16.40 o10 d wiltshire

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Observational Tests of the Timescape Cosmology David L. Wiltshire (University of Canterbury, NZ) DLW: New J. Phys. 9 (2007) 377 Phys. Rev. Lett. 99 (2007) 251101 Phys. Rev. D78 (2008) 084032 Phys. Rev. D80 (2009) 123512 Class. Quantum Grav. 28 (2011) 164006 B.M. Leith, S.C.C. Ng & DLW: ApJ 672 (2008) L91 P.R. Smale& DLW, MNRAS 413 (2011) 367 P.R. Smale, MNRAS (2011) in press NZIP Conference, Wellington, 18 October 2011 – p.1/??

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Page 1: 16.40 o10 d wiltshire

Observational Tests of theTimescape Cosmology

David L. Wiltshire (University of Canterbury, NZ)

DLW: New J. Phys. 9 (2007) 377

Phys. Rev. Lett. 99 (2007) 251101

Phys. Rev. D78 (2008) 084032

Phys. Rev. D80 (2009) 123512

Class. Quantum Grav. 28 (2011) 164006

B.M. Leith, S.C.C. Ng & DLW:

ApJ 672 (2008) L91

P.R. Smale & DLW, MNRAS 413 (2011) 367

P.R. Smale, MNRAS (2011) in press

NZIP Conference, Wellington, 18 October 2011 – p.1/??

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Overview of timescape cosmology

Standard cosmology, with 22% non-baryonic darkmatter, 74% dark energy assumes universe expands assmooth fluid, ignoring structures on scales<∼

100h−1 Mpc

Actual observed universe contains vast structures ofvoids (most of volume), plus walls and filamentscontaining galaxies

Timescape scenario - first principles model reanalysingcoarse-graining of “dust” in general relativity

Hypothesis: must understand nonlinear evolution withbackreaction, AND gravitational energy gradients withinthe inhomogeneous geometry

NZIP Conference, Wellington, 18 October 2011 – p.2/??

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6df: voids & bubble walls (A. Fairall, UCT)

NZIP Conference, Wellington, 18 October 2011 – p.3/??

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Within a statistically average cell

Need to consider relative position of observers overscales of tens of Mpc over which δρ/ρ∼−1.

GR is a local theory: gradients in spatial curvature andgravitational energy can lead to calibration differencesbetween our rulers and clocks and volume averageones

NZIP Conference, Wellington, 18 October 2011 – p.4/??

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Relative deceleration scale

(i)

0.4

0.6

0.8

1.0

1.2

0 0.05 0.1 0.15 0.2 0.25

−1010 m/s 2

z

α

(ii)

0.02

0.04

0.06

0.08

0.10

0.12

0 2 4 6 8 10z

α /(Hc)

/(Hc)α

Instantaneous relative volume deceleration of walls relative to volume average background

α = H0cγw

˙γw/(q

γ2w − 1) computed for timescape model which best fits supernovae

luminosity distances: (i) as absolute scale nearby; (ii) divided by Hubble parameter to large z.

With α0∼ 7× 10−11m s−2 and typically α∼ 10−10m s−2 for

most of life of Universe, get 37% difference incalibration of volume average clocks relative to our own

NZIP Conference, Wellington, 18 October 2011 – p.5/??

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Apparent cosmic acceleration

Volume average observer sees no apparent cosmicacceleration

q =2 (1 − fv)

2

(2 + fv)2.

As t → ∞, fv → 1 and q → 0+.

A wall observer registers apparent cosmic acceleration

q =− (1 − fv) (8fv

3 + 39fv

2− 12fv − 8)

(

4 + fv + 4fv

2)2

,

Effective deceleration parameter starts at q∼ 12, for

small fv; changes sign when fv = 0.58670773 . . ., andapproaches q → 0− at late times.

NZIP Conference, Wellington, 18 October 2011 – p.6/??

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Cosmic coincidence problem solvedSpatial curvature gradients largely responsible forgravitational energy gradient giving clock rate variance.

Apparent acceleration starts when voids start to open.

NZIP Conference, Wellington, 18 October 2011 – p.7/??

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Best fit parameters

Hubble constant H0+ ∆H

0= 61.7+1.2

−1.1 km/s/Mpc

present void volume fraction fv0 = 0.76+0.12−0.09

bare density parameter ΩM0= 0.125+0.060

−0.069

dressed density parameter ΩM0= 0.33+0.11

−0.16

non–baryonic dark matter / baryonic matter mass ratio(ΩM0

− ΩB0)/ΩB0

= 3.1+2.5−2.4

bare Hubble constant H0 = 48.2+2.0−2.4 km/s/Mpc

mean phenomenological lapse function γ0

= 1.381+0.061−0.046

deceleration parameter q0

= −0.0428+0.0120−0.0002

wall age universe τ0

= 14.7+0.7−0.5 Gyr

NZIP Conference, Wellington, 18 October 2011 – p.8/??

