Archive for February 28, 2014

Inflationary Opinion Poll

Posted in The Universe and Stuff with tags , , , , , on February 28, 2014 by telescoper

Compare and contrast this abstract of a paper on the arXiv from Guth et al. from last year:

Models of cosmic inflation posit an early phase of accelerated expansion of the universe, driven by the dynamics of one or more scalar fields in curved spacetime. Though detailed assumptions about fields and couplings vary across models, inflation makes specific, quantitative predictions for several observable quantities, such as the flatness parameter (Ωk=1−Ω) and the spectral tilt of primordial curvature perturbations (ns−1=dlnPR/dlnk), among others—predictions that match the latest observations from the Planck satellite to very good precision. In the light of data from Planck  as well as recent theoretical developments in the study of eternal inflation and the multiverse, we address recent criticisms of inflation by Ijjas, Steinhardt, and Loeb. We argue that their conclusions rest on several problematic assumptions, and we conclude that cosmic inflation is on a stronger footing than ever before.

and this one, just out,  by Ijjas et al.:

Classic inflation, the theory described in textbooks, is based on the idea that, beginning from typical initial conditions and assuming a simple inflaton potential with a minimum of fine-tuning, inflation can create exponentially large volumes of space that are generically homogeneous, isotropic and flat, with nearly scale-invariant spectra of density and gravitational wave fluctuations that are adiabatic, Gaussian and have generic predictable properties. In a recent paper, we showed that, in addition to having certain conceptual problems known for decades, classic inflation is for the first time also disfavored by data, specifically the most recent data from WMAP, ACT and Planck2013. Guth, Kaiser and Nomura and Linde have each recently published critiques of our paper, but, as made clear here, we all agree about one thing: the problematic state of classic inflation. Instead, they describe an alternative inflationary paradigm that revises the assumptions and goals of inflation, and perhaps of science generally.

I’m not sure how much of a “schism” (to use Ijjas et al.’s word) there actually is, but it seems like an appropriate subject for a totally unscientific Friday lunchtime opinion poll:

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The faces of highly followed astronomers on Twitter

Posted in The Universe and Stuff with tags , on February 28, 2014 by telescoper

On Twitter? Looking for an astronomer or astrophysicist to follow? Here’s a Rogues Gallery…