Browsing by Author "Teraguchi, Shunsuke"

Now showing 1 - 6 of 6

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.
E(6) grand unified theory with three generations from heterotic string theory
(2011-05-19)
Ito, Motoharu
;
Kuwakino, Shogo
;
Maekawa, Nobuhiro
;
Moriyama, Sanefumi
;
Takahashi, Keijiro
We construct two more supersymmetric E(6) grand unified models with three generations within the framework of Z(12) asymmetric orbifold compactification of the heterotic string theory. Such an asymmetric orbifold is missing in the classification in the literature, which concludes that only one E(6) model is possible. In both of the new models, an adjoint Higgs field is obtained in virtue of the diagonal embedding method. This method mods out the three E(6) factors of an even self-dual momentum-lattice by a permutation symmetry. In order to realize the (E(6))(3) even self-dual lattice, we utilize the lattice engineering technique. Among the eight possible orbifold actions in our setup, two lead to new E(6) models. Though these models still share the unsatisfactory issues with the known one, our discovery raises hopes that excellent models that solve all the problems in the supersymmetric grand unified models will be found in this framework.
E-6 grand unified theory with three generations from heterotic string theory
(2011-05-19)
Ito, Motoharu
;
Kuwakino, Shogo
;
Maekawa, Nobuhiro
;
Moriyama, Sanefumi
;
Takahashi, Keijiro
We construct two more supersymmetric E-6 grand unified models with three generations within the framework of Z(12) asymmetric orbifold compactification of the heterotic string theory. Such an asymmetric orbifold is missing in the classification in the literature, which concludes that only one E-6 model is possible. In both of the new models, an adjoint Higgs field is obtained in virtue of the diagonal embedding method. This method mods out the three E-6 factors of an even self-dual momentum-lattice by a permutation symmetry. In order to realize the (E-6)(3) even self-dual lattice, we utilize the lattice engineering technique. Among the eight possible orbifold actions in our setup, two lead to new E-6 models. Though these models still share the unsatisfactory issues with the known one, our discovery raises hopes that excellent models that solve all the problems in the supersymmetric grand unified models will be found in this framework.
Heterotic E(6) GUTs and partition functions
(2011-12-01)
Ito, Motoharu
;
Kuwakino, Shogo
;
Maekawa, Nobuhiro
;
Moriyama, Sanefumi
;
Takahashi, Keijiro
The E(6) grand unified theory is an attractive candidate intermediate theory between the standard model and string theory. However, only one E(6) grand unified model with three generations and at least one adjoint Higgs field has been derived from string theory in the literature, and this model is phenomenologically unsatisfactory. Recently, in arXiv:1012.1690, we have constructed two new such E(6) grand unified models in heterotic asymmetric orbifolds. Although our new models themselves cannot resolve the unsatisfactory point in the previous model, our discovery raises hopes that one can construct many other such models in this framework and find better models. Here, by giving partition functions explicitly, we explain the details of our construction. Utilizing the lattice engineering technique and the diagonal embedding method, we can construct models systematically. We hope that these techniques and the details of our construction will lead to more phenomenologically desirable models.
Heterotic E-6 GUTs and partition functions
(2011-12-01)
Ito, Motoharu
;
Kuwakino, Shogo
;
Maekawa, Nobuhiro
;
Moriyama, Sanefumi
;
Takahashi, Keijiro
The E-6 grand unified theory is an attractive candidate intermediate theory between the standard model and string theory. However, only one E-6 grand unified model with three generations and at least one adjoint Higgs field has been derived from string theory in the literature, and this model is phenomenologically unsatisfactory. Recently, in arXiv:1012.1690, we have constructed two new such E-6 grand unified models in heterotic asymmetric orbifolds. Although our new models themselves cannot resolve the unsatisfactory point in the previous model, our discovery raises hopes that one can construct many other such models in this framework and find better models. Here, by giving partition functions explicitly, we explain the details of our construction. Utilizing the lattice engineering technique and the diagonal embedding method, we can construct models systematically. We hope that these techniques and the details of our construction will lead to more phenomenologically desirable models.
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.