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1.	Anderson, Lara B., et al. (författare) Generalized vanishing theorems for Yukawa couplings in heterotic compactifications 2021 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :5 Tidskriftsartikel (refereegranskat)abstract Heterotic compactifications on Calabi-Yau threefolds frequently exhibit textures of vanishing Yukawa couplings in their low energy description. The vanishing of these couplings is often not enforced by any obvious symmetry and appears to be topological in nature. Recent results used differential geometric methods to explain the origin of some of this structure [1, 2]. A vanishing theorem was given which showed that the effect could be attributed, in part, to the embedding of the Calabi-Yau manifolds of interest inside higher dimensional ambient spaces, if the gauge bundles involved descended from vector bundles on those larger manifolds. In this paper, we utilize an algebro-geometric approach to provide an alternative derivation of some of these results, and are thus able to generalize them to a much wider arena than has been considered before. For example, we consider cases where the vector bundles of interest do not descend from bundles on the ambient space. In such a manner we are able to highlight the ubiquity with which textures of vanishing Yukawa couplings can be expected to arise in heterotic compactifications, with multiple different constraints arising from a plethora of different geometric features associated to the gauge bundle.
2.	Braun, Andreas P., et al. (författare) Gauged 2-form symmetries in 6D SCFTs coupled to gravity 2021 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :12 Tidskriftsartikel (refereegranskat)abstract We study six dimensional supergravity theories with superconformal sectors (SCFTs). Instances of such theories can be engineered using type IIB strings, or more generally F-Theory, which translates field theoretic constraints to geometry. Specifically, we study the fate of the discrete 2-form global symmetries of the SCFT sectors. For both (2, 0) and (1, 0) theories we show that whenever the charge lattice of the SCFT sectors is non-primitively embedded into the charge lattice of the supergravity theory, there is a subgroup of these 2-form symmetries that remains unbroken by BPS strings. By the absence of global symmetries in quantum gravity, this subgroup much be gauged. Using the embedding of the charge lattices also allows us to determine how the gauged 2-form symmetry embeds into the 2-form global symmetries of the SCFT sectors, and we present several concrete examples, as well as some general observations. As an alternative derivation, we recover our results for a large class of models from a dual perspective upon reduction to five dimensions.
3.	Braun, Andreas P., et al. (författare) Infinitely many M2-instanton corrections to M-theory on G(2)-manifolds 2018 Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :9 Tidskriftsartikel (refereegranskat)abstract We consider the non-perturbative superpotential for a class of four-dimensional N = 1 vacua obtained from M-theory on seven-manifolds with holonomy G(2). The class of G(2)-holonomy manifolds we consider are so-called twisted connected sum (TCS) constructions, which have the topology of a K3-fibration over S-3. We show that the non-perturbative superpotential of M-theory on a class of TCS geometries receives infinitely many inequivalent M2-instanton contributions from infinitely many three-spheres, which we conjecture are supersymmetric (and thus associative) cycles. The rationale for our construction is provided by the duality chain of [1], which relates M-theory on TCS G(2) manifolds to E-8 x E-8 heterotic backgrounds on the Schoen Calabi-Yau threefold, as well as to F-theory on a K3-fibered Calabi-Yau fourfold. The latter are known to have an infinite number of instanton corrections to the superpotential and it is these contributions that we trace through the duality chain back to the G(2)-compactification.
4.	Candelas, Philip, et al. (författare) 4 Type IIB flux vacua from G-theory I 2015 Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :2 Tidskriftsartikel (refereegranskat)abstract We construct non-perturbatively exact four-dimensional Minkowski vacua of type IIB string theory with non-trivial fluxes. These solutions are found by gluing together, consistently with U-duality, local solutions of type IIB supergravity on T-4 x C with the metric, dilaton and flux potentials varying along C and the flux potentials oriented along T-4. We focus on solutions locally related via U-duality to non-compact Ricci-flat geometries. More general solutions and a complete analysis of the supersymmetry equations are presented in the companion paper [1]. We build a precise dictionary between fluxes in the global solutions and the geometry of an auxiliary K3 surface fibered over CP1. In the spirit of F-theory, the flux potentials are expressed in terms of locally holomorphic functions that parametrize the complex structure moduli space of the K3 fiber in the auxiliary geometry. The brane content is inferred from the monodromy data around the degeneration points of the fiber.
