Browsing by Author "Yang, Y"

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Generalization of the Lunin-Maldacena transformation on the AdS(5) x S-5 background
(2005-11-01)
Rashkov, RC
;
Viswanathan, KS
;
Yang, Y
;
電子物理學系
;
Department of Electrophysics
In this paper we consider a simple generalization of the method of Lunin and Maldacena for generating new string backgrounds based on TsT transformations. We study multishift Ts(...)sT transformations applied to backgrounds with at least two U(1) isometries. We prove that the string currents in any two backgrounds related by Ts(...)sT transformations are equal. Applying this procedure to the AdS(5)xS(5), we find a new background and study some properties of the semiclassical strings.
High energy scattering amplitudes of superstring theory
(2006-03-20)
Chan, CT
;
Lee, JC
;
Yang, Y
;
電子物理學系
;
Department of Electrophysics
We use three different methods to calculate the proportionality constants among high-energy scattering amplitudes of different string states with polarizations on the scattering plane. These are the decoupling of high-energy zero-norm states (HZNS), the Virasoro constraints and the saddle-point calculation. These calculations are performed at arbitrary but fixed mass level for the NS sector of 10D open superstring. All three methods give the consistent results, which generalize the previous works on the high-energy 26D open bosonic string theory. In addition, we discover new leading order high-energy scattering amplitudes, which are still proportional to the previous ones, with polarizations orthogonal to the scattering plane. These scattering amplitudes are of subleading order in energy for the case of 26D open bosonic string theory. The existence of these new high-energy scattering amplitudes is due to the worldsheet fermion exchange in the correlation functions and is, presumably, related to the high-energy massive spacetime fermionic scattering amplitudes in the R-sector of the theory. (c) 2006 Elsevier B.V. All rights reserved.
High-energy zero-norm states and symmetries of string theory
(2006-05-05)
Chan, CT
;
Ho, PM
;
Lee, JC
;
Teraguchi, S
;
Yang, Y
High-energy limit of zero-norm states in the old covariant first quantized spectrum of the 26D open bosonic string, together with the assumption of a smooth behavior of string theory in this limit, are used to derive infinitely many linear relations among the leading high-energy, fixed-angle behavior of four-point functions of different string states. As a result, ratios among all high-energy scattering amplitudes of four arbitrary string states can be calculated algebraically and the leading order amplitudes can be expressed in terms of that of four tachyons as conjectured by Gross in 1988. A dual calculation can also be performed and equivalent results are obtained by taking the high-energy limit of Virasoro constraints. Finally, we compute all high-energy scattering amplitudes of three tachyons and one massive state at the leading order by saddle-point approximation to verify our results.
Semiclassical analysis of string-gauge duality on noncommutative space
(2004-10-01)
Rashkov, RC
;
Viswanathan, KS
;
Yang, Y
;
電子物理學系
;
Department of Electrophysics
We use semiclassical methods to study closed strings in the modified AdS(5)xS(5) background with constant B fields. The pointlike closed strings and the stretched closed strings rotating around the big circle of S-5 are considered. Quantization of these closed string leads to a time-dependent string spectrum, which we argue corresponds to the renormalization-group flow of the dual noncommutative Yang-Mills theory.
Solving all 4-point correlation functions for bosonic open string theory in the high-energy limit
(2005-10-03)
Chan, CT
;
Ho, PM
;
Lee, JC
;
Teraguchi, S
;
Yang, Y
We study the implication of decoupling zero-norm states in the high-energy limit, for the 26-dimensional bosonic open string theory. Infinitely many linear relations among 4-point functions are derived algebraically, and their unique solution is found. Equivalent results are also obtained by taking the high-energy limit of Virasoro constraints, and as an independent check, we compute all 4-point functions of 3 tachyons and an arbitrary massive state by saddle-point approximation. (c) 2005 Elsevier B.V. All rights reserved.