(* Yi Wang, 2013, tririverwangyi@gmail.com, GPLv3 *)

BeginPackage["MathGR`frwadm`", {"MathGR`tensor`", "MathGR`decomp`", "MathGR`gr`", "MathGR`util`", "MathGR`ibp`"}]

DeclareIdx[{UP, DN}, DefaultDim, LatinIdx]

PdT[Mp,_]:=0

PdT[a|H|\[Epsilon]|\[Eta], PdVars[_DN, ___]]:=0

SimpHook = {DefaultDim->3, Pd[a, DE@0]->a*H, PdT[a, PdVars[DE@0,DE@0]] -> a H^2 - a H^2 \[Epsilon],

Pd[H, DE@0]->-\[Epsilon]*H*H, PdT[H, PdVars[DE@0,DE@0]] -> 2 H^3 \[Epsilon]^2 - H^3 \[Epsilon] \[Eta],

PdT[H, PdVars[DE@0,DE@0,DE@0]] -> -6 H^4 \[Epsilon]^3 + 7 H^4 \[Epsilon]^2 \[Eta] - H^4 \[Epsilon] \[Eta]^2 - H^4 \[Epsilon] \[Eta] \[Eta]2,

Pd[\[Epsilon], DE@0]->H*\[Epsilon]*\[Eta], Pd[\[Eta], DE@0] -> H*\[Eta]2*\[Eta], Pd[\[Eta]2, DE@0] -> H*\[Eta]3*\[Eta]2 }

LapseN = 1 + Eps * \[Alpha]

ShiftN[DN@i_] := Eps * Pd[\[Beta], DN@i] + Eps * b[DN@i]

PdT[b[DN@i_], PdVars[DN@i_, ___]]:= 0

b /: b[DN@i_] k[DN@i_]:= 0 (* Above expression in momentum space. *)

Sqrtg:= LapseN*Exp[3*Eps*\[Zeta]] * a^3

UseMetric[h]

h[DN@i_, DN@j_]:= a * a * Exp[2*Eps*\[Zeta]] * Dta[DN@i, DN@j]

h[UP@i_, UP@j_]:= Exp[-2*Eps*\[Zeta]] * Dta[DN@i, DN@j] /a /a

(* 4d metric is used to be decomposed and be replaced. *)

DecompHook = {

g[DN@i_, DN@j_]:> h[DN@i, DN@j],

g[DE@0, DE@0]:> (-LapseN^2 + h[UP@#1, UP@#2]ShiftN[DN@#1]ShiftN[DN@#2] &@Uq[2]),

g[DE@0, DN@i_]:> ShiftN[DN@i],

g[UP@i_, UP@j_]:> (h[UP@i, UP@j] - ShiftN[DN@#1]ShiftN[DN@#2]h[UP@#1, UP@i]h[UP@#2, UP@j]/LapseN^2 &@Uq[2]),

g[UE@0, UE@0]:> -1/LapseN^2,

g[UE@0, UP@i_]:> (h[UP@i, UP@#]ShiftN[DN@#]/LapseN^2 &@Uq[1])}

SetAttributes[DecompG2H, HoldAll]

DecompG2H[f_]:= Decomp0i@WithMetric[g, {UTot, DTot}, MetricContract[f]]

PdT[k|Eps, _]:=0

fourier2RuleList = Dispatch@{PdT[f_, PdVars[DN@i_, DN@i_, j___]] :> -k^2 PdT[f, PdVars[j]],

PdT[f_, PdVars[DN@i_, a___]] PdT[g_, PdVars[DN@i_, b___]] :> k^2 PdT[f, PdVars[a]] PdT[g, PdVars[b]],

PdT[f_, PdVars[DN@i_, j___]]^2 :> k^2 PdT[f, PdVars[j]]^2,

PdT[f_, PdVars[DN@i_, j___]] b_[DN@i_] :> -I k[DN@i] PdT[f, PdVars[j]] b[DN@i]}

Fourier2[e_]:= (e//.fourier2RuleList//Expand)//.fourier2RuleList

EndPackage[]