5.	Candelas, Philip, et al. (författare) Type IIB flux vacua from G-theory II 2015 Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :2 Tidskriftsartikel (refereegranskat)abstract We find analytic solutions of type IIB supergravity on geometries that locally take the form Mink x M-4 x C with M-4 a generalised complex manifold. The solutions involve the metric, the dilaton, NSNS and RR flux potentials (oriented along the M-4) parametrised by functions varying only over C. Under this assumption, the supersymmetry equations are solved using the formalism of pure spinors in terms of a finite number of holomorphic functions. Alternatively, the solutions can be viewed as vacua of maximally supersymmetric supergravity in six dimensions with a set of scalar fields varying holomorphically over C. For a class of solutions characterised by up to five holomorphic functions, we outline how the local solutions can be completed to four-dimensional flux vacua of type IIB theory. A detailed study of this global completion for solutions with two holomorphic functions has been carried out in the companion paper [1]. The fluxes of the global solutions are, as in F-theory, entirely codified in the geometry of an auxiliary K3 fibration over CP1. The results provide a geometric construction of fluxes in F-theory.
6.	Chialva, Diego, et al. (författare) Deforming, revolving and resolving : New paths in the string theory landscape 2008 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; 02 Tidskriftsartikel (refereegranskat)abstract In this paper we investigate the properties of series of vacua in the string theory landscape. In particular, we study minima to the flux potential in type IIB compactifications on the mirror quintic. Using geometric transitions, we embed its one-dimensional complex structure moduli space in that of another Calabi-Yau with h1,1 = 86 and h2,1 = 2. We then show how to construct infinite series of continuously connected minima to the mirror quintic potential by moving into this larger moduli space, applying its monodromies, and moving back. We provide an example of such series, and discuss their implications for the string theory landscape
7.	Danielsson, Ulf, et al. (författare) 4D black holes and holomorphic factorization of the 0A matrix model Tidskriftsartikel (refereegranskat)
8.	Danielsson, Ulf, et al. (författare) 4D black holes and holomorphic factorization of the 0A matrix model 2005 Ingår i: Journal of High Energy Physics. ; 0510, s. 046- Tidskriftsartikel (refereegranskat)abstract n this letter, we relate the free energy of the 0A matrix model to the sum of topological and anti-topological string amplitudes. For arbitrary integer multiples of the matrix model self-dual radius we describe the geometry on which the corresponding topological string propagates. This geometry is not the one that follows from the usual ground ring analysis, but in a sense its "holomorphic square root". Mixing of terms for different genus in the matrix model free energy yields one-loop terms compatible with type II strings on compact Calabi-Yau target spaces. As an application, we give an explicit example of how to relate the 0A matrix model free energy to that of a four-dimensional black hole in type IIB theory, compactified on a compact Calabi-Yau. Variables, Legendre transforms, and large classical terms on both sides match perfectly.
9.	Danielsson, Ulf, et al. (författare) Stability of flux vacua in the presence of charged black 2006 Ingår i: JHEP. ; 09, s. 069- Tidskriftsartikel (refereegranskat)abstract In this letter we consider a charged black hole in a flux compactification of type IIB string theory. Both the black hole and the fluxes will induce potentials for the complex structure moduli. We choose the compact dimensions to be described locally by a deformed conifold, creating a large hierarchy. We demonstrate that the presence of a black hole typically will not change the minimum of the moduli potential in a substantial way. However, we also point out a couple of possible loop-holes, which in some cases could lead to interesting physical consequences such as changes in the hierarchy.
10.	Danielsson, Ulf, et al. (författare) The world next door: Results in landscape topography 2007 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; 03, s. 080- Tidskriftsartikel (refereegranskat)abstract Recently, it has become clear that neighboring multiple vacua might have interesting consequences for the physics of the early universe. In this paper we investigate the topography of the string landscape corresponding to complex structure moduli of flux compactified type IIB string theory. We find that series of continuously connected vacua are common. The properties of these series are described, and we relate the existence of infinite series of minima to certain unresolved mathematical problems in group theory. Numerical studies of the mirror quintic serve as illustrating examples.
