Timeline for Is there an invariant similar to the delta invariant that distinguishes an $A_2$ node form an $A_1$ node?
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
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| Nov 17, 2011 at 15:21 | vote | accept | Ritwik | ||
| Nov 17, 2011 at 15:16 | comment | added | naf | The singularities in the family correspond to multiple roots of the polynomial $a + bx + cx^2 + x^4$. Since this is of degree $4$, it can never have both a double root and a triple root. | |
| Nov 17, 2011 at 15:12 | comment | added | naf | The miniversal deformation of any planar singularity is easy to write down. See for example Hartshorne's "Deformation theory", section 14. | |
| Nov 17, 2011 at 14:56 | comment | added | Ritwik | By the way, how do we know that the family you wrote has no singularities of type A_1 and A_2? | |
| Nov 17, 2011 at 14:53 | comment | added | Ritwik | Thank you. Is the miniversal deformation of any ADE singularity known? I wanted to show that two nodes and one cusp can not collide to a strict A_4 node. And is the miniversal deformation of E_7 node known? | |
| Nov 17, 2011 at 7:58 | history | answered | naf | CC BY-SA 3.0 |