Results 1  10
of
13
A nogo theorem for string warped compactifications
, 2000
"... We give necessary conditions for the existence of perturbative heterotic and type II string warped compactifications preserving eight and four supersymmetries to four spacetime dimensions, respectively. In particular, we find that the only compactifications of heterotic string with the spin connecti ..."
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Cited by 60 (21 self)
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We give necessary conditions for the existence of perturbative heterotic and type II string warped compactifications preserving eight and four supersymmetries to four spacetime dimensions, respectively. In particular, we find that the only compactifications of heterotic string with the spin connection embedded in the gauge connection and type II strings are those on CalabiYau manifolds with constant dilaton. We obtain similar results for compactifications to six and to two dimensions.
CalabiYau connections with torsion on toric bundles
"... We find sufficient conditions for principal toric bundles over compact Kähler manifolds to admit CalabiYau connections with torsion, as well as conditions to admit strong Kähler connections with torsion. With the aid of a topological classification, we construct such geometry on (k −1)(S 2 ×S 4)#k( ..."
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Cited by 24 (0 self)
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We find sufficient conditions for principal toric bundles over compact Kähler manifolds to admit CalabiYau connections with torsion, as well as conditions to admit strong Kähler connections with torsion. With the aid of a topological classification, we construct such geometry on (k −1)(S 2 ×S 4)#k(S 3 ×S 3) for all k ≥ 1. 1.
Hypekähler torsion structure invariant by nilpotent Lie groups
"... Abstract. We study HKT structures on nilpotent Lie groups and on associated nilmanifolds. We exhibit three weak HKT structures on R 8 which are homogeneous with respect to extensions of Heisenberg type Lie groups. The corresponding hypercomplex structures are of a special kind, called abelian. We pr ..."
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Cited by 18 (8 self)
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Abstract. We study HKT structures on nilpotent Lie groups and on associated nilmanifolds. We exhibit three weak HKT structures on R 8 which are homogeneous with respect to extensions of Heisenberg type Lie groups. The corresponding hypercomplex structures are of a special kind, called abelian. We prove that on any 2step nilpotent Lie group all invariant HKT structures arise from abelian hypercomplex structures. Furthermore, we use a correspondence between abelian hypercomplex structures and subspaces of sp(n) to produce continuous families of compact and noncompact of manifolds carrying non isometric HKT structures. Finally, geometrical properties of invariant HKT structures on 2step nilpotent Lie groups are obtained. 1.
Reduction of HKTStructures
, 2008
"... Abstract: KTgeometry is the geometry of a Hermitian connection whose torsion is a 3form. HKTgeometry is the geometry of a hyperHermitian connection whose torsion is a 3form. We identify nontrivial conditions for a reduction theory for these types of geometry. 1 ..."
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Cited by 14 (2 self)
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Abstract: KTgeometry is the geometry of a Hermitian connection whose torsion is a 3form. HKTgeometry is the geometry of a hyperHermitian connection whose torsion is a 3form. We identify nontrivial conditions for a reduction theory for these types of geometry. 1
On some properties of the manifolds with skewsymmetric torsion and holonomy SU(n) and Sp(n
"... Abstract In this paper we provide examples of hypercomplex manifolds which do not carry HKT structure, thus answering a question in [13]. We also prove that the existence of HKT structure is not stable under small deformations. Similarly we provide examples of compact complex manifolds with vanishin ..."
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Cited by 12 (4 self)
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Abstract In this paper we provide examples of hypercomplex manifolds which do not carry HKT structure, thus answering a question in [13]. We also prove that the existence of HKT structure is not stable under small deformations. Similarly we provide examples of compact complex manifolds with vanishing first Chern class which do not admit a Hermitian structure with restricted holonomy of its Bismut connection in SU(n), thus providing a counterexample of the conjecture in [15]. Again we prove that such property is not stable under small deformations. 1.
MultiAngle Fivebrane Intersections
, 1998
"... We find new solutions of IIA supergravity which have the interpretation of intersecting NS5branes at Sp(2)angles on a string preserving at least 3/32 of supersymmetry. We show that the relative position of every pair of NS5branes involved in the superposition is determined by four angles. In ad ..."
