Quantum Fusion of Domain Walls with Fluxes

We study how fluxes on the domain wall world volume modify quantum fusion of two distant parallel domain walls into a composite wall. The elementary wall fluxes can be separated into parallel and antiparallel components. The parallel component affects neither the binding energy nor the process of quantum merger. The antiparallel fluxes, instead, increase the binding energy and, against naive expectations, suppress quantum fusion. In the small flux limit we explicitly find the bounce solution and the fusion rate as a function of the flux. We argue that at large (antiparallel) fluxes there exists a critical value of the flux (versus the difference in the wall tensions), which switches off quantum fusion altogether. This phenomenon of flux-related wall stabilization is rather peculiar: it is unrelated to any conserved quantity. Our consideration of the flux-related all stabilization is based on substantiated arguments that fall short of complete proof.Comment: 17 pages, 3 figure

Higher Winding Strings and Confined Monopoles in N=2 SQCD

We consider composite string solutions in N=2 SQCD with the gauge group U(N), the Fayet--Iliopoulos term \xi \neq 0 and N (s)quark flavors. These bulk theories support non-Abelian strings and confined monopoles identified with kinks in the two-dimensional world-sheet theory. Similar and more complicated kinks (corresponding to composite confined monopoles) must exist in the world-sheet theories on composite strings. In a bid to detect them we analyze the Hanany--Tong (HT) model, focusing on a particular example of N=2. Unequal quark mass terms in the bulk theory result in the twisted masses in the N=(2,2) HT model. For spatially coinciding 2-strings, we find three distinct minima of potential energy, corresponding to three different 2-strings. Then we find BPS-saturated kinks interpolating between each pair of vacua. Two kinks can be called elementary. They emanate one unit of the magnetic flux and have the same mass as the conventional 't Hooft--Polyakov monopole on the Coulomb branch of the bulk theory (\xi =0). The third kink represents a composite bimonopole, with twice the minimal magnetic flux. Its mass is twice the mass of the elementary confined monopole. We find instantons in the HT model, and discuss quantum effects in composite strings at strong coupling. In addition, we study the renormalization group flow in this model.Comment: 41 pages, 11 figure

Confinement and Localization on Domain Walls

We continue the studies of localization of the U(1) gauge fields on domain walls. Depending on dynamics of the bulk theory the gauge field localized on the domain wall can be either in the Coulomb phase or squeezed into flux tubes implying (Abelian) confinement of probe charges on the wall along the wall surface. First, we consider a simple toy model with one flavor in the bulk at weak coupling (a minimal model) realizing the latter scenario. We then suggest a model presenting an extension of the Seiberg--Witten theory which is at strong coupling, but all theoretical constructions are under full control if we base our analysis on a dual effective action. Finally, we compare our findings with the wall in a "nonminimal" theory with two distinct quark flavors that had been studied previously. In this case the U(1) gauge field trapped on the wall is exactly massless because it is the Goldstone boson of a U(1) symmetry in the bulk spontaneously broken on the wall. The theory on the wall is in the Coulomb phase. We explain why the mechanism of confinement discussed in the first part of the paper does not work in this case, and strings are not formed on the walls.Comment: 55 pp; v2: several remarks adde

Supersymmetric Q Solitons of Arbitrary Genus

We construct "Flying Saucer" solitons in supersymmetric N=2 gauge theory which is known to support BPS domain walls with a U(1) gauge field localized on its worldvolume. We demonstrate that this model supports exotic particle-like solitons whose topology is largely arbitrary: closed orientable surfaces in three-dimensional space which can have arbitrary genus. In particular, we focus on Q tori. Q tori and similar solitons of higher genera are obtained by folding the domain wall into an appropriate surface. Nontrivial cycles on the domain wall worldvolume (handles) are stabilized by crossed electric and magnetic fields inside the folded domain wall. Three distinct frameworks are used to prove the existence of these Flying Saucer solitons and study their properties: the worldvolume description (including the Dirac-Born-Infeld action), the bulk theory description in the sigma-model limit, and the bulk theory description in the thin-edge approximation. In the sigma-model framework the Q torus is shown to be related to the Hopf Skyrmion studied previously.Comment: 54 pages, 20 figures; v. 2: reference added; v.3:references added, title changed. Final version accpted for publication in PR

Interplay of the volume and surface plasmons in the electron energy loss spectra of C60_{60}

The results of a joint experimental and theoretical investigation of the C60 collective excitations in the process of inelastic scattering of electrons are presented. The shape of the electron energy loss spectrum is observed to vary when the scattering angle increases. This variation arising due to the electron diffraction of the fullerene shell is described by a new theoretical model which treats the fullerene as a spherical shell of a finite width and accounts for the two modes of the surface plasmon and for the volume plasmon as well. It is shown that at small angles, the inelastic scattering cross section is determined mostly by the symmetric mode of the surface plasmon, while at larger angles, the contributions of the antisymmetric surface plasmon and the volume plasmon become prominent.Comment: 11 pages, 3 figure