11.	de la Ossa, Xenia, et al. (författare) Almost contact structures on manifolds with a G(2) structure 2022 Ingår i: Advances in Theoretical and Mathematical Physics. - : INT PRESS BOSTON, INC. - 1095-0761 .- 1095-0753. ; 26:1, s. 143-216 Tidskriftsartikel (refereegranskat)abstract We review the construction of almost contact metric (three-) struc-tures, abbreviated ACM(3)S, on manifolds with a G2 structure. These are of interest for certain supersymmetric configurations in string and M-theory. We compute the torsion of the SU(3) struc-ture associated to an ACMS and apply these computations to het -erotic G2 systems and supersymmetry enhancement. We initiate the study of the space of ACM3Ss, which is an infinite dimensional space with a local product structure and interesting topological features. Tantalising links between ACM3Ss and associative and coassociative submanifolds are observed.
12.	de la Ossa, Xenia, et al. (författare) Almost contact structures on manifolds with a G2 structure 2021 Annan publikation (övrigt vetenskapligt/konstnärligt)abstract We review the construction of almost contact metric (three-) structures, abbreviated ACM(3)S, on manifolds with a G2 structure. These are of interest for certain supersymmetric configurations in string and M-theory. We compute the torsion of the SU(3) structure associated to an ACMS and apply these computations to heterotic G2 systems and supersymmetry enhancement. We initiate the study of the space of ACM3Ss, which is an infinite dimensional space with a local product structure and interesting topological features. Tantalising links between ACM3Ss and associative and coassociative submanifolds are observed.
13.	de la Ossa, Xenia, et al. (författare) Exploring SU(3) structure moduli spaces with integrable G(2) structures 2015 Ingår i: Advances in Theoretical and Mathematical Physics. - 1095-0761 .- 1095-0753. ; 19:4, s. 837-903 Tidskriftsartikel (refereegranskat)abstract We study the moduli space of SU(3) structure manifolds X that form the internal compact spaces in four-dimensional N = 1/2 domain wall solutions of heterotic supergravity with flux. Together with the direction perpendicular to the four-dimensional domain wall, X forms a non-compact 7-manifold Y with torsionful G(2) structure. We use this G(2) embedding to explore how X(t) varies along paths C(t) in the SU(3) structure moduli space. Our analysis includes the Bianchi identities which strongly constrain the flow. We show that requiring that the SU(3) structure torsion is preserved along the path leads to constraints on the G(2) torsion and the embedding of X in Y. Furthermore, we study flows along which the torsion classes of X go from zero to non-zero values. In particular, we present evidence that the flow of half-flat SU(3) structures may contain Calabi-Yau loci, in the presence of non-vanishing H-flux.
14.	de la Ossa, Xenia, et al. (författare) Infinitesimal moduli of G2 holonomy manifolds with instanton bundles 2016 Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :11 Tidskriftsartikel (refereegranskat)abstract We describe the infinitesimal moduli space of pairs (Y, V) where Y is a manifold with G(2) holonomy, and V is a vector bundle on Y with an instanton connection. These structures arise in connection to the moduli space of heterotic string compactifications on compact and non-compact seven dimensional spaces, e.g. domain walls. Employing the canonical G(2) cohomology developed by Reyes-Carrion and Fern\'andez and Ugarte, we show that the moduli space decomposes into the sum of the bundle moduli H-d(sic)A(1)(Y, End(V)) plus the moduli of the G(2) structure preserving the instanton condition. The latter piece is contained in H-d(sic)theta(1)(Y, TY), and is given by the kernel of a map F(sic) which generalises the concept of the Atiyah map for holomorphic bundles on complex manifolds to the case at hand. In fact, the map F(sic) is given in terms of the curvature of the bundle and maps H-d(sic)theta(1)(Y, TY) into H-d(sic)A(2) (Y, End(V)), and moreover can be used to define a cohomology on an extension bundle of TY by End(V). We comment further on the resemblance with the holomorphic Atiyah algebroid and connect the story to physics, in particular to heterotic compactifications on (Y,V) when alpha'=0.
15.	de la Ossa, Xenia, et al. (författare) Restrictions of Heterotic G2 Structures and Instanton Connections 2017 Ingår i: Proceedings, Nigel Hitchin’s 70th Birthday Conference. - Oxford : Oxford University Press. - 9780198802020 Konferensbidrag (refereegranskat)abstract This note revisits recent results regarding the geometry and moduli of solutions of the heterotic string on manifolds Y with a G2 structure. In particular, such heterotic G2 systems can be rephrased in terms of a differential Dˇ acting on a complex Ωˇ∗(Y,Q), where Q=T∗Y⊕End(TY)⊕End(V), and Dˇ is an appropriate projection of an exterior covariant derivative D which satisfies an instanton condition. The infinitesimal moduli are further parametrized by the first cohomology H1Dˇ(Y,Q). We proceed to restrict this system to manifolds X with an SU(3) structure corresponding to supersymmetric compactifications to four-dimensional Minkowski space, often referred to as Strominger–Hull solutions. In doing so, we derive a new result: the Strominger-Hull system is equivalent to a particular holomorphic Yang–Mills covariant derivative on Q\|X=T∗X⊕End(TX)⊕End(V).
