Alan Boyle uses the occasion of Neal Turok’s appointment as executive director of the Perimeter Institute for Theoretical Physics to interview the scientist on topics dear to the heart of Centauri Dreams readers. The ekpyrotic universe idea championed by Turok uses the idea of multidimensional ‘branes’ whose occasional collisions spark events like the Big Bang. A cyclic model emerges that sees multiple ‘bangs,’ using today’s accelerating universe as a condition for the arrival of the next cycle. It’s fascinating stuff, but does it assume the eventual validation of string theory? Boyle quotes Turok:
“In my opinion, string theory is the most promising avenue we have for the unification of gravity and the fundamental forces. But that doesn’t mean I’m not critical of it. I think sometimes people do exaggerate its achievements thus far. We need to keep an open mind.”
Turok, as director of Cambridge University’s Center for Theoretical Cosmology, worked with Princeton’s Barry Steinhardt on Endless Universe: Beyond the Big Bang (Doubleday, 2007), which belongs on your bookshelf. Did an exhausted earlier universe help to spawn the one we live in today, and is another one likely to form a trillion years from now? Don’t look for experimental evidence any time soon, but the ekpyrotic universe is a model whose startling conclusions may offer insights into both dark matter and energy, and the role of each in the universe’s growth. Ekpyrotic, incidentally, derives from the Greek word for ‘conflagration.’
Other weekend reading might involve the latest Carnival of Space, held this week at the Space Cynics site. This week I’ll send you to Bad Astronomy‘s essay on the role our position in the galaxy may play in mass extinctions. This is Phil Plait’s take on a story we looked at briefly here on Centauri Dreams , involving the Solar System’s passage through the galactic plane, which may trigger a rain of comets from the outer system to move toward the Sun. So, at least, says a team at the Cardiff Centre for Astrobiology, which can point to our current galactic position as a sign that we may be nearing another such period. Check as well Brian Wang’s treatment of the laser comb technology we looked at yesterday.
Hi Folks;
The idea of a sea of membranes as in p-brane theory and other brane theory versions is intriguing. The general readership may well be aware that there may be no reason, in theory, why there could not be infinite dimensional space with membranes of all manner of dimensionality floating around within the socalled Bulk. I have a special love of membranes as I am involved in inventive concepts involving membranes although in a much more down to Earth and different context than those of the subject of Paul’s above article.
I could see how setting up huge membranes to enclose cosmically large sizes of the universe or otherwise bound such regions as far distant future cosmic engineering projects, might some how, through general relativistic effects or other global space time effects, effect the structures, space-time curvature, rate of expansion, zero point fields, and the like within regions enclosed and just exterior to the bounding membranes. Note that there have been some unsubstatiated effects reported in terms of gravity modification in experiments that have utilized geometric arrangments of, I believe, rotating superconductive piecies of material or the like. Also, the zero point electromagnetic field effects produced in Casimar experiment setups have produced their well known effects in an easily repeatable manner.
Given that in at least some versions of string theory, distance scales near the level of the Planck distance scale but much smaller than the Planck distance scale are indistinguishable from macroscopic distance scales, perhaps setting up a membrane or otherwise bounding a region of space of appropriately cosmic dimensions in just the right manner might have an effect on the phenomena on the scale of strings and thus the related laws of physics, or perhaps even more significantly, have an effect on the degree and shape of curvature or compactification of the compactified dimensions of the 26-D, 11-D, or 10-D spacetimes of the older and newer versions of string theory respectively.
Thanks;
Jim
How quantum is the big bang?
Authors: Martin Bojowald
(Submitted on 8 May 2008)
Abstract: When quantum gravity is used to discuss the big bang singularity, the most important, though rarely addressed, question is what role genuine quantum degrees of freedom play. Here, complete effective equations are derived for isotropic models with an interacting scalar to all orders in the expansions involved. The resulting coupling terms show that quantum fluctuations do not affect the bounce much. Quantum correlations, however, do have an important role and could even eliminate the bounce. How quantum gravity regularizes the big bang depends crucially on properties of the quantum state.
Comments: 4 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics – Theory (hep-th)
Report number: IGC-08/4-3
Cite as: arXiv:0805.1192v1 [gr-qc]
Submission history
From: Martin Bojowald [view email]
[v1] Thu, 8 May 2008 16:37:42 GMT (9kb)
http://arxiv.org/abs/0805.1192
Who cares if it’s not even wrong?
