Browsing by Author "Chan, Chuan-Tsung"

Now showing 1 - 4 of 4

Comments on the high energy limit of bosonic open string theory
(2006-08-14)
Chan, Chuan-Tsung
;
Ho, Pei-Ming
;
Lee, Jen-Chi
;
Teraguchi, Shunsuke
;
Yang, Yi
In previous works, ratios among four-point scattering amplitudes at the leading order in the high-energy limit were derived for the bosonic open string theory. The derivation was based on Ward identities derived from the decoupling of zero-norm states and was purely algebraic. The only assumption of the derivation was that the momentum polarization can be approximated by the longitudinal polarization at high energies. In this paper, using the decoupling of spurious states, we reduce this assumption to a much weaker one which can be easily verified by simple power counting in most cases. For the special cases which are less obvious, we verify the new assumption for an example by saddle-point approximation. We also provide a new perspective to our previous results in terms of DDF states. In particular, we show that, by using DDF states, one can easily see that there is only one independent high energy scattering amplitude for each fixed mass level. (c) 2006 Elsevier B.V. All rights reserved.
Notes on high-energy limit of bosonic closed string scattering amplitudes
(2006-08-14)
Chan, Chuan-Tsung
;
Lee, Jen-Chi
;
Yang, Yi
;
電子物理學系
;
Department of Electrophysics
We study bosonic closed string scattering amplitudes in the high-energy limit. We find that the methods of decoupling of high-energy zero-norm states and the high-energy Virasoto constraints, which were adopted in the previous works to calculate the ratios among high-energy open string scattering amplitudes of different string states, persist for the case of closed string. However, we clarify the previous saddle-point calculation for high-energy open string scattering amplitudes and claim that only (t, u) channel of the amplitudes is suitable for saddle-point calculation. We then discuss three evidences to show that saddle-point calculation for high-energy closed string scattering amplitudes is not reliable. By using the relation of tree-level closed and open string scattering amplitudes of Kawai, Lewellen and Tye (KLT), we calculate the high-energy closed string scattering amplitudes for arbitrary mass levels. For the case of high-energy closed string four-tachyon amplitude, our result differs from the previous one of Gross and Mende, which is NOT consistent with KLT formula, by an oscillating factor. (c) 2006 Elsevier B.V. All rights reserved.
Scatterings of massive string states from D-brane and their linear relations at high energies
(2007-02-26)
Chan, Chuan-Tsung
;
Lee, Jen-Chi
;
Yang, Yi
;
電子物理學系
;
Department of Electrophysics
We study scatterings of bosonic massive closed string states at arbitrary mass levels from D-brane. We discover that all the scattering amplitudes can be expressed in terms of the generalized hypergeometric function F-3(2) with special arguments, which terminates to a finite sum and, as a result, the whole scattering amplitudes consistently reduce to the usual beta function. For the simple case of D-particle, we explicitly calculate high-energy limits of a series of the above scattering amplitudes for arbitrary mass levels, and derive infinite linear relations among them for each fixed mass level. The ratios of these high-energy scattering amplitudes are found to be consistent with the decoupling of high-energy zero-norm states of our previous works. (c) 2006 Elsevier B.V. All rights reserved.
Zero-norm states and stringy symmetries
(2006)
Chan, Chuan-Tsung
;
Ho, Pei-Ming
;
Lee, Jen-Chi
;
Teraguchi, Shunsuke
;
Yi-Yang
We identify spacetime symmetry charges of string theory from an infinite number of zero-norm states (ZNS) with arbitrary high spin in the old covariant first quantized string spectrum. We give various evidences to support this identification. These include massive sigma-model calculation, Witten string field theory calculation, 2D string theory calculation and, most importantly, three methods of high-energy stringy scattering amplitude calculation. The last calculations explicitly prove Gross\'s conjectures in 1988 on high energy symmetry of string theory.