Difference between revisions of "Problems on Deligne-Mumford spaces"

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As shown in [Auroux, Ex. 2.6], <math>\overline\mathcal{M}_4</math> is homeomorphic to a closed interval, with one endpoint corresponding to a collision of the first two inputs <math>z_1, z_2</math> and the other corresponding to a collision of <math>z_2, z_3</math>.
 
As shown in [Auroux, Ex. 2.6], <math>\overline\mathcal{M}_4</math> is homeomorphic to a closed interval, with one endpoint corresponding to a collision of the first two inputs <math>z_1, z_2</math> and the other corresponding to a collision of <math>z_2, z_3</math>.
 
Work out which polygon/polyhedron <math>\overline\mathcal{M}_5, \overline\mathcal{M}_6</math> are equal to.
 
Work out which polygon/polyhedron <math>\overline\mathcal{M}_5, \overline\mathcal{M}_6</math> are equal to.
(Keep in mind that when <math>\geq 3</math> marked points collide simultaneously, there is a continuous family
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(Keep in mind that when <math>\geq 3</math> marked points collide simultaneously, there is a continuous family of ways that this collision can take place.)

Revision as of 14:07, 26 May 2017


poset underlying associahedra

As described in Deligne-Mumford space, for any d\geq 1, \overline {\mathcal  {M}}_{{d+1}} is a (d-2)-dimensional manifold with boundary and corners which parametrizes nodal trees of disks with d+1 marked points, one of them distinguished (we think of the d undistinguished resp. 1 distinguished marked points as "input" resp. "output" marked points). As shown in [Auroux, Ex. 2.6], \overline {\mathcal  {M}}_{4} is homeomorphic to a closed interval, with one endpoint corresponding to a collision of the first two inputs z_{1},z_{2} and the other corresponding to a collision of z_{2},z_{3}. Work out which polygon/polyhedron \overline {\mathcal  {M}}_{5},\overline {\mathcal  {M}}_{6} are equal to. (Keep in mind that when \geq 3 marked points collide simultaneously, there is a continuous family of ways that this collision can take place.)