Spectral flow as a map between N=(2,0)-models

The space of $(2,0)$ models is of particular interest among all heterotic-string models because it includes the models with the minimal $SO(10)$ unification structure, which is well motivated by the Standard Model of particle physics data. The fermionic $\mathbb{Z}_2\times \mathbb{Z}_2$ heterotic-string models revealed the existence of a new symmetry in the space of string configurations under the exchange of spinors and vectors of the $SO(10)$ GUT group, dubbed spinor-vector duality. Such symmetries are important for the understanding of the landscape of string vacua and ultimately for the possible operation of a dynamical vacuum selection mechanism in string theory. In this paper we generalize this idea to arbitrary internal rational Conformal Field Theories (RCFTs). We explain how the spectral flow operator normally acting within a general $(2,2)$ theory can be used as a map between $(2,0)$ models. We describe the details, give an example and propose more simple currents that can be used in a similar way.Comment: 14 pages, v2: minor changes, added one referenc

Enhanced surface plasmon polariton propagation induced by active dielectrics

We present numerical simulations for the propagation of surface plasmon polaritons in a dielectric-metal-dielectric waveguide using COMSOL multiphysics software. We show that the use of an active dielectric with gain that compensates metal absorption losses enhances substantially plasmon propagation. Furthermore, the introduction of the active material induces, for a specific gain value, a root in the imaginary part of the propagation constant leading to infinite propagation of the surface plasmon. The computational approaches analyzed in this work can be used to define and tune the optimal conditions for surface plasmon polariton amplification and propagation

Deep Supported Excavation in Difficult Ground Conditions in the City of Patras, Greece — Measured vs. Predicted Behavior

The technical characteristics of a deep supported excavation project using anchored diaphragm walls and the measured (by inclinometers) behavior of the soil retaining system are presented. The measured behavior is then compared with the predicted behavior using a finite element model of the excavation. The comparison shows a good agreement in a location where the soil profile is well defined. However, differences in the magnitude of the displacements were observed when the information on the soil profile was incomplete due to the variability of the deposits on site

Heterotic free fermionic and symmetric toroidal orbifold models

Free fermionic models and symmetric heterotic toroidal orbifolds both constitute exact backgrounds that can be used effectively for phenomenological explorations within string theory. Even though it is widely believed that for Z2xZ2 orbifolds the two descriptions should be equivalent, a detailed dictionary between both formulations is still lacking. This paper aims to fill this gap: We give a detailed account of how the input data of both descriptions can be related to each other. In particular, we show that the generalized GSO phases of the free fermionic model correspond to generalized torsion phases used in orbifold model building. We illustrate our translation methods by providing free fermionic realizations for all Z2xZ2 orbifold geometries in six dimensions.Comment: 1+49 pages latex, minor revisions and references adde

Using Network Analysis to Understand Knowledge Mobilization in a Community-based Organization

Background Knowledge mobilization (KM) has been described as putting research in the hands of research users. Network analysis is an empirical approach that has potential for examining the complex process of knowledge mobilization within community-based organizations (CBOs). Yet, conducting a network analysis in a CBO presents challenges. Purpose The purpose of this paper is to demonstrate the value and feasibility of using network analysis as a method for understanding knowledge mobilization within a CBO by (1) presenting challenges and solutions to conducting a network analysis in a CBO, (2) examining the feasibility of our methodology, and (3) demonstrating the utility of this methodology through an example of a network analysis conducted in a CBO engaging in knowledge mobilization activities. Method The final method used by the partnership team to conduct our network analysis of a CBO is described. Results An example of network analysis results of a CBO engaging in knowledge mobilization is presented. In total, 81 participants completed the network survey. All of the feasibility benchmarks set by the CBO were met. Results of the network analysis are highlighted and discussed as a means of identifying (1) prominent and influential individuals in the knowledge mobilization process and (2) areas for improvement in future knowledge mobilization initiatives. Conclusion Findings demonstrate that network analysis can be feasibly used to provide a rich description of a CBO engaging in knowledge mobilization activities

