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 not deleted user 5963

Real algebraic geometry is the study of real solutions to algebraic equations with real coefficients. Its methods are rather different from classical algebraic geometry, which is typically done over an algebraically closed field (like the complex numbers).

1 vote

Hermitian forms with real coefficients

For $d=1$ this is true because $H(z)$ is a bilinear form on $\mathbb{R}^n$ and nonpositive definite by assumption, so it is of the form $H(z) = -\lVert Az\rVert^2$ for some real matrix $A$, and theref …
Noah Stein's user avatar
  • 8,501
45 votes
5 answers
9k views

Real algebraic geometry vs. algebraic geometry

This question is predicated on my understanding that real algebraic geometry (henceforth RAG) is the version of algebraic geometry (AG) one gets when replacing (esp. algebraically closed) fields with …
Noah Stein's user avatar
  • 8,501
14 votes
Accepted

Effective algorithm to test positivity

If by effective you mean "is this computable", then yes, the computational versions of Tarski-Seidenberg such as cylindrical algebraic decomposition give you a finite algorithm. (I suppose this is ass …
Noah Stein's user avatar
  • 8,501