2024 Annual NPACT Meeting

19 Jun 2024, 12:00 → 21 Jun 2024, 21:30 Europe/Oslo

Naftadjupet (NTNU Ålesund Campus)

The annual meeting of the NPACT network

Wednesday 19 June

12:00 → 13:00 Welcome and lunch

13:00 → 16:00 Plenary presentations: round 1

Convener: Ben David Normann (NTNU)

13:00 Geometry of Scattering Amplitudes

The geometry of field space governs on-shell scattering amplitudes. We formulate a geometric description of effective field theories which extends previous results for scalars and gauge fields to fermions. The field-space geometry reorganizes and simplifies the computation of quantum loop corrections. Using this geometric framework, we calculate the fermion loop contributions to the renormalization group equations for bosonic operators in the Standard Model Effective Field Theory up to mass dimension eight. We also derive novel relations between scattering amplitudes in terms of soft theorems.

Speaker: Andreas Helset (CERN)

Geometry_Amplitudes.pdf

13:20 Virtual particles

The common claim that vacuum is filled with virtual particles buzzing in and out of existence, has always bother me.
I will here argue for why I do not think this is a correct interpretation of the mathematics of QFT.
Note that I am not questioning any of the mathematics of QFT, merely the metaphysical interpretation often presented.

Speaker: Nils-Erik Bomark (UiA)

13:45 Break a leg

14:00 Reheating and dark matter through dark glueballs

Taking axion inflation as an example, we consider a scenario where the inflaton is coupled solely to a pure SU(3) Yang-Mills sector. In the low-energy phase of this sector, glueball states are formed. If non-renormalizable operators are considered, these glueballs may become unstable and reheat the standard model fields. Yet, for a certain parameter range, C-parity can protect part of the glueball species from decay and the C-odd glueballs can provide a viable dark matter candidate. We study the constraints related to dark matter stability and minimal reheating temperature of the standard model and conclude that this scenario is very predictive.

Speaker: Helena Kolesova (University of Stavanger)

NPACT_Kolesova.pdf

14:20 Swampland and The Distance Conjecture

The Swampland Distance Conjecture states that at infinite distance in the scalar moduli space an infinite tower of particles become exponentially massless. I will review this topic, and its evidence from dualities. I will give an example in the context of heterotic string compactifications.

Speaker: Eirik Eik Svanes (University of Stavanger)

14:45 Break a leg

15:00 NLP resummation in slepton pair production

Threshold resummation is a key complement to perturbative QCD for predicting cross-sections at hadron colliders. Logarithms that grow large in the threshold limit, when emitted gluons are soft, are included to all orders in the strong coupling, thus stabilizing the theoretical predictions. Resummation of these logarithms has been studied extensively, e.g. reaching next-to-next-to-leading logarithmic (NNLL) accuracy for the Drell-Yan process, in what is called leading-power (LP) resummation. Recently, more focus has been put on resumming also those logarithms that are kinematically suppressed with respect to the LP ones, which may also give an appreciable contribution. These are referred to as next-to-leading-power (NLP) logarithms.

In this talk I will briefly outline how NLP logarithms arise and are resummed in the Drell-Yan process, before applying this resummation to the pair-production of sleptons, which are produced similarly. I will discuss how their production cross-section is impacted by the inclusion of these effects, both by a shift in the cross-section prediction and by lowering the dependence upon the renormalization scale.

Speaker: Tore Klungland (University of Oslo)

NPACT2024_Klungland.pdf

15:20 SUSY after Run 2 with GAMBIT

In this talk, I will show recent GAMBIT global fits of SUSY scenarios. These combine many collider searches performed during Run 2 of the LHC to constrain the electro-weak sector of the MSSM, both with and without an additional light gravitino. Fits will show parameter regions where the combination of collider searches displays behaviour that would not be trivial to see from studying search exclusion limits independently. Whilst none of these should have a high significance, they indicate parameter regions that deserve to be targeted with extra attention in future collider searches.

Speaker: Christopher Chang (University of Oslo)

15:40 Primordial Black Holes as Dark Matter

Primordial Black Holes is a particular candidate for Dark Matter. In this talk I will present the case for, and against, Primordial Black Holes and the limits we can set on them today.
In addition, I will discuss how their existence could be probed by considering how Black Holes of asteroid like mass could affect the Neutron Star population at the center of the Milky Way.

Speaker: Halvor Melkild (University of Oslo)

Thursday 20 June

09:00 → 10:00 Let's chalk

A classroom with blackboards is reserved in case someone wants to come in early to discuss projects

10:00 → 12:00 Plenary presentations: Round 2

10:00 On instabilities of perturbations in some homogeneous color-electric and -magnetic backgrounds in $SU(2)$ gauge theory.

We consider the instabilities of field perturbations around a homogeneous background color-electric and/or -magnetic field in SU(2) pure gauge theory. We investigate a number of distinct cases of background magnetic and electric fields, and compute the dispersion relations in the linearised theory, identifying stable and unstable momentum modes. In the case of a net homogenous non-abelian $B$-field, we compute the non-linear (quadratic and cubic) corrections to the equation of motion, and quantify to what extent the instabilities are tempered by these non-linearities.