16.	de la Ossa, Xenia, et al. (författare) Superpotential of three dimensional N=1 heterotic supergravity 2020 Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :1 Tidskriftsartikel (refereegranskat)abstract We dimensionally reduce the ten dimensional heterotic supergravity action on spacetimes of the form M-(1,M- 2) x Y, where M-(1,M- 2) is three dimensional maximally symmetric Anti de Sitter or Minkowski space, and Y is a compact seven dimensional manifold with G(2) structure. In doing so, we derive the real superpotential functional of the corresponding three dimensional N = 1 theory. We confirm that extrema of this functional correspond to supersymmetric heterotic compacti:fications on manifolds of G(2) structure in the large volume, weak coupling limit to first order in a'. We make some comments on the role of the superpotential functional with respect to the coupled moduli problem of instanton bundles over G(2) manifolds.
17.	de la Ossa, Xenia, et al. (författare) The Infinitesimal Moduli Space of Heterotic G2 Systems 2018 Ingår i: Communications in Mathematical Physics. - : Springer Science and Business Media LLC. - 0010-3616 .- 1432-0916. ; 360:2, s. 727-775 Tidskriftsartikel (refereegranskat)abstract Heterotic string compactifications on integrable G(2) structure manifolds Y with instanton bundles (V, A), (TY, (theta) over tilde )yield supersymmetric three-dimensional vacua that are of interest in physics. In this paper, we define a covariant exterior derivative D and show that it is equivalent to a heterotic G(2) system encoding the geometry of the heterotic string compactifications. This operator D acts on a bundle Q = T*Y circle plus End (V) circle plus End (TY) and satisfies a nilpotency condition (sic)(2) = 0, for an appropriate projection of D. Furthermore, we determine the infinitesimal moduli space of these systems and show that it corresponds to the finite-dimensional cohomology group (sic)(1)((sic)) (Q). We comment on the similarities and differences of our result with Atiyah's well-known analysis of deformations of holmorphic vector bundles over complex manifolds. Our analysis leads to results that are of relevance to all orders in the alpha' expansion.
18.	Freyhult, Lisa, 1977-, et al. (författare) Kontextrika problem för effektiv problemlösning i en avancerad mekanikkurs 2017 Ingår i: Proceedings från 6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar. Konferensbidrag (refereegranskat)
19.	Freyhult, Lisa, 1977-, et al. (författare) Working with context rich problems to teach problem solving 2017 Ingår i: Transforming patterns through the scholarship of teaching and learning. Konferensbidrag (refereegranskat)abstract The ability to solve problems is an important ability for scientists as well as engineers and something we identify as a key competence for our students. Problem solving is often examined but still students complain about the difficulty of the examination, describing the problems as more difficult than the problems they have encountered previously.Our study suggests that our students often use inefficient strategies for problem solving, like pattern matching or trying to find a mathematical formula that fits the situation. It is clear that these strategies will not work and they become less and less useful the further the students get in their education.To train problem solving and to prepare students to handle unknown problems and situations cooperative problem solving and context rich problems have been identified as efficient strategies [1,2]. These methods have specifically been used in early courses in mechanics and similar experiences with open ended but shorter problems have been described in [3,4,5]. We have applied these strategies in a more advanced course in Lagrangian mechanics. Students perceive this topic as somewhat abstract and disconnected from everyday experience and lack a clear relevance to their professional role. We describe our work as a team of teachers and our experience introducing a new methodology in the course with the goal to teach in a way that discourages inefficient problem solving strategies.ReferencesHeller, P och Heller, K (2010) Cooperative Problem Solving in Physics A User’s ManualHeller, P, Keith, R och Andersson (1992), Teaching problem solving through cooperative grouping. Part 1: Group versus individual problem solving, S, Am. J. Phys. 60, 627; Heller, P och Hollabaugh, M (1992), Teaching problem solving through cooperative grouping. Part 2: Designing problems and structuring groups, Am. J. Phys. 60, 637Maloney, D., Research on problem solving in physics, in D. Gabel (ed.) (1994), Handbook of research in science teaching and learning, New YorkWedelin, D., Adawi, T., Jahan T. and Andersson, S., (2015), Investigating and developing engineering students’ mathematical modelling and problem-solving skills, European Journal of Engineering Education, 40:5, pp. 557-572Wedelin, D. och Adawi, D. (2015), Warming up for PBL: a course in mathematical modelling and problem solving for engineering students Högre utbildning Vol. 5, No. 1, pp. 23-34
