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Alexander Vilenkin
1982· Person
ProvenTested many times; part of working physics.
Alexander Vilenkin (born 1949), Soviet-born American cosmologist at Tufts University, known for creation from nothing and eternal inflation.
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Born in Kharkiv, Ukraine, then part of the USSR, Vilenkin was barred from Soviet graduate school and worked odd jobs, including as a zoo night watchman, while studying physics on his own. He emigrated in 1976, earned a PhD at the University at Buffalo in 1977 and joined Tufts in 1978. He studied cosmic strings, proposed tunneling from nothing (1982), found that inflation tends to go on forever (1983), and with Arvind Borde and Alan Guth proved (2003) that an inflating universe must have a past boundary.
Why it matters
He helped make the universe's origin a mathematical subject. His 2003 theorem is widely cited in both physics and philosophy-of-religion debates about whether the universe had a beginning.
How the work held up
His theorems are accepted mathematics. Cosmic strings have not been found, though gravitational-wave searches now tightly limit them. Creation from nothing and eternal inflation remain untested proposals.
Still a mystery
His theorem shows inflation cannot run forever into the past, but not what happened at that boundary. Whether eternal inflation's endless bubbles can ever be tested is unresolved.
Connections (2)
▸Alexander Vilenkin proposed A universe tunneling from nothingSpeculative
The relationship
Vilenkin took Tryon's idea further. Instead of a fluctuation in existing space, he described the creation of a small closed universe from 'nothing', meaning no space, time or matter. Once born, its high vacuum energy drives inflation, enlarging it into something like ours. He then argued for a specific quantum starting rule, his 'tunneling wave function'.
How the link was found
Vilenkin, 'Creation of universes from nothing', Physics Letters B, 1982, developed through 1984–88. Andrei Linde, and Yakov Zeldovich with Alexei Starobinsky, published related ideas in 1984.
Is it proven?
Unconfirmed. His rule and Hartle–Hawking's predict opposite things: his favors universes starting with high energy, which inflate a lot; theirs seemed to favor low energy. Data cannot yet separate them.
Open questions and mysteries
Which quantum starting rule, if any, nature uses is unknown. Both rely on equations not yet derived from a full theory of quantum gravity.
▸Alexander Vilenkin co-proposed Eternal inflation and bubble universesSpeculative
The relationship
Vilenkin took the inflaton's quantum jitters, the same ones that seed galaxies, and asked what they do to inflation itself. He found that in some regions they push the field back uphill faster than it rolls down. Those regions keep inflating and grow fastest, so inflating space expands forever, while ordinary universes form in pockets within it.
How the link was found
Alexander Vilenkin at Tufts University, in his 1983 paper 'Birth of inflationary universes', which applied the 1982 calculations of quantum jitters to the inflaton's whole history.
Is it proven?
It follows from the standard quantum treatment of the inflaton, applied to regions far beyond view. Most inflation theorists accept the math; no observation can directly confirm it.
Open questions and mysteries
Vilenkin and Jaume Garriga argued (2001) it implies every possible history repeats endlessly in distant pockets. How to assign probabilities among infinitely many pockets is unsolved.