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where D g stands for the gluon D -term [3] and H g DD is built as a one dimensional section of a two-variable double distribution: 

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The profile function h ( b $^{)}$( β, α ) is parameterized as 

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The parameter b characterizes the strength of ξ dependence of the resulting GPD. The usual choice for the gluon case is b = 2. This is motivated by the interpretation of the α dependence like a meson distribution amplitude for hard exclusive processes. The cases b = 2 correspond to the asymptotic behavior of a gluon distribution amplitude ∼ (1 − α $^{2}$)$^{2}$. 

The achieved theoretical understanding of both theoretical and experimental aspects of GPD physics hints (see e.g. [12, 13, 18]) at the necessity to introduce new GPD parametriza- tions which should be more general and flexible than the basic form of the RDDA employed in present-day mainstream phenomenology. 

The possible alternative way to parameterize GPDs is the so-called dual parametriza- tion [15] (see [16, 19–22] for the recent development and discussion). Originally, the dual parametrization was formulated for the case of quark GPDs. Now we are going to generalize this approach for the gluon case. 

In the framework of the dual parametrization GPDs are presented as infinite sums of the t -channel 2 Regge exchanges [23]. Let us stress that the term “dual” is intended to lay emphasis on the natural association with the old idea of duality in hadron-hadron low energy scattering. The essence of the duality hypothesis for binary scattering amplitudes [24, 25] can be summarized as the assumption that the infinite sum over only the cross-channel Regge exchanges may provide the complete description of the whole scattering amplitude in a certain domain of kinematical variables. 

More technically, in the dual parametrization the t -channel matrix element of the partic- ular non-local light ray operator ˆ O between the hadron states which enters the definition of 

