Explore the vast range of titles available.

Abstract Estimating the contribution from axial-vector intermediate states to hadronic light-by-light scattering requires input on their transition form factors (TFFs). Due to the Landau–Yang theorem, any experiment sensitive to these TFFs needs to involve at least one virtual photon, which complicates their measurement. Phenomenologically, the situation is best for the f 1(1285) resonance, for which information is available from e + e − → e + e − f 1, f 1 → 4π, f 1 → ργ, f 1 → ϕγ, and f 1 → e + e − . We provide a comprehensive analysis of the f 1 TFFs in the framework of vector meson dominance, including short-distance constraints, to determine to which extent the three independent TFFs can be constrained from the available experimental input — a prerequisite for improved calculations of the axial-vector contribution to hadronic light-by-light scattering. In particular, we focus on the process f 1 → e + e − , evidence for which has been reported recently by SND for the first time, and discuss the impact that future improved measurements will have on the determination of the f 1 TFFs.

There are two distinct regimes of Yang-Mills theory where we can demonstrate confinement, the existence of a mass gap, and the multi-branch structure of the effective potential as a function of the theta angle using a reliable semi-classical calculation. The two regimes are deformed Yang-Mills theory on ℝ3 × S1, and Yang-Mills theory on ℝ2 × T2 where the torus is threaded by a ’t Hooft flux. The weak coupling regime is ensured by the small size of the circle or torus. In the first case the confinement mechanism is related to self-dual monopoles, whereas in the second case self-dual center-vortices play a crucial role. These two topological objects are distinct. In particular, they have different mutual statistics with Wilson loops. On the other hand, they carry the same topological charge and action. We consider the theory on ℝ × T2 × S1 and extrapolate both the monopole and vortex regimes to a quantum mechanical domain, where a cross-over takes place. Both sides of the cross-over are described by a deformed ℤN TQFT. On ℝ2 × S1 × S1, we derive an effective field theory (EFT) of vortices from the EFT of monopoles in the presence of a ’t Hooft flux. This construction is based on a two-stage Higgs mechanism, reducing SU(N) to U(1)N−1 in 3d first, followed by reduction to a ℤN EFT in 2d in the second step. This result shows how monopoles transmute into center-vortices, and suggests adiabatic continuity between the two confinement mechanisms. The basic mechanism is flux fractionalization: the magnetic flux of the monopoles splits up and is collimated in such a way that 2d Wilson loops detect it as a center vortex.

We consider the effects of a non-vanishing strange-quark mass in the determination of the full basis of dimension six matrix elements for Bs mixing, in particular we get for the ratio of the V − A Bag parameter in the Bs and Bd system: B¯Q1s/B¯Q1d=0.987−0.009+0.007\\[ {\\overline{B}}_{Q_1}^s/{\\overline{B}}_{Q_1}^d={0.987}_{-0.009}^{+0.007} \\]. Combining these results with the most recent lattice values for the ratio of decay constants fBs/fBd\\[ {f}_{B_s}/{f}_{B_d} \\] we obtain the most precise determination of the ratio ξ=fBsB¯Q1s/fBdB¯Q1d=1.2014−0.0072+0.0065\\[ \\xi ={f}_{B_s}\\sqrt{{\\overline{B}}_{Q_1}^s}/{f}_{B_d}\\sqrt{{\\overline{B}}_{Q_1}^d}={1.2014}_{-0.0072}^{+0.0065} \\] in agreement with recent lattice determinations. We find ΔMs = (18.5− 1.5+ 1.2)ps− 1 and ΔMd = (0.547− 0.046+ 0.035)ps− 1 to be consistent with experiments at below one sigma. Assuming the validity of the SM, our calculation can be used to directly determine the ratio of CKM elements |Vtd/Vts| = 0.2045− 0.0013+ 0.0012, which is compatible with the results from the CKM fitting groups, but again more precise.

Abstract M-theory on local G 2-manifolds engineers 4d minimally supersymmetric gauge theories. We consider ALE-fibered G 2-manifolds and study the 4d physics from the view point of a partially twisted 7d supersymmetric Yang-Mills theory and its Higgs bundle. Euclidean M2-brane instantons descend to non-perturbative effects of the 7d supersymmetric Yang-Mills theory, which are found to be in one to one correspondence with the instantons of a colored supersymmetric quantum mechanics. We compute the contributions of M2-brane instantons to the 4d superpotential in the effective 7d description via localization in the colored quantum mechanics. Further we consider non-split Higgs bundles and analyze their 4d spectrum.

A bstract In earlier work with N. Seiberg, we explored connections between monopole operators, the Coulomb branch modulus, and vortices for 3d, N =2 supersymmetric, U(1) k Chern-Simons matter theories. We here extend the monopole / vortex matching analysis, to theories with general matter electric charges. We verify, for general matter content, that the spin and other quantum numbers of the chiral monopole operators match those of corresponding BPS vortex states, at the top and bottom of the tower associated with quantizing the vortices’ Fermion zero modes. There are associated subtleties from non-normalizable Fermi zero modes, which contribute non-trivially to the BPS vortex spectrum and monopole operator matching; a proposed interpretation is further discussed here.

