| | SLO | ENG | Piškotki in zasebnost

Večja pisava | Manjša pisava

Iskanje po katalogu digitalne knjižnice Pomoč

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju

Opcije:
  Ponastavi


1 - 10 / 20
Na začetekNa prejšnjo stran12Na naslednjo stranNa konec
1.
2.
Geometry design and analysis of an electric bus for the interior ther-mal modelling
Costica Nituca, Gabriel Chiriac, Georgel Gabor, Ilie Nucǎ, Vadim Cazac, Marcel Burduniuc, 2021, izvirni znanstveni članek

Opis: The heating, ventilation and air-conditioning (HVAC) system represents the main auxiliary load for any type of bus. Being the most significant energy-consuming auxiliary load for the electric bus, it must be given special attention in an electric bus system design. To study the heat transfer and thermal optimization for passenger comfort in the electric bus computer-aided design (CAD) is used. The geometry of an electric bus interior is designed considering the main components of the vehicle: passenger cabin, driver’s cabin, windows, walls, and seats. Materials of the same type as those used in the real bus are considered for the geometry model. Based on the heat transfer theory, a thermal model and simulations are made for the heat transfer inside the electric bus. The simulated data are compared with measurement data, and based on these, it can be concluded that the thermal model of the electric bus can be validated and used further for a wide variety of thermal simulation types.
Ključne besede: heat transfer, electric bus, passenger comfort, geometry design, thermal modelling
Objavljeno v DKUM: 13.11.2023; Ogledov: 199; Prenosov: 3
.pdf Celotno besedilo (1,04 MB)
Gradivo ima več datotek! Več...

3.
Root bundles and towards exact matter spectra of F-theory MSSMs
Martin Bies, Mirjam Cvetič, Ron Donagi, Mingqiang Liu, Marielle Ong, 2021, izvirni znanstveni članek

Opis: Motivated by the appearance of fractional powers of line bundles in studies of vector-like spectra in 4d F-theory compactifications, we analyze the structure and origin of these bundles. Fractional powers of line bundles are also known as root bundles and can be thought of as generalizations of spin bundles. We explain how these root bundles are linked to inequivalent F-theory gauge potentials of a G(4)-flux. While this observation is interesting in its own right, it is particularly valuable for F-theory Standard Model constructions. In aiming for MSSMs, it is desired to argue for the absence of vector-like exotics. We work out the root bundle constraints on all matter curves in the largest class of currently-known F-theory Standard Model constructions without chiral exotics and gauge coupling unification. On each matter curve, we conduct a systematic "bottom"-analysis of all solutions to the root bundle constraints and all spin bundles. Thereby, we derive a lower bound for the number of combinations of root bundles and spin bundles whose cohomologies satisfy the physical demand of absence of vector-like pairs. On a technical level, this systematic study is achieved by a well-known diagrammatic description of root bundles on nodal curves. We extend this description by a counting procedure, which determines the cohomologies of so-called limit root bundles on full blow-ups of nodal curves. By use of deformation theory, these results constrain the vector-like spectra on the smooth matter curves in the actual F-theory geometry.
Ključne besede: F-theory, differential geometry, algebraic geometry
Objavljeno v DKUM: 16.10.2023; Ogledov: 236; Prenosov: 15
.pdf Celotno besedilo (979,06 KB)
Gradivo ima več datotek! Več...

4.
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: 217; Prenosov: 11
.pdf Celotno besedilo (444,13 KB)
Gradivo ima več datotek! Več...

5.
Machine learning and algebraic approaches towards complete matter spectra in 4d F-theory
Martin Bies, Mirjam Cvetič, Ron Donagi, Ling Lin, Mingqiang Liu, Fabian Ruehle, 2021, izvirni znanstveni članek

