Identifying and Eliminating the Problem with Einstein's Cosmological Constant

Abstract

The cosmological constant, lambda, was first introduced into Einstein's field equations in the early 20th century. It was introduced as a quantity of outward-pushing energy in space that would counteract the contracting force of gravity thereby keeping the universe in a balanced and static state. Einstein willingly removed it once the universe was observed to be dynamic rather than static. However, as the decades have gone by, lambda has maintained its supporters and has continually been reintroduced to solve problems in cosmology. Presently, there is good reason to believe that lambda or something like it is indeed present in our universe. In the 1960s, in an effort to provide a physical basis for lamda, particle physicists turned to quantum vacuum energy and have since estimated a value for lamdba to be significantly greater than its observationally constrained value. This discrepancy has come to be known as the cosmological constant problem. Any effort to resolve the inconsistency must also account for the various observations we attribute to lambda, such as cosmic inflation and cosmic acceleration. To date, there are two basic approaches to resolving the cosmological constant problem that we may call the Identity approach and the Eliminativist approach. The Identity approach entails that vacuum energy is responsible for all the relevant observations and the problem is to be solved by some cancellation mechanism within the internal components of the vacuum. The Eliminativist approach explicitly rejects the reality and cosmological efficacy of vacuum energy, seeks alternative explanations for the observations and eliminates the cosmological constant problem by eliminating the cosmological constant. The benefit of having a crisis between these two views at this particular stage in cosmology's history is that they can be tested against each other in an experimental situation. Whatever the outcome of the experiments, we will be clearer about the work needed to resolve the cosmological constant problem once and for all.