20.	Johnson, Matthew C, et al. (författare) Field dynamics and tunneling in a flux landscape 2008 Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 78:8, s. 0835341-08353423 Tidskriftsartikel (refereegranskat)
21.	Johnson, Matthew C, et al. (författare) Obstacle to populating the string theory landscape 2008 Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 78:12, s. 1235131-1235135 Tidskriftsartikel (refereegranskat)abstract We construct domain walls and instantons in a class of models with coupled scalar fields, determining, in agreement with previous studies, that many such solutions contain naked timelike singularities. Vacuum bubble solutions of this type do not contain a region of true vacuum, obstructing the ability of eternal inflation to populate other vacua. We determine a criterion that potentials must satisfy to avoid the existence of such singularities and show that many domain wall solutions in type IIB string theory are singular.
22.	Kohl, Finn Bjarne, et al. (författare) F-theory on 6D symmetric toroidal orbifolds 2022 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. Tidskriftsartikel (refereegranskat)abstract In this work we study F-theory on symmetric toroidal orbifolds that exhibit roto-translations, which are point group rotations accompanied by fractional lattice shifts. These geometries admit a rich class of effects, such as twisted affine folded fibers, multiple fibers, and up to three distinct torus-fibrations that yield different M/F-theory lifts. We discuss the six-dimensional physics of the F-theory lifts, which generically host superconformal subsectors and a IIB axio-dilaton fixed to strong coupling. In addition we find that these theories exhibit a rich set of p = 0,1, 2 discrete p-form gauge symmetries. We discuss six-dimensional gauge and supergravity anomalies and match the rank and tensor branch dimension to the Hodge numbers that were computed using heterotic world sheet techniques.
23.	Larfors, Magdalena, 1978-, et al. (författare) Calabi-Yau manifolds and SU(3) structure 2019 Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :1 Tidskriftsartikel (refereegranskat)abstract We show that non-trivial SU(3) structures can be constructed on large classes of Calabi-Yau three-folds. Specifically, we focus on Calabi-Yau three-folds constructed as complete intersections in products of projective spaces, although we expect similar methods to apply to other constructions and also to Calabi-Yau four-folds. Among the wide range of possible SU(3) structures we find Strominger-Hull systems, suitable for heterotic or type II string compactifications, on all complete intersection Calabi-Yau manifolds. These SU(3) structures of Strominger-Hull type have a non-vanishing and non-closed three-form flux which needs to be supported by source terms in the associated Bianchi identity. We discuss the possibility of finding such source terms and present first steps towards their explicit construction. Provided suitable sources exist, our methods lead to Calabi-Yau compactifications of string theory with a non Ricci-flat, physical metric which can be written down explicitly and in analytic form.
24.	Larfors, Magdalena, 1978-, et al. (författare) Explore and Exploit with Heterotic Line Bundle Models 2020 Ingår i: Fortschritte der Physik. - : Wiley. - 0015-8208 .- 1521-3978. ; 68:5 Tidskriftsartikel (refereegranskat)abstract We use deep reinforcement learning to explore a class of heterotic SU(5) GUT models constructed from line bundle sums over Complete Intersection Calabi Yau (CICY) manifolds. We perform several experiments where A3C agents are trained to search for such models. These agents significantly outperform random exploration, in the most favourable settings by a factor of 1700 when it comes to finding unique models. Furthermore, we find evidence that the trained agents also outperform random walkers on new manifolds. We conclude that the agents detect hidden structures in the compactification data, which is partly of general nature. The experiments scale well with h((1, 1)), and may thus provide the key to model building on CICYs with large h((1, 1)).
