Area Physics for electrotechnology / Relativistic physics for electrotechnology IEV ref 113-07-42 Symbol $◊$ (Unicode: U+25CA) en four-nablaquabladiamond four-dimensional generalization of three-dimensional nabla operator $\nabla$ given by the four-vector $◊=\left(\frac{\partial }{\partial {x}_{0}},\frac{\partial }{\partial {x}_{1}},\text{\hspace{0.17em}}\frac{\partial }{\partial {x}_{2}},\text{\hspace{0.17em}}\frac{\partial }{\partial {x}_{3}}\right)=\left(\frac{\partial }{\partial \text{j}{c}_{0}t};\nabla \right)$ Note 1 to entry: Four-nabla is useful in STR. In general theory of relativity (GTR) for non-flat space-time, a more sophisticated method is used. Note 2 to entry: In the International System of Quantities, the dimension of four-nabla is ${\mathrm{L}}^{-1}$. fr quadrinabla, m généralisation quadridimensionelle de l'opérateur nabla $\nabla$ tridimensionnel, donnée par le quadrivecteur $◊=\left(\frac{\partial }{\partial {x}_{0}},\frac{\partial }{\partial {x}_{1}},\text{\hspace{0.17em}}\frac{\partial }{\partial {x}_{2}},\text{\hspace{0.17em}}\frac{\partial }{\partial {x}_{3}}\right)=\left(\frac{\partial }{\partial \text{j}{c}_{0}t};\nabla \right)$ Note 1 à l’article: Le quadrinabla est utile en relativité restreinte. En relativité générale (GTR) pour un espace-temps non plat, une méthode plus élaborée est utilisée. Note 2 à l’article: Dans le Système international de grandeurs, la dimension du quadrinabla est ${\mathrm{L}}^{-1}$.