Opened 4 years ago

Last modified 3 years ago

#1646 confirmed defect

McLachlan does not give a reference for the gauge evolution equations

Reported by: Roland Haas Owned by:
Priority: minor Milestone:
Component: EinsteinToolkit thorn Version: development version
Keywords: McLachlan Cc:


McLachlan_BSSN.m does not seem to contain any information (eg in evolCalc) that would tell me from which paper the different expressions for the shift and lapse evolution expression are taken from (which may be useful to understand what the different coefficients mean, since parsing the multiple factors of the type XXXFactor * AAA + (1-XXXFactor) * BBB to get either AAA or BBB is confusing).

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Change History (2)

comment:1 Changed 4 years ago by Ian Hinder

Status: newconfirmed

I believe this is addressed in the rewrite branch. We have not yet switched to the rewrite branch, so I am leaving this ticket open just in case. We should also make sure that the references stay up-to-date (e.g. if the equations are changed, this should be noted in the comment).

comment:2 Changed 3 years ago by Roland Haas

No references for the gauge evolution are given in the rewrite code (as of git hash 387e14a) where the relevant Kranc code still reads:

    dotalpha   -> - (harmonicF alpha^harmonicN
                         + trK - IfCCZ4[2 Theta, 0]
                         + alphaDriver (alpha - 1)]),
    dot[alpha] -> (+ dotalpha
                   + IfThen[advectLapse!=0, Upwind[beta[ua], alpha, la], 0]
                   + Dissipation[alpha]),

    (* TODO: add not only advection terms, but full Lie derivatives! *)
    dot[beta[ua]] -> (+ dotbeta[ua]
                      + IfThen[advectShift!=0,
                               Upwind[beta[ub], beta[ua], lb],
                      + Dissipation[beta[ua]]),

    dot[B[ua]] -> IfB[+ dotXt[ua]
                      + IfThen[fixAdvectionTerms!=0,
                               Upwind[beta[ub], Xt[ua], lb],
                      - (betaDriverValue
                         (+ B[ua]
                          + IfThen[fixAdvectionTerms!=0 && advectShift!=0,
                                   Upwind[beta[ub], beta[ua], lb] /
                                   (shiftGammaCoeffValue alpha^shiftAlphaPower),
                      + IfThen[fixAdvectionTerms==0 && advectShift!=0,
                               Upwind[beta[ub], B[ua], lb],
                      + Dissipation[B[ua]],

ie not reference is given at all.

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