Hi Clem,
I was thinking of something slightly different. For B2 alone, the non-jack
spectra comes from B2 x B2. The jackknife is (B2_1 - B2_2) x (B2_1 - B2_2)
as you say.
In the case of cross-spectra, the non-jack version is B2 x Keck. So for a
jackknife I propose (B2_1 - B2_2) x (Keck_1 - Keck_2). This only contains
contributions from a B2 map cross a Keck map. What you propose
(B2_1-Keck_2) x (B2_2-Keck_1) = B2_1 x B2_2 + Keck_1 x Keck_2 - B2_1 x
Keck_1 - B2_2 x Keck_2 contains contributions from a B2 map cross a B2 map,
a Keck map cross a Keck map, and the B2 Keck cross. So it's not constructed
entirely from cross spectra. B2_1 x B2_2 already appears in the B2-internal
jackknife so there's no reason to test it again. I prefer a cross spectra
jackknife that's independent in this way from the B2-internal or
Keck-internal jackknives.
For EB, TB, and TE there are two independent jackknives depending on which
experiment contributes E/B. For example,
(B2_1E - B2_2E) x (Keck_1B - Keck_2B) and
(B2_1B - B2_2B) x (Keck_1E - Keck_2E)
My thinking here is informed by a framework we developed in QUIET for null
tests for the 40 GHz-- 90 GHz cross spectra.
Immanuel Buder
Postdoctoral Fellow
Harvard-Smithsonian Center for Astrophysics
(office) 617 495 7567
(office) 160 Concord Ave., M-114C
(mail) 60 Garden St. MS 42
Cambridge, MA 02138
ibuder(a)cfa.harvard.edu
On Wed, Mar 27, 2013 at 4:33 PM, Clem Pryke <pryke(a)physics.umn.edu> wrote:
Hi Immanuel,
One suggestion here is to run jackknives of the
cross spectra
What specifically do you mean? For us jackknife usually means make two
subset
maps, difference them, and then take spectra of the difference map. Do you
mean take for a given 1,2 subset split take B2_1-Keck_2 and cross with
B2_2-Keck_1? Or something different?...
Clem
--
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Clem Pryke - Associate Professor - Physics
University of Minnesota,
Room 313 Tate, 116 Church Street S.E. Minneapolis, MN, 55455
Tel: 612-624-7578 Fax: 612-624-4578 email: pryke(a)physics.umn.edu
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