<p>We present a calculable toy model of an axion coupled to magnetic monopoles and electric charges, with manifest electric-magnetic duality. Our axion-photon coupling incurs periodic corrections due to monopoles (equivalently UV instantons), which are large for light monopoles. Axion periodicity is manifestly duality invariant since the axion itself transforms under duality. Our model is the original Seiberg-Witten theory, which naturally hosts an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">R</mi></math>-axion and light monopoles. We calculate the axion-photon amplitude in different duality frames and prove its duality invariance.</p>

United States

Csaba Csáki

Israel

Rotem Ovadia

Maximilian Ruhdorfer

Ofri Telem

John Terning

Seiberg-Witten axion

The dilaton, a pseudo-Nambu-Goldstone boson (pNGB) of broken scale invariance, is an appealing ultralight dark matter (DM) candidate. Its mass is protected by conformal invariance and it can be searched for in tabletop experiments. However, contrary to standard pNGBs of internal symmetries, the dilaton generically has a large non-derivative self-coupling, leading to radiative contributions to its mass of the order of its decay constant. Hence typical ultralight dilatons should also have sub-eV decay constants, which would incur significant deviations from standard DM behavior at structure formation times, in severe tension with observations. Therefore, a fine-tuning is required to generate a hierarchy between the mass and the decay constant. In this work, we consider whether supersymmetry (SUSY) can be used to protect this hierarchy from quantum corrections. To ensure an ultralight dilaton mass robust against realistic SUSY-breaking contributions, we must consider a novel dilaton stabilization mechanism. The observed DM abundance can be produced by the misalignment mechanism for dilaton masses ranging from 10 to 1 eV. Unfortunately, irreducible SUSY-breaking corrections due to gravity restrict the couplings between the dilaton and the Standard Model to be extremely small, beyond the reach of any current or proposed experiments. Our work demonstrates that constructing a consistent model of ultralight dilaton DM is quite involved.

Abhishek Banerjee

Michael Geller

Zamir Heller-Algazi

Ameen Ismail

Ultralight Dilatonic Dark Matter

Models which solve the strong CP problem by employing discrete spacetime symmetries generically suffer fine-tuning and quality problems. We demonstrate that these issues are greatly ameliorated when the only source of spontaneous CP breaking is from the chiral condensate of a strongly coupled hidden sector. This is shown explicitly in a model with the SM extended by a vector-like quark family and a complex scalar portal to QCD-like dark sector with $\textit{N}$ families of dark fermions that confines at a high scale. The dark pions of the hidden sector are natural dark matter candidates, with the correct relic abundance obtained via freeze-in. These “confining” Nelson-Barr solutions connect phenomenological questions regarding the strong CP problem to recent developments in the understanding of confining gauge theories, and present ample room for further model building.

Samuel Homiller

South Korea

Taewook Youn

Strong CP from a hidden chiral condensate

We calculate the $\textit{θ}$ dependence in a cousin of QCD, where the vacuum structure can be analyzed exactly. The theory is $$ \mathcal{N} $$ = 2 SU(2) gauge theory with $\textit{N}$ = 0, 1, 2, 3 flavors of fundamentals, explicitly broken to $$ \mathcal{N} $$ = 1 via an adjoint superpotential, and coupled to anomaly mediated supersymmetry breaking (AMSB). The hierarchy $\textit{m}$ ≪ $\textit{μ}$ ≪ Λ ensures the validity of our IR analysis. As expected from ordinary QCD, the vacuum energy is a function of $\textit{θ}$ which undergoes 1st order phase transitions between different vacua where the various dyons condense. For $\textit{N}$ = 0 we find the expected phase transition at $\textit{θ}$ = $\textit{π}$, while for $\textit{N}$ = 1, 2, 3 we find phase transitions at fractional values of $\textit{π}$.

Japan

Teruhiko Kawano

Hitoshi Murayama

Phase transitions at unusual values of $\textit{θ}$

We calculate energy correlators in a general holographic model of confinement, involving an asymptotically anti-de Sitter (AdS) warped extra dimension. Building on a recent computation in a minimal hard-wall model of confinement, we show that the shockwave method for efficiently computing energy correlators in AdS generalizes to an arbitrary warped geometry. This is possible because exact, linear shockwave solutions to the 5D field equations exist in any warped background. We apply our formalism to compute the two-point energy correlator for two simple models of confinement with interesting infrared spectra — one with a gapped continuum spectrum and one with linear Regge trajectories. The results differ from the simple hard-wall model and from each other, demonstrating that the details of the confining dynamics affect the shape of the energy correlator observables.

