The Carrollian limit of a field theory is always composed of an electric case and a magnetic case, usually referred to as electric and magnetic contractions in the literature. Carrollian ModMax theory is no different. It was expected that both the electric contraction and the magnetic contraction were covariant under the action of a same group, albeit the action itself may differ and, indeed, that was the case.
As can be seen from the generators and as was shown in the poster, both limits admit the same kind of symmetries but slightly differ on how they are expressed in the field parts. As can be noted by looking at their respective generators:
By virtue of the differences in the generators shown above, the flows that characterize their respective group actions differ, as will be shown in what follows.
Symmetries of the Carrollian electric limit of ModMax
The finite symmetry transformations of the Carrollian electric limit of ModMax theory were found by constructing the flows hX associated with each generator X. These flows are as follows:
where a,b,c∈N0, A∈{1,2,3}, iA:R⟶R3 is the canonical injection map to the A-th coordinate, this is i1(λ)=(λ,0,0), i2(λ)=(0,λ,0) and i3(λ)=(0,0,λ); ωA(λ) are factors given by
sing these, we can write the two families of matrices that characterize the action of special conformal Carrollian transformations act on the electric and magnetic field. The first family of matrices is TA(λ), where each one is given by
These matrices have two important properties that were relevant to proving that special conformal carrollian transformations are a symmetry of the Carrollian magnetic limit of ModMax. Said properties are relative to the R3-inner product
which corresponds to the infinite-dimensional sector of these symmetries.
Symmetries of the Carrollian magnetic limit of ModMax
Finding the finite symmetry transformations of the Carrollian magnetic limit of ModMax direcly proved computationally demandant and difficult, so instead we employed a two-step process. First, we constructed the flow for each symmetry generator of the Carrollian magnetic limit of Maxwell theory, which are:
Second, we proved the symmetries of both theories coincide. The workaround we found was inspired by the formula of the canonical momenta conjugate to the vector potential A of this theory. This allowed us to find a map between the Carrollian magnetic limit of Maxwell theory and that of ModMax, given by
E=Em+2eγsinhγBm2Bm⋅EmBmB=Bm,
and with inverse given by
Em=E−2e−γsinhγB2E⋅BBBm=B.
Using this map, it was possible to show that the symmetries of both theories coincide.
Restriction to the space-time sector
It can be seen from looking at the transformations in both cases that the part pertaining to the space-time sector is the same. This is because they correspond to the action of the same space-time symmetries, with distinctions only in how they act on the electric and magnetic fields.
Even if that much is clear, it is always useful to have an explicit way of writting it. Recall that each generator is a vector field in the tangent space TE, where (E,π,C3+1) is a fiber bundle with projection map
π:E(s,x,E,B)⟶C3+1⟼π(s,x,E,B)=(s,x).
Then the restriction to the spatial part corresponds to simply the composition of the flows with the projection map