分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-05
摘要： The CFT dual of string theory on AdS3×S3×S3×S1 is conjectured to be the symmetric orbifold of the Sκ theory, provided that one of the two Q±5 quantum numbers is a multiple of the other. We determine the BPS spectrum of the symmetric orbifold in detail, and show that it reproduces precisely the BPS spectrum that was recently calculated in supergravity. We also determine the BPS spectrum of the world-sheet theory that is formulated in terms of WZW models, and show that, apart from some gaps (which are reminiscent of those that appear in the corresponding T4 calculation), it also reproduces this BPS spectrum. In fact, the matching seems to work as well as for the familiar T4 case, and thus our results give strong support for this proposal.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-05
摘要： The BPS spectrum of string theory on AdS3×S3×S3×S1 is determined using a world-sheet description in terms of WZW models. It is found that the theory only has BPS states with j+=j− where j± refer to the spins of the su(2) algebras of the large N=4 superconformal algebra. We then re-examine the BPS spectrum of the corresponding supergravity and find that, in contradistinction to previous claims in the literature, also in supergravity only the states with j+=j− are BPS. This resolves a number of long-standing puzzles regarding the BPS spectrum of string theory and supergravity in this background.magnetic field is separated into potential part and non-potential part. We first fit the potential part by using the sum of magnetic multi-poles, whereas the non-potential part is approximated by the magnetic field induced by some properly fitted current densities. Then the total field is numerically modified in terms of Maxwell's equations. Based on the initial magnetic fields obtained in such a way, we can further compute various complex asymmetric corona structures by solving MHD equations. In order to verify this procedure, we compute the 2-D coronal structures prior to the December, 1996 CME and August, 1999 CME events. The numerical result is on the whole in agreement with observations, and hence set proper backgrounds for further studying the propagation of CME in various coronal structures using numerical computations. © Copyright 2001 by the American Geophysical Union.
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