Simple question, in materials publications I often see the relative change of volume in a system reported as $$ \Delta \left (V \right )/V $$ is the denominator volume supposed to be initial or the ...
What does it mean by the entanglement spectrum of a quantum system? A brief introduction and a few key references would be appreciated.
I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
I've read some papers recently that talk about gapped Hamiltonians or gapless systems, but what does it mean? Edit: Is an XX spin chain in a magnetic field gapped? Why or why not?