Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 4428
3 votes
Accepted

Counting maximally tangent conics relative to a cubic

If $X$ is a cubic and $P \in X$ is a point such that there is totally tangent at $P$ conic then $$ 6P = 2H, $$ where $H$ is the restriction to $X$ of the line class of $\mathbb{P}^2$. Thus, the set of …
Sasha's user avatar
  • 39.3k
6 votes

Embedding $G(2,n)$ into $G(k,n)$

Let $V = k^n$. The map in question is the composition of the canonical map $$ f:G(2,V) \to G(k,S^{k-1}V) $$ given by the $(k-1)$-th symmetric power of the tautological bundle, and the (noncanonical) …
Sasha's user avatar
  • 39.3k
10 votes
Accepted

Counting curves of degree 4 in $\mathbb{P}^{3}$

Zero. Indeed, if the intersection $Q_1 \cap Q_2$ of two quadrics is singular at $p_1$, then there is a quadric $Q$ in the pencil generated by $Q_1$ and $Q_2$ which is singular at $p_1$. On the other h …
Sasha's user avatar
  • 39.3k
2 votes
Accepted

Degree three, codimension one subvarieties lying on a quadratic hypersurface

If the linear span of $V$ has dimension $n-1$, then $V$ is a cubic hypersurface in a hyperplane. Otherwise, $V$ is a variety of minimal degree, hence it is a cone over a linear section of $\mathbb{P}^ …
Sasha's user avatar
  • 39.3k