Physicists apply holographic duality to granular matter

Researchers from the Institute of Theoretical Physics (ITP) of the Chinese Academy of Sciences (CAS) and Shanghai University

Jiao Tong (SJTU) found that granular matter (e.g., sand) and some models of black holesexhibit similar nonlinear effects. They are united by a holographic duality.  

It makes it possible to compare unsolved physical problems with solvable multidimensional gravitational analogues and vice versa.The mapping between different dimensions is reminiscent of the optical holographic projection technique, hence the name.

Although holographic duality originated from string theory and was part of the search for a coherent theory of quantum gravity, it has also been widely applied in quantum chromodynamics, condensed matter physics, and  quantum information.

In this work, the idea of holographic duality is extended to a specific type of athermic, disordered solids —granular materials.Since the granules are usually macroscopic in size, thermal fluctuations and quantum effects can be neglected, they noteChinese scientists.

Schematic representation of holographic duality. 
Gravitational models live in (3 1) dimensions, while efficient field theories/amorphous solids are in (2 1) dimensions. ITP Image

Moreover, the traditional theory of elasticityordered crystals is no longer applicable due to the disordered nature of granular materials (i.e., there is no periodic lattice structure for the spatial distribution of grains). Understanding the physical properties of granular matter, such as complex mechanical reactions, remains a theoretical challenge.

Granular materials may, to a certain extentdegree to resist deformation and maintain its structural integrity. However, when the strain exceeds a certain threshold, the material breaks, a phenomenon known as yielding. In some cases, shear can lead to strengthening of the grain system (i.e., an increase in shear modulus), which manifests itself as a nonlinear response to external deformation.

This study predicts internalrelationship between nonlinear elasticity, fluidity and entropy of granular matter based on the holographic principle of duality and effective field theory methods. Computer simulations of granular models confirm theoretical predictions. 

The new work not only expands the fieldapplications of holographic duality, but also reveals potential connections between black hole physics and amorphous materials, opening new possibilities for the study and understanding of complex systems. 

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