## Publications

162 results found

Gkountoumis G, Hull C, Stemerdink K,
et al., 2023, Freely acting orbifolds of type IIB string theory on T<SUP>5</SUP>, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

Hull C, 2022, Gravity, duality and conformal symmetry, *PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES*, Vol: 478, ISSN: 1364-5021

Arvanitakis AS, Hohm O, Hull C,
et al., 2022, Homotopy transfer and effective field theory II: strings and double field theory, *Fortschritte Der Physik/Progress of Physics*, Vol: 70, Pages: 1-26, ISSN: 0015-8208

We continue our study of effective field theory via homotopy transfer ofL∞-algebras, and apply it to tree-level non-Wilsonian effective actions of thekind discussed by Sen in which the modes integrated out are comparable inmass to the modes that are kept. We focus on the construction of effectiveactions for string states at fixed levels and in particular on the construction ofweakly constrained double field theory. With these examples in mind, wediscuss closed string theory on toroidal backgrounds and resolve some subtleissues involving vertex operators, including the proper form of cocycle factorsand of the reflector state. This resolves outstanding issues concerning theconstruction of covariant closed string field theory on toroidal backgrounds.The weakly constrained double field theory is formally obtained from closedstring field theory on a toroidal background by integrating out all but the‘doubly massless’ states and homotopy transfer then gives a prescription fordetermining the theory’s vertices and symmetries. We also discuss consistenttruncation in the context of homotopy transfer.

Arvanitakis AS, Hohm O, Hull C,
et al., 2022, Homotopy transfer and effective field theory I: tree-level, *Fortschritte Der Physik/Progress of Physics*, Vol: 70, Pages: 1-36, ISSN: 0015-8208

We use the dictionary between general field theories and strongly homotopyalgebras to provide an algebraic formulation of the procedure of integratingout of degrees of freedom in terms of homotopy transfer. This includes moregeneral effective theories in which some massive modes are kept while othermodes of a comparable mass scale are integrated out, as first explored by Senin the context of closed string field theory. We treatL∞-algebras both in termsof a nilpotent coderivation and, on the dual space, in terms of a nilpotentderivation (corresponding to the BRST charge of the field theory) and provideexplicit formulas for homotopy transfer. These are then shown to govern theintegrating out of degrees of freedom at tree level, while the generalization toloop level will be explored in a sequel to this paper.

Hull C, Marcus E, Stemerdink K,
et al., 2020, Black holes in string theory with duality twists, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 4

Chaemjumrus N, Hull CM, 2020, Special holonomy manifolds, domain walls, intersecting branes and T-folds, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 2

Chaemjumrus N, Hull CM, 2019, The doubled geometry of nilmanifold reductions, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 3

Gautier Y, Hull CM, Israel D, 2019, Heterotic/type II duality and non-geometric compactifications, *The Journal of High Energy Physics*, Vol: 214, Pages: 1-44, ISSN: 1029-8479

We present a new class of dualities relating non-geometric Calabi-Yau com- pactifications of type II string theory to T-fold compactifications of the heterotic string, both preserving four-dimensional N = 2 supersymmetry. The non-geometric Calabi-Yau space is a K 3 fibration over T2 with non-geometric monodromies in the duality group O(Γ4,20); this is dual to a heterotic reduction on a T4 fibration over T2 with the O(Γ4,20) monodromies now viewed as heterotic T-dualities. At a point in moduli space which is a minimum of the scalar potential, the type II compactification becomes an asymmetric Gepner model and the monodromies become automorphisms involving mirror symmetries, while the heterotic dual is an asymmetric toroidal orbifold. We generalise previous constructions to ones in which the automorphisms are not of prime order. The type II construction is perturbatively consistent, but the naive heterotic dual is not modular invariant. Modular invariance on the heterotic side is achieved by including twists in the circles dual to the winding numbers round the T2, and this in turn introduces non-perturbative phases depending on NS5-brane charge in the type II construction.

Chaemjumrus N, Hull CM, 2019, Degenerations of K3, orientifolds and exotic branes, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 8

Hull C, Szabo RJ, 2019, Noncommutative gauge theories on D-branes in non-geometric backgrounds, *The Journal of High Energy Physics*, Vol: 51, Pages: 1-41, ISSN: 1029-8479

We investigate the noncommutative gauge theories arising on the worldvolumes of D-branes in non-geometric backgrounds obtained by T-duality from twisted tori. We revisit the low-energy effective description of D-branes on three-dimensional T-folds, examining both cases of parabolic and elliptic twists in detail. We give a detailed description of the decoupling limits and explore various physical consequences of the open string non-geometry. The T-duality monodromies of the non-geometric backgrounds lead to Morita duality monodromies of the noncommutative Yang-Mills theories induced on the D-branes. While the parabolic twists recover the well-known examples of noncommutative principal torus bundles from topological T-duality, the elliptic twists give new examples of noncommutative fibrations with non-geometric torus fibres. We extend these considerations to D-branes in backgrounds with R-flux, using the doubled geometry formulation, finding that both the non-geometric background and the D-brane gauge theory necessarily have explicit dependence on the dual coordinates, and so have no conventional formulation in spacetime.

