What is the holographic dual of an ordinary solid? Using insight from effective field theory (EFT), I will argue that an answer is provided by an SO(d) magnetic monopole in (d+1)-dimensional AdS space. We call such field configuration “solidon”. The low-energy spectrum of the boundary theory can be derived analytically from the gravity dual, and the result confirms that the effective theory consists of a set of phonons having dispersion relations that match those expected from EFT. Next we obtain some numerical solutions including backreaction and calculate the free energy, finding evidence that the solidon “melts” into a black hole as the temperature is raised, which we interpret as a solid-to-liquid phase transition on the field theory side.

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- Théorie