Brana

A brane (from a membrane ) in string theory ( M-theory ) is a hypothetical fundamental multidimensional physical object of dimension less than the dimension of the space in which it is located (an extended p-dimensional membrane, where p is the number of spatial dimensions). The material point is 0-brane, the string is 1-brane, the membrane is 2-brane localized in the ( Euclidean ) space-time , instanton is (−1)-brane, etc. Stable${\displaystyle \mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">p</span></span>}}$ {\ displaystyle p} -branes preserve the baryon charge and satisfy the generalized Dirac quantization conditions. The main types of stable${\displaystyle \mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">p</span></span>}}$ {\ displaystyle p} bran are${\displaystyle \mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">D</span></span>}}$ {\ displaystyle D} branes${\displaystyle \mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">M</span></span>}}$ {\ displaystyle M} branes and NS5 branes.