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TOPIC: Cyclic Universe
Blobrana


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The Phoenix Universe
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Title: Proliferation of the Phoenix Universe
Authors: Jun Zhang

Cyclic cosmology, in which the universe will experience alternating periods of gravitational collapse and expansion, provides an interesting understanding of the early universe and is described as "The Phoenix Universe". In usual expectation, the cyclic universe should be homogeneous, however, with studying the cosmological perturbations, we find that the amplification of curvature perturbations on the large scale may rip the homogeneous universe into a fissiparous multiverse after one or several cycles. Thus, we suggest that the cyclic universe not only rebirths in the "fire" and will never ended, like the Phoenix, but also proliferates eternally.    

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Blobrana


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RE: Cyclic Universe
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Title: The Matter Bounce Curvaton Scenario
Authors: Yi-Fu Cai, Robert Brandenberger, Xinmin Zhang (Arizona State, McGill and IHEP Beijing)

Massless scalar fields originating in a quantum vacuum state acquire a scale-invariant spectrum of fluctuations in a matter-dominated contracting universe. We show that these isocurvature fluctuations transfer to a scale-invariant spectrum of curvature fluctuations during a non-singular bounce phase. This provides a mechanism for enhancing the primordial adiabatic fluctuations and suppressing the ratio of tensor to scalar perturbations. Moreover, this mechanism leads to new sources of non-Gaussianity of curvature perturbations.

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Blobrana


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Professor Sir Roger Penrose, along with his colleague Vahe Gurzadyan, had crunched through the publicly-available data on this ever-so-slightly jumbled glow of light that permeates the whole of the cosmos.
They found neat, circular rings of order in the CMB, a feature which would support a theory of Professor Penrose's: that the Big Bang is just the latest in an endless cycle, rather than a beginning per se.
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Blobrana


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Big Bounce
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Title: Observing the Big Bounce with Tensor Modes in the Cosmic Microwave Background: Phenomenology and Fundamental LQC Parameters
Authors: J. Grain, A. Barrau, T. Cailleteau, J. Mielczarek
(Version v2)

Cosmological models where the standard big bang is replaced by a bounce have been studied for decades. The situation has, however, dramatically changed in the past years for two reasons: first, because new ways to probe the early Universe have emerged, in particular, thanks to the cosmic microwave background, and second, because some well grounded theories -especially loop quantum cosmology- unambiguously predict a bounce, at least for homogeneous models. In this article, we investigate into the details the phenomenological parameters that could be constrained or measured by next-generation B-mode cosmic micorwave background experiments. We point out that an important observational window could be opened. We then show that those constraints can be converted into very meaningful limits on the fundamental loop quantum cosmology parameters. This establishes the early Universe as an invaluable quantum gravity laboratory.

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Blobrana


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RE: Cyclic Universe
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Title: A search for concentric circles in the 7-year WMAP temperature sky maps
Authors: I. K. Wehus, H. K. Eriksen

In a recent analysis of the 7-year WMAP temperature sky maps, Gurzadyan and Penrose claim to find evidence for violent pre-Big Bang activity in the form of concentric low-variance circles at high statistical significance. In this paper, we perform an independent search for such concentric low-variance circles, employing both chi^2 statistics and matched filters, and compare the results obtained from the 7-year WMAP temperature sky maps with those obtained from LCDM simulations. Our main findings are the following: We do reproduce the claimed ring structures observed in the WMAP data as presented by Gurzadyan and Penrose, thereby verifying their computational procedures. However, the results from our simulations do not agree with those presented by Gurzadyan and Penrose. On the contrary we obtain a substantially larger variance in our simulations, to the extent that the observed WMAP sky maps are fully consistent with the LCDM model as measured by these statistics.

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Blobrana


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No evidence of time before Big Bang
Our view of the early Universe may be full of mysterious circles - and even triangles - but that doesn't mean we're seeing evidence of events that took place before the Big Bang. So says a trio of papers taking aim at a recent claim that concentric rings of uniform temperature within the cosmic microwave background - the radiation left over from the Big Bang - might, in fact, be the signatures of black holes colliding in a previous cosmic 'aeon' that existed before our Universe.
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Blobrana


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Pre-Big Bang Universe
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Title: Are There Echoes From The Pre-Big Bang Universe? A Search for Low Variance Circles in the CMB Sky
Authors: Amir Hajian

The existence of concentric low variance circles in the CMB sky, generated by black-hole encounters in an aeon preceding our big bang, is a prediction of the Conformal Cyclic Cosmology. Detection of three families of such circles in WMAP data was recently reported by Gurzadyan & Penrose (2010). We reassess the statistical significance of those circles by comparing with Monte Carlo simulations of the CMB sky with realistic modelling of the anisotropic noise in WMAP data. We find that the circles are not anomalous and that all three groups are consistent at 3sigma level with a Gaussian CMB sky as predicted by inflationary cosmology model.

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Blobrana


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RE: Cyclic Universe
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Cosmos may show echoes of events before Big Bang

Evidence of events that happened before the Big Bang can be seen in the glow of microwave radiation that fills the Universe, scientists have asserted.
Renowned cosmologist Roger Penrose said that analysis of this cosmic microwave background showed echoes of previous Big Bang-like events.
The events appear as "rings" around galaxy clusters in which the variation in the background is unusually low.
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Blobrana


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Roger Penrose hunts for traces of other big bangs

Inflationary cosmology, which is the current model of how physics sees space and time, gets pretty tangled in how it describes the Big Bang and its immediate after-effects. All sorts of odd quantum states, asymmetries, and exotic particles had to come into existence after a violent event that carved out an ever-expanding bubble of space, started time, and hurled out vast quantities of matter out of which just over 4% survived. But while a whole lot of time and effort has been spent mining the subatomic world to confirm the mechanics of what we know as matter, what the Big Bang actually is, and what caused it, are still a mystery. After decades of trying to pin down a reliable culprit with little success, some physicists are trying to drastically simplify the universe, and others are looking at other cosmological models. Following this trend, the physics great Roger Penrose has dusted off the cyclical universe and decided to look for evidence of it in the sky. And he found it. Sort of.
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Blobrana


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Posts: 131433
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Conformal cyclic cosmology
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Title: Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity
Authors: V.G.Gurzadyan, R.Penrose

Conformal cyclic cosmology (CCC) posits the existence of an aeon preceding our Big Bang 'B', whose conformal infinity 'I' is identified, conformally, with 'B', now regarded as a spacelike 3-surface. Black-hole encounters, within bound galactic clusters in that previous aeon, would have the observable effect, in our CMB sky, of families of concentric circles over which the temperature variance is anomalously low, the centre of each such family representing the point of 'I' at which the cluster converges. These centres appear as fairly randomly distributed fixed points in our CMB sky. The analysis of Wilkinson Microwave Background Probe's (WMAP) cosmic microwave background 7-year maps does indeed reveal such concentric circles, of up to 6{\sigma} significance. This is confirmed when the same analysis is applied to BOOMERanG98 data, eliminating the possibility of an instrumental cause for the effects. These observational predictions of CCC would not be easily explained within standard inflationary cosmology.

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