## Tuesday, December 19, 2006

### Cosmic ray spallation

As this NASA chart indicates, 70 percent or more of the universe consists of dark energy, about which we know next to nothing
Other explanations of dark energy, called "quintessence," originate from theoretical high-energy physics. In addition to baryons, photons, neutrinos, and cold dark matter, quintessence posits a fifth kind of matter (hence the name), a sort of universe-filling fluid that acts like it has negative gravitational mass. The new constraints on cosmological parameters imposed by the HST supernova data, however, strongly discourage at least the simplest models of quintessence.

Of course my mind is thinking about the cosmic triangle of an event in the cosmos. So I am wondering what is causing the "negative pressure" as "dark energy," and why this has caused the universe to speed up.

SNAP-Supernova / Acceleration Probe-Studying the Dark Energy of the Universe
The discovery by the Supernova Cosmology Project (SCP) and the High-Z Supernova team that the expansion of the universe is accelerating poses an exciting mystery — for if the universe were governed by gravitational attraction, its rate of expansion would be slowing. Acceleration requires a strange “dark energy’ opposing this gravity. Is this Einstein’s cosmological constant, or more exotic new physics? Whatever the explanation, it will lead to new discoveries in astrophysics, particle physics, and gravitation.

By defining the context of particle collisions it was evident that such a place where such a fluid could have dominated by such energy in stars, are always interesting as to what is ejected from those same stars. What do those stars provide for the expression of this universe while we are cognoscente of the "arrow of time" explanation.

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion.

So of course these thoughts are shared by the perspective of educators to help us along. But if one did not understand the nature of the physical attributes of superfluids, how would one know to think of the relativistic conditions that high energy provides for us?

NASA/WMAP Scientific Team: Expanding Universe

So recognizing where these conditions are evident would be one way in which we might think about what is causing a negative pressure in the cosmos.

Given the assumption that the matter in the universe is homogeneous and isotropic (The Cosmological Principle) it can be shown that the corresponding distortion of space-time (due to the gravitational effects of this matter) can only have one of three forms, as shown schematically in the picture at left. It can be "positively" curved like the surface of a ball and finite in extent; it can be "negatively" curved like a saddle and infinite in extent; or it can be "flat" and infinite in extent - our "ordinary" conception of space. A key limitation of the picture shown here is that we can only portray the curvature of a 2-dimensional plane of an actual 3-dimensional space! Note that in a closed universe you could start a journey off in one direction and, if allowed enough time, ultimately return to your starting point; in an infinite universe, you would never return.

Of course it is difficult for me to understand this process, but I am certainly trying. If one had found that in the relativistic conditions of high energy scenarios a "similarity to a flattening out" associated with an accelerating universe what would this say about information travelling from the "origins of our universe" quite freely. How would this effect dark energy?

In physics, a perfect fluid is a fluid that can be completely characterized by its rest frame energy density ρ and isotropic pressure p.

Real fluids are "sticky" and contain (and conduct) heat. Perfect fluids are idealized models in which these possibilities are neglected. Specifically, perfect fluids have no shear stresses, viscosity, or heat conduction.

In tensor notation, the energy-momentum tensor of a perfect fluid can be written in the form

$$T^{\mu\nu}=(\rho+p)\, U^\mu U^\nu + P\, \eta^{\mu\nu}\,$$

where U is the velocity vector field of the fluid and where ημν is the metric tensor of Minkowski spacetime.

Perfect fluids admit a Lagrangian formulation, which allows the techniques used in field theory to be applied to fluids. In particular, this enables us to quantize perfect fluid models. This Lagrangian formulation can be generalized, but unfortunately, heat conduction and anisotropic stresses cannot be treated in these generalized formulations.

Perfect fluids are often used in general relativity to model idealized distributions of matter, such as in the interior of a star.

So events in the cosmos ejected the particles, what geometrical natures embued such actions, to have these particle out in space interacting with other forms of matter to create conditions that would seem conducive to me, for that negative pressure?

Cosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of elements from the impact of cosmic rays on an object. Cosmic rays are energetic particles outside of Earth ranging from a stray electron to gamma rays. These cause spallation when a fast moving particle, usually a proton, part of a cosmic ray impacts matter, including other cosmic rays. The result of the collision is the expulsion of large members of nucleons (protons and neutrons) from the object hit. This process goes on not only in deep space, but in our upper atmosphere due to the impact of cosmic rays.

Cosmic ray spallation produces some light elements such as lithium and boron. This process was discovered somewhat by accident during the 1970s. Models of big bang nucleosynthesis suggested that the amount of deuterium was too large to be consistent with the expansion rate of the universe and there was therefore great interest in processes that could generate deuterium after the big bang.

Cosmic ray spallation was investigated as a possible process to generate deuterium. As it turned out, spallation could not generate much deuterium, and the excess deuterium in the universe could be explained by assuming the existence of non-baryonic dark matter. However, studies of spallation showed that it could generate lithium and boron. Isotopes of aluminum, beryllium, carbon(carbon-14), chlorine, iodine and neon, are also formed through cosmic ray spallation.

Talk about getting tongue tied, can you imagine, "these fluctuations can generate their own big bangs in tiny areas of the universe." Read on.

Photo credit: Lloyd DeGrane/University of Chicago News Office
Carroll and Chen’s scenario of infinite entropy is inspired by the finding in 1998 that the universe will expand forever because of a mysterious force called “dark energy.” Under these conditions, the natural configuration of the universe is one that is almost empty. “In our current universe, the entropy is growing and the universe is expanding and becoming emptier,” Carroll said.

But even empty space has faint traces of energy that fluctuate on the subatomic scale. As suggested previously by Jaume Garriga of Universitat Autonoma de Barcelona and Alexander Vilenkin of Tufts University, these fluctuations can generate their own big bangs in tiny areas of the universe, widely separated in time and space. Carroll and Chen extend this idea in dramatic fashion, suggesting that inflation could start “in reverse” in the distant past of our universe, so that time could appear to run backwards (from our perspective) to observers far in our past.