Universe will expand or collapse?

I have a question about the modern physics.
According to some theory, the universe will first expand then collapse if its mass is less than some constant C. We also know that the value of an object's mass is different if we observe it in different inertial reference systems. Suppose there is a small universe and two observers in different inertial reference systems. One finds that its mass is larger than the constant C and he will observe an expanding then collapse. The other finds that its mass is smaller than C so he observes an forever expanding. Is it possible?