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Statistics of limit root bundles relevant for exact matter spectra of F-theory MSSMs
Martin Bies, Mirjam Cvetič, Mingqiang Liu, 2021, izvirni znanstveni članek

Opis: In the largest, currently known, class of one quadrillion globally consistent F-theory Standard Models with gauge coupling unification and no chiral exotics, the vectorlike spectra are counted by cohomologies of root bundles. In this work, we apply a previously proposed method to identify toric base threefolds, which are promising to establish F-theory Standard Models with exactly three quark doublets and no vectorlike exotics in this representation. The base spaces in question are obtained from triangulations of 708 polytopes. By studying root bundles on the quark-doublet curve Cð3;2Þ1=6 and employing well-known results about desingularizations of toric K3 surfaces, we derive a triangulation independent lower bound Nˇ ð3Þ P for the number Nð3Þ P of root bundles on Cð3;2Þ1=6 with exactly three sections. The ratio Nˇ ð3Þ P =NP, where NP is the total number of roots on Cð3;2Þ1=6 , is largest for base spaces associated with triangulations of the eighth three-dimensional polytope Δ∘ 8 in the Kreuzer-Skarke list. For each of these Oð1015Þ threefolds, we expect that many root bundles on Cð3;2Þ1=6 are induced from F-theory gauge potentials and that at least every 3000th root on Cð3;2Þ1=6 has exactly three global sections and thus no exotic vectorlike quark-doublet modes.
Ključne besede: astrophysics, compactification, string theory models, geometry, higher-dimensional field theories, mathematical physics, quantum fields in curved spacetime, string phenomenology, supersymmetric models, topology
Objavljeno v DKUM: 16.10.2023; Ogledov: 172; Prenosov: 11
.pdf Celotno besedilo (444,13 KB)
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Reflections on the matter of 3D N=1 vacua and local Spin(7) compactifications
Mirjam Cvetič, Jonathan J. Heckman, Ethan Torres, Gianluca Zoccarato, 2022, izvirni znanstveni članek

Opis: We use Higgs bundles to study the 3D N = 1 vacua obtained from M-theory compactified on a local Spin(7) space given as a four-manifold M-4 of ADE singularities with further generic enhancements in the singularity type along one-dimensional subspaces. There can be strong quantum corrections to the massless degrees of freedom in the low energy effective field theory, but topologically robust quantities such as "parity" anomalies are still calculable. We show how geometric reflections of the compactification space descend to 3D reflections and discrete symmetries. The parity anomalies of the effective field theory descend from topological data of the compactification. The geometric perspective also allows us to track various perturbative and nonperturbative corrections to the 3D effective field theory. We also provide some explicit constructions of well-known 3D theories, including those which arise as edge modes of 4D topological insulators, and 3D N = 1 analogs of grand unified theories. An additional result of our analysis is that we are able to track the spectrum of extended objects and their transformations under higher-form symmetries.
Ključne besede: Compactification, geometry, M-theory, quantum field theory, string theory techniques in condensed matter, strings & branes, supersymmetry, topology
Objavljeno v DKUM: 25.09.2023; Ogledov: 154; Prenosov: 17
.pdf Celotno besedilo (910,15 KB)
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Interoperability of infrastructure and transportation information models: A public transport case study
Nenad Čuš Babič, Sara Guerra de Oliveira, Andrej Tibaut, 2022, izvirni znanstveni članek

Opis: The duplication of semantic data modelled in different disciplines poses interoperability challenges. Information models that benefit from the application of standards that enable data reusability and prevent redundancy and misuse should be compatible, particularly when different systems are used in the same domain-specific area, as in the case of public transportation. Transportation information models, leading and providing reliable and robust public transport services, can nowadays be enriched with information found in building information models devoted to transportation infrastructure. Therefore, in the present paper, a mapping between the standards and technical specifications that support each modelling approach is explored, analysed, and aligned to maximise the best out of the current common practices used. The information from the Industry Foundation Classes IFC specification-based models complements the conceptual and physical transportation models, where Transmodel and NeTEx are well-established, with accurate (as-built) detailed characteristics of the transportation infrastructure (stop places, quays, entrances, access spaces and equipment as ramps, staircases, and escalators). The extraction of topological information stored in IFC models allows for navigation-network extraction, information about spaces, and passages between spaces. A specific public transport case study focused on a train station is detailed to better corroborate and illustrate the advantages and uses of compatible and complementing modelling approaches. As building-information-modelling awareness and use is growing, the validated mapping approach can benefit from the future application of automation procedures.
Ključne besede: transmodel, NeTEx, IFC, interoperability, building topology, navigation network
Objavljeno v DKUM: 22.09.2023; Ogledov: 386; Prenosov: 11
.pdf Celotno besedilo (3,15 MB)
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Designing the gear body structure to control vibration behaviour
Riad Ramadani, 2018, doktorska disertacija

Opis: This research presents a new approach aiming to reduce gear vibration as well as its weight by modifying the gear body structure. The primary objective was to reduce vibration and noise emission of spur gears. For this purpose, a solid gear body was replaced by a cellular lattice structure, which was expected to raise the torsional elasticity of the gear body. The cellular lattice structure was designed and optimized by FE-based topology optimization software CAESS ProTOp, which is based on strain energy control. For experimental purposes, the optimized gear was produced from Titanium alloy Ti-6Al-4V ELI by using Selective Laser Melting technique. A polymer matrix was added to increase the damping of the structure. In order to test the gears, a new test rig with closed loop was conceived, designed and produced. The test rig is equipped with two gear pairs: with the tested one and with the driving one. The gears have been run and tested at different speeds and torque. The acceleration, strain and sound pressure of a running gear pair was measured. The final processing of the signal was done by a specially developed software based on LabView. By employing the fast Fourier transformation the time signal of acceleration, strain and sound pressure has been converted to the frequency spectrum and time frequency spectrogram. The results obtained by testing the solid and cellular lattice gear body were compared. It was experimentally confirmed that the cellular lattice structure of a gear body and addition of a polymer matrix may significantly reduce the vibration.
Ključne besede: Gear vibration, cellular lattice structure, topology optimization, test rig
Objavljeno v DKUM: 27.02.2018; Ogledov: 2313; Prenosov: 226
.pdf Celotno besedilo (13,76 MB)

