Monday, 1 January 2018

research level - Large gauge transformations for higher p-form gauge fields


Question: What is the large gauge transformations for higher p-form gauge field on a spatial d-dimensional torus Td or a generic (compact) manifold M? for p=1,2,3, etc or any other integers. Is there a homotopy group to label distinct classes of large gauge transformations for p-form gauge field on d-dimensional torus Td or any M manifold ? (shall we assume the theory is a topological field theory, or not necessary?) References are welcome.




Background: Large gauge transformation has been of certain interests. The Wiki introduces it as




Given a topological space M, a topological group G and a principal G-bundle over M, a global section of that principal bundle is a gauge fixing and the process of replacing one section by another is a gauge transformation. If a gauge transformation isn't homotopic to the identity, it is called a large gauge transformation. In theoretical physics, M often is a manifold and G is a Lie group.



1-form: The well-known example is a connection A as Lie algebra value 1-form. We have the finite gauge transformation. Ag(A+d)g1 An example of a large gauge transformation of a Schwarz-type Chern-Simons theory, AdA, on 2-dimensional T2 torus of the size L1×L2 with spatial coordinates (x1,x2) can be g=exp[i2π(n1x1L1+n2x2L2)]. This way, for the constant gauge profile (a1(t),a2(t)) (constant respect to the space, satisfying EOM dA=0), the large gauge transformation identifies: (a1,a2)(a1,a2)+2π(n1L1,n2L2)


This seems the two Z2 integer indices (n1,n2) remind me the homotopy group: π1(T2)=π1(S1×S1)=Z2.


2-form: If we consider a 2-form B field for a Schwarz-type TQFT, do we have the identification by π2(M) on the M as the based manifold? (Note that π2(Td)=0 - ps. from the math fact that π2(G)=0 for any compact connected Lie group G.) Is this the correct homotopy group description? How does large gauge transformation work on Td or M?


3-form: is there a homotopy group description on large gauge transformation? How does its large gauge transform on Td or M?




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