A Geometric Monte Carlo Algorithm for the Antiferromagnetic Ising model with "Topological" Term at θ=π\theta=\pi

In this work we study the two and three-dimensional antiferromagnetic Ising model with an imaginary magnetic field $i\theta$ at $\theta=\pi$. In order to perform numerical simulations of the system we introduce a new geometric algorithm not affected by the sign problem. Our results for the $2D$ model are in agreement with the analytical solutions. We also present new results for the $3D$ model which are qualitatively in agreement with mean-field predictions

Critical behavior of 3D Z(N) lattice gauge theories at zero temperature

Three-dimensional $Z(N)$ lattice gauge theories at zero temperature are studied for various values of $N$. Using a modified phenomenological renormalization group, we explore the critical behavior of the generalized $Z(N)$ model for $N=2,3,4,5,6,8$. Numerical computations are used to simulate vector models for $N=2,3,4,5,6,8,13,20$ for lattices with linear extension up to $L=96$. We locate the critical points of phase transitions and establish their scaling with $N$. The values of the critical indices indicate that the models with $N>4$ belong to the universality class of the three-dimensional $XY$ model. However, the exponent $\alpha$ derived from the heat capacity is consistent with the Ising universality class. We discuss a possible resolution of this puzzle. We also demonstrate the existence of a rotationally symmetric region within the ordered phase for all $N\geq 5$ at least in the finite volume.Comment: 25 pages, 4 figures, 8 table

A New Perspective on Clustered Planarity as a Combinatorial Embedding Problem

The clustered planarity problem (c-planarity) asks whether a hierarchically clustered graph admits a planar drawing such that the clusters can be nicely represented by regions. We introduce the cd-tree data structure and give a new characterization of c-planarity. It leads to efficient algorithms for c-planarity testing in the following cases. (i) Every cluster and every co-cluster (complement of a cluster) has at most two connected components. (ii) Every cluster has at most five outgoing edges. Moreover, the cd-tree reveals interesting connections between c-planarity and planarity with constraints on the order of edges around vertices. On one hand, this gives rise to a bunch of new open problems related to c-planarity, on the other hand it provides a new perspective on previous results.Comment: 17 pages, 2 figure

Technology acceptance and leadership 4.0: A quali-quantitative study

With the rapid advancement of Industry 4.0, new technologies are changing the nature of work and organizations. Nevertheless, technology acceptance is still an open issue and research, and practice interventions should investigate its antecedents and implement actions in order to reduce the risks of resistance and foster acceptance and effective usage of the new tools and systems. This quali-quantitative study was aimed at exploring perceptions about Industry 4.0 and its transformations and investigating job antecedents of technology acceptance. Whilst not many studies in the literature on technology acceptance have considered workers’ well-being, in this study, its association with work engagement has also been examined. The qualitative study used focus groups to collect perceptions of 14 key roles in a company that was implementing Industry 4.0. In the same company, the quantitative study involved 263 employees who filled in a questionnaire. The results confirmed that both job resources, namely supervisor support and role clarity, were antecedents of technology acceptance, which, in turn, was associated with work engagement. This study provides useful suggestions for interventions aimed at foster technology acceptance and workers’ well-being in companies that are facing Industry 4.0 transformations. Particularly, investments in both leadership 4.0 development and communication programs are essential

The phase transitions in 2D Z(N) vector models for N>4

We investigate both analytically and numerically the renormalization group equations in 2D Z(N) vector models. The position of the critical points of the two phase transitions for N>4 is established and the critical index \nu\ is computed. For N=7, 17 the critical points are located by Monte Carlo simulations and some of the corresponding critical indices are determined. The behavior of the helicity modulus is studied for N=5, 7, 17. Using these and other available Monte Carlo data we discuss the scaling of the critical points with N and some other open theoretical problems.Comment: 19 pages, 8 figures, 10 tables; version to appear on Phys. Rev.