arXiv subjects

Jorgen Rasmussen

Publications and source records attributed to Jorgen Rasmussen.

At least 73 records · Page 4Linked to original sources

arXiv2005

Non-commutative ADE geometries as holomorphic wave equations

Borrowing ideas from the relation between classical and quantum mechanics, we study a non-commutative elevation of the ADE geometries involved in building Calabi-Yau manifolds. We derive the corresponding geometric hamiltonians and the holomorphic wave equations representing these non-commutative geometries. The spectrum of the holomorphic waves is interpreted as the quantum moduli space. Quantum A_1 geometry is analyzed in some details and is found to be linked to the Whittaker differential equation.

hep-th↗

arXiv2005

On logarithmic solutions to the conformal Ward identities

A general discussion of the conformal Ward identities is presented in the context of logarithmic conformal field theory with conformal Jordan cells of rank two. The logarithmic fields are taken to be quasi-primary. No simplifying assumptions are made about the operator-product expansions of the primary or logarithmic fields. Based on a very natural and general ansatz about the form of the two- and three-point functions, their complete solutions are worked out. The results are in accordance with and extend the known results. It is demonstrated, for example, that the correlators exhibit hierarchical structures similar to the ones found in the literature pertaining to certain simplifying assumptions.

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arXiv2005

Superstring Theory on pp Waves with ADE Geometries

We study the BMN correspondence between certain Penrose limits of type IIB superstrings on pp-wave orbifolds with $ADE$ geometries, and the set of four-dimensional $\mathcal{N}=2$ superconformal field theories constructed as quiver gauge models classified by finite $ADE$ Lie algebras and affine $\hat{ADE}$ Kac-Moody algebras. These models have 16 preserved supercharges and are based on systems of D3-branes and wrapped D5- and D7-branes. We derive explicitly the metrics of these pp-wave orbifolds and show that the BMN extension requires, in addition to D5-D5 open strings in bi-fundamental representations, D5-D7 open strings involving orientifolds with $Sp(N)$ gauge symmetry. We also give the correspondence rule between leading string states and gauge-invariant operators in the $\mathcal{N}=2$ quiver gauge models.

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arXiv2005

On conformal Jordan cells of finite and infinite rank

This work concerns in part the construction of conformal Jordan cells of infinite rank and their reductions to conformal Jordan cells of finite rank. It is also discussed how a procedure similar to Lie algebra contractions may reduce a conformal Jordan cell of finite rank to one of lower rank. A conformal Jordan cell of rank one corresponds to a primary field. This offers a picture in which any finite conformal Jordan cell of a given conformal weight may be obtained from a universal covering cell of the same weight but infinite rank.

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arXiv2005

On toric geometry, Spin(7) manifolds, and type II superstring compactifications

We consider type II superstring compactifications on the singular Spin(7) manifold constructed as a cone on SU(3)/U(1). Based on a toric realization of the projective space CP^2, we discuss how the manifold can be viewed as three intersecting Calabi-Yau conifolds. The geometric transition of the manifold is then addressed in this setting. The construction is readily extended to higher dimensions where we speculate on possible higher-dimensional geometric transitions. Armed with the toric description of the Spin(7) manifold, we discuss a brane/flux duality in both type II superstring theories compactified on this manifold.

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arXiv2004

On SU(2) Wess-Zumino-Witten models and stochastic evolutions

It is discussed how stochastic evolutions may be connected to SU(2) Wess-Zumino-Witten models. Transformations of primary fields are generated by the Virasoro group and an affine extension of the Lie group SU(2). The transformations may be treated and linked separately to stochastic evolutions. A combination allows one to associate a set of stochastic evolutions to the affine Sugawara construction. The singular-vector decoupling generating the Knizhnik-Zamolodchikov equations may thus be related to stochastic evolutions. The latter are based on an infinite-dimensional Brownian motion.

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arXiv2004

Note on SLE and logarithmic CFT

It is discussed how stochastic evolutions may be linked to logarithmic conformal field theory. This introduces an extension of the stochastic Loewner evolutions. Based on the existence of a logarithmic null vector in an indecomposable highest-weight module of the Virasoro algebra, the representation theory of the logarithmic conformal field theory is related to entities conserved in mean under the stochastic process.

math-ph↗

arXiv2004

Logarithmic limits of minimal models

It is discussed how a limiting procedure of (super)conformal field theories may result in logarithmic (super)conformal field theories. The construction is illustrated by logarithmic limits of (unitary) minimal models in conformal field theory and in N=1 superconformal field theory.

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arXiv2004

On Stochastic Evolutions and Superconformal Field Theory

Links between certain stochastic evolutions of conformal maps and conformal field theory have been studied in the realm of SLE and by utilizing singular vectors in highest-weight modules of the Virasoro algebra. It was recently found that this scenario could be extended to stochastic evolutions of superconformal maps of N=1 superspace with links to superconformal field theory and singular vectors of the N=1 superconformal algebra in the Neveu-Schwarz sector. Here we discuss the analogous extension to the Ramond sector. We also discuss how the links are modified when an unconventional superconformal structure or superderivative is employed.

math-ph↗

arXiv2004

SLE-type growth processes and the Yang-Lee singularity

The recently introduced SLE growth processes are based on conformal maps from an open and simply-connected subset of the upper half-plane to the half-plane itself. We generalize this by considering a hierarchy of stochastic evolutions mapping open and simply-connected subsets of smaller and smaller fractions of the upper half-plane to these fractions themselves. The evolutions are all driven by one-dimensional Brownian motion. Ordinary SLE appears at grade one in the hierarchy. At grade two we find a direct correspondence to conformal field theory through the explicit construction of a level-four null vector in a highest-weight module of the Virasoro algebra. This conformal field theory has central charge c=-22/5 and is associated to the Yang-Lee singularity. Our construction may thus offer a novel description of this statistical model.

