Asymptotic Safety meets Particle Physics & Friends

16 Dec 2024, 12:00 → 19 Dec 2024, 16:00 Europe/Zurich

FLASH experimental hall "Albert Einstein" (DESY Hamburg)

Welcome to the homepage of the 2024 edition of the  'Asymptotic Safety meets Particle Physics and Friends' workshop, taking place on Dec 16th - 19th at DESY, Hamburg.

The aim of this informal workshop is to bring together QFT practitioners from different areas to discuss new ideas, progress, and challenges at the interface between formal theory and model building and data. Topics to be covered range from critical phenomena,  particle physics, condensed matter, gravity, to new directions in model building and LHC phenomenology, and more. This is the 11th event of this kind. The previous workshop is found here.

 

There is no conference fee! Registration will soon open for invited participants, with further information to follow shortly. 

We have reserved 30 rooms at the DESY hostel from Dec 15 to Dec 19.

 

 

The workshop will take place "Im Quantenfeld" at the Albert Einstein Hall, DESY, Hamburg. The building is marked as 28c in sector 1c on the DESY map. Please head to the seminar room on the second floor.

 

 

 

 

The conference dinner will take place Tuesday 19:00 at Dübelsbrücker Kajüt, Elbchaussee 303, 22605 Hamburg. To get there, take bus line 1 outside DESY main entrance towards “Rissen” or “Sieversstücken”. Exit at “Elbe-Einkaufzentrum” and take the bus line 21 to Teufelsbrück.

 

 

 

 

 

 

 

 

 

 

 

 

This workshop is supported by the Helmholtz Alliance ``Physics at the Terascale". 

The workshop is also supported by the MERCUR project to bring together theoretical particle and solid state physics.

Monday 16 December

Talks: BSM I

1 Welcome

Speaker: Daniel Litim (University of Sussex)

2024-Desy.pdf

2 Probing Quantum Gravity Effects via Magnetic Conversion of Electromagnetic Waves into Gravitational Waves and Vice Versa?

Speaker: Andreas Ringwald

asymptotic_safety_workshop_2024_lsw.pdf

3 The cosmological constant problem and the effective potential of a gravity-coupled scalar

Speaker: Roberto Percacci

DESY.pdf

15:15 Coffee

4 Exploring the Majorana Landscape: Planck Safe Models with Majorana Fermions

Speaker: Kai Jürgen Spychala

5 Avoiding quantum gravity-induced chiral symmetry breaking

Speaker: Gabriel Picanco Costa

main.pdf

6 Asymptotic Safety and a CPT-Symmetric Universe

I will present the idea that the big bang is a type of mirror -- in particular a "CPT mirror". I will review the evidence for this idea, its explanatory power, and its predictions. Recently, we have come to think this idea is closely tied to the asymptotic safety idea, and I will present a new result to this effect (in collaboration with Neil Turok and Vatsalya Vaibhav -- to appear soon).

Speaker: Latham Boyle (Higgs Centre for Theoretical Physics, University of Edinburgh)

7 Discussion

Tuesday 17 December

Talks: QFT / CFT

8 A Nonlocal Schwinger Model

Speaker: Christopher Herzog

DESY2024.pdf

9 Emergent Symmetries in 2D Dirac Systems

Speaker: Max Uetrecht (TU Dortmund University)

Emergent_Symmetries_Uetrecht.pdf

10:45 Coffee

10 Dilaton Physics from Asymptotic Freedom

Speaker: Charlie Cresswell-Hogg

dilaton.pdf

11 Quantum critical Dirac semimetals and finite-temperature effects

The chiral Ising-, XY-, and Heisenberg models serve as effective descriptions of Dirac semimetals undergoing a quantum phase transition into a symmetry-broken ordered state. Interestingly, their quantum critical points govern the physical behavior of the system in the vicinity of the transition even at finite temperatures. In this contribution, we explore the chiral models at zero and finite temperature, both in the Dirac phase as well as in the symmetry-broken phases. To that end, we set up a functional renormalization group approach, which allows us to systematically track (1) the phenomenon of pre-condensation, (2) the manifestation of the Mermin-Wagner-Hohenberg theorem due to pseudo-Goldstone fluctuations at finite temperatures, and (3) the quantitative behavior of the system in the quantum critical fan, e.g., by calculating the quasiparticle weight. Our work aims at a more holistic understanding of chiral models near their quantum critical point, including, e.g., the description of non-Dirac-liquid behavior, in analogy to the non-Fermi-liquid behavior in metallic quantum critical points.