Abou-Zeid M, Hull CM, Lindstroem U,
et al., 2019, T-duality in (2,1) superspace, *Journal of High Energy Physics*, Vol: 2019, ISSN: 1029-8479

We find the T-duality transformation rules for 2-dimensional (2,1) supersymmetric sigma-models in (2,1) superspace. Our results clarify certain aspects of the (2,1) sigma model geometry relevant to the discussion of T-duality. The complexified duality transformations we find are equivalent to the usual Buscher duality transformations (including an important refinement) together with diffeomorphisms. We use the gauging of sigma-models in (2,1) superspace, which we review and develop, finding a manifestly real and geometric expression for the gauged action. We discuss the obstructions to gauging (2,1) sigma-models, and find that the obstructions to (2,1) T-duality are considerably weaker.

Hull C, LindstrÃ¶m U, 2019, The Generalised Complex Geometry of (p, q) Hermitian Geometries, *Communications in Mathematical Physics*, ISSN: 0010-3616

Giribet G, Hull C, Kleban M,
et al., 2018, Superstrings on AdS(3) at k=1, *The Journal of High Energy Physics*, Vol: 2018, ISSN: 1029-8479

We study superstring theory in three dimensional Anti-de Sitter spacetime with NS-NS flux, focusing on the case where the radius of curvature is equal to the string length. This corresponds to the critical level k = 1 in the formulation as a Wess-Zumino-Witten model. Previously, it was argued that a transition takes place at this special radius, from a phase dominated by black holes at larger radius to one dominated by long strings at smaller radius. We argue that the infinite tower of modes that become massless at k = 1 is a signal of this transition. We propose a simple two-dimensional conformal field theory as the holographic dual to superstring theory at k = 1. As evidence for our conjecture, we demonstrate that our putative dual exactly reproduces the full spectrum of the long strings of the weakly coupled string theory, including states unprotected by supersymmetry.

Hull CM, Israel D, Sarti A, 2017, Non-geometric Calabi-Yau backgrounds and K3 automorphisms, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

Hull C, Lindstrom U, 2017, All (4,0): Sigma models with (4,0) off-shell supersymmetry, *Journal of High Energy Physics*, Vol: 2017, ISSN: 1029-8479

Off-shell (4, 0) supermultiplets in 2-dimensions are formulated. These are usedto construct sigma models whose target spaces are vector bundles over manifolds that arehyperk¨ahler with torsion. The off-shell supersymmetry implies that the complex structuresare simultaneously integrable and allows us to write actions using extended superspace andprojective superspace, giving an explicit construction of the target space geometries.

Gaberdiel MR, Gopakumar R, Hull C, 2017, Stringy AdS(3) from the worldsheet, *The Journal of High Energy Physics*, ISSN: 1029-8479

We investigate the behaviour of the bosonic string on AdS3 with H-flux at stringy scales, looking in particular for a ‘tensionless’ limit in which there are massless higher spin gauge fields. We do this by revisiting the physical spectrum of the sl(2, R)k WZW model and considering the limit in which k becomes small. At k = 3 we find that there is an infinite stringy tower of massless higher spin fields which are part of a continuum of light states. This can be viewed as a novel tensionless limit, which appears to be distinct from that inferred from the symmetric orbifold description of superstring AdS3 vacua.

Hull C, Lindstrom U, 2017, All (4,1): Sigma models with (4, q) off-shell supersymmetry, *Journal of High Energy Physics*, Vol: 2017, ISSN: 1029-8479

Off-shell (4, q) supermultiplets in 2-dimensions are constructed for q = 1, 2, 4.These are used to construct sigma models whose target spaces are hyperk¨ahler with torsion.The off-shell supersymmetry implies the three complex structures are simultaneouslyintegrable and allows us to construct actions using extended superspace and projectivesuperspace, giving an explicit construction of the target space geometries.

Chaemjumrus N, Hull CM, 2016, Finite gauge transformations and geometry in extended field theory, *Physical Review D*, Vol: 93, ISSN: 2470-0010

The recently derived expressions for finite gauge transformations in double field theory with duality group O(d,d) are generalized to give expressions for finite gauge transformations for extended field theories with duality group SL(5,R), SO(5,5) and E6. The generalized metrics are discussed.

Hull CM, 2015, Finite gauge transformations and geometry in double field theory, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 40

Hull CM, Lambert N, 2014, Emergent time and the M5-brane, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 15

Hull C, Lindstrom U, Rocek M,
et al., 2012, Generalized Kahler geometry in (2,1) superspace, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 7

Hohm O, Hull C, Zwiebach B, 2010, Generalized metric formulation of double field theory, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 396

Hull CM, Lindstrom U, Rocek M,
et al., 2010, Generalized Calabi-Yau metric and generalized Monge-Ampere equation, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 12

Hohm O, Hull C, Zwiebach B, 2010, Background independent action for double field theory, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 320

Hull CM, Lindstrom U, Rocek M,
et al., 2009, Generalized Kahler geometry and gerbes, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 11

Hull C, Zwiebach B, 2009, Double field theory, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 549

Hull CM, Reid-Edwards RA, 2009, Flux compactifications of string theory on twisted tori, *FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS*, Vol: 57, Pages: 862-894, ISSN: 0015-8208

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- Citations: 59

Hull C, Zwiebach B, 2009, The gauge algebra of double field theory and Courant brackets, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 75

Hull CM, Reid-Edwards RA, 2009, Non-geometric backgrounds, doubled geometry and generalised T-duality, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 90

Hull CM, Lindstrom U, dos Santos LM,
et al., 2009, Geometry of the <i>N</i>=2 supersymmetric sigma model with Euclidean worldsheet, *JOURNAL OF HIGH ENERGY PHYSICS*, ISSN: 1029-8479

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- Citations: 1

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