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arXiv2004

On string backgrounds and (logarithmic) CFT

We discuss the link between string backgrounds and the associated world-sheet CFTs. In the search for new backgrounds and CFTs, Penrose limits and Lie algebra contractions are important tools. The Nappi-Witten construction and the recently discovered logarithmic CFT by Bakas and Sfetsos, are considered as illustrations. We also speculate on possible extensions.

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arXiv2003

Stochastic evolutions in superspace and superconformal field theory

Some stochastic evolutions of conformal maps can be described by SLE and may be linked to conformal field theory via stochastic differential equations and singular vectors in highest-weight modules of the Virasoro algebra. Here we discuss how this may be extended to superconformal maps of N=1 superspace with links to superconformal field theory and singular vectors of the N=1 superconformal algebra in the Neveu-Schwarz sector.

math-ph↗

arXiv2002

Maximally symmetric D-branes in gauged WZW models

Gluing conditions are proposed to characterize the D-branes in gauged WZW models. From them the boundary conditions for the group-valued and the subgroup-valued fields are determined. We construct a gauged WZW action for open strings that coincides classically with those written previously, when the gluing conditions are imposed.

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arXiv2002

N-point and higher-genus osp(1|2) fusion

We study affine osp(1|2) fusion, the fusion in osp(1|2) conformal field theory, for example. Higher-point and higher-genus fusion is discussed. The fusion multiplicities are characterized as discretized volumes of certain convex polytopes, and are written explicitly as multiple sums measuring those volumes. We extend recent methods developed to treat affine su(2) fusion. They are based on the concept of generalized Berenstein-Zelevinsky triangles and virtual couplings. Higher-point tensor products of finite-dimensional irreducible osp(1|2) representations are also considered. The associated multiplicities are computed and written as multiple sums.

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arXiv2002

A non-reductive N=4 superconformal algebra

A new N=4 superconformal algebra (SCA) is presented. Its internal affine Lie algebra is based on the seven-dimensional Lie algebra su(2)\oplus g, where g should be identified with a four-dimensional non-reductive Lie algebra. Thus, it is the first known example of what we choose to call a non-reductive SCA. It contains a total of 16 generators and is obtained by a non-trivial Inönü-Wigner contraction of the well-known large N=4 SCA. The recently discovered asymmetric N=4 SCA is a subalgebra of this new SCA. Finally, the possible affine extensions of the non-reductive Lie algebra g are classified. The two-form governing the extension appearing in the SCA differs from the ordinary Cartan-Killing form.

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arXiv2001

Fusion multiplicities as polytope volumes: N-point and higher-genus su(2) fusion

We present the first polytope volume formulas for the multiplicities of affine fusion, the fusion in Wess-Zumino-Witten conformal field theories, for example. Thus, we characterise fusion multiplicities as discretised volumes of certain convex polytopes, and write them explicitly as multiple sums measuring those volumes. We focus on su(2), but discuss higher-point (N>3) and higher-genus fusion in a general way. The method follows that of our previous work on tensor product multiplicities, and so is based on the concepts of generalised Berenstein-Zelevinsky diagrams, and virtual couplings. As a by-product, we also determine necessary and sufficient conditions for non-vanishing higher-point fusion multiplicities. In the limit of large level, these inequalities reduce to very simple non-vanishing conditions for the corresponding tensor product multiplicities. Finally, we find the minimum level at which the higher-point fusion and tensor product multiplicities coincide.

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arXiv2001

su(N) tensor product multiplicities and virtual Berenstein-Zelevinsky triangles

Information on su(N) tensor product multiplicities is neatly encoded in Berenstein-Zelevinsky triangles. Here we study a generalisation of these triangles by allowing negative as well as non-negative integer entries. For a fixed triple product of weights, these generalised Berenstein-Zelevinsky triangles span a lattice in which one may move by adding integer linear combinations of so-called virtual triangles. Inequalities satisfied by the coefficients of the virtual triangles describe a polytope. The tensor product multiplicities may be computed as the number of integer points in this convex polytope. As our main result, we present an explicit formula for this discretised volume as a multiple sum. As an application, we also address the problem of determining when a tensor product multiplicity is non-vanishing. The solution is represented by a set of inequalities in the Dynkin labels. We also allude to the question of when a tensor product multiplicity is greater than a given non-negative integer.

math-ph↗

arXiv2001

Purely affine elementary su(N) fusions

We consider three-point couplings in simple Lie algebras -- singlets in triple tensor products of their integrable highest weight representations. A coupling can be expressed as a linear combination of products of finitely many elementary couplings. This carries over to affine fusion, the fusion of Wess-Zumino-Witten conformal field theories, where the expressions are in terms of elementary fusions. In the case of su(4) it has been observed that there is a purely affine elementary fusion, i.e., an elementary fusion that is not an elementary coupling. In this note we show by construction that there is at least one purely affine elementary fusion associated to every su(N>3).

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