Timeline for What is known about first cohomology of the units in a number field?
Current License: CC BY-SA 3.0
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| Jul 30, 2012 at 15:18 | comment | added | Will Sawin | in fact this gives you a lower bound on the class number of a quadratic field, I think. You can also see it's contained in the subgroup generated by certain powers of the ramified primes which makes sense since you can be less and more ramified. But I don't know how to deal with the class number problem | |
| Jul 30, 2012 at 4:35 | comment | added | Victor Ostrik | Dear Will, thanks for your answer! I think that the image of the norm is contained in the subgroup generated by ramified primes but it is often much smaller (say for quadratic fields the image is of order $\le 4$ but we can have arbitrarily many ramified primes. | |
| Jul 27, 2012 at 22:02 | history | answered | Will Sawin | CC BY-SA 3.0 |