Browsing by Author "Fu, Chih-Hao"

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A note on on-shell recursion relation of string amplitudes
(2013-02-01)
Chang, Yung-Yeh
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Feng, Bo
;
Fu, Chih-Hao
;
Lee, Jen-Chi
;
Wang, Yihong
In the application of on-shell recursion relation to string amplitudes, one challenge is the sum over infinite intermediate on-shell string states. In this note, we show how to sum these infinite states explicitly by including unphysical states to make complete Fock space.
An algebraic approach to BCJ numerators
(2013-03-01)
Fu, Chih-Hao
;
Du, Yi-Jian
;
Feng, Bo
;
電子物理學系
;
Department of Electrophysics
One important discovery in recent years is that the total amplitude of gauge theory can be written as BCJ form where kinematic numerators satisfy Jacobi identity. Although the existence of such kinematic numerators is no doubt, the simple and explicit construction is still an important problem. As a small step, in this note we provide an algebraic approach to construct these kinematic numerators. Under our Feynman-diagram-like construction, the Jacobi identity is manifestly satisfied. The corresponding color ordered amplitudes satisfy off-shell BCJ relation and off-shell BCJ relation similar to the color ordered scalar theory. Using our construction, the dual DDM form is also established.
Dual-color decompositions at one-loop level in Yang-Mills theory
(2014-06-26)
Du, Yi-Jian
;
Feng, Bo
;
Fu, Chih-Hao
;
電子物理學系
;
Department of Electrophysics
In this work we extend two dual color decompositions of Yang-Mills amplitude to one-loop level. Starting from double-copy expression we translate the Yang-Mills integrand into the dual Del Duca-Dixon-Maltoni formulation and subsequently to the dual color-ordered formula. The dual trace factors are obtained after simultaneously solving the one-loop Kleiss-Kuijf relations, the reflection relation, and the relation that expresses the kinematic factors in the dual Del Duca-Dixon-Maltoni form.
Note on construction of dual-trace factor in Yang-Mills theory
(2013-10-11)
Fu, Chih-Hao
;
Du, Yi-Jian
;
Feng, Bo
;
電子物理學系
;
Department of Electrophysics
In this note we provide a new construction of BCJ dual-trace factor using the kinematic algebra proposed in arXiv:1105.2565 and arXiv:1212.6168. Different from the construction given in arXiv:1304.2978 based on the proposal of arXiv:1103.0312, the method used in this note exploits the adjoint representation of kinematic algebra and the use of inner product in dual space. The dual-trace factor defined in this way naturally satisfies cyclic symmetry condition but not KK-relation, just like the trace of U(N) Lie algebra satisfies cyclic symmetry condition, but not KK-relation. In other words the new construction naturally leads to formulation sharing more similarities with the color decomposition of Yang-Mills amplitude.
Note on soft graviton theorem by KLT relation
(2014-11-18)
Du, Yi-Jian
;
Feng, Bo
;
Fu, Chih-Hao
;
Wang, Yihong
;
電子物理學系
Recently, new soft graviton theorem proposed by Cachazo and Strominger has inspired a lot of works. In this note, we use the KLT-formula to investigate the theorem. We have shown how the soft behavior of color ordered Yang-Mills amplitudes can be combined with KLT relation to give the soft behavior of gravity amplitudes. As a byproduct, we find two nontrivial identities of the KLT momentum kernel must hold.
Note on symmetric BCJ numerator
(2014-08-18)
Fu, Chih-Hao
;
Du, Yi-Jian
;
Feng, Bo
;
電子物理學系
;
Department of Electrophysics
We present an algorithm that leads to BCJ numerators satisfying manifestly the three properties proposed by Broedel and Carrasco in [42]. We explicitly calculate the numerators at 4, 5 and 6-points and show that the relabeling property is generically satisfied.
Recurrence relations of higher spin BPST vertex operators for open strings
(2013-08-19)
Fu, Chih-Hao
;
Lee, Jen-Chi
;
Tan, Chung-I
;
Yang, Yi
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電子物理學系
We calculate higher-spin Brower-Polchinski-Strassler-Tan (BPST) vertex operators for an open bosonic string and express these operators in terms of a Kummer function of the second kind. We derive an infinite number of recurrence relations among BPST vertex operators of different string states. These recurrence relations among BPST vertex operators lead to the recurrence relations among Regge string scattering amplitudes discovered recently.
The construction of dual-trace factor in Yang-Mills theory
(2013-07-01)
Du, Yi-Jian
;
Feng, Bo
;
Fu, Chih-Hao
;
電子物理學系
;
Department of Electrophysics
Recently, a BCJ dual of the color-ordered formula for Yang-Mills amplitude was proposed, where the dual-trace factor satisfies cyclic symmetry and KK-relation. In this paper, we present a systematic construction of the dual-trace factor based on its proposed relations to kinematic numerators in dual-DDM form. We show that the construction presented respects relabeling symmetry. In addition, we show that using relabeling symmetry as conditions, the same construction can be solved independently.