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The Borde–Guth–Vilenkin (BGV) theorem is a theorem in physical cosmology which deduces that any universe that has, on average, been expanding throughout its history cannot be infinite in the past but must have a past spacetime boundary. [1]
The Borde–Guth–Vilenkin theorem, according to which any universe that has, on average, been expanding throughout its history cannot have been expanding indefinitely but must have had a past boundary at which inflation began. [45] Professor Alexander Vilenkin, one of the authors of the Borde–Guth–Vilenkin theorem, writes: [46]
In 1982, Paul Steinhardt presented the first model of eternal inflation, Vilenkin showed that eternal inflation is generic. [9] Furthermore, working with Arvind Borde and Alan Guth, he developed the Borde–Guth–Vilenkin theorem, showing that a period of inflation must have a beginning and that a period of time must precede it. [10]
For scientific evidence of the finitude of the past, Craig refers to the Borde-Guth-Vilenkin theorem, which posits a past boundary to cosmic inflation, and the general consensus on the standard model of cosmology, which refers to the origin of the universe in the Big Bang. [44] [45]
Since Guth's early work, each of these observations has received further confirmation, most impressively by the detailed observations of the cosmic microwave background made by the Planck spacecraft. [72] This analysis shows that the Universe is flat to within 1 / 2 percent, and that it is homogeneous and isotropic to one part in 100,000.
In 1982-1983, Steinhardt, Linde and Alexander Vilenkin realized that exponential expansion in the new inflation scenario, once it begins, continues without end in some parts of the universe. On the basis of this scenario, Linde proposed a model of a self-reproducing inflationary universe consisting of different parts.
[1] [18] [19] That same year, Guth received the Golden Plate Award of the American Academy of Achievement. [20] In 2005, Guth won the award for the messiest office in Boston, organised by The Boston Globe. He was entered by colleagues who hoped it would shame him into tidying up, [21] but Guth is quite proud of the award. [22]
These proposals have been criticized as inconsistent with the Borde–Guth–Vilenkin theorem, however their modifications with only one bounce (as opposed to cyclic series of bounces) circumvent this problem (particularly if the contracting phase is empty, i.e. compactified Milne, and (2+1)-dimensional, due to the inherent stabilizing rigidity ...