Almost Flat Planar Diagrams

We continue our study of matrix models of dually weighted graphs. Among the attractive features of these models is the possibility to interpolate between ensembles of regular and random two-dimensional lattices, relevant for the study of the crossover from two-dimensional flat space to two-dimensional quantum gravity. We further develop the formalism of large $N$ character expansions. In particular, a general method for determining the large $N$ limit of a character is derived. This method, aside from being potentially useful for a far greater class of problems, allows us to exactly solve the matrix models of dually weighted graphs, reducing them to a well-posed Cauchy-Riemann problem. The power of the method is illustrated by explicitly solving a new model in which only positive curvature defects are permitted on the surface, an arbitrary amount of negative curvature being introduced at a single insertion.Comment: harvmac.tex and pictex.tex. Must be compiled "big". Diagrams are written directly into the text in pictex command

Dressing and Wrapping

We prove that the validity of the recently proposed dressed, asymptotic Bethe ansatz for the planar AdS/CFT system is indeed limited at weak coupling by operator wrapping effects. This is done by comparing the Bethe ansatz predictions for the four-loop anomalous dimension of finite-spin twist-two operators to BFKL constraints from high-energy scattering amplitudes in N=4 gauge theory. We find disagreement, which means that the ansatz breaks down for length-two operators at four-loop order. Our method supplies precision tools for multiple all-loop tests of the veracity of any yet-to-be constructed set of exact spectral equations. Finally we present a conjecture for the exact four-loop anomalous dimension of the family of twist-two operators, which includes the Konishi field.Comment: 20 pages, 2 tables, no figures; v2: references added, conjecture on exact four-loop twist-two result state

Lean supply chain planning: Simulation of lean techniques integration

Lean Supply Chain (LSC) has become a strategic configuration in order to satisfy customer's expectations efficiently and effectively. LSC concept is the implementation of Lean principles and techniques outside single company boundaries, creating the flow and making SC reacting instead of foreseeing. Supply Chain Planning (SCP) is a part of SCM management strategy that allows managers to align operations of different companies and so improve operations efficiency and effectiveness. Lean Supply Chain Planning (LSCP) is a new SCP model that is growing interest among both academics and practitioners, but it is not well studied yet. This paper aims at providing a theoretical and practical guidelines about Lean techniques implementations impact in SCP. To reach it, a Discret-event-simulation (DES) simulation model of a three-echelon and multi-product supply chain has been set. This research focuses on three principles of Lean production: identifying the value, creating flow to the customer and pull. The results achieved demonstrate that LSCP techniques have a positive impact on inventories levels and in particular, they demonstrate synergy among techniques so that total benefit is greater than the sum of benefits of single technique implementations

Strong coupling from the Hubbard model

It was recently observed that the one dimensional half-filled Hubbard model reproduces the known part of the perturbative spectrum of planar N=4 super Yang-Mills in the SU(2) sector. Assuming that this identification is valid beyond perturbation theory, we investigate the behavior of this spectrum as the 't Hooft parameter \lambda becomes large. We show that the full dimension \Delta of the Konishi superpartner is the solution of a sixth order polynomial while \Delta for a bare dimension 5 operator is the solution of a cubic. In both cases the equations can be solved easily as a series expansion for both small and large \lambda and the equations can be inverted to express \lambda as an explicit function of \Delta. We then consider more general operators and show how \Delta depends on \lambda in the strong coupling limit. We are also able to distinguish those states in the Hubbard model which correspond to the gauge invariant operators for all values of \lambda. Finally, we compare our results with known results for strings on AdS_5\times S^5, where we find agreement for a range of R-charges.Comment: 14 pages; v2: 17 pages, 2 figures, appendix and references added; typos fixed, minor changes; v3 fixed figures; v4 more references added, minor correctio

An improvement's project model to foster sustainable continuous improvement

Continuous Improvement programs are constantly applied amongst companies to reach competitive advantages. However, it is known that companies struggle to sustain benefits of continuous improvement projects in long-Term periods. Indeed, there is not a common shared framework assessing which are the managerial variables that can guarantee improvement's projects success. This research presents a model and a pool of improvement's projects could be framed and carried out accordingly. The model and its enabler mechanisms foster the importance that the outstanding literature assign to human focused factors and soft practices to sustain continuous improvement benefits in the long-Term period. This study presents a first assessment analysis of the model, even if not statistically valid, highlighting its enablers and barriers for a correct application. Then, based on the first data collected on a sample of improvement's projects framed with the model described, the study draws some considerations about which are the critical success factors for improvement's projects

How Industry 4.0 and Lean Management Are Interrelated with Green Paradigm

Recently, sustainability has been tackled several times due to the impending climate change the earth is facing. Numerous techniques have been applied to reverse the direction companies were going into. In this paper, it is explained the importance that Lean Manufacturing tools and Industry 4.0 technologies can have on the sustainable side of a company. The aim of this work is to fill the scientific gap related to studies deepening the combination of these different paradigms, Industry 4.0-Lean-Green, which have been scarcely investigated together. Thus, a Systematic Literature Review has been performed to detect which were the key variables of these three fields and then, it was studied what their interaction was. This study is giving the opportunity to understand the main variables of Industry 4.0 and Lean manufacturing on which companies have to act in order to have an impact on green variables and their overall sustainability

Probing molecular dynamics at the nanoscale via an individual paramagnetic center

Understanding the dynamics of molecules adsorbed to surfaces or confined to small volumes is a matter of increasing scientific and technological importance. Here, we demonstrate a pulse protocol using individual paramagnetic nitrogen vacancy (NV) centers in diamond to observe the time evolution of 1H spins from organic molecules located a few nanometers from the diamond surface. The protocol records temporal correlations among the interacting 1H spins, and thus is sensitive to the local system dynamics via its impact on the nuclear spin relaxation and interaction with the NV. We are able to gather information on the nanoscale rotational and translational diffusion dynamics by carefully analyzing the time dependence of the NMR signal. Applying this technique to various liquid and solid samples, we find evidence that liquid samples form a semi-solid layer of 1.5 nm thickness on the surface of diamond, where translational diffusion is suppressed while rotational diffusion remains present. Extensions of the present technique could be adapted to highlight the chemical composition of molecules tethered to the diamond surface or to investigate thermally or chemically activated dynamical processes such as molecular folding

Exact solution of discrete two-dimensional R2^{2} gravity

We exactly solve a special matrix model of dually weighted planar graphs describing pure two-dimensional quantum gravity with a R^2 interaction in order to study the intermediate regimes between the gravitating and flat metric. The flat space is modeled by a regular square lattice, while localized curvature is being introduced through defects of the lattice. No ``flattening'' phase transition is found with respect to the R^2 coupling: the infrared behaviour of the system is that of pure gravity for any finite R^2 coupling. In the limit of infinite coupling, we are able to extract a scaling function interpolating between pure gravity and a phase of a dilute gas of curvature defects on a flat background. We introduce and explain some novel techniques concerning our method of large N character expansions and the calculation of Schur characters on big Young tableaux

Advances in large N group theory and the solution of two-dimensional R2^{2} gravity

We review the recent exact solution of a matrix model which interpolates between flat and random lattices. The importance of the results is twofold: Firstly, we have developed a new large N technique capable of treating a class of matrix models previously thought to be unsolvable. Secondly, we are able to make a first precise statement about two-dimensional R^2 gravity. These notes are based on a lecture given at the Cargese summer school 1995. They contain some previously unpublished results