What about the negative side of the t-axis?  Nothing forbids an expansion in that direction as well.  The equations of classical or quantum physics make no fundamental distinction between the two time directions.  A completely time-symmetric solution of Einstein's equations for the vacuum will give exponential expansion on both sides of the time axis, proceeding away from t = 0, where the initial quantum fluctuation was located. 

 This implies the existence of another part of our universe, separated from our present part along the time axis.  From our point of view, that part is in our deep past, exponentially deflating to the void prior to the quantum fluctuation that then grew to our current universe.  However, from the point of view of observers in the universe at that time, their future is into our past - the direction of increasing entropy on that side of the axis.  They would experience a universe expanding into their future, just as we experience one expanding into our future.  In other words, each side of the time axis has an arrow pointing away from the origin. 

 Unless physics is completely deterministic, which is not believed to be the case, there is no reason to expect these different parts of the universe to be identical, i.e., mirror images of one another.  They would more likely be two different worlds, each expanding in its own way, filled with random events unique to each, and perhaps with different kinds of life.  Fundamentally, the universe as a whole is time-symmetric, running all the way from minus eternity to plus eternity with no preferred direction, no "arrow" of time.  Indeed, the whole notion of beginning is meaningless in a time-symmetric universe.  And without a beginning, the whole Kalam cosmological argument for a creator fails because of the failure of step (2) in Craig's syllogism. 

 Conclusion

 Stenger has described a scenario for an infinite, eternal, and symmetric universe that had no beginning (and, symmetrically, no end).  The quantum fluctuation occurs at a random spatial and temporal point in an infinite void.  He admits that his scenario will be criticized as speculative by theists; however, unlike the ID hypothesis, it is based on established science.  Thus, it is less speculative than the god-as-designer claim. 

 The wave function theory represents one successful example of how the process of spontaneous structure formation from underlying symmetry and chaos may have come about.