25.	Larfors, Magdalena (författare) Generalised Geometry and Flux Vacua : A very short review 2016 Konferensbidrag (refereegranskat)abstract This note discusses the connection between generalised geometry and flux compactifications of string theory. Firstly, we explain in a pedestrian manner how the supersymmetry constraints of type II flux compactifications can be restated as integrability constraints on certain generalised complex structures. This reformulation uses generalised complex geometry, a mathematical framework that geometrizes the B-field. Secondly, we discuss how exceptional generalised geometry may provide a similar geometrization of the RR fields. Thirdly, we examine the connection between generalised geometry and non-geometry, and finally we present recent developments where generalised geometry is used to construct explicit examples of flux compactifications to flat space.
26.	Larfors, Magdalena, 1978-, et al. (författare) Heterotic line bundle models on generalized complete intersection Calabi Yau manifolds 2021 Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :5 Tidskriftsartikel (refereegranskat)abstract The systematic program of heterotic line bundle model building has resulted in a wealth of standard-like models (SLM) for particle physics. In this paper, we continue this work in the setting of generalised Complete Intersection Calabi Yau (gCICY) manifolds. Using the gCICYs constructed in ref. [1], we identify two geometries that, when combined with line bundle sums, are directly suitable for heterotic GUT models. We then show that these gCICYs admit freely acting Z(2) symmetry groups, and are thus amenable to Wilson line breaking of the GUT gauge group to that of the standard model. We proceed to a systematic scan over line bundle sums over these geometries, that result in 99 and 33 SLMs, respectively. For the first class of models, our results may be compared to line bundle models on homotopically equivalent Complete Intersection Calabi Yau manifolds. This shows that the number of realistic configurations is of the same order of magnitude.
27.	Larfors, Magdalena, 1978-, et al. (författare) Learning Size and Shape of Calabi-Yau Spaces 2021 Ingår i: Machine Learning and the Physical Sciences Workshop at the 35th Conference on Neural Information Processing Systems (NeurIPS) December 13, 2021. Konferensbidrag (refereegranskat)abstract We present a new machine learning library for computing metrics of string compact-ification spaces. We benchmark the performance on Monte-Carlo sampled integralsagainst previous numerical approximations and find that our neural networks aremore sample- and computation-efficient. We are the first to provide the possibilityto compute these metrics for arbitrary, user-specified shape and size parameters ofthe compact space and observe a linear relation between optimization of the partialdifferential equation we are training against and vanishing Ricci curvature
28.	Larfors, Magdalena, 1978-, et al. (författare) Line Bundle Cohomologies on CICYs with Picard Number Two 2019 Ingår i: Fortschritte der Physik. - : Wiley. - 0015-8208 .- 1521-3978. ; 67:12 Tidskriftsartikel (refereegranskat)abstract We analyse line bundle cohomologies on all favourable co-dimension two Complete Intersection Calabi Yau (CICY) manifolds of Picard number two. Our results provide further evidence that the cohomology dimensions of such line bundles are given by analytic expressions, which change between regions in the line bundle charge space. This agrees with recent observations of CY line bundles presented in Refs. [1, 2]. In many cases, the expressions for bundle cohomology dimensions are polynomial functions of the line bundle charges (of degree at most 3), and the regions are cones. A more novel observation is that for some CICY manifolds, the cohomologies are more succinctly determined by recursive relationships. There can also be boundaries between regions where a polynomial fit fails, and we link these exceptional cases to irregular behaviour of the index of the line bundle. Finally, our observations provide evidence for similarities in the line bundle cohomologies for CICY manifolds that share rows in the configuration matrix. Among such related CICY manifolds, we find both that the line bundle charge space is partitioned in the same manner, and that the same, or closely related, analytical descriptions apply for the cohomology dimensions in these regions.
29.	Larfors, Magdalena, 1978-, et al. (författare) Numerical metrics for complete intersection and Kreuzer-Skarke Calabi-Yau manifolds 2022 Ingår i: Machine Learning. - : Institute of Physics (IOP). - 2632-2153. ; 3:3 Tidskriftsartikel (refereegranskat)abstract We introduce neural networks (NNs) to compute numerical Ricci-flat Calabi-Yau (CY) metrics for complete intersection and Kreuzer-Skarke (KS) CY manifolds at any point in Kahler and complex structure moduli space, and introduce the package cymetric which provides computation realizations of these techniques. In particular, we develop and computationally realize methods for point-sampling on these manifolds. The training for the NNs is carried out subject to a custom loss function. The Kahler class is fixed by adding to the loss a component which enforces the slopes of certain line bundles to match with topological computations. Our methods are applied to various manifolds, including the quintic manifold, the bi-cubic manifold and a KS manifold with Picard number two. We show that volumes and line bundle slopes can be reliably computed from the resulting Ricci-flat metrics. We also apply our results to compute an approximate Hermitian-Yang-Mills connection on a specific line bundle on the bi-cubic.