Framing COVID-19: How we conceptualize and discuss the pandemic on Twitter

Doctors and nurses in these weeks are busy in the trenches, fighting against a new invisible enemy: Covid-19. Cities are locked down and civilians are besieged in their own homes, to prevent the spreading of the virus. War-related terminology is commonly used to frame the discourse around epidemics and diseases. Arguably the discourse around the current epidemic will make use of war-related metaphors too,not only in public discourse and the media, but also in the tweets written by non-experts of mass communication. We hereby present an analysis of the discourse around #Covid-19, based on a corpus of 200k tweets posted on Twitter during March and April 2020. Using topic modelling we first analyze the topics around which the discourse can be classified. Then, we show that the WAR framing is used to talk about specific topics, such as the virus treatment, but not others, such as the effects of social distancing on the population. We then measure and compare the popularity of the WAR frame to three alternative figurative frames (MONSTER, STORM and TSUNAMI) and a literal frame used as control (FAMILY). The results show that while the FAMILY literal frame covers a wider portion of the corpus, among the figurative framings WAR is the most frequently used, and thus arguably the most conventional one. However, we conclude, this frame is not apt to elaborate the discourse around many aspects involved in the current situation. Therefore, we conclude, in line with previous suggestions, a plethora of framing options, or a metaphor menu, may facilitate the communication of various aspects involved in the Covid-19-related discourse on the social media, and thus support civilians in the expression of their feelings, opinions and ideas during the current pandemic.Comment: 41 pages, 6 figure

Optimization of VR application in texturing cultural heritage

The research question underlying this short essay refers to the possibility of realizing through a well-established workflow a high level of immersivity in the VR representation of Cultural Heritage to be used as a working tool by architects and renovators as well as heritage scholars. At present active or passive 3D scanning techniques are a known reality where the choice of data acquisition system depends both on the final purpose and characteristics of the object to be surveyed. With the maturity achieved in point cloud acquisition, post processing phases and the development of BIM-based systems, the model has given the possibility to become a repository of information related to the existing, to be used for maintenance or renovation processes. If the model can represent the existing with a certain level of detail, it can be assumed that a differentiated Level of Immersivity can be organized depending on the specific needs it intends to fulfil. In the context of renovation or preservation of Cultural Heritage, the potential offered by VR becomes more interesting when it can provide a realistic portrait not only of the geometry, but also of the materiality and state of preservation of the buildings. This research opens new possibilities to develop tools to aid designers and renovators in degradation analysis, intervention projects, and scheduled maintenance. The research question starts analyzing the possibility of creating photorealistic immersive environments that are easy to access, organized based on surveys of existing heritage buildings using specific datasets

Reliability in the identification of metaphors in (filmic) multimodal communication

Research on multimodal communication is complex because multimodal analyses require methods and procedures that offer the possibility of disentangling the layers of meaning conveyed through different channels. We hereby propose an empirical evaluation of the Filmic Metaphor Identification Procedure (FILMIP, Bort-Mir, L. (2019). Developing, applying and testing FILMIP: the filmic metaphor identification procedure, Ph.D. dissertation. Universitat Jaume I, Castellón.), a structural method for the identification of metaphorical elements in (filmic) multimodal materials. The paper comprises two studies: (i) A content analysis conducted by independent coders, in which the reliability of FILMIP is assessed. Here, two TV commercials were shown to 21 Spanish participants for later analysis with the use of FILMIP under two questionnaires. (ii) A qualitative analysis based on a percentage agreement index to check agreement among the 21 participants about the metaphorically marked filmic components identified on the basis of FILMIP’s seven steps. The results of the two studies show that FILMIP is a valid and reliable tool for the identification of metaphorical elements in (filmic) multimodal materials. The empirical findings are discussed in relation to multimodal communication open challenges

Point cloud management for a holographic visualization

This document aims to describe and verify the workflow from a digital survey of a building of historical value to its set up in an innovative holographic view. Via Lulli is a low-cost building of the beginning of the century organized in a closed-block part of a complex with rather small courtyards; the research topic concerns the verification of the process from acquisition with digital survey to convert the survey dataset into a hologram, considering the huge potential of this display system. Comparison among different point clouds, with different accuracy and dimension are related to the final navigation when transformed in holograms; several tests have been carried out to compare cloud density with the ability to see holograms in details with different zooms in to display small details, and zooms out in real time to view the entire model. First possibility to extend workflow with unity support and other plug-ins are supposed

CULTURAL HERITAGE DISSEMINATION: BIM MODELLING AND AR APPLICATION FOR A DIACHRONIC TALE

The research purpose is to present a project of cultural dissemination and enhancement of the “Madonna della Pace” Sanctuary at Rocchetta di Airuno (Lecco - Italy), based on an immersive experience of knowledge of the history and places that characterize not only the sanctuary but also the “Cammino di Sant’Agostino” (of which it is one of the stages). The research goal focuses on the direct employment and exploitation of HBIM models for the digital fruition project. An integrated digital survey based on a terrestrial laser scanner and photogrammetry was conducted to provide a complete geometrical representation of the sanctuary and its surroundings. Both output point clouds were employed as metric and geometric references to create the reality-based parametric model. Specifically, the work focuses on creating a three-dimensional chronological model of the sanctuary, which not only represents the current state of the cultural asset but is also enriched through the definition of different evolutionary phases of the architectural artifact based on an indepth study of the photographic and bibliographic documentations. Four Project Phasing has been identified to represent the most significant transformations of the building and were managed using the time parameter in the same BIM project. The sanctuary geometric and parametric models were displayed and navigable thanks to the aid of Virtual and Augmented Reality applications. A VR environment was defined to display in the first person the textured model. Finally, an AR smartphone app prototype was developed to show tourists the sanctuary’s historical transformation over time