Electrodynamics/Electrostatic Stress Tensor
Force on a Charge 
When we want to discuss the force on a charge due to a charge distribution, there are two options. The first is a more traditional method: an integral over a volume containing the charge distribution. The second method is less traditional but is easier to do: a surface integral over a special stress tensor.
Volume Integral Version 
Electrostatic Stress Tensor 
Surface Integral Version 
The Maxwell Stress Tensor 
Tij is called the Maxwell Stress Tensor, it has two indices and is not a vector so is given a double arrow.