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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]
Guth described the inflationary universe as the "ultimate free lunch": [108] [109] new universes, similar to our own, are continually produced in a vast inflating background. Gravitational interactions, in this case, circumvent (but do not violate) the first law of thermodynamics ( energy conservation ) and the second law of thermodynamics ...
In physical cosmology, the graceful exit problem refers to an inherent flaw in the initial proposal of the inflationary universe theory proposed by Alan Guth in 1981. [1]In Guth’s model, the period of accelerated expansion (a.k.a. inflation) makes the universe homogeneous and flat but can never end.
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 ...
[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]