Speakers: Mireia Tolosa Simeon (Ruhr-Universität Bochum), Mireia Tolosa Simeón

GNY_finite_T.pdf

Lunch

Talks: Quantum Gravity with and beyond Perturbation Theory

12 Fixed Points of Quantum Gravity from Dimensional Regularisation

We investigate $\beta$-functions of quantum gravity using dimensional regularisation. In contrast to minimal subtraction, a non-minimal renormalisation scheme is employed which is sensitive to power-law divergences from mass terms or dimensionful couplings. By construction, this setup respects global and gauge symmetries, including diffeomorphisms, and allows for systematic extensions to higher loop orders. We exemplify this approach in the context of four-dimensional quantum gravity. By computing one-loop $\beta$-functions, we find a non-trivial fixed point. It shows two real critical exponents and is compatible with Weinberg's asymptotic safety scenario. Moreover, the underlying structure of divergences suggests that gravity becomes, effectively, two-dimensional in the ultraviolet. We discuss the significance of our results as well as further applications and extensions to higher loop orders.

Speaker: Mr Yannick Kluth (University of Manchester)

13 Asymptotic Safety within on-shell perturbation theory

Speaker: Renata Ferrero

DESY_Ferrero.pdf

15:30 Coffee

14 Exploring Asymptotically Safe Quantum Gravity on the lattice

Speaker: Marc Schiffer (Radboud University Nijmegen)

DESY_MS.pdf

15 Substructures of the Weyl group

I will introduce the concept of restricted Weyl invariances and discuss their advantages for matter fields in curved space and their disadvantages for quantum gravity.

Speaker: Riccardo Martini (UniBo and INFN - Bologna)

restrictedW.pdf

16 Discussion

Dinner

Wednesday 18 December

Talks: QFT at finite Temperature

17 A seeded electroweak phase transition

Speaker: Dr Simone Blasi (DESY)

Asymptotic talk.pdf

18 UV complete local field theory of persistent symmetry breaking in 2+1 dimensions

Spontaneous symmetry breaking can persist at all temperatures in certain biconical $\mathrm{O}(N)\times \mathbb{Z}_2$ vector models when the underlying field theories are ultraviolet complete. So far, the existence of such theories has been established in fractional dimensions for local but nonunitary models or in 2+1 dimensions but for nonlocal models. Here, we study local models at zero and finite temperature directly in 2+1 dimensions employing functional methods. At zero temperature, we establish that our approach describes the quantum critical behaviour with high accuracy for all $N\geq 2$. We then exhibit the mechanism of discrete symmetry breaking from $\mathrm{O}(N)\times \mathbb{Z}_2\to \mathrm{O}(N)$ for increasing temperature near the biconical critical point when $N$ is finite but large. We calculate the corresponding finite-temperature phase diagram and further show that the Hohenberg-Mermin-Wagner theorem is fully respected within this approach, i.e., symmetry breaking only occurs in the $\mathbb{Z}_2$ sector. Finally, we determine the critical $N$ above which this phenomenon can be observed to be $N_c \approx 15$.

