LIO International Conference 2025 on "New Approaches to Naturalness"

May 20, 2025, 1:30 PM → May 23, 2025, 6:00 PM Europe/Paris

Dirac/RdC-Amphithéâtre (IP2I)

Aldo Deandrea (IP2I - Université Lyon 1), Florian NORTIER (chair) (CNRS/IN2P3 - IP2I Lyon), Nazila Mahmoudi (Lyon University), Luc Darmé (IP2I - Université Lyon 1)

The aim of this workshop is to bring together theorists working on emerging ideas to tackle naturalness issues in theories of the fundamental interactions. Various approaches will be discussed and confronted. The program includes the historical topics related to naturalness:

• Electroweak Hierarchy,
• Flavor Puzzle,
• Strong CP Problem,
• Dark Energy & Inflation.

 

Participation in the conference (max 50 participants) and talks are only on invitation. There is no registration fee.

Important Notice: Conference Housing Information

The conference is not affiliated with any third-party agencies offering housing or accommodation services. We strongly advise participants to ignore any e-mail from third parties claiming to represent the conference.

Tue, May 20

1:30 PM → 1:55 PM Registration

1:55 PM → 2:05 PM Welcome Words

Speaker: Dr Florian NORTIER (CNRS/IN2P3 - IP2I Lyon)

welcome.pdf

2:05 PM → 4:00 PM Gravity, Forms & Generalized Symmetries

Convener: Dr Florian NORTIER (CNRS/IN2P3 - IP2I Lyon)

2:05 PM Physics of θ-vacua in Standard Model and Gravity

Speaker: Gia Dvali

talk_Gia_LYON_05_25.pdf

3:00 PM New insights from the θ-vacua of the Standard Model

Speaker: Otari Sakhelashvili

talk_Otari.pdf

3:30 PM Naturalness and Generalized Symmetries

Speaker: Seth Koren

KorenLyonTalkExpanded.pdf

4:00 PM → 4:30 PM Coffee Break

4:30 PM → 5:25 PM Wild Card: 1

Convener: Aldo Deandrea (IP2I - Université Lyon 1)

4:30 PM The Experimental Way

Speaker: Raffaele DAgnolo

dagnolo_Lyon.pdf

5:25 PM → 6:50 PM Cosmological Selection of Vacuum

Convener: Aldo Deandrea (IP2I - Université Lyon 1)

5:25 PM A cosmological solution to the doublet-triplet splitting problem

Speaker: Pablo Sesma (IPhT Saclay)

LIO - Pablo SESMA.pdf

5:55 PM The Relaxion: An update

In this talk, I re-visit the original relaxion model by Graham-Kaplan-Rajendran in the regime where the relaxion is subject to large fluctuations during its dynamics. I discuss the modified stopping conditions for such dynamics of the relaxion and the new parameter space. Interestingly, in a significant region of the parameter space, the relaxion can naturally account for the observed dark matter density in the universe.

Speaker: Geraldine Servant (CERN)

Lyon-Naturalness-2025-SERVANT.pdf

Wed, May 21

9:00 AM → 10:00 AM Cosmological Selection of Vacuum

Convener: Dr Giacomo Cacciapaglia (LPTHE)

9:00 AM A Critical Look at the Higgs

Self-organised criticality, realised through cosmological dynamics in the early universe, is an alternative paradigm for addressing the electroweak hierarchy problem. In this scenario, an unnaturally light Higgs boson is the result of dynamics driving the electroweak vacuum towards a near-critical metastable point where the Higgs mass is bounded from above by the vacuum instability scale. To lower the vacuum instability scale close to the weak scale, previous realisations of this mechanism introduced new vector-like fermions coupled to the Higgs. Here we show that an Axion-Like Particle (ALP) coupling to the Higgs is an alternative possibility for achieving criticality with another well-motivated and naturally light candidate for new physics, thus leading to an entirely different set of testable phenomenological signatures. Our Axion-Higgs criticality model predicts an ALP in the MeV to O(10) GeV range. The entire natural region of parameter space can be thoroughly explored by a combination of future colliders, flavour experiments, and cosmological observatories.

