Posted: Jul 17, 2018 8:12 pm
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Theoretical concerns in cosmology are debated hotly...
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Paul Steinhardt, one of the founding fathers of inflationary cosmology, has recently become one of its sharpest critics. He calls 'bad inflation' a period of accelerated expansion whose outcome conflicts with observations, and 'good inflation' one compatible with them: "Not only is bad inflation more likely than good inflation, but no inflation is more likely than either [...]
Roger Penrose considered all the possible configurations of the inflaton and gravitational fields. Some of these configurations lead to inflation [...] Other configurations lead to a uniform, flat universe directly – without inflation. Obtaining a flat universe is unlikely overall. Penrose's shocking conclusion, though, was that obtaining a flat universe without inflation is much more likely than with inflation – by a factor of 10 to the googol (10 to the 100) power!"[4][116] Together with Anna Ijjas and Abraham Loeb, he wrote articles claiming that the inflationary paradigm is in trouble in view of the data from the Planck satellite.[144][145] Counter-arguments were presented by Alan Guth, David Kaiser, and Yasunori Nomura[146] and by Andrei Linde,[147] saying that "cosmic inflation is on a stronger footing than ever before".[146]
Theoretical concerns in cosmology are debated hotly...