From a813f541d7f6e3ee7b380570d8f3f413c530fd6e Mon Sep 17 00:00:00 2001
From: Christopher Wipf <wipf@ligo.mit.edu>
Date: Wed, 8 Apr 2020 16:10:08 -0700
Subject: [PATCH] Fix an error in the coating brownian noise calculation
A discrepancy was found by Gabriele Vajente between the gwinc
CTN calculation and several other codes, especially in the case
of large Poisson ratio in the coating.
See: https://git.ligo.org/gabriele-vajente/thermal-noise-models
This commit resolves the discrepancy by fixing an apparent error
in the Yam et al calculation that was implemented in gwinc.
---
gwinc/noise/coatingthermal.py | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/gwinc/noise/coatingthermal.py b/gwinc/noise/coatingthermal.py
index 41a642a4..3dfba514 100644
--- a/gwinc/noise/coatingthermal.py
+++ b/gwinc/noise/coatingthermal.py
@@ -89,10 +89,10 @@ def coating_brownian(f, materials, wavelength, wBeam, dOpt):
zdir = -1
dcdp_z = zdir * dcdp # z-dir only matters here
- # layer contrubutions (b_j in PhysRevD.91.042002)
- brLayer = ( (1 - nN * dcdp_z / 2)**2 * (Ysub / yN) +
- (1 - pratsub - 2 * pratsub**2)**2 * yN /
- ((1 + pratN)**2 * (1 - 2 * pratN) * Ysub) )/ (1 - pratN)
+ # layer contributions, b_j (eq 1) from doi:10.1103/PhysRevD.91.042002, errors corrected
+ brLayer = ( 1/(1-pratN) *
+ ( (1-nN*dcdp_z/2)**2 * (1-2*pratN)*(1+pratN)*Ysub / ((1-2*pratsub)*(1+pratsub)*yN) +
+ (1-2*pratsub)*(1+pratsub)*yN / ((1+pratN)*Ysub) ) )
# sum them up for total
w = 2 * pi * f
--
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