Starobinsky–Bel–Robinson Gravity

A novel string-inspired gravitational theory in four spacetime dimensions is proposed as a sum of the modified $(R+\alpha R^2)$ gravity motivated by the Starobinsky inflation and the leading Bel–Robinson-tensor-squared correction to the gravitational effective action of superstrings/M-theory compactified down to four dimensions. The possible origin of the theory from higher dimensions is revealed. The proposed Starobinsky–Bel–Robinson action has only two free parameters, which makes it suitable for verifiable physical applications in black hole physics, cosmological inflation and Hawking radiation.