The Moonshine and LHC di-Photon Excess

The spinor-vector duality was discovered in free fermionic constructions of the heterotic-string in four dimensions. It played a key role in the construction of heterotic-string models with an anomaly free extra $Z^\prime$ symmetry that may remain unbroken down to low energy scales. A generic signature of the low scale string derived $Z^\prime$ model is via di--photon excess that may be within reach of the LHC. A fascinating possibility is that the spinor-vector duality symmetry is rooted in the structure of the heterotic-string compactifications to two dimensions. The two dimensional heterotic-string theories are in turn related to the so--called moonshine symmetries that underlie the two dimensional compactifications. In this paper we embark on exploration of this connection by the free fermionic formulation to classify the symmetries of the two dimensional heterotic-string theories. We use two complementary approaches in our classification. The first utilises a construction which is akin to the one used in the spinor-vector duality. Underlying this method is the triality property of $SO(8)$ representations. In the second approach we use the free fermionic tools to classify the twenty four dimensional moonshine lattices

On the road to somewhere: Brain potentials reflect language effects on motion event perception

Recent studies have identified neural correlates of language effects on perception in static domains of experience such as colour and objects. The generalization of such effects to dynamic domains like motion events remains elusive. Here, we focus on grammatical differences between languages relevant for the description of motion events and their impact on visual scene perception. Two groups of native speakers of German or English were presented with animated videos featuring a dot travelling along a trajectory towards a geometrical shape (endpoint). English is a language with grammatical aspect in which attention is drawn to trajectory and endpoint of motion events equally. German, in contrast, is a non-aspect language which highlights endpoints. We tested the comparative perceptual saliency of trajectory and endpoint of motion events by presenting motion event animations (primes) followed by a picture symbolising the event (target): In 75% of trials, the animation was followed by a mismatching picture (both trajectory and endpoint were different); in 10% of trials, only the trajectory depicted in the picture matched the prime; in 10% of trials, only the endpoint matched the prime; and in 5% of trials both trajectory and endpoint were matching, which was the condition requiring a response from the participant. In Experiment 1 we recorded event-related brain potentials elicited by the picture in native speakers of German and native speakers of English. German participants exhibited a larger P3 wave in the endpoint match than the trajectory match condition, whereas English speakers showed no P3 amplitude difference between conditions. In Experiment 2 participants performed a behavioural motion matching task using the same stimuli as those used in Experiment 1. German and English participants did not differ in response times showing that motion event verbalisation cannot readily account for the difference in P3 amplitude found in the first experiment. We argue that, even in a non-verbal context, the grammatical properties of the native language and associated sentence-level patterns of event encoding influence motion event perception, such that attention is automatically drawn towards aspects highlighted by the grammar

Relations in the space of (2,0) heterotic string models

Understanding better the landscape of string models and eventually finding, if possible, a dynamical way to select among them is one of the most interesting, open problems in string theory. In this thesis, we investigate aspects of the heterotic landscape and discuss relations among large classes of vacua. The first part of the thesis is devoted to the equivalence between free fermionic models and orbifolds. Free fermionic models and symmetric heterotic toroidal orbifolds both constitute exact backgrounds that can be used effectively for phenomenological explorations within string theory. It is widely believed that for Z_2xZ_2 orbifolds the two descriptions should be equivalent, but a detailed dictionary between both formulations was lacking. A detailed account of how the input data of both descriptions can be related to each other can be found in this thesis. In particular, we show that the generalized GSO phases of the free fermionic model correspond to generalized torsion phases used in orbifold model building. We illustrate our translation methods by providing free fermionic realizations for all Z_2xZ_2 orbifold geometries in six dimensions. In the second half of the thesis, we turn our attention to a novel idea called spinor-vector duality. In its original form, spinor-vector duality was limited to Z_2 structures. Here, we use the language of simple currents to generalize this idea to theories with arbitrary internal RCFTs. We also elucidate the underlying spectral flow structure. Even though the spectral flow has been traditionally used to relate states within a single model, we offer a new way to look at it, allowing relations between different models. Contrary to the equivalence between free fermionic models and orbifolds, many of the models related by the spectral flow are not physically equivalent. Nevertheless, the The idea of grouping together models into families according to the spectral flow orbit is quite important: the spectra of the models, though not identical, are related and we can make statements about models in the entire family by examining one representative. The grouping also offers a conceptual handle, acting as an organization principle in a vast landscape of models