Tuesday, December 27, 2005

Acoustic Hawking Radiation

What did we learn from studying acoustic black holes? by Renaud Parentani

The study of acoustic black holes has been undertaken to provide new insights about the role of high frequencies in black hole evaporation. Because of the infinite gravitational redshift from the event horizon, Hawking quanta emerge from configurations which possessed ultra high (trans-Planckian) frequencies. Therefore Hawking radiation cannot be derived within the framework of a low energy effective theory; and in all derivations there are some assumptions concerning Planck scale physics. The analogy with condensed matter physics was thus introduced to see if the asymptotic properties of the Hawking phonons emitted by an acoustic black hole, namely stationarity and thermality, are sensitive to the high frequency physics which stems from the granular character of matter and which is governed by a non-linear dispersion relation. In 1995 Unruh showed that they are not sensitive in this respect, in spite of the fact that phonon propagation near the (acoustic) horizon drastically differs from that of photons. In 2000 the same analogy was used to establish the robustness of the spectrum of primordial density fluctuations in inflationary models. This analogy is currently stimulating research for experimenting Hawking radiation. Finally it could also be a useful guide for going beyond the semi-classical description of black hole evaporation.


I am held to a state of profound thinking when I thnk about Einstein in a dream I had. Where his satisfaction was raised, as a surpize, as I listen to the very sound of ice in a glass jug as I slowly turned it? From it, a certain recognition by Einstein held him in amazement as this sound seem to satisfy what he was so long search for in his answers. Yes it is a dream, but this set the stage from what I had been doing previous as I was thinking about the Webber bars and the way research was moving along this avenue to detect grvaiational waves. Movements to the giant Ligo inteferometers, to help us in our pursuate.

I know it is not always easy to understand the thinking here as it is piecemealed, while my minds works to weave a cohesive picture here. So, my apologies.

There is a special class of fluids that are called superfluids. Superfluids have the property that they can flow through narrow channels without viscosity. However, more fundamental than the absence of dissipation is the behavior of superfluids under rotation. In contrast to the example of a glass of water above, the rotation in superfluids is always inhomogeneous (figure). The fluid circulates around quantized vortex lines. The vortex lines are shown as yellow in the figure, and the circulating flow around them is indicated by arrows. There is no vorticity outside of the lines because the velocity near each line is larger than further away. (In mathematical terms curl v = 0, where v(r) is the velocity field.)


Early on the very idea of measuring discrete functions in relation to how we might percieve quark and gluonic natures which arose from the gold ion collisions, raises the very idea of how we may look at the analogies sought to help shape perspective from the horizon, to what is emitted? A Virtual Photon released in pair production at the horizon can become?

While I had come to recognize the differences in thermodynamic principals held in context of the blackhole, the very idea of He4raises some interesting scenario's in relation to sound values, while "extreme curvature" had been lead too as a singularity in the blackhole?? This singuarity thought to besimlar to the hawking no bondary proposal would not sit well with how the very nature of the blackhole actually becomes the superfluid that we hav come to recognize in the collider perspectives. This changes things somewhat. How fortunate is it in relation to how we see the supersymmetry that coudl arise inthe action fo symmetry break that signs could be lea dto the nature of the phton release and stretched under the aupsice of theis grvaiutional field?

Overlap of "quantum" and "classical" behaviour

Explanations of Hawking radiation around a black hole often use a description of quantum-mechanical pair production effects occurring on a curved spacetime background. Although this paradigm does not obviously lend itself to a "classical" reinterpretation, research on the black hole membrane paradigm has revealed some overlap between "classical" and "quantum" descriptions.


Plato:
What conditions would have allowed such a scene to be developed in supersymmetrical view, that I had wondered, could such a perfect fluid be the example needed? What blackholes hole would allow such a view to be carried down to this level in gold ion collisions, that we might see the results of string theory, as a useful analogy in the discernation of what can now be brought forward for inspection.


So having recognized the two phases of superfluids that ha dbeen created how woud such analogies move th emind to coisder this other nature of of a helium whose viscosity woud have allowed the sound to travel under the same aupsice held in context of the photon whose naure would havebeen rvealled in redshifting? Would suchj a thing held in context of blue shifting be cancelled out in quark/gluonic phases. that the analogy no longer suits our purpose? While sound i analogy in helium may have revealled the very nature of the superfluid designs we woudl like to see in comparsion to how thephotons are looked at with such short distances? They are cancelled out here?


Thorne: Black holes and time warps…, chapter 11, "What is reality?"

The laws of black-hole physics, written in this membrane paradigm, are completely equivalent to the corresponding laws of the curved-spacetime paradigm – as long as one restricts attention to the hole's exterior. Consequently, the two paradigms give precisely the same predictions for the outcomes of all experiments or observations that anyone might make outside a black hole …"


What is a Phonon/Photon?

Phonon:
A particle of sound. The energy E of a phonon is given by the Einstein relation, E = hf. Here f is the frequency of the sound and h is Planck's constant. The momentum p of a photon is given by the de Broglie relation, p = h/λ. Here λ is the wavelength of the sound


Photon:
A particle of light. The energy E of a photon is given by the Einstein relation, E = hf. Here f is the frequency of the light and h is Planck's constant. The momentum p of a photon is given by the de Broglie relation, p = h/λ. Here λ is the wavelength of the light.




As you look at the picture above, the very depths to which vision might have been imparted in recognition of this supefluid, what value would be assign something held in the context of the wave nature to have seen it described as a granulization and then thought of in terms of the langangrian perspective as cosmic strings which cross this universe? Make sure you click on the picutre.

Granularity of the Fluid?

Taken from the horizon, how would this fluid look if held in context of William Unruh's previously thought "continous nature" or as a discretium release of Hawking like phonons? It may be "by analogy" help physicists with respect to the nature of gravitational blackholes?