothesis (ETH). To do so we study three approximations: (a) a linear plaquette chain in a reduced Hilbert space limiting the electric field basis to j=0,1/2 , (b) a two-dimensional honeycomb lattice with periodic or closed boundary condition and the same Hilbert space constraint, and (c) a chain of only three plaquettes but such a sufficiently large electric field Hilbert space (j≤7/2) that convergence of all energy eigenvalues in the analyzed energy window is observed. Further, we discuss the above systems in the light of Entanglement Entropy (EE). We show page curve behavior of spatial subsystems and the real time evolution of EE for excited states. Also, we present evidence for the absence of quantum many-body scars in the ergodic parameter range of 2+1D SU(2) Lattice Gauge Theory when sufficiently high electric field representations are included. This suggests the continuum 2+1D SU(2) gauge theory is a “fast” scrambler.
  • Literature [arXiv:2308.16202][arXiv:2401.15184]