It had been proved that the curvature tensor is a curl(grad),not zero except in Eucldean space,and so discovered the essence of Bianchi identity:div(rot(grad))=0,the curvature,forming tube field,is invariant along the tube,i.

• 证实 :曲率它正是非欧氏空间不为零的梯度的旋度 .；并发现 :Bianchi等式实质是div(rot(grad) ) =0；曲率形成管形场；沿管不变