Opis: Motivated by engineering vector-like (Higgs) pairs in the spectrum of 4d Ftheory compactifications, we combine machine learning and algebraic geometry techniques to analyze line bundle cohomologies on families of holomorphic curves. To quantify jumps of these cohomologies, we first generate 1.8 million pairs of line bundles and curves embedded in dP3, for which we compute the cohomologies. A white-box machine learning approach trained on this data provides intuition for jumps due to curve splittings, which we use to construct additional vector-like Higgs-pairs in an F-Theory toy model. We also find that, in order to explain quantitatively the full dataset, further tools from algebraic geometry, in particular Brill-Noether theory, are required. Using these ingredients, we introduce a diagrammatic way to express cohomology jumps across the parameter space of each family of matter curves, which reflects a stratification of the F-theory complex structure moduli space in terms of the vector-like spectrum. Furthermore, these insights provide an algorithmically efficient way to estimate the possible cohomology dimensions across the entire parameter space.
Ključne besede: Differential Geometry, Algebraic Geometry, F-Theory, Flux Compactifications, Field Theories, Higher Dimensions
Objavljeno v DKUM: 13.10.2023; Ogledov: 221; Prenosov: 13
.pdf Celotno besedilo (889,92 KB)
Gradivo ima več datotek! Več...

6.
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: 213; Prenosov: 18
.pdf Celotno besedilo (910,15 KB)
Gradivo ima več datotek! Več...

7.
Brill-Noether-general limit root bundles: absence of vector-like exotics in F-theory standard models
Martin Bies, Mirjam Cvetič, Ron Donagi, Marielle Ong, 2022, izvirni znanstveni članek

Opis: Root bundles appear prominently in studies of vector-like spectra of 4d F-theory compactifications. Of particular importance to phenomenology are the Quadrillion F-theory Standard Models (F-theory QSMs). In this work, we analyze a superset of the physical root bundles whose cohomologies encode the vector-like spectra for the matter representations (3, 2)(1/6), ((3) over bar ,1)(-2/3) and (1,1)(1) For the family B-3(Delta(4)degrees) consisting of O(10(11)) F-theory QSM geometries, we argue that more than 99.995% of the roots in this superset have no vector-like exotics. This indicates that absence of vector-like exotics in those representations is a very likely scenario in the O(10(11)) QSM geometries B-3(Delta(4)degrees). The QSM geometries come in families of toric 3-folds B-3(Delta(4)degrees) obtained from triangulations of certain 3-dimensional polytopes Delta degrees. The matter curves in X-Sigma is an element of B-3(Delta(4)degrees) can be deformed to nodal curves which are the same for all spaces in B-3(Delta(4)degrees). Therefore, one can probe the vector-like spectra on the entire family B-3(Delta(4)degrees) from studies of a few nodal curves. We compute the cohomologies of all limit roots on these nodal curves. In our applications, for the majority of limit roots the cohomologies are determined by line bundle cohomology on rational tree-like curves. For this, we present a computer algorithm. The remaining limit roots, corresponding to circuit-like graphs, are handled by hand. The cohomologies are independent of the relative position of the nodes, except for a few circuits. On these jumping circuits, line bundle cohomologies can jump if nodes are specially aligned. This mirrors classical Brill-Noether jumps. B-3(Delta(4)degrees) admits a jumping circuit, but the root bundle constraints pick the canonical bundle and no jump happens.
Ključne besede: differential geometry, algebraic geometry, F-theory, string phenomenology, brane phenomenology
Objavljeno v DKUM: 17.08.2023; Ogledov: 263; Prenosov: 18
.pdf Celotno besedilo (946,02 KB)
Gradivo ima več datotek! Več...

8.
Compactifications of deformed conifolds, branes and the geometry of qubits
Mirjam Cvetič, G. W. Gibbons, Christopher N. Pope, 2016, izvirni znanstveni članek

