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arXiv 0707.2283hep-thgr-qc
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共形引力对弦论的挑战

Conformal Gravity Challenges String Theory

Philip D. Mannheim

摘要:

宇宙学常数问题和引力与量子力学的相容性问题是引力理论中最紧迫的两个问题。虽然弦论很好地解决了后者,但到目前为止,它还没有为前者提供任何令人信服的解决方案。另一方面,虽然共形引力很好地解决了宇宙学常数的问题(通过自然地消除宇宙学常数的引力,而不是消除宇宙学常数本身),但四阶导数共形理论一直被认为在量子化时有一个幽灵。然而,它最近已表明本德和曼海姆,不仅没有理论的基础上四阶导数方程的运动没有鬼,他们实际上从来没有任何开始,与明显存在的鬼完全是由于治疗运营商这不是厄米特的实轴,好像他们。当这是通过一个潜在的$\cal P$ $\cal T$对称性,这样的理论被发现拥有照顾,那么根本没有鬼和$S$ -矩阵是完全酉的。因此,共形引力是作为一个完全相容的四维替代十维弦论而提出的。

英文摘要:

The cosmological constant problem and the compatibility of gravity with quantum mechanics are the two most pressing problems in all of gravitational theory. While string theory nicely addresses the latter, it has so far failed to provide any compelling solution to the former. On the other hand, while conformal gravity nicely addresses the cosmological constant problem (by naturally quenching the amount by which the cosmological constant gravitates rather than by quenching the cosmological constant itself), the fourth order derivative conformal theory has long been thought to possess a ghost when quantized. However, it has recently been shown by Bender and Mannheim that not only do theories based on fourth order derivative equations of motion not have ghosts, they actually never had any to begin with, with the apparent presence of ghosts being due entirely to treating operators which were not Hermitian on the real axis as though they were. When this is taken care of via an underlying $\cal P$$\cal T$ symmetry that such theories are found to possess, there are then no ghosts at all and the $S$-matrix is fully unitary. Conformal gravity is thus advanced as a fully consistent four-dimensional alternative to ten-dimensional string theory.

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