“So what would you do if string theory is wrong?” asks string
theorist Moataz Emam in a paper posted on arXiv yesterday…
http://physicsworld.com/blog/2008/05/who_cares_if_its_not_even_wron_1.html
Life in the Milky Way: Do Galactic Cycles Influence Earth’s Biological History?
Horoscope enthusiasts will be happy to hear that a grand cosmic force does indeed seem to be responsible for controlling the direction of all life on Earth. However, this grand cosmic cycle has more to do with extinction than finding a tall, handsome stranger.
Early last year, research revealed that the rise and fall of species on Earth seems to be driven by the undulating motions of our solar system as it travels through the Milky Way. Some scientists believe that this cosmic force may offer the answer to some of the biggest questions in our Earth’s biological history.
The University of California, Berkeley found that marine fossil records show that biodiversity increases and decreases based on a 62-million-year cycle. At least two of the Earth’s great mass extinctions-the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago-correspond with peaks of this cycle, which can’t be explained by evolutionary theory.
Early last year, a team of researchers at the University of Kansas came up with an out-of-this-world explanation for the phenomenon. Their idea hinges upon the fact that stars move through space and sometimes rush headlong through galaxies, or approach closely enough to cause a brief cosmic tryst.
Our own star moves toward and away from the Milky Way’s center, and also up and down through the galactic plane. One complete up-and-down cycle takes 64 million years- suspiciously close to the Earth’s biodiversity cycle.
Once the researchers independently confirmed the biodiversity cycle, they then proposed a novel mechanism whereby which the Sun’s galactic travels is causing it.
Full article (and a really nice photo of the Milky Way) here:
http://www.dailygalaxy.com/my_weblog/2008/07/do-galactic-for.html
>>Our own star moves toward and away from the Milky Way’s center, and also up and down through the galactic plane. <<
I like the way you explained that – very visual – and an accurate description of our solar systems motion against the back drop of the galaxy. There is growing evidence for the theory that our sun is a binary star, and that the reason for the bobbing above and below the galactic plane is because of the orbit around a center of gravity (most likely a small black hole) between the two stars. See orbit of binary stars http://www.oglethorpe.edu/faculty/~m_rulison/Astronomy/Chap%2017/Images/binary_star_orbit.gif
The discovery of exoplanet Sedna and its strange orbit is just one recent piece of evidence that supports this theory. The theory is that we cannot see or detect our second sun, which ranges only 1 to 3 light years away locked in an elongated elliptical orbit around the black hole. Our Sun’s sister star will supposedly peek out from behind the black hole, for a brief period of time, during the galactic alignment.
Following the logic of this theory, the mass extinctions by “Comet Showers” is made possible, by the Sun’s twin star when the two come into closer proximity around the center causing an intense gravitational disturbance of the Ort Belt , home to trillions of comets. During that time period the solar system would be careening with comets. (Time to stop focusing on Homeland Security and start revving up our Home Planet Security)
A big proponent of the binary star theory is The Binary Research Institute. http://www.binaryresearchinstitute.org
The Return of the Phoenix Universe
Authors: Jean-Luc Lehners, Paul J. Steinhardt, Neil Turok
(Submitted on 5 Oct 2009)
Abstract: Georges Lemaitre introduced the term “phoenix universe” to describe an oscillatory cosmology with alternating periods of gravitational collapse and expansion. This model is ruled out observationally because it requires a supercritical mass density and cannot accommodate dark energy. However, a new cyclic theory of the universe has been proposed that evades these problems.
In a recent elaboration of this picture, almost the entire universe observed today is fated to become entrapped inside black holes, but a tiny region will emerge from these ashes like a phoenix to form an even larger smooth, flat universe filled with galaxies, stars, planets, and, presumably, life. Survival depends crucially on dark energy and suggests a reason why its density is small and positive today.
Comments: 5 pages, Honorable Mention at the 2009 Gravity Research Foundation essay competition
Subjects: High Energy Physics – Theory (hep-th); Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:0910.0834v1 [hep-th]
Submission history
From: Jean-Luc Lehners [view email]
[v1] Mon, 5 Oct 2009 19:59:49 GMT (6kb)
http://arxiv.org/abs/0910.0834