Embeds the product P^m × P^n into P^{(m+1)(n+1)−1} via the outer-product coordinates x_i y_j. Image is cut out by the 2×2 minors of the (m+1)×(n+1) matrix (x_i y_j). P^1 × P^1 → P^3 sends the product to a smooth quadric surface. Shows:…
Embeds the product P^m × P^n into P^{(m+1)(n+1)−1} via the outer-product coordinates x_i y_j. Image is cut out by the 2×2 minors of the (m+1)×(n+1) matrix (x_i y_j). P^1 × P^1 → P^3 sends the product to a smooth quadric surface. Shows:…