$C_2$-Equivariant Orthogonal Calculus

In this thesis, we construct a new version of orthogonal calculus for functors $F$ from $C_2$-representations to $C_2$-spaces, where $C_2$ is the cyclic group of order 2. For example, the functor $BO(-)$, which sends a $C_2$-representation $V$ to the classifying space of its orthogonal group $BO(V)$. We obtain a bigraded sequence of approximations to $F$, called the strongly $(p,q)$-polynomial approximations $T_{p,q}F$. The bigrading arises from the bigrading on $C_2$-representations. The homotopy fibre $D_{p,q}F$ of the map from $T_{p+1,q}{T}_{p,q+1}F$ to $T_{p,q}F$ is such that the approximation $T_{p+1,q}{T}_{p,q+1}{D}_{p,q}F$ is equivalent to the functor $D_{p,q}F$ itself and the approximation $T_{p,q}{D}_{p,q}F$ is trivial. A functor with these properties is called $(p,q)$-homogeneous. Via a zig-zag of Quillen equivalences, we prove that $(p,q)$-homogeneous functors are fully determined by orthogonal spectra with a genuine action of $C_2$ and a naive action of the orthogonal group $O(p,q)$.