Effective topological charge cancelation mechanism
Luka Mesarec, Wojciech Góźdź, Aleš Iglič, Samo Kralj, 2016, izvirni znanstveni članek

Opis: Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy.
Ključne besede: topological defects, topological charge, numerical studies, orientational ordering, nematic liquid crystals, liquid crystalline shells, biological membranes, nanoparticles, Gaussian curvature, electrostatic analogy, annihilation, topology
Objavljeno v DKUM: 23.06.2017; Ogledov: 1001; Prenosov: 335
.pdf Celotno besedilo (2,15 MB)
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Inverse limits in the category of compact Hausdorff spaces and upper semicontinuous functions
Iztok Banič, Tina Sovič, 2013, izvirni znanstveni članek

Opis: V članku obravnavamo inverzne limite v kategoriji ▫$mathcal{CHU}$▫ kompaktnih Hausdorffovih prostorov in navzgor polzveznih (u.s.c) preslikav. Vpeljemo pojem šibkih inverznih limit in pokažemo, da inverzne limite z navzgor polzveznimi veznimi preslikavami skupaj s projekcijami niso nujno inverzne limite v ▫$mathcal{CHU}$▫, so pa vedno šibke inverzne limite v tej kategoriji. Med drugim gre za realizacijo kategorijalnega pristopa k reševanju problema, ki ga je zastavil W. T. Ingram.
Ključne besede: topologija, kategorije, navzgor polzvezne funkcije, inverzne limite, posplošene inverzne limite, šibke inverzne limite, topology, upper semi-continuous functions, inverse limits, generalized inverse limits, weak inverse limits
Objavljeno v DKUM: 10.07.2015; Ogledov: 26540; Prenosov: 94
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Inverse limits with generalized Markov interval functions
Iztok Banič, Tjaša Lunder, 2013, izvirni znanstveni članek

Opis: V [S. Holte, Inverse limits of Markov interval maps, Topology Appl. 123, 2002,421-427] so bile predstavljene markovske preslikave in dokazano je bilo, da sta inverzni limiti z markovskimi veznimi funkcijami z enakim vzorcem homeomorfni. V tem članku predstavimo posplošene markovske preslikave, ki so posplošitev markovskih preslikav na večlične preslikave in pokažemo, da sta inverzni limiti s posplošenimi markovskimi veznimi preslikavami z enakim vzorcem homeomorfni.
Ključne besede: topologija, inverzne limite, navzgor polzvezne funkcije, posplošene markovske preslikave, topology, inverse limits, upper semi-continuous functions, generalized Markov interval functions
Objavljeno v DKUM: 10.07.2015; Ogledov: 1272; Prenosov: 96
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Inducing functions between inverse limits with upper semicontinuous bonding functions
Iztok Banič, Matevž Črepnjak, Goran Erceg, Matej Merhar, Uroš Milutinović, 2013, izvirni znanstveni članek

Opis: V članku predstavljamo kategorijo ▫$mathcal{CU}$▫, kjer so objekti kompaktni metrični prostori ▫$X$▫ morfizmi med njimi pa navzgor polzvezne preslikave iz ▫$X$▫ v ▫$2^Y$▫. Vpeljemo tudi kategorijo ▫$mathcal{ICU}$▫ inverznih zaporedij v ▫$mathcal{CU}$▫. Proučujemo inducirane funkcije med inverznimi limitami kompaktnih metričnih prostorov z navzgor polzveznimi veznimi funkcijami. Podamo kriterije za njihov obstoj in dokažemo imajo pod določenimi pogoji surjektivne grafe. Pokažemo tudi da predpis, ki objektom iz ▫$mathcal{ICU}$▫ priredi njihove inverzne limite, ki so objekti v ▫$mathcal{CU}$▫, morfizmom pa priredi inducirane preslikave ni funktor iz ▫$mathcal{ICU}$▫ v ▫$mathcal{CU}$▫, (je pa temu zelo blizu). Na koncu podamo še uporabno aplikacijo dokazanih rezultatov.
Ključne besede: topologija, inverzne limite, navzgor polzvezne funkcije, inducirane funkcije, inducirani morfizmi, topology, inverse limits, upper semi-continuous functions, induced functions, induced morphisms
Objavljeno v DKUM: 10.07.2015; Ogledov: 1005; Prenosov: 39
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Ważewski's universal dendrite as an inverse limit with one set-valued bonding function
Iztok Banič, Matevž Črepnjak, Matej Merhar, Uroš Milutinović, Tina Sovič, 2012, izvirni znanstveni članek

Opis: Konstruirana je družina navzgor polzveznih večličnih funkcij ▫$f:[0,1] rightarrow 2^{[0,1]}$▫, za katere velja, da je inverzna limita inverznega zaporedja intervalov ▫$[0,1]$▫ in ▫$f$▫ kot edine vezne preslikave homeomorfna univerzalnemu dendritu Ważevskega.
Ključne besede: topologija, kontinuum, inverzna limita, večlična funkcija, dendrit, univerzalni dendrit Ważevskega, topology, continua, inverse limits, upper semi-continuous functions, dendrites, Ważewski's universal dendrite
Objavljeno v DKUM: 10.07.2015; Ogledov: 1317; Prenosov: 150
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