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2-category 2-category-theory abelian-categories adjoint algebra algebraic algebraic-geometry algebraic-topology analysis analytic-geometry arithmetic arithmetic-geometry book bundles calculus categorical categories category category-theory chern-weil-theory cohesion cohesive-homotopy-type-theory cohomology colimits combinatorics complex complex-geometry computable-mathematics computer-science constructive cosmology deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry digraphs duality elliptic-cohomology enriched fibration foundation foundations functional-analysis functor gauge-theory gebra geometric-quantization geometry graph graphs gravity grothendieck group group-theory harmonic-analysis higher higher-algebra higher-category-theory higher-differential-geometry higher-geometry higher-lie-theory higher-topos-theory homological homological-algebra homotopy homotopy-theory homotopy-type-theory index-theory integration integration-theory internal-categories k-theory lie-theory limits linear linear-algebra locale localization logic mathematics measure measure-theory modal modal-logic model model-category-theory monad monads monoidal monoidal-category-theory morphism motives motivic-cohomology nlab noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pages pasting philosophy physics pro-object probability probability-theory quantization quantum quantum-field quantum-field-theory quantum-mechanics quantum-physics quantum-theory question representation representation-theory riemannian-geometry scheme schemes set set-theory sheaf simplicial space spin-geometry stable-homotopy-theory stack string string-theory superalgebra supergeometry svg symplectic-geometry synthetic-differential-geometry terminology theory topology topos topos-theory tqft type type-theory universal variational-calculus

1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeJan 26th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexslightly expanded the section [Duality with M-theory](https://ncatlab.org/nlab/show/orientifold+plane#DualityWithMTheory), mentioning more of the MO-planes and giving more pointers <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/10">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/10">v10</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   slightly expanded the section Duality with M-theory, mentioning more of the MO-planes and giving more pointers

   diff, v10, current

2. • CommentRowNumber2.
   • CommentAuthorUrs
   • CommentTimeJan 26th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexadded more references on the correspondence MO5/O4 under M/II-duality, and added a graphics <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/11">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/11">v11</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   added more references on the correspondence MO5/O4 under M/II-duality, and added a graphics

   diff, v11, current

3. • CommentRowNumber3.
   • CommentAuthorUrs
   • CommentTimeFeb 4th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexadded some more details ([here](https://ncatlab.org/nlab/show/orientifold+plane#OPlaneChargeForFlatOrientifolds)) on how the O$p$-plane charge of $- 2^{p-4}$ comes about via T-duality <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/13">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/13">v13</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   added some more details (here) on how the O$p$-plane charge of $- 2^{p-4}$ comes about via T-duality

   diff, v13, current

4. • CommentRowNumber4.
   • CommentAuthorUrs
   • CommentTimeMay 14th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexadded brief pointer to modified O-plane charges in the presence of discrete torsion ([here](https://ncatlab.org/nlab/show/orientifold+plane#WithDiscreteTorsion)) <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/17">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/17">v17</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   added brief pointer to modified O-plane charges in the presence of discrete torsion (here)

   diff, v17, current

5. • CommentRowNumber5.
   • CommentAuthorUrs
   • CommentTimeMay 15th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexin the section on O-plane charges I made explicit that the previous absolute numbers there must be understood in [[physical unit|units]] of the corresponding D-brane charge $q_{Dp}$, so that the second table of charges is indeed consistent with the first, using $q_{Dp} = 1/2$ (as befits the orientifolding). <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/18">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/18">v18</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   in the section on O-plane charges I made explicit that the previous absolute numbers there must be understood in units of the corresponding D-brane charge $q_{Dp}$, so that the second table of charges is indeed consistent with the first, using $q_{Dp} = 1/2$ (as befits the orientifolding).

   diff, v18, current

6. • CommentRowNumber6.
   • CommentAuthorUrs
   • CommentTimeAug 28th 2019
   • PermaLink
   Author: Urs
   Format: MarkdownItexexpanded a little the remark ([here](https://ncatlab.org/nlab/show/orientifold+plane#ContingOfDBranesOnOrientifolds)) on counting of D-branes in orientifolds <a href="https://ncatlab.org/nlab/revision/diff/orientifold+plane/26">diff</a>, <a href="https://ncatlab.org/nlab/revision/orientifold+plane/26">v26</a>, <a href="https://ncatlab.org/nlab/show/orientifold+plane">current</a>

   expanded a little the remark (here) on counting of D-branes in orientifolds

   diff, v26, current

7. • CommentRowNumber7.
   • CommentAuthorperezl.alonso
   • CommentTimeOct 20th 2023
   • PermaLink
   Author: perezl.alonso
   Format: MarkdownItexHere it says that: "* O-planes carry effective negative RR-charge which may (must) cancel against the actual RR- D-brane charge via RR-field tadpole cancellation.*" Wasn't there some discussion about $O^-$ and $O^+$ planes and how that requires a choice of sign in $KR$-theory?

   Here it says that: “* O-planes carry effective negative RR-charge which may (must) cancel against the actual RR- D-brane charge via RR-field tadpole cancellation.*”

   Wasn’t there some discussion about $O^-$ and $O^+$ planes and how that requires a choice of sign in $KR$-theory?

8. • CommentRowNumber8.
   • CommentAuthorperezl.alonso
   • CommentTimeOct 20th 2023
   • PermaLink
   Author: perezl.alonso
   Format: MarkdownItexAh I see you mention it in [p.4 of 1909.12277](https://arxiv.org/pdf/1909.12277.pdf#page=4).

   Ah I see you mention it in p.4 of 1909.12277.