Tunneling in real structural glasses: A universal theory

We present a universal theory that describes the low-temperature properties of real structural glasses. The key ingredient is a mapping of real and possibly complex glasses on Lennard-Jones glasses. A dimensional analysis allows us to find a general explicit expression that relates the tunneling parameters [density of tunneling systems (TS's), coupling constant between TS's and heat bath] to material constants. Experimental evidence is presented, and the relation to recent numerical calculations on the NiP system is discussed.