30.	Larfors, Magdalena, 1978- (författare) Pierced, Wrapped and Torn : Aspects of String Theory Compactifications 2009 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract An outstanding problem in physics is to find a unified framework for quantum mechanics and general relativity. This is required for a better understanding of black holes and the early cosmology of the universe. String theory provides such a unification. In this thesis, we study aspects of compactifications of type IIB string theory. In the first part of the thesis, we study four-dimensional black holes consisting of D3-branes wrapping cycles in the compact dimensions. We discuss the correspondence between these black holes, topological string theory and matrix models. We then study the influence of black holes on the stability of flux compactifications. In the second part of the thesis, we turn to investigations of the type IIB landscape, i.e. the collection of stable and metastable vacua obtained from flux compactifications on conformal Calabi-Yau manifolds. We show that monodromies are important for the topographic structure of the landscape. In particular we find that there are long series of continuously connected vacua in the complex structure moduli space of the internal manifold. We also use geometric transitions to connect the moduli spaces of different manifolds, and create longer series of vacua. Finally, we investigate the stability of string theory vacua by constructing semiclassical instantons. These results have implications for the population of the landscape by eternal inflation.
31.	Magill, Matthew (författare) Aspects of vacuum moduli in string theory 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In this thesis we explore geometric aspects of the space of vacua in supersymmetric string compactifications. More specifically, we will look at heterotic strings compactified on Calabi-Yau manifolds and, separately, G2 structure manifolds. After reviewing the basic concepts underlying the thesis, specifically dimensional reduction of supergravity theories and G structures on manifolds, we begin looking at the vacua leading to supersymmetric three dimensional theories. The underlying compact manifold has a G2 structure. We investigate some structures that further refine the G2 structure: almost contact metric three-structures. We report on a relation between these structures and (co)associative cycles in the G2 structure manifold, and initiate an exploration of the topological properties of the moduli space of such structures. Next, we identify a superpotential whose critical locus is precisely the moduli space of supersymmetry preserving backgrounds, including both gauge and geometric fields. Finally, we study the Yukawa couplings of heterotic string compactifications on Calabi-Yau manifolds. Using sheaf cohomological tools, we find widely applicable vanishing theorems, which can constrain the Yukawa couplings of the effective four dimensional theory.
32.	Schneider, Robin (författare) Heterotic Compactifications in the Era of Data Science 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The goal of this thesis is to review and investigate recent applications of machine learning to problems in string theory. String theory, the leading candidate for a uniﬁcation of gravity and the standard model of particle physics, requires the introduction of additional space-time dimensions. To match experimental observations of our universe, these additional dimensions need to be curled up on a compact space. The most common choice to describe this compact space are manifolds of Calabi-Yau type. These manifolds come with favourable mathematical and phenomenological properties.In the ﬁrst half of this thesis Calabi-Yau manifolds, which are complex Kähler manifolds admitting a Ricci-ﬂat metric, are introduced. The popular construction as complete intersections in products of complex projective space is explained and the necessary mathematical machinery to compute their topological quantities presented. This part is followed by a review of machine learning applications to study their Hodge numbers and the cohomologies of line bundles. In a next step the new Python library cymetric is presented for modeling numerical approximations of the unknown Ricci-ﬂat metric. The metric tensor is a required component in the calculation of Yukawa couplings. It is learned by a neural network trained against a custom loss function, that encodes all the necessary mathematical properties.In the second half Calabi-Yau manifolds are used to compactify the heterotic string and con-struct standard model like vacua. Those are vacua which match the particle content and gaugegroup of a supersymmetric extension of the standard model. First, the popular compactiﬁcationprocedure utilising line bundle sums is reviewed and applied to the newly discovered construc-tions of generalized complete intersection Calabi-Yau manifolds. Second, an exploration ofsuch models is initiated in so far uncharted territories. This includes two Calabi-Yau manifoldswith more than 7 Kähler moduli, which are beyond systematic computational reach. In total19538 new models are found by using Actor-Critic agents from deep reinforcement learning.

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