cosmic inflation

From Physical Review D: We investigate the initial conditions of inflation in a Bianchi I universe that is homogeneous but not isotropic. We use the Eisenhart lift to describe such a theory geometrically as geodesics on a field-space manifold. We construct the phase-space manifold of the theory by considering the tangent bundle of the field space and equipping it with a natural metric. We find that the total volume of this manifold is finite for a wide class of inflationary models. We therefore take the initial conditions to be uniformly distributed over it in accordance with Laplace’s principle of indifference. This results in a normalizable, reparametrization invariant measure on the set of initial conditions of inflation in a Bianchi I Read More ›

Error alone does not apparently explain the discrepancy in these figures: For some methods, which rely on using the light from supernova and pulsing stars called Cepheid variables to determine their changing distance, it appears that objects move away from the Earth 73 kilometers per second faster for every 3.26 million additional light-years, also called a megaparsec. For other measuring methods, which rely on the electromagnetic radiation that reaches us from the early universe called the cosmic microwave background, the value is around 67 kilometers per second per megaparsec. … Most recently, a new result from scientists running the Dark Energy Survey has muddied the waters. Using measurements from supernovae, they in fact measured a Hubble constant of 67.7 kilometers Read More ›

An “expert voice” astrophysicist explains that the Big Bang is now the “vanilla Big Bang,” which is unpopular because it doesn’t explain all observations: The Big Bang model is our most successful explanation for the history of the universe that we live in, and it’s ridiculously easy to encapsulate its core framework in a single, T-shirtable sentence… But But there’s no reason for our universe to be flat. At large scales it could’ve had any old curvature it wanted. Our cosmos could’ve been shaped like a giant, multidimensional beach ball, or a horse-riding saddle. But, no, it picked flat. And not just a little bit flat. For us to measure no curvature to a precision of a few percent in Read More ›