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1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeMay 6th 2022
   • PermaLink
   Author: Urs
   Format: MarkdownItexstarting something, but not done yet <a href="https://ncatlab.org/nlab/revision/Haldane+model/1">v1</a>, <a href="https://ncatlab.org/nlab/show/Haldane+model">current</a>

   starting something, but not done yet

   v1, current

2. • CommentRowNumber2.
   • CommentAuthorUrs
   • CommentTimeMay 18th 2022
   • PermaLink
   Author: Urs
   Format: MarkdownItexstarted adding some actual content to this file. not done yet, but need to interrupt <a href="https://ncatlab.org/nlab/revision/diff/Haldane+model/10">diff</a>, <a href="https://ncatlab.org/nlab/revision/Haldane+model/10">v10</a>, <a href="https://ncatlab.org/nlab/show/Haldane+model">current</a>

   started adding some actual content to this file.

   not done yet, but need to interrupt

   diff, v10, current

3. • CommentRowNumber3.
   • CommentAuthorUrs
   • CommentTimeMay 18th 2022
   • (edited May 18th 2022)
   • PermaLink
   Author: Urs
   Format: MarkdownItexnow some content in place. This follows the nice Delft Topology Course page ([here](https://topocondmat.org/w4_haldane/haldane_model.html#first-try)), but I have now tried to bring out a few aspects that I had found easy to miss when first entering this discussion, notably the fact that it is the *constant* mass term (hence the actual mass term as commonly understood) which leads to the topologically trivial insulator phase. <a href="https://ncatlab.org/nlab/revision/diff/Haldane+model/13">diff</a>, <a href="https://ncatlab.org/nlab/revision/Haldane+model/13">v13</a>, <a href="https://ncatlab.org/nlab/show/Haldane+model">current</a>

   now some content in place.

   This follows the nice Delft Topology Course page (here), but I have now tried to bring out a few aspects that I had found easy to miss when first entering this discussion, notably the fact that it is the constant mass term (hence the actual mass term as commonly understood) which leads to the topologically trivial insulator phase.

   diff, v13, current

4. • CommentRowNumber4.
   • CommentAuthorUrs
   • CommentTimeMay 18th 2022
   • PermaLink
   Author: Urs
   Format: MarkdownItexadded a figure ([here](https://ncatlab.org/nlab/show/Haldane+model#PhaseDiagram)) showing the phase diagram as discussed in the text <a href="https://ncatlab.org/nlab/revision/diff/Haldane+model/14">diff</a>, <a href="https://ncatlab.org/nlab/revision/Haldane+model/14">v14</a>, <a href="https://ncatlab.org/nlab/show/Haldane+model">current</a>

   added a figure (here) showing the phase diagram as discussed in the text

   diff, v14, current

5. • CommentRowNumber5.
   • CommentAuthorUrs
   • CommentTimeMay 19th 2022
   • PermaLink
   Author: Urs
   Format: MarkdownItexwith that out of the way, I have now added a section [here](https://ncatlab.org/nlab/show/Haldane+model#KTheoryClassification) which shows that this behaviour of the Haldane model is compatible with the conjecture that topological semi-metal phases are classified in *flat differential* K-theory of the complement of the nodal points. <a href="https://ncatlab.org/nlab/revision/diff/Haldane+model/17">diff</a>, <a href="https://ncatlab.org/nlab/revision/Haldane+model/17">v17</a>, <a href="https://ncatlab.org/nlab/show/Haldane+model">current</a>

   with that out of the way, I have now added a section here which shows that this behaviour of the Haldane model is compatible with the conjecture that topological semi-metal phases are classified in flat differential K-theory of the complement of the nodal points.

   diff, v17, current