 | This article includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this article byintroducing more precise citations.(November 2010) (Learn how and when to remove this message) |
Andrei Linde | |
|---|---|
 Linde in 2018 | |
| Born | (1948-03-02)March 2, 1948 (age 77) |
| Alma mater | Moscow State University |
| Known for | Work oncosmic inflation KKLT mechanism |
| Spouse | Renata Kallosh |
| Awards | 2018 Gamow Prize 2014 Kavli Prize 2012 Breakthrough Prize in Fundamental Physics 2004 Gruber Prize in Cosmology 2002 Dirac Medal 2002 Oskar Klein Medal |
| Scientific career | |
| Fields | Theoretical physics Physical Cosmology |
| Institutions | Lebedev Physical Institute CERN Stanford University |
| Doctoral advisor | David Kirzhnits |
Andrei Dmitriyevich Linde (Russian:Андре́й Дми́триевич Ли́нде; born March 2, 1948) is a Russian-Americantheoreticalphysicist and theHarald Trap Friis Professor of Physics atStanford University.
Linde is one of the main authors of theinflationary universe theory, as well as the theory ofeternal inflation and inflationarymultiverse. He received hisBachelor of Science degree fromMoscow State University. In 1975, Linde was awarded aPhD from theLebedev Physical Institute inMoscow. He worked atCERN (European Organization for Nuclear Research) since 1989 and moved to the United States in 1990, where he became professor of physics atStanford University. Among the various awards he has received for his work oninflation, in 2002 he was awarded theDirac Medal, along withAlan Guth ofMIT andPaul Steinhardt ofPrinceton University. In 2004 he received, along with Alan Guth, theGruber Prize in Cosmology for the development ofinflationary cosmology. In 2012 he, along with Alan Guth, was an inaugural awardee of theBreakthrough Prize in Fundamental Physics. In 2014 he received the Kavli Prize in Astrophysics "for pioneering the theory of cosmic inflation", together with Alan Guth andAlexei Starobinsky. In 2018 he received the Gamow Prize.
During 1972 to 1976, David Kirzhnits and Andrei Linde developed a theory of cosmologicalphase transitions. According to this theory, there was not much difference betweenweak,strong andelectromagnetic interactions in thevery early universe. These interactions became different from each other only gradually, after thecosmological phase transitions which happened when the temperature in the expandingUniverse's became sufficiently small. In 1974, Linde found that theenergy density ofscalar fields thatbreak the symmetry between different interactions can play the role of thevacuum energy density (thecosmological constant) in theEinstein equations. Between 1976 and 1978, Linde demonstrated that the release of this energy during the cosmological phase transitions may be sufficient to heat up the universe.
These observations became the main ingredients of the first version of theinflationary universe theory proposed byAlan Guth in 1980. This theory, now called the "old inflation theory",[citation needed] was based on the assumption that the universe was initially hot. It then experienced the cosmological phase transitions and was temporarily stuck in asupercooledmetastablevacuum state (afalse vacuum). The universe thenexpanded exponentially – "inflated" – until the false vacuum decayed and the universe became hot again. This idea attracted much attention because it could provide a unique solution to many difficult problems of the standardBig Bang theory. In particular, it could explain why the universe isso large and so uniform. However, as Guth immediately realized, this scenario did not quite work as intended: the decay of the false vacuum would make the universe extremelyinhomogeneous.
In 1981, during a seminar byStephen Hawking on quantum gravity, Linde developed another version of inflationary theory that he called "new inflation".[citation needed] He demonstrated that the bubbles not joining up (see page 138 ofA Brief History of Time, Chapter 8) could be solved if there was a bubble that contained our region of the universe in it. He also said that the phase transition must have taken place slowly inside the bubble. This theory resolved the problems of the original model proposed by Guth while preserving most of its attractive features. A few months later, a similar scenario was proposed byAndreas Albrecht andPaul Steinhardt which referenced Linde's paper. Soon after that, it was realized that the new inflationary scenario also suffered from some problems. Most of them arose because of the standard assumption that the early universe initially was very hot, and inflation occurred during the cosmological phase transitions.
In 1983, Linde abandoned some of the key principles of old and new inflation and proposed a more general inflationary theory,chaotic inflation. Chaotic inflation occurs in a much broader class of theories, without any need for the assumption of initialthermal equilibrium. The basic principles of this scenario became incorporated in most of the presently existing realistic versions of inflationary theory. Chaotic inflation changed the way we think about the beginning of inflation. Later on, Linde also proposed a possible modification of the way in which inflation may end, by developing thehybrid inflation scenario. In that model, inflation ends due to the "waterfall" instability[clarification needed].
