### Workshop

#### Axions across boundaries between Particle Physics, Astrophysics, Cosmology and forefront Detection Technologies

**Apr 26, 2023 - Jun 09, 2023**

**Abstract**

The purpose of this workshop is to bring together scientists with different backgrounds and expertise to discuss open problems, recent developments and future directions in axion physics, a field that is notoriously replete with interdisciplinary connections. The aim is to foster a fruitful cross breeding between different theoretical areas, with a focus on certain open issues in axion particle physics, astrophysics and cosmology. Quantitative assessments of the axion contribution to Cold Dark Matter (CDM) involve top-notch lattice simulations of non- perturbative QCD effects, as well as of the cosmic evolution of axionic topological defects. Astrophysical observations provide strong bounds on axion properties because stellar evolution would be affected by the existence of axions and, intriguingly, some excesses in star energy losses have been reported. Cosmological scenarios in which the PQ symmetry is broken before inflation foresee axions imprints in the CMB, while in post-inflationary scenarios axion miniclusters, with overdensities several orders of magnitude larger than the local density of CDM, are expected to form, and a reliable assessment of their properties is of utmost importance. From the experimental side, a blossoming of potentially game-changing ideas, with an exciting crossover from experimental particle physics to materials science and cutting-edge technologies is inspiring new methods for axion searches. Novel techniques have been put forth that, besides exploiting the axion- photon coupling, aim to reveal axions via their couplings to nucleons and electrons. The interaction between the experimental and theoretical communities will foster the merging of `how to search’ with `where to search’ into optimized strategies to hunt for the axion.

**Topics**

* Training week (1st week: April 26

^{(*)}- 28)

* Axion astrophysics (2nd & 3rd weeks: May 2

^{(*)}- 12)

* Axion cosmology (3rd & 4th weeks: May 8 -19)

* Axions in particle physics (4th & 5th weeks: May 15 - 26)

* Axion experiments (5th & 6th weeks: May 22 - June 1

^{(*)})

* Conference week (7th week: June 5 - 9)

^{(*)}

*Note that April 25th, May 1st and June 2nd are days of holidays in Italy*

##### A preliminary list of participants per week is available here

**Organizers**

Gianpaolo Carosi (LLNL, carosi2@llnl.gov)

Kiwoon Choi (IBS, Daejeon, CTPU, kchoi@ibs.re.kr)

Luca Di Luzio (University of Padua and INFN - Padua, luca.diluzio@unipd.it)

Babette Döbrich (CERN, babette.dobrich@cern.ch)

Inma Domínguez (University of Granada, inma@ugr.es)

Maurizio Giannotti (Barry University, MGiannotti@barry.edu)

Igor Garcia Irastorza (University of Zaragoza, igor.irastorza@cern.ch)

Enrico Nardi (INFN - LNF, enrico.nardi@lnf.infn.it)

Andreas Ringwald (DESY, andreas.ringwald@desy.de)

Pierre Sikivie (University of Florida, sikivie@phys.ufl.edu)

Julia Vogel (LLNL & University of Zaragoza, Julia.Vogel@cern.ch)

**Local organizer**

Enrico Nardi (INFN - LNF)

**Contact**

enrico.nardi@lnf.infn.it

**Related events**

Axions across boundaries between Particle Physics, Astrophysics, Cosmology and forefront Detection Technologies (Training Week) - Apr 26, 2023

Axions across boundaries between Particle Physics, Astrophysics, Cosmology and forefront Detection Technologies (Conference) - Jun 05, 2023

**Talks**

Date | Speaker | Title | Type | Useful Links | ||||
---|---|---|---|---|---|---|---|---|

May 02, 2023 - 14:00-14:30 | Participants two minutes self presentation |
Introduction | ||||||

May 02, 2023 - 14:30-15:30 | Canceled | Seminar | ||||||

May 03, 2023 - 14:00-15:00 | Oscar Straniero |
Overview of axion astrophysics and perspectives from future astronomical probes | Seminar | Slides | Video | |||

