901 reputation
11122
bio website preschema.com
location Essen, Germany
age 23
visits member for 4 years, 9 months
seen 6 hours ago

Jul
30
awarded  Critic
Jul
27
answered Geometric flavored textbook on algebra
Jul
27
accepted Projective transformation between polygons.
Jul
26
asked Projective transformation between polygons.
Jul
25
accepted Linear transformation takes a polygon to another one.
Jul
25
comment eBook readers for mathematics
PDF panning and zooming was actually just added to the Kindle yesterday. (It's a software update so you can just download it.)
Jul
25
answered Marey's problem: Generating all prime numbers in $[n_1,n_2]$
Jul
25
comment Experimental Mathematics
Schwartz and Tabachnikov found a few sets of interesting elementary theorems in projective geometry by computer experiment: math.brown.edu/~res/Papers/intelligencer4.pdf.
Jul
25
asked Linear transformation takes a polygon to another one.
Jul
20
accepted Examples of computing Ext and Tor functors?
May
25
awarded  Teacher
May
25
answered Undergraduate Level Math Books
May
19
awarded  Autobiographer
May
19
comment Examples of computing Ext and Tor functors?
@Jack Schmidt: Thanks! Exactly what I was looking for. @Martin Brandenburg: I have consulted several. Do you know of one that goes through an example like this?
May
17
awarded  Scholar
May
17
asked Examples of computing Ext and Tor functors?
May
17
accepted Coinciding induced maps
May
17
comment Coinciding induced maps
Sorry, I mean complexes $0 \to I_0 \to I_1 \to \cdots$ with $I_i$ injective or $\cdots \to P_1 \to P_0 \to 0$ with $P_i$ projective. Because then you can construct homotopy maps inductively.
May
17
awarded  Supporter
May
17
comment Coinciding induced maps
Yes, of course it's not true in general — I asked "when" is it true. I feel it should be true when both complexes consist of either all projective or all injective modules, and are bounded. In the unbounded case it seems false.