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Cited by 6 (0 self)
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We find new solutions of IIA supergravity which have the interpretation of intersecting NS5branes at Sp(2)angles on a string preserving at least 3/32 of supersymmetry. We show that the relative position of every pair of NS5branes involved in the superposition is determined by four angles. In addition we explore Most of the recent progress in understanding the various dualities of superstring theories as well as their applications in black holes and superymmetric YangMills is due to the investigation of intersecting brane configurations. There are many ways to view such configurations. One way is as classical solutions of supergravity
AND HOLONOMY SU(N) AND SP(N)
, 2003
"... Abstract In this paper we provide examples of hypercomplex manifolds which do not carry HKT structure, thus answering a question in [16]. We also prove that the existence of HKT structure is not stable under small deformations. Similarly we provide examples of compact complex manifolds with vanishin ..."
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Abstract In this paper we provide examples of hypercomplex manifolds which do not carry HKT structure, thus answering a question in [16]. We also prove that the existence of HKT structure is not stable under small deformations. Similarly we provide examples of compact complex manifolds with vanishing first Chern class which do not admit a Hermitian structure with restricted holonomy of its Bismut connection in SU(n), thus providing a counterexample of the conjecture in [18]. Again we prove that such property is not stable under small deformations. 1.
Supersymmetric sigma models, gauge theories and vortices
"... This thesis considers one and two dimensional supersymmetric nonlinear sigma models. First there is a discussion of the geometries of one and two dimensional sigma models, with rigid supersymmetry. For the onedimensional case, the supersymmetry is promoted to a local one and the required gauge fiel ..."
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This thesis considers one and two dimensional supersymmetric nonlinear sigma models. First there is a discussion of the geometries of one and two dimensional sigma models, with rigid supersymmetry. For the onedimensional case, the supersymmetry is promoted to a local one and the required gauge fields are introduced. The most general Lagrangian, including these gauge fields, is found. The constraints of the system are analysed, and its Dirac quantisation is investigated. In the next chapter we introduce equivariant cohomology which is used later in the thesis. Then actions are constructed for (p,0) and (p,1) supersymmetric, 1 ≤ p ≤ 4, twodimensional gauge theories coupled to nonlinear sigma model matter with a WessZumino term. The scalar potential for a large class of these models is derived. It is then shown that the Euclidean actions of the (2,0) and (4,0)supersymmetric
DAMTP, University of Cambridge,
, 1998
"... We present a geometric construction of a new class of hyperKähler manifolds with torsion. This involves the superposition of the fourdimensional hyperKähler geometry with torsion associated with the NS5brane along quaternionic planes in H k. We find the moduli space of these geometries and show ..."
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We present a geometric construction of a new class of hyperKähler manifolds with torsion. This involves the superposition of the fourdimensional hyperKähler geometry with torsion associated with the NS5brane along quaternionic planes in H k. We find the moduli space of these geometries and show that it can be constructed using the bundle space of the canonical quaternionic line bundle over a quaternionic projective space. We also investigate several special cases which are associated with certain classes of quaternionic planes in H k. We then show that the eightdimensional geometries we have found can be constructed using quaternionic calibrations. We generalize our construction to superpose the same fourdimensional hyperKähler geometry with torsion along complex planes in C 2k. We find that the resulting geometry is Kähler with torsion. The moduli space of these geometries is also investigated. In addition the applications of these new geometries to Mtheory and sigma models are presented. In particular, we find new solutions of IIA supergravity with the interpretation of intersecting NS5branes
Instantons at Angles
, 1997
"... We find solutions of the YangMills field equations with gauge group SU(2) in 4k dimensions which have the interpretation of fourdimensional instantons at angles. These configurations satisfy a BPSlike condition which arises in the context of twodimensional (4,0)supersymmetric sigma models. More ..."
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We find solutions of the YangMills field equations with gauge group SU(2) in 4k dimensions which have the interpretation of fourdimensional instantons at angles. These configurations satisfy a BPSlike condition which arises in the context of twodimensional (4,0)supersymmetric sigma models. Moreover we show that these solutions are examples of HermitianEinstein connections on E 4k.In the past twenty years, much work has been done to find classical solutions of the YangMills field equations and to interpret them in the context of classical or quantum theory. A particular class of such configurations are the so called BPS ones. These configurations saturate a bound and when embedded in a supersymmetric extension of the YangMills theory preserve a proportion of the supersymmetry. Examples of such configurations in four dimensions are the BPS monopoles and instantons. The former configurations saturate a bound for the energy of a YangMills theory coupled to scalars in the adjoint representation of the gauge group while the latter configurations saturate a bound for the Euclidean action of the YangMills theory. Instantons configurations are characterized by the