Nordic Lattice 2024 in Lund

10 Jun 2024, 13:00 → 12 Jun 2024, 12:00 Europe/Stockholm

HUB (364-366) (Fysicum)

Johan Bijnens, Nils Hermansson Truedsson

We are very happy to organise the fourth Nordic Lattice meeting, this time in Lund, Sweden. With a wide range of research topics in our Nordic community, we envisage a rich scientific program at this workshop. Please remember to sign up. 

NB: If you would like to give a talk, email the title and abstract to the organisers (deadline May 20). 

Practical information:

Reaching Lund:

The city is very easy to access with a direct train from the well-connected Copenhagen Airport. The train ride to Lund C is most conveniently purchased in the Skånetrafiken app (or online at https://www.skanetrafiken.se/, or, alternatively, in Skånetrafiken ticket machines at the airport). The physics building (Fysicum) is a short (~15 minute) walk north east from the train station.

Hotels:

Lund is a popular place for tourists, especially in summer. Despite the numerous hotels, we suggest you book your stay early enough. Here are some suggestions for you (that previous guests have enjoyed):

Downtown (~15-20 minutes walking to Fysicum):

Hotell Bishop's Arms (https://www.bishopsarms.com/vara-hotell/lund/)

Hotell Concordia (https://www.concordia.se/sv.aspx)

Hotell Lundia (https://www.lundia.se/)

Grand Hotel (https://www.grandilund.se/)

A bit outside the city centre:

Elite Hotel Ideon (https://www.elite.se/hotell/lund/elite-hotel-ideon-lund/, ~15 minutes from Fysicum)

First Hotel Planetstaden (https://www.firsthotels.se/hotell/sverige/lund/first-hotel-planetstaden/, ~25 minutes from Fysicum)

To see whilst here:

With roughly 1000 years of history and a university dating back to 1666 from the time the surrounding area became Swedish, there are many things to see in Lund. A good webpage with information and suggestions in English (as well as a map) is

https://visitlund.se/en/to-do-in-lund/activities-and-nature/lund-on-foot---a-walking-tour

This is a picture of the main University square, Lundagård (site number 3 in the tourist guide linked above). [Source: Lund universitets bildbank]

Monday, 10 June

13:15 → 13:30 Welcome Session

Conveners: Johan Bijnens, Nils Hermansson Truedsson

Welcome_NHT.pdf

13:30 → 15:00 Talks: Session 1

Talks

Conveners: Johan Bijnens, Nils Hermansson Truedsson

13:30 Rindlisbacher: Entanglement entropy in SU(N) lattice gauge theory: an update

Despite progress in the past few years, the accurate determination of entanglement measures in SU(N) lattice gauge theory remains a challenging task; in particular as the number of colors, N, is increased. I will discuss some of the difficulties that emerge for N>3 and our approach to overcome them.

entanglement_in_sun_lgt_opt.pdf

14:00 Salami: The deconfinement interface tension in SU(N) gauge theories at large N

We present preliminary results from an investigation of the N-dependency of the confined-deconfined interface tension in pure SU(N) gauge theories. The interface tension is determined from the amplitudes of the long-wavelength surface fluctuations of the interface, a method that has not been widely used so far and can be considered complementary to the established histogram method. Its application, however, becomes easier if the transition gets stronger making it particularly suited for probing the large-N behaviour

14:30 Sjö: Three-meson systems in finite and infinite volume

In the quest to better understand the structure and spectrum of hadrons using lattice QCD, hadronic resonances play an important but challenging role. Being resonances, they overlap strongly with the state of their decay products, which typically consist of two or three light hadrons. Such systems have large finite-volume effects and have so far only been simulated at large pion mass. However, both the finite-volume and pion-mass dependence can be captured using the K-matrix formalism, which relates them to the elastic infinite-volume scattering amplitude of the same particles, which can be computed with conventional tools such as chiral perturbation theory. I describe the recent NLO K-matrix calculation in all three-pion channels, which (unlike earlier LO results) agrees well with lattice data. I also describe the prospect of including kaons.

three-pion stuff.pdf

15:00 → 15:30 Coffee Break

15:30 → 18:00 Talks: Session 2

Talks

Conveners: Johan Bijnens, Nils Hermansson Truedsson

15:30 Jäger: Simulating Physics Beyond the Standard Model

We explore the implications of extending the Standard Model by examining the Quantum Chromodynamics (QCD) Corrigan and Ramond large-$N_c$ limit with a single Dirac quark in the two-index antisymmetric representation. This theoretical approach enables a correspondence with the bosonic sector of Super Yang-Mills theory. Through lattice simulations, we aim to uncover new information regarding the spectrum and dynamic properties of Super Yang-Mills theory. These simulations provide valuable insights into the potential structures and interactions present in theories beyond the Standard Model.

