# QSNS universality - Leggett et al


## Vural-Leggett 2011-2013

[Universal Sound Absorption in Amorphous Solids: A Theory of Elastically Coupled Generic Blocks](https://arxiv.org/abs/1103.5530)
Dervis C. Vural, Anthony J. Leggett

[Vural's thesis](https://arxiv.org/pdf/1203.1281.pdf)

- 2013 [Is TTLS model successful because it is unique, or because it is a special case of **a much more general scenario?**](http://people.physics.illinois.edu/Leggett/TTLS.pdf)
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universal value of Q-1 due to fact that **absorbed entity (phonon) identical to one whose exchange generates effective interaction.** 
Small value of Q-1 a result of (a) **multiplicity of phonon modes and stress-tensor matrix elements** (b) logarithmic factor **arising from real-space scaling**
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“Smoking – gun” tests? - Problem: alternative scenario at present **too generic to make many specific predictions**⏎
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## resonant scattering

2013 [The "Tunneling Two-Level Systems" Model of the Low-Temperature Properties of Glasses: Are "Smoking-Gun" Tests Possible?](https://arxiv.org/abs/1310.3387) Authors: Anthony James Leggett, Dervis Can Vural

compare with the derivation of resonant scattering
1972 [Jackle - relaxation regime and resonant regimes](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5378/10.1007_BF01401204.pdf) 
1971 [Anomalous Low-temperature Thermal Properties of Glasses and Spin Glasses](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5394/14786437208229210.pdf) By P. w. ANDERSON, B. I. HALPERIN and c. M. VARMA


## [Yu-Leggett 1991](https://ps.uci.edu/~cyu/publications/TLS_AJL.pdf)


- [Leggett 1991](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5373/Leggett%2B1991%2Bwhy%2Bsimilar.pdf)


## 2015 [A Generic Microscopic Theory for the Universality of TTLS Model Meissner-Berret Ratio in Low-Temperature Glasses](https://arxiv.org/abs/1510.05528) Di Zhou [published pdf](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5467/zhou%2Bwithout%2Bajl.pdf) , Anthony J. Leggett

Shukla [γl and γt as the coupling-strength for two amorphous molecules mediated by longitudinal and transverse phonons (also referred as Meissner-Berret ratio)](https://arxiv.org/pdf/2101.00492.pdf)

- 2016 [Random Nonlinear Infinite-Level-System Model for **Amorphous Solid Phonon Echo and Saturation Phenomena**](https://arxiv.org/abs/1510.05538)
Di Zhou, Anthony J. Leggett

- [Zhou thesis](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5466/ZHOU-DISSERTATION-2016.pdf)



## addendum

[2018 - Enss](https://publish.illinois.edu/leggettcelebration/files/2018/05/Enss-AJLat80.pdf)



# Parents

* Small coupling- low-T glasses
* Cross-section and types of scattering

# Attachments

* [](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5466/ZHOU-DISSERTATION-2016.pdf)
* [](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5467/zhou%2Bwithout%2Bajl.pdf)