We study the near horizon 2d gravity theory which captures the near extremal thermodynamics of Kerr black holes where a linear combination of excess angular momentum $\delta J $ and excess mass $\delta M$ is held fixed. These correspond to processes where both the mass and the angular momenta of extremal Kerr black holes are perturbed leaving them near extremal. For the Kerr $AdS_4$ we hold $\delta J-\mathcal{ L}\,\delta M=0 $ while for Myers-Perry(MP) type Kerr black hole in $AdS_5$ we hold $\delta J_{ \varphi_{ 1,2}}\hspace{ -0.2cm}-\mathcal{ L}_{ \varphi_{ 1,2}}\,\delta M=0$. We show that in near horizon, the 2d Jackiw-Teitelboim theory is able to capture the thermodynamics of the higher dimensional black holes at small near extremal temperatures $T_H$. We show this by generalizing the near horizon limits found in literature by parameters $\mathcal{ L}$ and $\mathcal{ L}_{ \varphi_{ 1,2}}$ for the two geometries. The resulting JT theory captures the near extremal thermodynamics of such geometries provided we identify the temperature $T^{ (2)}_H$ of the near horizon $AdS_2$ geometry to be $T^{ (2)}_H=T_H/(1-\mu\,\mathcal{ L})$ for 4d Kerr and $T^{ (2)}_H=T_H/(1-\mu\,(\mathcal{ L}_{ \varphi_1}+\mathcal{ L}_{ \varphi_2}))$ for 5d Kerr where $\mu$ is their chemical potential, with $\mu\,\mathcal{ L}<1$ and $\mu\,(\mathcal{ L}_{ \varphi_1}+\mathcal{ L}_{ \varphi_2})<1$ respectively. We also argue that such a theory embeds itself non-trivially in the higher dimensional theory dual to the Kerr geometries.
Categories: hep-th