Steven Ferrante

Holographic energy correlators for soft walls

We propose a model that provides a simultaneous solution to the doublet-triplet splitting problem of grand unified theories, the electroweak hierarchy problem and the strong CP problem. The mechanism is based on the dynamics of two axion-like particles that would crunch the universe at the time of the QCD phase transition if triplets were light or had a VEV or if doublets were heavy or did not have a VEV. The only trace left at low energies are these two axion-like particles. They are weakly coupled to the Standard Model and could be detected at upcoming axion experiments or by a combination of neutron EDM measurements and the astrophysical detection of fuzzy dark matter.

France

Raffaele D’Agnolo

Eric Kuflik

Pablo Sesma

A cosmological solution to the doublet-triplet splitting problem

We examine the phase structure of a QCD-like theory at   <math> <mover> <mi>θ</mi> <mo>¯</mo> </mover> </math>  $$ \overline{\theta} $$  = π obtained from supersymmetric SU(N) QCD perturbed by a small amount of supersymmetry breaking via anomaly mediation (AMSB QCD). The spectrum of this theory matches that of QCD at the massless level, though the superpartners are not decoupled. In this theory it is possible to nail down the phase structure at   <math> <mover> <mi>θ</mi> <mo>¯</mo> </mover> </math>  $$ \overline{\theta} $$  = π as a function of the quark masses and the number of flavors F. For one flavor we find that there is a critical quark mass, below which CP is unbroken, while above the critical mass CP is spontaneously broken. At the critical mass there is a second-order phase transition along with a massless η  ′ . We are able to analytically solve for the minima and the critical mass for N = 2, 3 as well as for the large N limit, while for other N one can find numerical results. For two flavors, we find that CP is always broken as long as the quark masses are equal and non-zero, however there is a non-trivial phase boundary for unequal quark masses, which we find numerically. For F ≥ 3 we obtain an intricate phase boundary which reproduces the various quark mass limits. All our results are in agreement with the predictions of refs. [1–5] for ordinary QCD that were based on anomaly matching arguments for generalized symmetries and the effective chiral Lagrangian. We also briefly comment on the domain wall solutions first discussed by Draper [6], and are able to present analytic results for the simplest case of SU(2) with one flavor.

Spontaneous CP breaking in a QCD-like theory

It is usually assumed that 4$\textit{D}$ instantons can only arise in non-Abelian theories. In this paper we re-examine this conventional wisdom by explicitly constructing instantons in an Abelian gauge theory: $\textit{QED}$ with $\textit{N}$ flavors of Dirac fermions, in the background of a Dirac monopole. This is the low-energy effective field theory for fermions interacting with a ’t Hooft-Polyakov monopole, in the limit where the monopole is infinitely heavy (hence pointlike) and static. This theory, whose non-topological sectors were studied by Rubakov and Callan, has a far richer structure than previously explored. We show how to calculate the topological instanton number, demonstrate the existence of ’t Hooft zero modes localized around such instantons, and show how instantons in the path integral provide the underlying mechanism for the Callan-Rubakov process: monopole-catalyzed baryon decay with a cross section that saturates the unitarity bound. Our computation relies on correctly identifying the relevant 2$\textit{D}$ EFT for monopole catalysis as $\textit{Axial QED}$ in an effective $\textit{AdS}$ metric.

Shimon Yankielowicz

Abelian instantons and monopole scattering

We present a holographic calculation of energy correlators in a simple model of confinement based on a warped extra dimension with an IR brane. For small distances we reproduce the constant correlators of a strongly-coupled conformal field theory, while for large distances the effects of confinement dominate and the correlators decay exponentially. We find exact shockwave solutions to the Einstein equations in the presence of the IR brane, hence avoiding the need for a perturbative expansion in terms of Witten diagrams. While some of the expected qualitative features of energy correlators in quantum chromodynamics (QCD) are reproduced, our crude model of confinement does not capture the effects of asymptotic freedom nor exhibit jetty behavior. We expect that our method can also be applied to more realistic models of confinement incorporating asymptotic freedom, which should fix some of the deviations from QCD.

Holographic energy correlators for confining theories

We study representations of the Poincaré group that have a privileged transformation law along a <math><mi>p</mi></math>-dimensional hyperplane, and uncover their associated spinor-helicity variables in <math><mi>D</mi></math> spacetime dimensions. Our novel representations generalize the recently introduced celestial states and transform as conformal primaries of <math><mi>S</mi><mi>O</mi><mo>(</mo><mi>p</mi><mo>,</mo><mn>1</mn><mo>)</mo></math>, the symmetry group of the <math><mi>p</mi></math>-hyperplane. We will refer to our generalized states as “partially celestial.” Following Wigner’s method, we find the induced representations, including spin degrees of freedom. Defining generalized spinor-helicity variables for every <math><mi>D</mi></math> and <math><mi>p</mi></math>, we are able to construct the little group covariant part of partially celestial amplitudes. Finally, we briefly examine the application of the pairwise little group to partially celestial states with mutually nonlocal charges.