Andreas Recknagel

Publications (11)13.48 Total impact

• Article: Moduli stabilisation on the worldsheet

  Jawad Arshad Deo, Neil Lambert, Andreas Recknagel
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  ABSTRACT: We consider compactifications of type II string theory using exact internal CFT’s with central charge c = 9 + ϵ, |ϵ| ≪ 1, leading to an effective potential for the dilaton. For ϵ > 0 the potential is positive and the dilaton is ultimately driven to weak coupling. For ϵ < 0 the dilaton is driven to strong coupling, but we can stabilise the background by including D-branes. The resulting minimum admits an AdS 4 solution where the cosmological constant is of the order ϵ 3 and the string coupling constant is of order ϵ. Furthermore these CFT’s typically do not possess any massless or tachyonic modes. Thus these vacua provide exact CFT descriptions of moduli stabilisation in weakly coupled string theory. KeywordsConformal Field Models in String Theory–Superstring Vacua–Flux compactifications
  Journal of High Energy Physics 04/2012; 2011(2):1-19. · 5.83 Impact Factor
• Source

  Available from: ArXiv

  Article: Algorithmic deformation of matrix factorisations

  Nils Carqueville, Laura Dowdy, Andreas Recknagel
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  ABSTRACT: Branes and defects in topological Landau-Ginzburg models are described by matrix factorisations. We revisit the problem of deforming them and discuss various deformation methods as well as their relations. We have implemented these algorithms and apply them to several examples. Apart from explicit results in concrete cases, this leads to a novel way to generate new matrix factorisations via nilpotent substitutions, and to criteria whether boundary obstructions can be lifted by bulk deformations.
  12/2011;
• Source

  Available from: ArXiv

  Article: Moduli Stabilisation on the Worldsheet

  Jawad Arshad, Neil Lambert, Andreas Recknagel
  [show abstract] [hide abstract]
  ABSTRACT: We consider compactifications of type II string theory using exact internal CFT's with central charge $c=9+\epsilon$, $|\epsilon| \ll 1$, leading to an effective potential for the dilaton. For $\epsilon>0$ the potential is positive and the dilaton is ultimately driven to weak coupling. For $\epsilon<0$ the dilaton is driven to strong coupling, but we can stabilise the background by including D-branes. The resulting minimum admits an $AdS_4$ solution where the cosmological constant is of the order $\epsilon^3$ and the string coupling constant is of order $\epsilon$. Furthermore these CFT's typically do not possess any massless or tachyonic modes. Thus these vacua provide exact CFT descriptions of moduli stabilisation in weakly coupled string theory.
  12/2010;
• Source

  Available from: Daniel Roggenkamp

  Article: Permutation branes and linear matrix factorisations

  Håkon Enger, Andreas Recknagel, Daniel Roggenkamp
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  ABSTRACT: All the known rational boundary states for Gepner models can be regarded as permutation branes. On general grounds, one expects that topological branes in Gepner models can be encoded as matrix factorisations of the corresponding Landau-Ginzburg potentials. In this paper we identify the matrix factorisations associated to arbitrary B-type permutation branes. Comment: 43 pages. v2: References added
  08/2005;
• Source

  Available from: arxiv.org

  Article: Permutation Branes

  Andreas Recknagel
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  ABSTRACT: N-fold tensor products of a rational CFT carry an action of the permutation group S_N. These automorphisms can be used as gluing conditions in the study of boundary conditions for tensor product theories. We present an ansatz for such permutation boundary states and check that it satisfies the cluster condition and Cardy's constraints. For a particularly simple case, we also investigate associativity of the boundary OPE, and find an intriguing connection with the bulk OPE. In the second part of the paper, the constructions are slightly extended for application to Gepner models. We give permutation branes for the quintic, together with some formulae for their intersections. Comment: 27 pages
  08/2002;
• Source