Abstract We propose bulk 3D N $$ \\mathcal{N} $$ = 4 rank-0 superconformal field theories, which are related to 2D N $$ \\mathcal{N} $$ = 1 supersymmetric minimal models, SM (2, ·) and SM (3, ·), via recently discovered non-unitary bulk-boundary correspondence. The correspondence relates a 3D N $$ \\mathcal{N} $$ = 4 rank-0 superconformal field theory to 2D chiral rational conformal field theories. A topologically twisted theory of the rank-0 SCFT supports the rational chiral algebra at the boundary upon a proper choice of boundary condition. We test the proposal by checking several non-trivial dictionaries of the correspondence.

A bstract We address the contribution of the 3 π channel to hadronic vacuum polarization (HVP) using a dispersive representation of the e + e − → 3 π amplitude. This channel gives the second-largest individual contribution to the total HVP integral in the anomalous magnetic moment of the muon ( g − 2) μ , both to its absolute value and uncertainty. It is largely dominated by the narrow resonances ω and ϕ , but not to the extent that the off-peak regions were negligible, so that at the level of accuracy relevant for ( g − 2) μ an analysis of the available data as model independent as possible becomes critical. Here, we provide such an analysis based on a global fit function using analyticity and unitarity of the underlying γ ∗ → 3 π amplitude and its normalization from a chiral low-energy theorem, which, in particular, allows us to check the internal consistency of the various e + e − → 3 π data sets. Overall, we obtain a μ 3 π | ≤1.8 GeV = 46 . 2(6)(6) × 10 −10 as our best estimate for the total 3 π contribution consistent with all (low-energy) constraints from QCD. In combination with a recent dispersive analysis imposing the same constraints on the 2 π channel below 1 GeV, this covers nearly 80% of the total HVP contribution, leading to a μ HVP = 692 . 3(3 . 3) × 10 −10 when the remainder is taken from the literature, and thus reaffirming the ( g −2) μ anomaly at the level of at least 3 . 4 σ . As side products, we find for the vacuum-polarization-subtracted masses M ω = 782 . 63(3)(1) MeV and M ϕ = 1019 . 20(2)(1) MeV, confirming the tension to the ω mass as extracted from the 2 π channel.

A bstract We present a detailed analysis of e + e − → π + π − data up to s = 1 GeV in the framework of dispersion relations. Starting from a family of ππ P -wave phase shifts, as derived from a previous Roy-equation analysis of ππ scattering, we write down an extended Omnès representation of the pion vector form factor in terms of a few free parameters and study to which extent the modern high-statistics data sets can be described by the resulting fit function that follows from general principles of QCD. We find that statistically acceptable fits do become possible as soon as potential uncertainties in the energy calibration are taken into account, providing a strong cross check on the internal consistency of the data sets, but preferring a mass of the ω meson significantly lower than the current PDG average. In addition to a complete treatment of statistical and systematic errors propagated from the data, we perform a comprehensive analysis of the systematic errors in the dispersive representation and derive the consequences for the two-pion contribution to hadronic vacuum polarization. In a global fit to both time- and space-like data sets we find a μ ππ | ≤ 1 GeV  = 495.0(1.5)(2.1) × 10 − 10 and a μ ππ | ≤ 0.63 GeV  = 132.8(0.4)(1.0) × 10 − 10 . While the constraints are thus most stringent for low energies, we obtain uncertainty estimates throughout the whole energy range that should prove valuable in corroborating the corresponding contribution to the anomalous magnetic moment of the muon. As side products, we obtain improved constraints on the ππ P -wave, valuable input for future global analyses of low-energy ππ scattering, as well as a determination of the pion charge radius, 〈 r π 2 〉 = 0 . 429(1)(4) fm 2 .

A bstract Heisenberg time evolution under a chaotic many-body Hamiltonian H transforms an initially simple operator into an increasingly complex one, as it spreads over Hilbert space. Krylov complexity, or ‘K-complexity’, quantifies this growth with respect to a special basis, generated by H by successive nested commutators with the operator. In this work we study the evolution of K-complexity in finite-entropy systems for time scales greater than the scrambling time t s > log( S ). We prove rigorous bounds on K-complexity as well as the associated Lanczos sequence and, using refined parallelized algorithms, we undertake a detailed numerical study of these quantities in the SYK 4 model, which is maximally chaotic, and compare the results with the SYK 2 model, which is integrable. While the former saturates the bound, the latter stays exponentially below it. We discuss to what extent this is a generic feature distinguishing between chaotic vs. integrable systems.