10,250 reputation
11128
bio website math.tulane.edu/~mjoyce3
location New Orleans, LA, USA
age 36
visits member for 3 years, 2 months
seen 2 days ago

I am interested in algebraic combinatorics related to Schubert calculus and the geometry of spherical varieties.


Oct
14
answered Proving or disproving A+B is invertible
Oct
14
answered A question about Klaus Hulek algebraic geometry
Oct
14
revised What is the ratio between the speed of the boat and speed of the water current?
edited tags
Oct
12
comment Is it true that $\langle a+cb, a+cb\rangle = \langle a,a\rangle + c^2 \langle b,b\rangle $ where $a,b \in \mathbb{R}^n$ and $c \in \mathbb{R}$?
It's not true in general. You need either $c = 0$ or $\langle a, b \rangle = 0$.
Oct
12
answered Game Theory - First move vs second move advantage?
Oct
11
answered Definition of equivariant map if one of the actions is a right action
Oct
6
comment Tom can choose from $4$ soups, $5$ salads and $4$ drinks for his lunch. How many different combinations of a soup, a salad, and a drink can he make?
Tom should go with French onion, Caesar, and water, and ignore any other combination. (But see Farzad's answer to see how many combinations he's excluding.)
Oct
6
answered how do we know that the rank of AB will be less than a number?
Oct
3
revised Proof that $\operatorname{ker}(A^{T}A) = \operatorname{ker}(A)$?
added 18 characters in body
Oct
3
answered Proof that $\operatorname{ker}(A^{T}A) = \operatorname{ker}(A)$?
Sep
30
awarded  Explainer
Sep
26
comment What is the difference between the algebraic function fields and the fields itself
$(F,K)$ is not a set. It is a pair of sets. So you cannot talk about an "element" of $(F,K)$.
Sep
25
comment Group and subgroup of $G$
I don't understand your sentence `The inverse of $H$ is not an integer.' $H$ is a subset, not an element. Moreover, the elements of $H$ themselves are not integers.
Sep
25
revised Group and subgroup of $G$
added LaTeX formatting
Sep
25
comment What is the difference between the algebraic function fields and the fields itself
It's not proper to write $z \in F / K$, because $F/K$ really refers to the field extension (as anon pointed out in the comments), not to the field $F$. Formally, you can think of a field extension as a pair $(F,K)$ of fields with $K \subseteq F$.
Sep
25
answered What is the difference between the algebraic function fields and the fields itself
Sep
19
comment Irreducible permutations in $S_n$
So if $\sigma(\{1,2,3\}) = \{1,2,3\}$, then do you see why that means that the permutation $\sigma$ does NOT act irreducibly. This is a matter of carefully reading the definition of acting irreducibility and parsing the logic of it.
Sep
18
comment General formula for $\det(A+I)$ where I is identity. Worked it out for $2 \times 2$ and $3 \times 3$.
Don't think there is any "nice" formula, but you can start here in your search: en.wikipedia.org/wiki/Characteristic_polynomial
Sep
17
comment Irreducible permutations in $S_n$
What is $\sigma(\{1,2,3\})$ if $\sigma = (123)(45)$?
Sep
15
reviewed Approve Why exactly does the distributive property work?