identical to the  low-energy constant $\mu_1$ as can be demonstrated by matching [@Beane:2002vq].

### Partially Twisted Isovector Magnetic Form Factor

In the infinite volume limit, the isovector magnetic moment can be extracted from the matrix element $$\langle p(\bm{q}) \downarrow | J_3^+  | n(\bm{0}) \uparrow \rangle 
= 
\frac{- i q  }{2 M} F_2(q^2)
,$$ in the case where $\bm{q} = (0,q,0)$. On the lattice, we can take both the source and sink to be at zero momentum, so that $\bm{q} = \bm{0}$. Momentum transfer can then be induced by giving the valence up and down quarks different twist angles. For simplicity we choose $\bm{B}^d = \bm{0}$ and $\bm{B}^u = (0,B,0)$. Calculation of the infinite volume isovector form factor then proceeds similarly to that above in Sect. \[s:momext\]. In partially twisted baryon , there are additional diagrams that contribute involving the hairpin interaction. These diagrams are shown in Fig. \[f:Nvecff\]. The sum of all hairpin diagrams, however, vanishes. With $m_j = m_u$,[^4] the infinite volume contributions from the diagrams in the Figure are identical to $F_2(q^2)$ in Eq.  under the simple replacement $q \to B$. This is the kinematic effect we expect from raising isospin with a twisted $u$-quark.

![One-loop contributions to 