U(1) lattice gauge theory with a topological action

We investigate the phase diagram of the compact U(1) lattice gauge theory in four dimensions using a non-standard action which is invariant under continuous de-formations of the plaquette angles. Just as for the Wilson action, we find a weakly first order transition, separating a confining phase where magnetic monopoles condense, and a Coulomb phase where monopoles are dilute. We also find a third phase where monopoles are completely absent. However, since the monopoles do not influence the long-distance prop-erties of the Coulomb phase, the physics is smooth across the singularity in the monopole density. The topological action offers an algorithmic advantage for the computation of the free energy

The so-Kazama-Suzuki models at large level

The large level limit of the N $$\mathcal{N}$$ = 2 SO(2 N ) Kazama-Suzuki coset models is argued to be equivalent to the orbifold of 4 N free fermions and bosons by the Lie group SO(2 N ) × SO(2). In particular, it is shown that the untwisted sector of the continuous orbifold accounts for a certain closed subsector of the coset theory. Furthermore, the ground states of the twisted sectors are identified with specific coset representations, and this identification is checked by various independent arguments

Lattice gauge theory without link variables

We obtain a sequence of alternative representations for the partition function of pure SU( N ) or U( N ) lattice gauge theory with the Wilson plaquette action, using the method of Hubbard-Stratonovich transformations. In particular, we are able to integrate out all the link variables exactly, and recast the partition function of lattice gauge theory as a Gaussian integral over auxiliary fields

Extended supersymmetry in AdS 3 higher spin theories

We determine the asymptotic symmetry algebra (for fields of low spin) of the M × M matrix extended Vasiliev theories on AdS 3 and find that it agrees with the W $$\mathcal{W}$$ -algebra of their proposed coset duals. Previously it was noticed that for M = 2 the supersymmetry increases from N = 2 $$\mathcal{N}=2$$ to N = 4 $$\mathcal{N}=4$$ . We study more systematically this type of supersymmetry enhancements and find that, although the higher spin algebra has extended supersymmetry for all M ≥ 2, the corresponding asymptotic symmetry algebra fails to be superconformal except for M = 2, when it has large N = 4 $$\mathcal{N}=4$$ superconformal symmetry. Moreover, we find that the Vasiliev theories based on s h s E N | 2 , ℝ $$\mathfrak{s}\mathfrak{h}{\mathfrak{s}}^E\left(\mathcal{N}\Big|2,\mathrm{\mathbb{R}}\right)$$ are special cases of the matrix extended higher spin theories, and hence have the same supersymmetry properties

On the coset duals of extended higher spin theories

We study the holographic duality between the M × M matrix extension of Vasiliev higher spin theories on AdS 3 and the large N limit of SU( N + M ) / SU( N ) × U(1) type cosets. We present a simplified proof for the agreement of the spectra and clarify the relation between this duality and the version in which the cosets are replaced by KazamaSuzuki models of Grassmannian type

A naturally light Higgs without light top partners

We demonstrate that the inclusion of a realistic lepton sector can relax significantly the upper bound on top partner masses in minimal composite Higgs models, induced by the lightness of the Higgs boson. To that extend, we present a comprehensive survey of the impact of different realizations of the fermion sectors on the Higgs potential, with a special emphasis on the role of the leptons. The non-negligible compositeness of the τ R in a general class of models that address the flavor structure of the lepton sector and the smallness of the corresponding FCNCs, can have a significant effect on the potential. We find that, with the τ R in the symmetric representation of SO(5), an increase in the maximally allowed mass of the lightest top partner of ≳ 1 TeV is possible for minimal quark setups like the MCHM 5,10 , without increasing the tuning. A light Higgs boson m H ∼ (100−200) GeV is a natural prediction of such models, which thus provide a new setup that can evade ultralight top partners without ad-hoc tuning in the Higgs mass. Moreover, we advocate a more minimal realization of the lepton sector than generally used in the literature, which still can avoid light partners due to its contributions to the Higgs mass in a different and very natural way, triggered by the seesaw mechanism. This allows to construct the most economical SO(5) / SO(4) composite Higgs models possible. Using both a transparent 4D approach, as well as presenting numerical results in the 5D holographic description, we demonstrate that, including leptons, minimality and naturalness do not imply light partners. Leptonic effects, not considered before, could hence be crucial for the viability of composite models

Local contributions to factorized soft graviton theorems at loop level

We analyze the low-energy behavior of scattering amplitudes involving gravitons at loop level in four dimensions. The single-graviton soft limit is controlled by soft operators which have been argued to separate into a factorized piece and a non-factorizing infrared divergent contribution. In this note we show that the soft operators responsible for the factorized contributions are strongly constrained by gauge and Poincaré invariance under the assumption of a local structure. We show that the leading and subleading orders in the soft-momentum expansion cannot receive radiative corrections. The first radiative correction occurs for the sub-subleading soft graviton operator and is one-loop exact. It depends on only two undetermined coefficients which should reflect the field content of the theory under consideration

NNLO QCD corrections to jet production at hadron colliders from gluon scattering

We present the next-to-next-to-leading order (NNLO) QCD corrections to dijet production in the purely gluonic channel retaining the full dependence on the number of colours. The sub-leading colour contribution in this channel first appears at NNLO and increases the NNLO correction by around 10% and exhibits a p T dependence, rising from 8% at low p T to 15% at high p T . The present calculation demonstrates the utility of the antenna subtraction method for computing the full colour NNLO corrections to dijet production at the Large Hadron Collider

Euclidean Dynamical Triangulation revisited: is the phase transition really 1st order?

The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [5, 9]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [5, 9] an artificial harmonic potential was added to the action and in [9] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated

A dictionary between R-operators, on-shell graphs and Yangian algebras

We translate between different formulations of Yangian invariants relevant for the computation of tree-level scattering amplitudes in N $$\mathcal{N}$$ = 4 super-Yang-Mills theory. While the R-operator formulation allows to relate scattering amplitudes to structures well known from integrability, it can equally well be connected to the permutations encoded by on-shell graphs