Help!How to express the multiplication of two variables in CVX?

Excuse me! In my program,Y1 and Y2 are shown below.I want to express the product of Y1 and Y2. When I use .* ,It threw an error, how should I express it? Can you give me some advice?

This is the error.

That means Y2 is concave and my model cannot be accepted by CVX?Then how can I solve it?

Have you proven it is a convex optimization problem (as directed by the link)? If not, then use a non-convex solver, such as available under YALMIP.