1,721,057 research outputs found
The E-3/Z(3) orbifold, mirror symmetry, and Hodge structures of Calabi-Yau type
No full textStarting from the Kähler moduli space of the rigid orbifold Z=E 3 ∕Z 3 one would expect for the cohomology of the generalized mirror to be a Hodge structure of Calabi–Yau type (1,9,9,1). We show that such a structure arises in a natural way from rational Hodge structures on Λ 3 Q[ω] 6 , where ω is a primitive third root of unity. We do not try to identify an underlying mirror geometry, but we show how special geometry arises in our abstract construction. We also show how such Hodge structure can be recovered as a polarized substructure of a bigger Hodge structure given by the third cohomology group of a six-dimensional abelian variety of Weil-type. Moreover, we recover a result of Zheng Zhang on the associates variation of Hodge structure
Plane waves from double extended spacetimes
Full text linkWe study exact string backgrounds (WZW models) generated by nonsemisimple algebras which are obtained as double extensions of generic D-dimensional semisimple algebras. Even if a suitable change of coordinates always exists which reduces these backgrounds to be the product of the non-trivial background associated to the original algebra and two-dimensional Minkowski, under Inönü-Wigner contraction the algebra reduces to a Nappi-Witten algebra and the corresponding plane wave spacetime, no more factorized, is the Penrose limit of the original background. We construct the spectrum of D-branes for the double-extended background and study their behavior under the Penrose limit. While in general D-branes become singular in this limit, we prove that a class of solutions with a well-defined limit exists and it gives rise to the spectrum of configurations of the contracted model. Therefore, all D-branes of the plane wave background can be obtained as suitable contractions of original ones. We also discuss the Penrose limit at the quantum level and argue that the procedures of contraction and quantization commute
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