Speaker: Maximilian Detering (King's College London)

ACriticalLookAtTheHiggs-Lyon.pdf

9:30 AM A Multiverse Outside of the Swampland

Speaker: Gabriele Rigo (IPhT, Saclay)

Presentation.pdf

10:00 AM → 10:30 AM Coffee Break

10:30 AM → 11:00 AM Cosmological Selection of Vacuum

Convener: Dr Giacomo Cacciapaglia (LPTHE)

10:30 AM The Higgs mass metastability bound

Speaker: Thomas Steingasser

Slides-Thomas.pdf

11:00 AM → 11:30 AM Flavor Puzzle

Convener: Dr Giacomo Cacciapaglia (LPTHE)

11:00 AM Infrared Neutrino Mass Models and how to test them

Speaker: Manuel Ettengruber

ManuelEttengruberSlides.pdf

11:30 AM → 12:25 PM Wild Card: 2

Convener: Dr Giacomo Cacciapaglia (LPTHE)

11:30 AM Hierarchy Problem Redux

After discussing some history of the hierarchy problem, I recast the hierarchy problem as a legitimate paradox. The premises and reasoning of the paradox are explained. I discuss how each premise has been attacked and what ideas are still standing and which directions are perhaps less interesting today after a generation of experimental and theoretical work.

Speaker: James Wells (University of Michigan)

Wells_Lyon_May2025.pdf

12:25 PM → 2:15 PM Lunch Break

2:15 PM → 4:05 PM Flavor Puzzle

Convener: Farvah Mahmoudi (Lyon University)

2:15 PM The gauge dual Standard Model: A new approach to naturalness and the flavour puzzle

Speaker: Dr Giacomo Cacciapaglia (LPTHE)

Cacciapaglia_LIO.pdf

3:10 PM Modular Symmetries for Flavour Physics

Speaker: Stephen F. King

Lyon King 25.pdf

4:05 PM → 4:15 PM Group Picture

4:15 PM → 4:45 PM Coffee Break

4:45 PM → 5:40 PM Flavor Puzzle

Convener: Farvah Mahmoudi (Lyon University)

4:45 PM Flavor Deconstruction

Speaker: Prof. Gino Isidori (University of Zurich)

Lyon.pdf

5:40 PM → 7:00 PM Free Time/Discussions

8:15 PM → 11:00 PM Conference Dinner

Thu, May 22

9:00 AM → 10:00 AM Fixed Point & Compositeness

Convener: Enrico Maria Sessolo (National Centre for Nuclear Research, Warsaw)

9:00 AM Phase of Chiral Gauge Theories

We study the IR fate of Chiral Gauge Theories through functional methods and the Effective Average Action. Our results show a rich structure, from the existence of IR conformality to new patterns of Chiral Symmetry Breaking.

Speaker: Shahram Vatani (CP3 UCLouvain)

Vatani_LIO.pdf

9:30 AM Revisiting Quantum Criticality and Naturalness with the Standard Model

Speaker: Juan Pablo Garcés Varas

Slides Juan.pdf

10:00 AM → 10:30 AM Coffee Break

10:30 AM → 12:25 PM Fixed Point & Compositeness

Convener: Enrico Maria Sessolo (National Centre for Nuclear Research, Warsaw)

10:30 AM Holographic analysis of near-conformal dynamics and light dilaton

We carry out a detailed analysis of the region slightly outside the conformal window of a non-trivial infrared fixed point in a generic bottom-up holographic setup. We focus on models, which study the dynamics of a scalar field, dual to quark degrees of freedom, in a (nearly) AdS geometry. Such models realize the picture expected for vector-like near-conformal theories from Dyson-Schwinger analysis. The analysis covers a toy model, which allows for analytic solutions, and a more general setup as well, which encompass a complete model for the ultraviolet physics. We analyze the conditions for the appearance of a parametrically light scalar state in the spectrum, which can act as a candidate for the Pseudo-Nambu-Goldstone boson arising from breaking of the approximate conformal symmetry. We also present detailed results for the vacuum structure, correlators, and Ward identities in the near-conformal regime.

