The cyclic model is a brane cosmology model of the creation of the universe, derived from the earlier ekpyrotic model. It was proposed in 2001 by Paul Steinhardt and Neil Turok.
Cyclic model - The model.
In the cyclic model, two parallel orbifold planes or M-branes collide periodically in a higher dimensional space. The visible four-dimensional universe lies on one of these branes. The collisions correspond to a reversal from contraction to expansion, or a big crunch followed immediately by a big ba ...
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Cosmic inflation is the idea, first proposed by Alan Guth in 1981, that the nascent universe passed through a phase of exponential expansion (the inflationary epoch) that was driven by a negative pressure vacuum energy density. This expansion is similar to a de Sitter universe with positive cosmological constant. As a direct consequence of this expansion, all of the observable universe originated in a small causally-connected region. Quantum fluctuations in this microscopic region, magnified to cosmic size, ...
Andrei Linde is an American physicist and professor of Physics at California's Stanford University. He was born March 2, 1948 in Moscow, Russia. Dr. Linde is best known for his work on the concept of the inflationary universe. He received his Bachelor of Science degree from Moscow State University. In 1975, Linde was awarded a Ph.D. from the Lebedev Physical Institute in Moscow. Among the various awards he's received for his work on inflation, in 2002 he was awarded the Dirac Medal, along with Alan Guth
The original model of inflation,[1] proposed by Alan Guth, had the universe in a false vacuum. The universe was in an exactly de Sitter phase. In this model, regions of non-inflating universe are created through the nucleation of bubbles of true vacuum, while the rest of the universe continues inflating. When two such bubbles collide, the vast energy of the bubble walls is converted into the particles seen at the beginning of the big bang. This process is c ...
The addition of gravity to the story leads to a considerably richer variety of phenomena. The key insight is that a false vacuum with positive potential energy density is a de Sitter vacuum, in which the potential energy acts as a cosmological constant and the universe is undergoing the exponential expansion of de Sitter space. This leads to a number of interesting effects, first studied by Coleman and de Luccia:[2]
Tunneling from a ...
The Dirac Medal of the ICTP is given each year by the Abdus Salam International Centre for Theoretical Physics(ICTP) in honour of physicist P.A.M. Dirac. The award, given each year on August 8 (Dirac's birthday), was first awarded in 1985.
An international committee of distinguished scientists selects the winners from a list of nominated candidates. The Committee invites nominations from scientists working in the fields of theoretical physics or mathematics.
The Dirac Medal is not awarded to Nobel Laureates, Fields Medalists, or Wolf Prize winners.See also:
Inflation resolves several problems in the Big Bang cosmology that were pointed out in the 1970s. Among these are the observed flatness of the universe (the flatness problem), its extraordinary homogeneity on large (non-causally-connected) scales (the horizon problem), and its lack of any observed topological defects (the monopole problem), predicted by many Grand Unified Theories. Predictions of the standard model of inflation include geometrical flatness of the universe and near scale invariance of the primordial density fluctuations of th ...
Observationally, it is hoped that improved measurements of the cosmic microwave background will tell us more about inflation. In particular, high precision measurements of the polarization of the background radiation will tell us if the energy scale of inflation predicted by the simplest models is correct, and measurements of the spectrum of primordial fluctuations will tell us if our naive models of inflation can produce the correct primordial fluctuations. A perfectly scale invariant spectrum is generally considered incompatible wit ...
Inflation resolves several problems in the Big Bang cosmology that were pointed out in the 1970s. Among these are the observed flatness of the universe (the flatness problem), its extraordinary homogeneity on large (non-causally-connected) scales (the horizon problem), and its lack of any observed topological defects (the monopole problem), predicted by many Grand Unified Theories. Predictions of the standard model of inflation include geometrical flatness of the universe and near scale invariance of the primordial density fluctuations of th ...
In their paper, Coleman and de Luccia noted:
The possibility that we are living in a false vacuum has never been a cheering one to contemplate. Vacuum decay is the ultimate ecological catastrophe; in the new vacuum there are new constants of nature; after vacuum decay, not only is life as we know it impossible, so is chemistry as we know it. However, one could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capa ...
The Paul Dirac Medal and Prize is awarded annually by the Institute of Physics for "outstanding contributions to theoretical (including mathematical and computational) physics". The award was decided upon by the Institute of Physics in 1985, and first granted in 1987.
Dirac Prize - Recipients.
1987 Stephen Hawking
1988 John Bell
1989 Roger Penrose
1990 Michael Berry
1991 Rudolf Peierls
1992 Anthony Leggett
1993 David Thouless
1994 ...
In a physical theory in a false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation.[1] In this, instanton effects cause a bubble to appear in which fields have their true vacuum values inside. Therefore, the interior of the bubble has a lower energy. The walls of the bubble (aka domain walls) have a surface tension, as energy is expended as the fields ...
