In this talk, we will introduce some recent progress in dealing with optimization problems over noncompact semialgebraic sets. We will start with the problem of optimizing a parametric linear function over a noncompact real algebraic variety. Then we will introduce how to compute the semidefinite representation or approximation of the convex hull of a noncompact semialgebraic set. Finally, we will show how to characterize the lifts of noncompact convex sets by the cone factorizations of properly defined slack operators.Optimizing a parametric linear function over a real algebraic variety We consider the problem of optimizing a parametric linear function over a real algebraic variety. . , Xn] and c = (c1, . . . , cn) denotes unspecified parameters. The optimal value c * 0 can be regarded as a function of the parameters c, i.e. the optimal value function.Our goal is to compute a polynomial Φ ∈ Q[c0, c1, . . . , cn] that defines a hypersurface in the parameters' space which contains the graph of this function.Assuming that V is irreducible, smooth and compact in R n , Rostalski and Sturmfels showed that the optimal value function is represented by the defining equation of the irreducible hypersurface V * dual to the projective closure of V in R n [11, Theorem 5.23]. Let C = cl (co (V ∩ R n )) be the closure of the convex hull of V ∩ R n , in [5, Theorem 1.5], we proved that this conclusion is still true for a noncompact real algebraic variety V ∩ R n when it is irreducible, smooth and the recession cone 0 + C of C is pointed (contains no lines). Although the conclusion is correct, the proof of [5, Theorem 1.5] works only if the convex hull of V ∩ R n is closed. The new proof can be found in [4, Corollary 3.2]. Moreover, in [4], we showed (−c * 0 : γ1 : · · · : γn) ∈ V * whenever the optimal value c * 0 is bounded at (γ1, . . . , γn) and V is smooth. When V is not smooth but its real trace is compact, we constructed recursively a finite number of dual varieties such that (−c * 0 : γ1 : · · · : γn) lies in the union of these dual varieties. For some special parameters' values, the representing polynomials of the dual variety V * can be identically zero, which give no information on the optimal value. We designed a parametric variant of [3] that identifies those regions of the parameters' space and computed for each of these regions a new polynomial defining the optimal value over the considered region.