Spatially Covariant Gravity Theories with Two Tensorial Degrees of Freedom

 Mr. YAO Zhi-Bang
Sun Yat-sen University


8 January 2020 (Wednesday)
2:00 pm
IAS4042, 4/F, Lo Ka Chung Building, Lee Shau Kee Campus, HKUST

Within the general framework of spatially covariant theories of gravity, the speaker and his research team study the conditions for having only the two tensorial degrees of freedom. Generally, there are three degrees of freedom propagating in the theory, of which two are tensorial and one is of the scalar type. Through a detailed Hamiltonian analysis, they find two necessary and sufficient conditions to evade the scalar type degree of freedom. The first condition implies that the lapse-extrinsic curvature sector must be degenerate. The second condition ensures that the dimension of the phase space at each spacetime point is even, so that the scalar type degree of freedom is eliminated completely. The speaker and his research team also compare the results with the previous studies, and apply their formalism to a simple example, in which the Lagrangian is quadratic in the extrinsic curvature.