* Astronomy

Blobrana · L

RE: Inflation

Blobrana · L

Stephen Hawking, who holds Newton's Lucasian Chair at the University of Cambridge, UK, and his colleague Thomas Hertog of the European Laboratory for Particle Physics at CERN in Geneva, Switzerland, are about to publish a paper claiming that the Universe had no unique beginning. Instead, they argue, it emerged out of a profusion of beginnings, the vast majority withered away without leaving any real imprint on the Universe we know today. Only a tiny fraction of them blended to make the current cosmos, Hawking and Hertog claim.
What's fascinating about this theory is that, by extension, it may be transferable to you as an individual observers. By applying a stronger variant of the anthropic principle, one could argue that the cosmos has structured itself around your very own existence.
That, they insist, is the only possible conclusion if we are to take quantum physics seriously.

"Quantum mechanics forbids a single history" - Thomas Hertog, European Laboratory for Particle Physics at CERN.

The researchers' theory comes in response to a problem raised by 'string theory', one of the best hopes for a theory of everything. String theory permits innumerable different kinds of universe, most of them very different from the one we inhabit. Some physicists suspect that an unknown factor will turn up that rules out most of these universes.
But Hawking and Hertog say that the countless 'alternative worlds' of string theory may actually have existed. We should picture the Universe in the first instants of the Big Bang as a river of all these possibilities; like a projection of billions of movies played on top of one another.

Read more

Blobrana · L

Cyclic Inflation

Blobrana · L

Inflation

Blobrana · L

Title: Flavon Inflation
Authors: S. Antusch (1), S. F. King (2), M. Malinsky (2), L. Velasco-Sevilla (3), I. Zavala (4) ((1) Munich, Max Planck Inst., (2) Southampton U., (3) ICTP, (4) Durham U., IPPP)
(Version v2)

We propose an entirely new class of particle physics models of inflation based on the phase transition associated with the spontaneous breaking of family symmetry responsible for the generation of the effective quark and lepton Yukawa couplings. We show that the Higgs fields responsible for the breaking of family symmetry, called flavons, are natural candidates for the inflaton field in new inflation, or the waterfall fields in hybrid inflation. This opens up a rich vein of possibilities for inflation, all linked to the physics of flavour, with interesting cosmological and phenomenological implications. Out of these, we discuss two examples which realise flavon inflation: a model of new inflation based on the discrete non-Abelian family symmetry group A_{4} or Delta_{27}, and a model of hybrid inflation embedded in an existing flavour model with a continuous SU(3) family symmetry. With the inflation scale and family symmetry breaking scale below the Grand Unification Theory (GUT) scale, these classes of models are free of the monopole (and similar) problems which are often associated with the GUT phase transition.

Read more (79kb, PDF)

Blobrana · L

Prof Stephen Hawking has come up with a new idea to explain why the Big Bang of creation led to the vast cosmos that we can see today.
Most models of the universe are bottom-up, that is, you start from well-defined initial conditions of the Big Bang and work forward. However, Prof Hertog and Prof Hawking say that we do not and cannot know the initial conditions present at the beginning of the universe. Instead, we only know the final state - the one we are in now.
Their idea is therefore to start with the conditions we observe today - like the fact that at large scales one does not need to adopt quantum lore to explain how the universe (it behaves classically, as scientists say) - and work backwards in time to determine what the initial conditions might have looked like.
In this way, they argue the universe did not have just one unique beginning and history but a multitude of different ones and that it has experienced them all.

Read more

Blobrana · L

The Hawking-Turok Instanton Theory
The result of Hawking's and Turok's collaboration was the theory that suggested our believed open, inflationary universe formed from miniscule particle called the "instanton." The instanton was popularized under the nickname of "pea." An instanton is a sort of theoretical particle developed in physics that is a "twist in matter and space-time." It got its name from the belief that it lasts for only an instant. It is much smaller than a pea, though its immense density makes its mass roughly equivalent to that of a pea. The instanton automatically turns itself into an open, inflationary universe.

Read more

Blobrana · L

Why was the big bang so very big?
It has been a struggle to explain why the infant universe expanded so rapidly. But now Stephen Hawking at the University of Cambridge, and colleagues, think they are close to perfecting an answer - by treating the early cosmos as a quantum object with a multitude of alternative universes that gradually blend into ours.
The idea that the universe expanded at a blistering rate in the first 10^-34 seconds after the big bang was proposed to explain why regions of the universe separated by vast distances have such a similar background temperature: before inflation occurred, these regions would have been close together with similar properties. But just why the universe inflated in the first place remains a mystery.

Read more

Blobrana · L

Title: A Hemispherical Power Asymmetry from Inflation
Authors: Adrienne L. Erickcek, Marc Kamionkowski, Sean M. Carroll (Caltech)

Measurements of temperature fluctuations by the Wilkinson Microwave Anisotropy Probe (WMAP) indicate that the fluctuation amplitude in one half of the sky differs from the amplitude in the other half. We show that such an asymmetry cannot be generated during single-field slow-roll inflation without violating constraints to the homogeneity of the Universe. In contrast, a multi-field inflationary theory, the curvaton model, can produce this power asymmetry without violating the homogeneity constraint. The mechanism requires the introduction of a large-amplitude superhorizon perturbation to the curvaton field, possibly a pre-inflationary remnant or a superhorizon curvaton-web structure. The model makes several predictions, including non-Gaussianity and modifications to the inflationary consistency relation, that will be tested with forthcoming CMB experiments.

Read more (494kb, PDF)

Blobrana · L

Title: Large Volume Axionic Swiss-Cheese Inflation
Authors: Aalok Misra, Pramod Shukla
(Version v5)

Continuing with the ideas of (section 4 of) [1], after inclusion of perturbative and non-perturbative alpha' corrections to the Kaehler potential and (D1- and D3-) instanton generated superpotential, we show the possibility of slow-roll axionic inflation in the large volume limit of Swiss-Cheese Calabi-Yau orientifold compactifications of type IIB string theory. We also include one- and two-loop corrections to the Kaehler potential but find the same to be subdominant to the (perturbative and non-perturbative) alpha' corrections. The NS-NS axions provide a flat direction for slow-roll inflation to proceed from a saddle point to the nearest dS minimum.

Read more (18kb, PDF)