Speaker: Bilal Hawashin (RUB)

desy_181224.pdf

10:45 Coffee

19 BSMPT v3 A Tool for Phase Transitions and Primordial Gravitational Waves in Extended Higgs Sectors

Strong first-order phase transitions (SFOPT) during the evolution of the Higgs potential in the early universe not only allow for the dynamical generation of the observed matter-antimatter asymmetry, they can also source a stochastic gravitational wave (GW) background possibly detectable with future space-based gravitational waves interferometers. As SFOPTs are phenomenologically incompatible with the Standard Model (SM) Higgs sector, the observation of GWs from SFOPTs provides an exciting interplay between cosmology and particle physics in the search for new physics. With the C++ code BSMPTv3, we present for the first time a tool that performs the whole chain from the particle physics model to the gravitational wave spectrum. Extending the previous versions BSMPTv1 and v2, it traces the phases of beyond-SM (BSM) Higgs potentials and is capable of treating multiple vacuum directions and multi-step phase transitions. During the tracing, it checks for discrete symmetries, flat directions, and electroweak symmetry restoration, and finally reports the transition history. The transition probability from the false to the true vacuum is obtained from the solution of the bounce equation which allows for the calculation of the nucleation, percolation and completion temperatures. The peak amplitude and frequency of the GWs originating from sound waves and turbulence, are evaluated after the calculation of the thermal parameters at the transition temperature, and finally the signal-to-noise ratio at LISA is provided. The code BSMPTv3 is a powerful self-contained tool that comes more than timely and will be of great benefit for investigations of the vacuum structure of the early universe of not only simple but also complicated Higgs potentials involving several vacuum directions, with exciting applications in the search for new physics.

Speakers: João Viana (Faculdade de Ciências da Universidade de Lisboa), João Viana

20 Planck Safe Phase Transitions in a Complex Singlet Model

Speaker: Moritz Bosse (TU Dortmund)

PlanckSafePT.pdf

Lunch

Talks: Quantum Gravity / Scattering

21 Entanglement in flavored scalar scattering

Speaker: Enrico Maria Sessolo

Sessolo_DESY_2024.pdf

22 Multiloop calculations (with MaRTIn)

Speaker: Joachim Brod (University of Cincinnati)

martin.pdf

15:15 Coffee

23 Extended scalar sectors

Speaker: Tania Natalie Robens (Rudjer Boskovic Institute (HR))

trobens_desy1224.pdf

24 Physical running in higher derivative gravity

Running coupling were introduced in quantum filed theory in order to preserve perturbativity in scattering amplitudes, despite the appearance of large logs of external momenta. It is commonly believed that these logarithms are directly related to UV divergencies in one-loop perturbation theory, however this is not completely true in higher derivative theories. On one hand, large logs can emerge also from UV finite loop integrals due to IR effects, on the other hand, some UV divergent diagrams do not depend on external momenta. We define a new set of beta functions for quadratic gravity based on the explicit computation of large logs of momenta and discuss their features concerning the asymptotic UV behavior of the theory. In particular, we observe the existence of a unique trajectory of the perturbative RG leading to asymptotic freedom without presence of tachyons.

Speaker: Diego Buccio (SISSA)

DESY_Buccio.pdf

25 Spectral Functions of Lorentzian Quantum Gravity

Speaker: Gabriel Assant

DESY_Assant.pdf

26 Discussion

Thursday 19 December

Talks: BSM II

27 Vacuum Stability in the Standard Model and Beyond

Speaker: Tom Steudtner

Steudtner.pdf

28 Extraction of top quark mass and strong coupling in experiment

Speaker: Katerina Lipka (Deutsches Elektronen-Synchrotron (DE))

mt_as_otherproblems.pdf

10:45 Coffee

29 TBD

Speaker: Geraldine Servant (Deutsches Elektronen-Synchrotron (DE))

30 Searching for a dark matter induced galactic axion gradient

An ultra-light axion with CP violating interactions with a dark sector and CP preserving interac- tions with the visible sector can act as a novel portal between dark matter and the Standard Model. In such theories, dark matter sources an axion field extending over the entire galaxy, the gradient of which can be searched for with precise spin precession experiments. A reinterpretation of existing co-magnetometer data already constrains theories that are consistent with astrophysical bounds, and near-future experiments will begin probing well-motivated models. The required interactions can arise from a confining hidden sector without necessitating fine-tuning of the axion’s mass.

Speaker: Juri Smirnov

DESY Axions 2024.pdf

31 Discussion and Goodbye

Lunch