According to the inflationary theory, allelementary particles in the universe emerged after the end of inflation, in a process calledreheating. The first version of the theory of reheating, which is essentially the theory of creation of matter in the universe, was developed in 1982 byAlexander Dolgov and Linde, and also byL.F. Abbott,Edward Farhi andMark B. Wise. In 1994, this theory was revised byL.A. Kofman, Linde andAlexei Starobinsky. They have shown that the process of creation of matter after inflation may be much more efficient due to the effect ofparametric resonance.[clarification needed]
Perhaps the most far-reaching prediction made by Linde was related to what is now called the theory of inflationarymultiverse, orstring theory landscape. In 1982-1983, Steinhardt, Linde andAlexander 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 aself-reproducing inflationary universe consisting of different parts. These parts are exponentially large and uniform, because of inflation. Therefore, for all practical purposes each of these parts looks like a separate mini-universe, or pocket universe, independent of what happens in other parts of the universe.
Inhabitants of each of these parts might think that the universe everywhere looks the same, and masses of elementary particles, as well as thelaws of their interactions, must be the same all over the world. However, in the context of inflationary cosmology, different pocket universes may have different laws of low-energy physics operating in each of them. Thus our world, instead of being a single spherically symmetric expanding balloon, becomes a hugefractal, an inflationary multiverse consisting of many different pocket universes with different properties. This provided a simple scientific interpretation of the cosmologicalanthropic principle: Our world may consist of different parts, but we can live only in those parts of the multiverse which can support life as we know it.
These ideas did not attract much attention at that time, in part because the anthropic principle was very unpopular, in part because the new inflationary scenario did not quite work and was replaced by the chaotic inflation scenario. However, in 1986 Linde found that in many versions of the chaotic inflation scenario, the process of exponential expansion of the universe also continues forever in some parts of the universe. Linde called this processeternal inflation. Quantum fluctuations produced during eternal chaotic inflation are so large that they can easily push different parts of the universe from onevacuum state to another, and even change the effectivedimensionality ofspacetime. This provided a very powerful realization of the theory of the multiverse.
Linde and his Stanford colleague Vitaly Vanchurin calculated the number of all possible universes, to be about 10^10^16 if we do not consider the fact that humans as observers are limited in their ability to distinguish more universes. If this is taken into account, there could be as many as 10^10^10^7 universes. By analyzing theslow-roll inflation mechanism that initially generated thequantum fluctuations, the scientists could estimate the number of resulting universes at 10^10^10^7.[1]
A significant advance in this area was obtained when the theory of inflationary multiverse was implemented in the context ofstring theory. In 2000,Raphael Bousso andJoseph Polchinski proposed using the regime of eternal inflation and transitions between many different vacua in string theory for solving thecosmological constant problem. At that time, no stable ormetastable vacua of string theory were actually known. A possible mechanism of string theory vacuum stabilization was proposed in 2003 byShamit Kachru,Renata Kallosh, Linde, andSandip Trivedi, who also found that all of these vacua describing expanding universe are metastable, i.e. they must eventually decay (seeKKLT mechanism).[2] ThenMichael R. Douglas and his collaborators[clarification needed] estimated that the total number of different stringy vacua can be as large as 10500, or even more,[vague] andLeonard Susskind developed thestring theory landscape scenario based on investigation of cosmological phase transitions between different string theory vacua.
One of the main challenges of this theory is to find theprobability of living in each of these different parts of the universe. However, once string theory is invoked, it is extremely difficult to return to the previous picture of a single universe. In order to do so, one would need to prove that only one of the many vacua of string theory is actually possible, and to propose an alternative solution of the many problems which can be solved by using the anthropic cosmological principle in the context of the theory of inflationary multiverse.,[3][4]
Linde continues his work on the theory of inflationary multiverse. In particular,Renata Kallosh and Andrei Linde, together with their collaborators, developed a theory of cosmological attractors. This is a broad class of versions ofinflationary cosmology which provide one of the best fits to the latest observational data.[5]
In July 2012, Linde was an inaugural awardee of theBreakthrough Prize in Fundamental Physics, the creation of physicist and internet entrepreneurYuri Milner. In 2014, he was a co-recipient, with Alan Guth andAlexei Starobinsky, of theKavli Prize awarded by theNorwegian Academy of Science and Letters.[6]
Linde is a member of theNational Academy of Sciences and of theAmerican Academy of Arts and Sciences.
Linde is married toRenata Kallosh. They have two sons.[7]
His parents were Soviet physicistsIrina Rakobolskaya andDmitry Linde [ru].
In February–March 2022, he signed an open letter by Russian scientists condemning the2022 Russian invasion of Ukraine,[8] and another open letter by Breakthrough Prize laureates with the same message.[9]
