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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]
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 ...
Guth proposed inflation in January 1981 to explain the nonexistence of magnetic monopoles; [51] [52] it was Guth who coined the term "inflation". [53] At the same time, Starobinsky argued that quantum corrections to gravity would replace the supposed initial singularity of the Universe with an exponentially expanding de Sitter phase. [ 54 ]
2003 – Arvind Borde, Alan Guth, and Alexander Vilenkin prove the Borde–Guth–Vilenkin theorem. [233] [234] 2002 – First data collection of the Laser Interferometer Gravitational-Wave Observatory (LIGO). 2002 – James Williams, Slava Turyshev, and Dale Boggs conduct stringent lunar test of violations of the principle of equivalence. [235]
Physical cosmology is the study of the largest-scale structures and dynamics of the Universe and is concerned with fundamental questions about its origin, structure, evolution, and ultimate fate.