Based on: https://arxiv.org/abs/2504.18623

Speaker: Deog Ki Hong

Hong.pdf

11:25 AM Conjugate Fermions - Restoring Naturalness to Composite Higgs Models

Speaker: Maya Hager

PresentationNaturalness2025_Hager.pdf

11:55 AM Composite Hybrid Inflation

I will describe a model of hybrid inflation coming from a general composite theory. Starting from an effective chiral Lagrangian with a dilaton and pions, we identify inflation occurring during the walking dynamics of the theory. A Z2 symmetry-breaking term in the pion sector induces a shift in the inflaton’s trajectory, which leads to a tachyonic instability phase. Curvature perturbations grow exponentially, producing copious primordial black holes and a stochastic gravitational wave background. We show that the primordial black hole mass and the gravitational wave frequency is strongly restricted by the anomalous dimension values, with larger anomalous dimensions giving lighter primordial black holes, and higher frequency gravitational waves. Future gravitational wave observatories are within the reach of probing associated signatures.

Speaker: Wanda Isnard (IP2I Lyon)

Talk_Composite_Inflation_May_2025.pdf

12:25 PM → 2:15 PM Lunch Break

2:15 PM → 3:10 PM Fixed Point & Compositeness

Convener: James Wells (University of Michigan)

2:15 PM Naturally small couplings from RG fixed points

Speaker: Kamila Kowalska

2025.05.22_Kowalska.pdf

3:10 PM → 3:40 PM ALPs, pNGBs & Accidents

Convener: James Wells (University of Michigan)

3:10 PM Custodial Naturalness: Electroweak hierarchy from conformal and custodial symmetry

Speaker: Andreas Trautner (Max-Planck-Institut fuer Kernphysik Heidelberg)

Custodial_Naturalness_Lyon_25_Trautner.pdf

3:40 PM → 4:10 PM Coffee Break

4:10 PM → 6:00 PM ALPs, pNGBs & Accidents

Convener: James Wells (University of Michigan)

4:10 PM Magnetic Compactifications

Speaker: Emilian Dudas (Ecole Polytechnique)

Slides_Emilian.pdf

5:05 PM Exploring the Boundaries of Naturalness

Speaker: Matthew McCullough (CERN)

Lyon.pdf

6:00 PM → 7:00 PM Free Time/Discussions

Fri, May 23

9:00 AM → 9:55 AM ALPs, pNGBs & Accidents

Convener: Luc Darmé (IP2I - Université Lyon 1)

9:00 AM Accelerated Cosmic Expansion, Mass Creation, and the QCD Axion

Speaker: Enrico Nardi (INFN Roma Italy & Universidad de Antioquia, Medellin Colombia)

Nardi_LIO2025.pdf

9:55 AM → 10:25 AM Coffee Break

10:25 AM → 11:50 AM ALPs, pNGBs & Accidents

Convener: Luc Darmé (IP2I - Université Lyon 1)

10:25 AM pNGB Higgs Naturalness at a Tipping Point

For pNGB-based approaches, the phenomenological question of Higgs naturalness finds itself at a tipping point between direct searches and precision. As we look ahead to the HL-LHC era and beyond, a scenario in which all measurements remain Standard Model-like would only sharpen the naturalness tension, driven increasingly by precision constraints. To illustrate this from a fresh perspective, we construct a maximally natural model, throwing into the mix three approaches to symmetry-based naturalness: Supersymmetry, Twin Higgs, and Gegenbauer-like pNGB Higgs models. We use the 'Kitchen Sink' model to discuss the interplay between direct exploration and precision, and the implications for FCC-ee and FCC-hh.

Speaker: Adriana Guerrero Menkara

kitchensink_Adriana.pdf

10:55 AM Accidentally light scalars

Speaker: Felix Bruemmer (LUPM Montpellier)

ly25.pdf

11:50 AM → 1:50 PM Lunch Break

1:50 PM → 3:40 PM UV/IR Mixing

Convener: Dr Florian NORTIER (CNRS/IN2P3 - IP2I Lyon)

1:50 PM Swampland & Naturalness Problems

Speaker: Irene Valenzuela (IFT UAM-CSIC Madrid)

talk_irene_valenzuela.pdf

2:45 PM UV/IR Mixing and Naturalness

Speaker: Steven Abel (IPPP)

UVIR 2024:25 Lyon.pdf

3:40 PM → 3:45 PM Last Words

Speaker: Dr Florian NORTIER (CNRS/IN2P3 - IP2I Lyon)

Last_words.pdf

3:45 PM → 4:15 PM Coffee Break

4:15 PM → 6:00 PM Free Time/Discussions