## Saturday, October 11, 2014

### Holometer

 The sensitivity of various experiments to fluctuations in space and time. Horizontal axis is the log of apparatus size (or duration times the speed of light), in meters; vertical axis is the log of the RMS fluctuation amplitude in the same units.

The Fermilab Holometer in Illinois is under construction and is intended to be the world's most sensitive laser interferometer when complete, surpassing the sensitivity of the GEO600 and LIGO systems, and theoretically able to detect holographic fluctuations in spacetime.[1][2][3]
According to the director of the project, the Holometer should be capable of detecting fluctuations in the light of a single attometer, meeting or exceeding the sensitivity required to detect the smallest units in the universe called Planck units.[1][4] Fermilab states: "Everyone is familiar these days with the blurry and pixelated images, or noisy sound transmission, associated with poor internet bandwidth. The Holometer seeks to detect the equivalent blurriness or noise in reality itself, associated with the ultimate frequency limit imposed by nature."[2]
***
How is holographic noise different from space-time foam?

John Wheeler's vision of quantum space-time was a roiling foam of virtual black holes. It was based on extrapolation of quantum field theory to the Planck scale. The holographic view is that space-time is not quantized like other fields, but emerges from a quantum system with fewer degrees of freedom than field theory. If this is right, foam is not the right way to visualize the smallest scales See: Holometer: Frequently asked Questions

***
The AdS/CFT correspondence is often described as a "holographic duality" because this relationship between the two theories is similar to the relationship between a three-dimensional object and its image as a hologram.[23] Although a hologram is two-dimensional, it encodes information about all three dimensions of the object it represents. In the same way, theories which are related by the AdS/CFT correspondence are conjectured to be exactly equivalent, despite living in different numbers of dimensions.

One physical system which has been studied using the AdS/CFT correspondence is the quark–gluon plasma, an exotic state of matter produced in particle accelerators. This state of matter arises for brief instants when heavy ions such as gold or lead nuclei are collided at high energies. Such collisions cause the quarks that make up atomic nuclei to deconfine at temperatures of approximately two trillion kelvins, conditions similar to those present at around $10^{-11}$ seconds after the Big Bang.[41]

***

Entropy, if considered as information (see information entropy), is measured in bits. The total quantity of bits is related to the total degrees of freedom of matter/energy.