Opis: We present three families of exact, cohomogeneity-one Einstein metrics in (2n + 2) dimensions, which are generalizations of the Stenzel construction of Ricci-flat metrics to those with a positive cosmological constant. The first family of solutions are Fubini-Study metrics on the complex projective spaces CPn+1, written in a Stenzel form, whose principal orbits are the Stiefel manifolds V-2(Rn+2) = SO(n+2)/SO(n) divided by Z(2). The second family are also Einstein-Kahler metrics, now on the Grassmannian manifolds G(2)(Rn+3) = SO(n+3)/((SO(n+1)xSO(2)), whose principal orbits are the Stiefel manifolds V-2(Rn+2) (with no Z(2) factoring in this case). The third family are Einstein metrics on the product manifolds Sn+1 x Sn+1, and are Kahler only for n = 1. Some of these metrics are believed to play a role in studies of consistent string theory compactifications and in the context of the AdS/CFT correspondence. We also elaborate on the geometric approach to quantum mechanics based on the Kahler geometry of Fubini-Study metrics on CPn+1, and we apply the formalism to study the quantum entanglement of qubits.
Ključne besede: conformal field models, string theory, models of quantum gravity, differential geometry, algebraic geometry
Objavljeno v DKUM: 27.06.2017; Ogledov: 1350; Prenosov: 390
.pdf Celotno besedilo (586,14 KB)
Gradivo ima več datotek! Več...

9.
General U(1) x U(1) F-theory compactifications and beyond: geometry of unHiggsings and novel matter structure
Mirjam Cvetič, Denis Klevers, Hernan Piragua, Washington Taylor, 2015, izvirni znanstveni članek

Opis: We construct the general form of an F-theory compactification with two U(1) factors based on a general elliptically fibered Calabi-Yau manifold with Mordell-Weil group of rank two. This construction produces broad classes of models with diverse matter spectra, including many that are not realized in earlier F-theory constructions with U(1) x U(1) gauge symmetry. Generic U(1) x U(1) models can be related to a Higgsed non-Abelian model with gauge group SU(2) x SU(2) x SU(3), SU(2)(3) x SU(3), or a subgroup thereof. The nonlocal horizontal divisors of the Mordell-Weil group are replaced with local vertical divisors associated with the Cartan generators of non-Abelian gauge groups from Kodaira singularities. We give a global resolution of codimension two singularities of the Abelian model; we identify the full anomaly free matter content, and match it to the unHiggsed non-Abelian model. The non-Abelian Weierstrass model exhibits a new algebraic description of the singularities in the fibration that results in the first explicit construction of matter in the symmetric representation of SU(3). This matter is realized on double point singularities of the discriminant locus. The construction suggests a generalization to U(1)(k) factors with k > 2, which can be studied by Higgsing theories with larger non-Abelian gauge groups.
Ključne besede: F-theory, differential geometry, algebraic geometry, gauge symmetry
Objavljeno v DKUM: 14.06.2017; Ogledov: 1191; Prenosov: 385
.pdf Celotno besedilo (1,36 MB)
Gradivo ima več datotek! Več...

10.
Prediction of the hardness of hardened specimens with a neural network
Matej Babič, Peter Kokol, Igor Belič, Peter Panjan, Miha Kovačič, Jože Balič, Timotej Verbovšek, 2014, izvirni znanstveni članek

Opis: In this article we describe the methods of intelligent systems to predict the hardness of hardened specimens. We use the mathematical method of fractal geometry in laser techniques. To optimize the structure and properties of tool steel, it is necessary to take into account the effect of the self-organization of a dissipative structure with fractal properties at a load. Fractal material science researches the relation between the parameters of fractal structures and the dissipative properties of tool steel. This paper describes an application of the fractal dimension in the robot laser hardening of specimens. By using fractal dimensions, the changes in the structure can be determined because the fractal dimension is an indicator of the complexity of the sample forms. The tool steel was hardened with different speeds and at different temperatures. The effect of the parameters of robot cells on the material was better understood by researching the fractal dimensions of the microstructures of hardened specimens. With an intelligent system the productivity of the process of laser hardening was increased because the time of the process was decreased and the topographical property of the material was increased.
Ključne besede: fractal dimension, fractal geometry, neural network, prediction, hardness, steel, tool steel, laser
Objavljeno v DKUM: 17.03.2017; Ogledov: 1866; Prenosov: 110
.pdf Celotno besedilo (632,41 KB)
Gradivo ima več datotek! Več...

Iskanje izvedeno v 5.04 sek.
Na vrh
Logotipi partnerjev Univerza v Mariboru Univerza v Ljubljani Univerza na Primorskem Univerza v Novi Gorici