Random enriched trees with applications to random graphs

We establish limit theorems that describe the asymptotic local and global geometric behaviour of random enriched trees considered up to symmetry. We apply these general results to random unlabelled weighted rooted graphs and uniform random unlabelled $k$-trees that are rooted at a $k$-clique of distinguishable vertices. For both models we establish a Gromov--Hausdorff scaling limit, a Benjamini--Schramm limit, and a local weak limit that describes the asymptotic shape near the fixed root

Search for H→bbˉ\text{H}\to \text{b}\bar{\text{b}} in association with single top quarks as a test of Higgs couplings

The associated production of Higgs boson and single top quark is of particular interest since it is senstive to the relative sign of the Higgs boson coupling to gauge bosons and the Yukawa coupling $y$ to fermions. The presented analysis is setting upper production limits on a model with $y_\text{t}=-1$, which has an enhanced cross section compared to the standard model expectation. For this it focusses on the Higgs boson decaying to a pair of b quarks and uses the full dataset of $pp$ collisions recorded with the CMS detector in 2012. It reports an upper limit on 7.57 times the expected cross section, with an expected sensitivity of 5.14. This translates into the exclusion of associated tHq production with $y_\text{t}=-1$-like characteristics with a cross section smaller than 1.77\,pb

Almost flat bundles and homological invariance of infinite K-area

We extend the notion of an almost flat bundle over a closed Riemannian manifold to bundles over simplicial complexes, and prove that up to a constant factor, this notion is invariant under pullback via maps which induce isomorphisms on fundamental groups. As an application, we show that the property of having infinite K-area only depends on the image of the fundamental class under the classifying map of the universal cover.Comment: 35 page

Initial Semantics for Reduction Rules

We give an algebraic characterization of the syntax and operational semantics of a class of simply-typed languages, such as the language PCF: we characterize simply-typed syntax with variable binding and equipped with reduction rules via a universal property, namely as the initial object of some category of models. For this purpose, we employ techniques developed in two previous works: in the first work we model syntactic translations between languages over different sets of types as initial morphisms in a category of models. In the second work we characterize untyped syntax with reduction rules as initial object in a category of models. In the present work, we combine the techniques used earlier in order to characterize simply-typed syntax with reduction rules as initial object in a category. The universal property yields an operator which allows to specify translations---that are semantically faithful by construction---between languages over possibly different sets of types. As an example, we upgrade a translation from PCF to the untyped lambda calculus, given in previous work, to account for reduction in the source and target. Specifically, we specify a reduction semantics in the source and target language through suitable rules. By equipping the untyped lambda calculus with the structure of a model of PCF, initiality yields a translation from PCF to the lambda calculus, that is faithful with respect to the reduction semantics specified by the rules. This paper is an extended version of an article published in the proceedings of WoLLIC 2012.Comment: Extended version of arXiv:1206.4547, proves a variant of a result of PhD thesis arXiv:1206.455

First Search for the Associated Production of a Higgs Boson with a Single Top Quark

The production of the Higgs boson in association with a single top quark is sensitive to the relative sign of the coupling parameters describing its interaction with fermions and gauge bosons. The tHq production mode therefore provides an good handle on the Yukawa coupling Yt. The first searches for single-top + Higgs in the H>bbbar, gamma gamma, tau+tau- and W+W- decay channels are presented, using the full 8 TeV dataset recorded with the CMS detector. Special emphasis is put on the analyses' peculiarities and their dominating systematic uncertainties, and a combination of all individual channels is performed. The analyses are optimized for a scenario of Yt=-1, which is enhanced by a factor of 13 with respect to the Standard Model production rate. The observed combined upper exclusion limit is 2.8 times the cross section of this exotic scenario (2.0 expected).Comment: Preprint of the proceedings for the contribution to the LHCP2015 conference, St. Petersburg, Russi