I am trying to do an exercise that invoves determining a representative for the class that generates $ H^3_{dR}(\mathbb{P^3}-Q,\mathbb{Q})$ , where $ Q$ is a quadric. I was told that it should be something like: $ \omega = \frac{\sum_{j=0}^3 x_jdx_0\wedge…\wedge \widehat{dx_j}\wedge…\wedge dx_3}{Q^2}$ , but apparently I don’t understand enough about closed and exact forms toRead more