May 04, 2023 - 11:00-12:00 | Jihn E. Kim |
Axions: a short historical review. Recent results on quintessential axions from a new confining force as source of Dark Energy | Seminar | Slides | ||||

May 04, 2023 - 14:00-15:00 | Giuseppe Lucente & Pierluca Carenza |
Progress on axions from supernovae. New production mechanism and prospects for detection | Seminar | Slides | Video | |||

May 05, 2023 - 14:00-15:00 | Javier Redondo & Giovanni Pierobon |
Axions in Cosmology | Seminar | Video | ||||

May 08, 2023 - 14:00-14:30 | Participants two minutes self presentation |
Introduction | ||||||

May 08, 2023 - 14:30-15:30 | Michael Dine |
Overview on axions: open problems and future directions | Seminar | Slides | Video | |||

May 09, 2023 - 14:00-15:00 | Edward Hardy |
Axion contribution from topological strings | Seminar | Video | ||||

May 10, 2023 - 11:00-12:00 | Kiwoon Choi |
Discussion on hep-th/2001.07152 "Consequences of the order of the limit of infinite spacetime volume and the sum over topological sectors..." | Discussion | Video | ||||

May 10, 2023 - 14:00-15:00 | Maurizio Giannotti & Sang Hui Im |
Axion physics with running axion couplings | Seminar | Slides | Video | |||

May 11, 2023 - 14:00-15:00 | Andreas Ringwald |
Electromagnetic Couplings of the Axion | Seminar | Slides | Video | |||

May 12, 2023 - 11:30-12:30 | GGI Seminar Series:Benoit Laurent (McGill U., Montréal, Canada) |
Model-indipendent bubble wall velocities in local thermal equilibrium |
Seminar |
Abstract
Determining the bubble wall velocity during a first-order phase transition is of great importance to accurately predict the resulting gravitational wave signals and matter-antimatter asymmetry. In this talk, I will explain how this calculation can be significantly simplified when local thermal equilibrium (LTE) is maintained in the plasma. Using this LTE assumption, I will show that the scalar fields' equations of motion can be replaced by a new matching condition which can be interpreted as the conservation of entropy. The resulting system of equations can be expressed in terms of only four parameters that completely characterize a particle physics model. I will present an efficient algorithm to solve these equations and discuss the properties of their solutions. Even when the LTE assumption is badly violated, these solutions can still be helpful as they provide an upper bound on the wall velocity. Finally, I will compute the kinetic energy fraction which is essential for predicting the gravitational wave spectrum produced during the phase transition. |
Video | |||

May 12, 2023 - 14:00-15:00 | Malte Buschmann & Joshua Foster |
Overview of axions and Neutron Stars | Seminar | Video | ||||

May 15, 2023 - 12:00-12:40 | Marco Gorghetto |
Formation of Ultralight Dark Matter Solar Halos | Talk |
Abstract
As yet undiscovered light bosons may constitute all or part of the dark matter (DM) of our Universe, and are expected to have (weak) self-interactions. We show that quartic self-interactions generically induce the capture of dark matter from the surrounding halo by external gravitational potentials such as those of stars, including the Sun. This leads to the subsequent formation of dark matter bound states supported by such external potentials, resembling gravitational atoms (e.g. a solar halo around our own Sun). Their growth is governed by the ratio ξfoc = λdB/R⋆ between the de Broglie wavelength of the incoming DM waves, λdB, and the radius of the ground state R⋆. For ξfoc ≲ 1, the gravitational atom grows to a steady state that balances the capture of particles and the inverse, stripping, process. For ξfoc ≳ 1, a significant gravitational-focusing effect leads to exponential accumulation of mass from the galactic DM halo into the atom. For instance, a dark matter axion with mass of the order of 10^{−14} eV and decay constant between 10^7 and 10^8 GeV would lead to formation of a dense halo, with local DM density at the position of the Earth O(10^4) times larger than that predicted by the standard halo model. For attractive self-interactions, after the formation, the gravitational atom is destabilized at a large density, leading to collapse accompanied by emission of relativistic bosons (‘Bosenova’) on a timescale that can be comparable to the lifetime of the Solar System. |
Slides | |||