  Available from: arxiv.org

  Article: Open Strings and Non-commutative Geometry of Branes on Group Manifolds

  Anton Yu. Alekseev, Andreas Recknagel, Volker Schomerus
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  ABSTRACT: In this contribution we review some recent work on the non-commutative geometry of branes on group manifolds. In particular, we show how fuzzy spaces arise in this context from an exact world-sheet description and we sketch the construction of a low-energy effective action for massless open string modes. The latter is given by a combination of a Yang-Mills and a Chern-Simons like functional on the fuzzy world-volume. It can be used to study condensation on various brane configurations in curved backgrounds. Comment: 14 pages; Proceedings contribution for Euroconference ``Brane New World and Noncommutative Geometry'', Villa Gualino, Torino, Italy, October 2000
  04/2001;
• Article: Non-commutative worldvolume geometries: D-branes on SU(2) and fuzzy spheres

  Anton Yu. Alekseev, Andreas Recknagel, Volker Schomerus
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  ABSTRACT: The geometry of D-branes can be probed by open string scattering. If the background carries a non-vanishing B-field, the world-volume becomes non-commutative. Here we explore the quantization of world-volume geometries in a curved background with non-zero Neveu-Schwarz 3-form field strength H = dB. Using exact and generally applicable methods from boundary conformal field theory, we study the example of open strings in the SU(2) Wess-Zumino-Witten model, and establish a relation with fuzzy spheres or certain (non-associative) deformations thereof. These findings could be of direct relevance for D-branes in the presence of Neveu-Schwarz 5-branes; more importantly, they provide insight into a completely new class of world-volume geometries.
  Journal of High Energy Physics 09/1999; 1999(09):023. · 5.83 Impact Factor
• Source

  Available from: arxiv.org

  Article: Moduli Spaces of D-branes in CFT-backgrounds

  Andreas Recknagel, Volker Schomerus
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  ABSTRACT: D-branes in curved backgrounds can be treated with techniques of boundary conformal field theory. We discuss the influence of scalar condensates on such branes, i.e. perturbations of boundary conditions by marginal boundary operators. A general criterion is presented that guarantees a boundary perturbation to be truly marginal in all orders of perturbation theory. Our results on boundary deformations have several interesting applications which are sketched at the end of this note.
  03/1999;
• Source

  Available from: arxiv.org

  Article: Generalization of the Knizhnik–Zamolodchikov Equations

  Anton Yu Alekeseev, Andreas Recknagel, Volker Schomerus
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  ABSTRACT: In this Letter, we introduce a generalization of the Knizhnik–Zamolodchikov equations from affine Lie algebras to a wide class of conformal field theories (not necessarily rational). The new equations describe correlations functions of primary fields and of a finite number of their descendents. Our proposal is based on Nahm''s concept of small spaces which provide adequate substitutes for the lowest energy subspaces in modules of affine Lie algebras. We explain how to construct the first order differential equations and investigate properties of the associated connections, thereby preparing the grounds for an analysis of quantum symmetries. The general considerations are illustrated in examples of Virasoro minimal models.
  Letters in Mathematical Physics 06/1997; 41(2):169-180. · 1.82 Impact Factor
• Article: Boundary deformation theory and moduli spaces of D-branes

  Andreas Recknagel, Volker Schomerus
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  ABSTRACT: Boundary conformal field theory is the suitable framework for a microscopic treatment of D-branes in arbitrary CFT backgrounds. In this work, we develop boundary deformation theory in order to study the changes of boundary conditions generated by marginal boundary fields. The deformation parameters may be regarded as continuous moduli of D-branes. We identify a large class of boundary fields which are shown to be truly marginal, and we derive closed formulas describing the associated deformations to all orders in perturbation theory. This allows us to study the global topology properties of the moduli space rather than local aspects only. As an example, we analyse in detail the moduli space of c = 1 theories, which displays various stringy phenomena.
  Nuclear Physics B.
• Source

  Available from: Jürg Fröhlich

  Article: Fundamental strings in Dp–Dq brane systems

  Jürg Fröhlich, Olivier Grandjean, Andreas Recknagel, Volker Schomerus
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  ABSTRACT: We study conformal field theory correlation functions relevant for string diagrams with open strings that stretch between several parallel branes of different dimensions. In the framework of conformal field theory, they involve boundary condition changing twist fields which intertwine between Neumann and Dirichlet conditions. A Knizhnik–Zamolodchikov-like differential equation for correlators of such boundary twist fields and ordinary string vertex operators is derived, and explicit integral formulas for its solutions are provided.
  Nuclear Physics B.