This New Scientist article:
My other universe is a Porsche 2006 Oct 05
says that there are ways of varying more than one 'constant' and arriving at habital universes.
quote:
It all comes down to numbers. Harnik argues that there will be countless more universes with myriad properties different from our own. By varying just one property, cosmologists have been too conservative. Harnik, Kribs and Perez decided to highlight this flaw in anthropic reasoning by taking a radical measure: they switched off the weak nuclear force, one of the four fundamental forces in nature. In practice, this means changing a multitude of parameters and constants simultaneously.
The weak force is responsible for the radioactive beta decay of atomic nuclei and is considered essential for a complex universe like ours. Take it away, and you might expect the "weakless" universe to be wildly different from our own.
Only Harnik, Kribs and Perez have discovered it isn't. They considered what would happen to crucial processes in the history of the universe - the forging of elements in the big bang, the powering of stars and supernovae explosions. By examining the equations that describe these processes, they made an astonishing discovery: the weakless universe is still capable of supporting observers.
and
quote:
Aguirre knew a good parameter to vary. Before the triumph of the hot big bang model, researchers had explored so-called cold big bang models to see the effect on phenomena such as galaxy formation. The crucial parameter that determines whether the big bang is hot or cold is the number of photons per baryon. In our universe it is about a billion. Aguirre wondered what would happen if it was in the range 0.1 to 100 - much, much cooler.
Aguirre's universe started off quite unlike our own (Physical Review D, vol 64, p 083508). After our hot big bang, the universe took tens of millions of years to cool to the point where matter could clump into stars. "But in the cold big bang universe, stars can begin to form within 100 years of the big bang," says Aguirre.
He even modelled an extreme cold big bang universe where the cosmological constant was 1017 times what it is in our universe. By rights, this strong repulsive force ought to fling matter apart, preventing the formation of galaxies. However, in the cold big bang universe, stars form so quickly that they are in place before this cosmological repulsion takes hold. "The stars then rush away from each other," says Aguirre. "It's a pretty dull universe with each star isolated in a vast ocean of space. Nevertheless, there is nothing to prevent such stars having planets and observers."
Now that we have found two islands in the multiverse - three, including our own - the question is: are there more? "Undoubtedly," says Harnik. "However, imagining what forms life may take and the finite time available to us to do this will always be an obstacle."
™ Version 4.2