NoLa24.pdf

16:00 Pasechnik: Cosmology of composite dynamics: dark matter, phase transitions and gravitational waves

In this talk, I briefly overview recent progress in strong coupling dynamics at finite temperatures and its cosmological implications in SU(N) gauge theories, with and without fermions. In a confining pure Yang-Mills theory of dark sector, the scalar glueballs are considered as possible candidates for Dark Matter. To predict the relic abundance of glueballs for the various gauge groups and scenarios of thermalization of the dark gluon gas, we employ a thermal effective theory that accounts or the strong-coupling dynamics in agreement with lattice simulations. In a QCD-like theory with N_f flavours, the Polyakov-loop Improved Linear Sigma Model in the Cornwall-Jackiw-Tomboulis formulation is employed to investigate the chiral phase transition in regimes that can mimic QCD-like theories incorporating in addition composite dynamics associated with the effects of confinement-deconfinement phase transition. We show that strong first-order phase transitions occur for weak effective couplings of the composite sector leading to gravitational-wave signals potentially detectable at future experimental facilities.

Lund-talk_Pasechnik.pdf

16:30 Tsang: Massive non-perturbative renormalisation

Tuesday, 11 June

09:00 → 10:30 Session 1: Talks

Conveners: Johan Bijnens, Nils Hermansson Truedsson

09:00 Ungersbäck: Quantum tachyonic preheating, revisited

In certain models of inflation, the postinflationary reheating of the Universe is not primarily due to perturbative decay of the inflaton field into particles, but proceeds through a tachyonic instability. In the process, long-wavelength modes of an unstable field, which is often distinct from the inflaton itself, acquire very large occupation numbers, which are subsequently redistributed into a thermal equilibrium state. We investigate this process numerically through quantum real-time lattice simulations of the Kadanoff-Baym equation, using a 1/N-NLO truncation of the 2PI-effective action. We identify the early-time maximum occupation number, the “classical” momentum range, the validity of the classical approximation and the effective IR temperature, and study the kinetic equilibration of the system and the equation of state.

09:30 Hermansson-Truedsson: QED_r, an infrared-improved finite-volume prescription

Precision calculations of flavour physics processes such as leptonic decays of pions and kaons allow for indirect searches of new physics. For instance, the Cabibbo-Kobayashi-Maskawa matrix elements $V_{ud}$ and $V_{us}$ accessible in these decays satisfy a unitarity relation within the Standard Model that can be probed with lattice QCD simulations. With a goal of (sub-)percent precision, isospin-breaking effects from quark-mass differences and electromagnetism have to be taken into account. The long-range nature of the electromagnetic force introduces systematic effects in the finite-volume lattice calculations, which have to be under good control for precision tests of the Standard Model. Motivated by recent results on weak decays of pions and kaons, we here present a finite-volume formulation of electromagnetism constructed to improve the associated systematic uncertainties in modern lattice simulations.

NOLA24_Indico_NHT.pdf

10:00 Martins: HiRep on GPUs

We have ported one of the available software libraries for lattice gauge theory simulations, HiRep, to GPUs. The code supports simulations of higher representations of Wilson Fermions, which are strongly limited by computational expense depending on the gauge group and dimension of the Fermion representation. We present details on the implementation, algorithmic checks, and benchmarks performed on various NVIDIA and AMD GPUs.

Presentation.pdf

10:30 → 11:00 Coffee Break

11:00 → 12:00 Session 2: Talks

Conveners: Johan Bijnens, Nils Hermansson Truedsson

11:00 Knuthson: Using quantum annealing to design lattice proteins

main.pdf

12:00 → 13:30 Lunch

13:30 → 16:00 Session 3: Talks

Conveners: Johan Bijnens, Nils Hermansson Truedsson

13:30 Bijnens: High order ChPT and the lattice

Speaker: Johan Bijnens

lundlattice24.pdf

14:00 Rothkopf: Space-time symmetry preserving discretizations for classical field theory

In this talk I present the latest results [1] from a collaborative project, which develops novel discretization methods for field theory. Building on an analogy with the world-line formalism for point particle mechanics [2] we construct a novel action, in which coordinate maps participate as dynamical degrees of freedom, together with the propagating fields.  In contrast to the conventional formulation of field theory, the action integral is formulated in terms of a set of (d+1) abstract parameters on which both the fields and coordinate maps depend. We show that by discretizing the underlying parameters, the space-time coordinates remain continuous and thus can accommodate infinitesimal space-time transformations, which are the foundation of Noether’s theorem. As long as a discretization is used that exactly mimics integration by parts in the discrete setting, the Noether charges remain exactly preserved. We illustrate the efficacy of the approach in (1+1)d scalar wave propagation.

Rothkopf_NoLAT_v1.pdf

15:00 General discussion and closing remarks

Closing_NHT.pdf

14:30 → 15:00 Coffee Break