Three principal invariants with respect to this quantity are named for Chern-Pontryagin, Euler, and Kretschmann. A renormalization method named for this quantity is used to find the order parameter of topological phase transitions. Non-zero values of this quantity necessitate generalizing the derivative operator to the (*) covariant derivative. (10[2])The (10[1])affine (10[1])connections vanish (10[1])for systems (10[1])in which this quantity (10[2])is equal to (10[1])zero. (-5[1])The contracted Bianchi identity relates a tensor (10[1])and a scalar describing this property, (10[1])both (10[1])of which are named for Ricci. (10[4]-5[1])Non-zero (10[2])values (10[3])of this quantity cause gravitational lensing, (10[1])or the bending of light. (-5[1])When this quantity is non-zero, straight lines are generalized into geodesics. For 10 points, what quantity is zero for (10[1])flat spacetime? ■END■ (10[2]0[2])