May 15, 2023 - 14:00-14:30 | Participants two minutes self presentation |
Introduction | ||||||

May 15, 2023 - 14:30-15:30 | Gia Dvali |
Strong CP and axions in the dual formulation | Seminar | Video | ||||

May 16, 2023 - 14:00-15:00 | Giovanni Villadoro |
Thermal axion production in the Early Universe | Seminar | Slides | Bonus material | Video | ||

May 17, 2023 - 11:00-12:00 | Gia Dvali |
One more discussion on hep-th/2001.07152 "Consequences of the order of the limit of infinite spacetime volume and the sum over topological sectors..." | Discussion | Video | ||||

May 17, 2023 - 14:00-15:00 | Robert Ziegler |
Axions and flavour | Seminar | Slides | ||||

May 18, 2023 - 14:00-15:00 | Wei Xue |
Boson stars | Seminar | Video | ||||

May 19, 2023 - 12:00-12:40 | Philip Soerensen |
Axion Kinetic Misalignment - What is it, what does it do, and how do you get it? | Talk |
Abstract
Axion kinetic misalignment is a mechanism that may enhance the dark matter relic found in models of QCD axions or axion-like-particles by considering initial conditions with large kinetic energy. This is interesting because it motivates axion dark matter at lower decay constants where the couplings to matter, incl. detectors, are stronger. As my contribution to this wonderful workshop, I will here give an introduction to this mechanism. I will discuss some of the phenomenology that arises from kinetic misalignment and I will also briefly discuss my recent work on how the mechanism can be realized. |
Video | |||

May 19, 2023 - 14:00-15:00 | Nicholas Rodd |
The axion background | Seminar | Slides | Video | |||

May 22, 2023 - 14:00-14:30 | Participants two minutes self presentation |
Introduction | ||||||

May 22, 2023 - 14:30-15:30 | Elisa Todarello |
The Echo Method for Axion Dark Matter Detection | Seminar | Slides | Video | |||

May 23, 2023 - 12:00-12:40 | Mario Reig Lopez |
Axion couplings in Grand Unified Theories | Talk |
Abstract
In this talk (based on 2206.07053) I discuss axion couplings to gauge bosons in Grand Unified Theories, where the Standard Model is embedded in a simple 4D gauge group. The topological nature of these couplings allows them to be matched from the UV to the IR, and the ratio of the anomaly with photons and gluons for any axion is fixed by unification. I will show that this implies that there is a single axion, the QCD axion, with an anomalous coupling to photons. Other light axion-like particles can couple to photons by mixing through the QCD axion portal and lie to the right of the QCD line prediction in the mass-coupling plane. Axions which break the unification relation between gluon and photon couplings are necessarily charged under the GUT gauge group and become heavy from perturbative mass contributions. As a result, a discovery of an axion to the left of the QCD line can rule out simple Grand Unified Theories. |
Slides | Video | ||

May 23, 2023 - 14:00-15:00 | Zurab Berezhiani |
Axions and where to find them.... New elements for the identikit | Seminar | Video | ||||

May 24, 2023 - 12:00-12:40 | Pablo Quilez |
Multiple QCD axions | Talk |
Abstract
How many QCD axions can there be? Can the standard ma-fa relation be modified without extra sources of PQ breaking? We will study in detail the possible masses and couplings to the nEDM of a multiple axion system. A novel sum rule linking multiple axion signals will be obtained and rigorously proved solely as a consequence of the PQ symmetry. |
Slides | Video | ||

May 24, 2023 - 14:00-15:00 | Pierre Sikivie |
How observations may tell axions and WIMPs apart | Seminar | Video | ||||

May 25, 2023 - 14:00-15:00 | Hyungjin Kim |
Wave dark matter | Seminar | Slides | Video | |||

