Is there a supernova bound on axions?

• Kfir Blum

Room: 4.50 We present a critical assessment of the SN1987A supernova cooling bound on axions and other light particles. Core-collapse simulations used in the literature to substantiate the bound omitted from the calculation the envelope exterior to the proto-neutron star (PNS). As a result, the only source of neutrinos in these simulations was, by construction, a cooling PNS. We show that if the canonical delayed neutrino mechanism failed to explode SN1987A, and if the pre-collapse star was rotating, then an accretion disk would form that could explain the late-time (t>~5 sec) neutrino events. Such accretion disk would be a natural feature if SN1987A was a collapse-induced thermonuclear explosion. Axions do not cool the disk and do not affect its neutrino output, provided the disk is optically-thin to neutrinos, as it naturally is. These considerations cast doubt on the supernova cooling bound on axions. Based on arXiv:1601.03422, 1811.11178, 1907.05020.

Scale invariance and the Standard Model

• Graham Garland Ross (University of Oxford (GB))

Anomaly free Froggatt-Nielsen models of flavor

• Jure Zupan (University of Cincinnati)

Room: Room 4.50

Axions are blind to anomalies

• Jeremie Quevillon (LPSC, Grenoble (CNRS))

Room: Room 4.50 The axion couplings to SM gauge bosons are derived in various models, and shown to always arise entirely from non-anomalous fermion loops. They are thus independent of the anomaly structure of the model. This fact is without consequence for vector gauge interactions like QCD and QED, but has a major impact for chiral gauge theories. For example, in the DFSZ axion model, the couplings of axions to electroweak gauge bosons do not follow the pattern expected from chiral anomalies, as we prove by an explicit calculation. The reason for this mismatch is traced back to triangle Feynman diagrams sensitive to the anomalous breaking of the vector Ward identity, and is ultimately related to the conservation of baryon and lepton numbers. Though our analyses are entirely done for true axion models, this observation could have important consequences for axion-like particle searches.

Magnetic compactifications

• Emilian Dudas (Ecole Polytechnique)

Room: Room 4.50

Partially Composite Supersymmetry

• Tony Gherghetta (University of Minnesota (US))

Room: Room 4.50

A Realistic U(2) Model of Flavor

• Robert Ziegler (CERN)

Room: Room 4.50 I will discuss a simple U(2) flavor model compatible with an SU(5) GUT structure. All hierarchies in fermion masses and mixings arise from powers of two small parameters that control the U(2) breaking pattern. In contrast to previous U(2) models this setup can be realized without supersymmetry and provides an excellent fit to all SM flavor observables including neutrinos, predicting an upper bound on the neutrino mass scale below current cosmological bounds. A variant of this model is based on a D_6 x U(1)_F flavor symmetry, which closely resembles the U(2) structure, but allows for Majorana neutrino masses from the Weinberg operator. Remarkably, in this case the structure of neutrino masses is closely tied to the quark sector, and one naturally obtains large mixing in the lepton sector from small mixing in the quark sector. Finally the model offers a natural option for adressing the Strong CP Problem and Dark Matter by identifying the Goldstone boson of the U(1)_F factor as the QCD axion.

Supersymmetry, g-2 and gauge coupling unification

• Kazuki Sakurai (University of Warsaw)

Room: Room 4.50

QCD Instanton Processes at Colliders

• Valentin V Khoze (Durham University)

Room: Room 4.50

Inflation and Bouncing Models

• Ido Ben-Dayan

Room: Room 4.50 Stochastic background gravitational waves allows to discern between different paradigms of the Early Universe.I will start with the most conservative scenario of Inflation and show how we can consider different inflationary models as different field redefinitions of a fixed Kahler geometry and a fixed superpotential in supergravity. Nevertheless, Inflation does not resolve the Big Bang singularity. It therefore makes sense to consider alternatives to Inflation. Non-singular bounces, where the scale factor never vanishes are such an alternative. I will then describe how slow contraction with sourced fluctuations allows for a nearly scale invariant tensor and scalar fluctuations that is in principle observable at CMB and LI scales. Finally, in an attempt to construct a valid bounce, I will discuss how a Bounce may be achieved close to the fixed point of Banks-Zaks/Unparticle theory. The talk is based on 1908.07052, 1812.06790, 1604.07899 and work in progress.