Speaker: DIVYARANI C G (University of Stavanger)

10:20 Pandemics, Particles and Parameter (s)Paces

Particle physics simulations and modelling of infectious diseases in a pandemic share computational challenges due to their heavy Monte Carlo models. Both types of models need to fit large numbers of parameters to data, making the calibration process time-consuming.
In particle physics, we use the GAMBIT software to compare Beyond Standard Model theories to data from experiments. In this cross-disciplinary project, we will use GAMBIT to calibrate infectious disease models of the covid-19 pandemic to real-world data.
In this presentation, I will give a brief introduction to GAMBIT-light, a light-weight GAMBIT interface, and an overview of infectious disease modelling, before I describe the ongoing project where we utilise GAMBIT to calibrate a model of the covid-19 pandemic.

Speaker: Ida-Marie Johansson (University of Oslo)

10:45 Break a leg

11:00 Gravitational wave echoes: an introduction

The talk will aim at an introduction to the topic of gravitational wave echoes, which are gravitational waves reflected from the surface of black holes (then by mechanism of some quantum effect), or some alternative to black holes known as Exotic Compact Objects (ECO).

Speaker: Mr Vegard Undheim (University of Stavanger - TN - IMF)

11:20 GPTreeO

Gaussian processes regression provides a principled Bayesian approach to regression problems. But many applications of GP regression are hampered by the fact that the training time for a naive GP implementation scales as the number of data points cubed. In this talk I will present a new software package, GPTreeO, that enables continual learning with GPs, i.e. a GP regression model that continually adapts to a never-ending data stream, and I will discuss how GPTreeO can be used in computationally expensive parameter estimation studies.

Speaker: Anders Kvellestad (University of Oslo)

11:40 Gravitational waves from nHz to GHz frequencies

The search for gravitational waves has literally opened up a new window into
the universe, not the least as a means to probe new physics beyond the
standard model. In this talk I provide some examples, with a strong personal
bias, how this statement applies to a very broad range of frequencies.
The confirmed nHz cosmological background signal, is for example consistent
with a dark sector phase transition, and I will show how this interpretation
already constrains the properties of such a dark sector. A future signal at
frequencies accessible by LISA, in the mHz range, might not only evidence
such a dark sector phase transition, but correlate this with the thermal
production of dark matter in a secluded dark sector. Finally, there is growing
interest in exploring the technological feasibility of observing gravitational
waves with ultra-high frequencies, which would correspond to a smoking-gun
signature for new physics.

Speaker: Torsten Bringmann (University of Oslo)

Bringmann_Aalesund.pdf

12:00 → 13:00 Lunch

13:00 → 14:20 Plenary presentations: Round 3

13:00 Strongly interacting massive particles as dark matter candidates

In this talk, we will present an introduction to strongly interacting massive particles (SIMPs) as dark matter candidates. In general, the SIMP scenario can have different realizations; however, we will mostly concentrate on the dark sector described by QCD-like theories. We will discuss the basics of various scenarios and motivate the necessity of next-to-leading-order calculations in the SIMP context.

Speaker: Mr Daniil Krichevskiy (University of Stavanger)

NPACT_2024_Krichevskiy.pdf

13:20 False violations of general relativity

General relativity has proven to be a highly successful theory of gravity since its inception. The theory has passed numerous experimental tests in different regimes. Observable gravitational waves (GWs) originate from regions of spacetime where gravity is extremely strong, making them a unique tool for testing GR, in previously inaccessible regions of large curvature, relativistic speeds, and strong gravity. Since their first detection, GWs have been extensively used to test GR, but no deviations have been found so far. Given GR's tremendous success in explaining current astronomical observations and laboratory experiments, accepting any deviation from it requires a very high level of statistical confidence and consistency of the deviation across GW sources. Here we begin to compile a comprehensive list of potential causes that can lead to a false identification of a GR violation in standard tests of GR on data from current and future ground-based GW detectors. These causes include detector noise, signal overlaps, gaps in the data, detector calibration, source model inaccuracy, missing physics in the source and in the underlying environment model, source misidentification, and mismodelling of the astrophysical population.

Speaker: Alex Nielsen

14:00 Jovian planet forced climate periods

Guest lecture by professor emeritus Harald Yndestad

Speaker: Prof. Harald Yndestad (NTNU)

15:00 → 16:00 Round table: Status quo & way forward

Friday 21 June

10:00 → 12:00 Plenary presentations: Round 4

10:00 Preserving continuum space-time symmetries on the lattice

I present recent work [1] on a new numerical approach to solving classical initial boundary value problems on the level of the system action, which is discretized in a way in which space-time symmetries remain preserved.

[1] W.A. Horowitz, J. Nordström, A. Rothkopf arXiv:2404.18676

Speaker: Alexander Rothkopf (UiS TN IMF)

Rothkopf_NPACT_v1.pdf

10:20 Stress-testing the 2PI formalism for real-time quantum field theory simulations.

I will present some work that Gerhard has done on simulations of real-time quantum fields using the 2PI effective action formalism.

Speaker: Anders Tranberg (UiS - TN - IMF)

10:45 Break a leg

12:00 → 13:00 Lunch