May 26, 2023 - 12:00-12:40 | Nick Houston |
Nuclear decay anomalies as a signature of axion dark matter | Talk |
Abstract
A number of nuclear decay anomalies have been reported in the literature, which purport to show periodic variations in the decay rates of certain radioisotopes. If these reports reflect reality, they would necessitate a seismic shift in our understanding of fundamental physics. We provide the first mechanism to explain these findings, via the misalignment mechanism of QCD axion dark matter, wherein oscillations of the effective theta angle induce periodic variation in nuclear binding energies and hence decay rates. Expecting this effect to be most pronounced in low-Q systems, we analyse 12 years of tritium decay data (Q ≃ 18.6 keV) taken at the European Commission’s Joint Research Centre. Finding no statistically significant excess, we then place novel constraints on the corresponding axion parameter space. |
Slides | Video | ||

May 26, 2023 - 14:00-15:00 | Junwu Huang |
Topological defects of light bosons | Seminar | Video | ||||

May 29, 2023 - 12:00-12:40 | Rustam Balafendiev |
Wire Metamaterials for Axion Search: ALPHA | Talk |
Abstract
Wire metamaterials have long been a subject of scientific inquiry due to their properties as artificial plasma materials. With the plasma frequency exclusively determined by the geometrical parameters of period and radius, a number of applications have been proposed in a large range of frequencies spanning from hundreds MHz to THz. Recently, wire metamaterials have found a new application in the proposed detectors of axion dark matter. Thanks to their plasma-like behavior when operating near plasma frequency wire metamaterials can be used as a low-loss ENZ materials, allowing for construction of large microwave cavities with a fundamental frequency on the order of tens of GHz. In this talk I will give a short introduction to wire metamaterials and ALPHA collaboration’s aim of implementing them in plasma haloscopes. |
Slides | Video | ||

May 29, 2023 - 14:00-14:30 | Participants two minutes self presentation |
Introduction | ||||||

May 29, 2023 - 14:30-15:30 | Gianpaolo Carosi |
Overview of experimental searches for Axion Dark Matter | Seminar | Slides | Video | |||

May 30, 2023 - 12:00-12:40 | Katherine Fraser |
Axion Mass from Magnetic Monopole Loops | Talk |
Abstract
We show that axions interacting with abelian gauge fields obtain a potential from loops of magnetic monopoles. This is a consequence of the Witten effect: the axion field causes the monopoles to acquire an electric charge and alters their energy spectrum. The axion potential can also be understood as a type of instanton effect due to a Euclidean monopole worldline winding around its dyon collective coordinate. We calculate this effect, which has features in common with both nonabelian instantons and Euclidean brane instantons. To provide consistency checks, we argue that this axion potential vanishes in the presence of a massless charged fermion and that it is robust against the presence of higher-derivative corrections in the effective Lagrangian. Finally, as a first step toward connecting with particle phenomenology and cosmology, we discuss the regime in which this potential is important in determining the dark matter relic abundance in a hidden sector containing an abelian gauge group, monopoles, and axions. |
Slides | |||

May 30, 2023 - 14:00-15:00 | Esther Ferrer-Ribas |
Detector development for solar axion searches | Seminar | Slides | Video | |||

May 31, 2023 - 14:00-15:00 | Andrew Geraci |
Status of the ARIADNE experiment and its challenges | Seminar | Slides | ||||

Jun 01, 2023 - 12:00-12:40 | Cristina Margalejo Blasco |
Data taking and analysis with the IAXO pathfinder system | Talk | Slides | ||||

Jun 01, 2023 - 14:00-15:00 | Amalia Madden |
The Piezoaxionic Effect | Seminar |
Abstract
In this talk I will demonstrate how the spontaneous violation of parity within piezoelectric materials can induce several new experimental observables for the QCD axion via their fundamental coupling to gluons. The first effect, termed "the piezoaxionic effect", involves the generation of an oscillating mechanical stress within a piezoelectric crystal due to the presence of QCD axion dark matter. Our proposed experimental setup could probe this effect for axion masses between 10^-11 eV and 10^-7 eV. The second effect, termed "the ferroaxionic effect", involves a QCD axion-mediated force that can be sourced by a piezoelectric crystal. This force can be detected via nuclear magnetic resonance and has sensitivity to axion masses between 10^-5 eV and 10^-2 eV. Together, these new observables could be used in the near future to probe two challenging mass ranges for most axion detection concepts. |
Slides |