У оквиру семинара Групе за гравитацију, честице и поља Института за физику у Београду, у среду, 27. октобра 2021. године у 13 часова путем BigBlueButton платформе, Волфганг Мартин Виланд (Аустријска академија наука, Институт за квантну оптику и квантну информацију, Беч), одржаће предавање:
How the Immirzi Parameter deforms the SL(2,R) Boundary Symmetries on the Light Cone
САЖЕТАК:
This talk describes how the Barbero–Immirzi parameter deforms the SL(2,R) symmetries on a null surface boundary. Our starting point is the definition of the action and its boundary terms. The action that we use is the usual Holst action. Compared to metric gravity it contains an additional coupling constant — the Barber Immirzi parameter. Given the action and the boundary conditions, we introduce the covariant phase space and explain how the Holst term alters the boundary symmetries on a null surface. This alteration only affects the algebra of the edge modes on a cross-section, whereas the algebra of the radiative modes is unchanged by the addition of the Barbero–Immirzi parameter. To compute the Poisson brackets explicitly, we work on an auxiliary phase space, where the SL(2,R) symmetries of the boundary fields are manifest. The physical phase space is obtained by imposing both first-class and second-class constraints. All gauge generators are at most quadratic in terms of the fundamental SL(2,R) variables. Finally, we discuss various strategies to quantise the system.