Inductors store energy in the form of this entity, since it arises when current passes through a solenoid, and it is defined as the curl of the vector potential A. This entity would not be divergence-free if monopoles existed that could operate similar to electric point charges.
In a two-dimensional system, the presence of this entity leads to Landau levels in a phenomenon wherein topological quantum numbers like the Chern numbers arise in calculating the conductivity due to this entity; that phenomenon is the quantum (*) Hall effect. Inductors store energy in the form of this entity, since it arises when current passes through a solenoid, and it is defined as the curl of the vector potential A. This entity would not be divergence-free if monopoles existed that could operate similar to electric point charges. For 10 points, name this entity often denoted B, a field most famously present around materials with north and south poles.
In a two-dimensional system, the presence of this entity leads to Landau levels in a phenomenon wherein topological quantum numbers like the Chern numbers arise in calculating the conductivity due to this entity; that phenomenon is the quantum (*) Hall effect.
{magnetic} field [or B field before mentioned]