Abstract
There have been a number of forms of a conjecture that there is a universal lower bound on the ratio, η/s, of the shear viscosity, η, to entropy density, s, with several different domains of validity. We examine the various forms of the conjecture. We argue that a number of variants of the conjecture are not viable due to the existence of theoretically consistent counterexamples. We also note that much of the evidence in favor of a bound does not apply to the variants which have not yet been ruled out.
Original language | English (US) |
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Article number | 026 |
Journal | Journal of High Energy Physics |
Volume | 2008 |
Issue number | 2 |
DOIs | |
State | Published - Feb 1 2008 |
Externally published | Yes |
Keywords
- 1/N expansion
- AdS-CFT correspondence
- QCD