Origin of CP and flavor

• Hans Peter Nilles (Univ. Bonn)

Room: Room 4.50

Higgs inflation, unitarity, and emergence of scalaron

• Yohei Ema

Room: Room 4.50 The vanilla Higgs inflation introduces a large non-minimal coupling between the Ricci scalar and Higgs that causes the tree-level unitarity violation well below the Planck scale. After reviewing the unitarity issue of the Higgs inflation during and after inflation, we show that the unitarity can be restored by summing over vacuum polarization-type diagrams. The scattering amplitude develops a pole after the resummation, which we identify as the scalar component of the metric, or the scalaron. It suggests that the Higgs inflation is actually a multi-field inflation model, i.e. Higgs and the scalaron, and does not suffer from the unitarity problem.

Gravitational wave energy budget in strongly supercooled phase transitions

• Marek Lewicki

Room: Room 4.50 We derive efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and find the conditions under which the bubble collisions can contribute significantly to the signal. We illustrate our findings in two examples, the Standard Model with an extra $|H|^6$ interaction and a classically scale-invariant $U(1)_{\rm B-L}$ extension of the Standard Model. The contribution to the GW spectrum from bubble collisions is found to be negligible in the $|H|^6$ model, whereas it can play an important role in parts of the parameter space in the scale-invariant $U(1)_{\rm B-L}$ model. In both cases the sound-wave period is much shorter than a Hubble time, suggesting a significant amplification of the turbulence-sourced signal. We find, however, that the peak of the plasma-sourced spectrum is still produced by sound waves with the slower-falling turbulence contribution becoming important off-peak. We also Investigate another complimentary signal in the form of primordial magnetic fields produced in the transition

Constraints on EFT from neutrino oscillations

• Adam Falkowski (LPT Orsay)

Room: Room 4.50 I will discuss how the existing data from neutrino oscillation experiments can be used to constrain Wilson coefficients of effective field theories (EFTs) extending the Standard Model. I will also clarify the relation between the proper EFT approach and the so-called NSI formalism popular in the neutrino literature.

Tunneling rates from the Minkowski path integral

• Carlos Tamarit (Technische Universität München)

Room: Room 4.50 We present the calculation of the Feynman path integral in real time for tunneling in quantum mechanics and field theory, including the first quantum corrections. For this purpose we use the well-known fact that Euclidean saddle points in terms of real fields can be analytically continued to complex saddles of the action in Minkowski space. We also use Picard-Lefschetz theory in order to determine the middle-dimensional steepest-descent surface in the complex field space, constructed from Lefschetz thimbles, on which the path integral is to be performed. As an alternative to extracting the decay rate from the imaginary part of the ground-state energy of the false vacuum, we use the optical theorem in order to derive it from the real-time amplitude for forward scattering. The latter amplitude is computed from the Minkowski path integral, i.e. evaluating the Gaussian integrals of fluctuations about the relevant complex saddle points. Although the equations for the steepest-descent integration surfaces are not holomorphic, which prevents a straightforward analytic continuation of the Euclidean results, we show how the eigenvalues and eigenfunctions of the fluctuation operators on a thimble can be related to their Euclidean counterparts, and we determine the path-integral measure on thimbles. This way, using real-time methods we recover the one-loop result by Callan and Coleman for the decay rate.

Gauge-protected clockwork and flavourful axions

• Quentin Bonnefoy

Room: Room 4.50 I will discuss the gauge protection of an axion shift-symmetry in two phenomenologically relevant scenarii: axions with a clockwork profile and flaxions/axiflavons arising in Froggatt-Nielsen models. I will mostly focus on the comparison between the original globally-symmetric models and their embeddings in gauged models.

Electroweak baryogenesis at colliders

• Mikael Chala (IPPP Durham)

Room: Room 4.50 Motivated by (but not restricted to) models of composite Higgs, I will discuss electroweak baryogenesis in different extensions of the Higgs sector. In particular, I will focus on smoking gun signatures that -surprisingly- have not yet been studied at colliders. I will also stress the complementarity with gravitational wave experiments.

Baryogenesis from Inflation with Chern-Simons Term

• Kyohei Mukaida (DESY)

Room: Room 4.50 The coupling of an inflaton to the Standard Model particle content through a Chern-Simons term generically sources a dual production of massless helical gauge fields and chiral fermions. We demonstrate that the interplay of these two components results in a highly predictive baryogenesis model, which requires no further ingredients beyond the Standard Model. If the helicity stored in the hyper magnetic field and the effective chemical potential induced by the chiral fermion production are large enough to avoid magnetic diffusion from the thermal plasma but small enough to sufficiently delay the chiral plasma instability then the non-vanishing helicity survives until the electroweak phase transition and sources a net baryon asymmetry which is in excellent agreement with the observed value. If any of these two conditions is violated the final baryon asymmetry vanishes. The observed baryon asymmetry can be reproduced if the energy scale of inflation is around Hinf∼10^10 - 10^12 GeV with a moderate dependence on inflation model parameters.