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Key observational tests

Best–fit parameters: H0

= 61.7+1.2−1.1 km/s/Mpc, Ωm = 0.33+0.11

−0.16

(1σ errors for SneIa only) [Leith, Ng & Wiltshire, ApJ 672(2008) L91]

NZIP Conference, Wellington, 18 October 2011 – p.9/??

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Test 1: SneIa luminosity distances

0 0.5 1 1.5 230

32

34

36

38

40

42

44

46

48

z

µ

Type Ia supernovae of Riess 2007 Gold data set fit withχ2 per degree of freedom = 0.9

Type Ia supernovae of Hicken 2009 MLCS17 set fit withχ2 per degree of freedom = 1.08

NZIP Conference, Wellington, 18 October 2011 – p.10/??

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Dressed “comoving distance” D(z)

0

0.5

1

1.5

2

1 2 3 4 5 6z

0

1

1z

(i)

(iii)(ii)

H0D

0

0.5

1

1.5

2

2.5

3

3.5

200 400 600 800 1000z

(i)(ii)(iii)

H0D

Best-fit timescape model (red line) compared to 3 spatially

flat ΛCDM models: (i) best–fit to WMAP5 only (ΩΛ = 0.75);(ii) joint WMAP5 + BAO + SneIa fit (ΩΛ = 0.72);(iii) best flat fit to (Riess07) SneIa only (ΩΛ = 0.66).

Three different tests with hints of tension with ΛCDMagree well with TS model.

NZIP Conference, Wellington, 18 October 2011 – p.11/??

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Supernovae systematics

H0

Ωm

0

Gold (167 SneIa)

56 58 60 62 64 66 680

0.1

0.2

0.3

0.4

0.5

0.6

0.7

H0

Ωm

0

SDSS−II 1st year (272 SneIa)

56 58 60 62 64 66 680

0.1

0.2

0.3

0.4

0.5

0.6

0.7

H0

Ωm

0

MLCS17 (219 SneIa)

56 58 60 62 64 66 680

0.1

0.2

0.3

0.4

0.5

0.6

H0

Ωm

0

MLCS31 (219 SneIa)

56 58 60 62 64 66 680

0.1

0.2

0.3

0.4

0.5

0.6

NZIP Conference, Wellington, 18 October 2011 – p.12/??

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Recent Sne Ia results; PR Smale + DLWSALT/SALTII fits (Constitution,SALT2,Union2) favourΛCDM over TS: ln BTS:ΛCDM = −1.06,−1.55,−3.46

MLCS2k2 (fits MLCS17,MLCS31,SDSS-II) favour TSover ΛCDM: ln BTS:ΛCDM = 1.37, 1.55, 0.53

Different MLCS fitters give different best-fit parameters;e.g. with cut at statistical homogeneity scale, forMLCS31 (Hicken et al 2009) ΩM0

= 0.12+0.12−0.11;

MLCS17 (Hicken et al 2009) ΩM0= 0.19+0.14

−0.18;SDSS-II (Kessler et al 2009) ΩM0

= 0.42+0.10−0.10

Supernovae systematics (reddening/extinction, intrinsiccolour variations) must be understood

TS model most obviously consistent if dust in othergalaxies not significantly different from Milky Way

NZIP Conference, Wellington, 18 October 2011 – p.13/??

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Baryon acoustic oscillation measures

(i)1

1.1

1.2

1.3

1.4

0 0.2 0.4 0.6 0.8 1

fAP

(i)

(ii)

z

(iii)

(ii) 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.2 0.4 0.6 0.8 1

H0 DV (i) (ii)(iii)

z

Best-fit timescape model (red line) compared to 3 spatially flat ΛCDM models as earlier: (i)

Alcock–Paczynski test; (ii) DV

measure.

BAO signal detected in galaxy clustering statistics

Current DV measure averages over radial andtransverse directions; little leverage for z <

∼1

Alcock–Paczynski measure - needs separate radial andtransverse measures - a greater discriminator for z <

∼1

NZIP Conference, Wellington, 18 October 2011 – p.14/??

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Gaztañaga, Cabre and Hui MNRAS 2009

z = 0.15-0.47 z = 0.15-0.30 z = 0.40-0.47

NZIP Conference, Wellington, 18 October 2011 – p.15/??

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Gaztañaga, Cabre and Hui MNRAS 2009

redshift ΩM0h2 ΩB0

h2 ΩC0/ΩB0

range0.15-0.30 0.132 0.028 3.70.15-0.47 0.12 0.026 3.60.40-0.47 0.124 0.04 2.1

Tension with WMAP5 fit ΩB0' 0.045, ΩC0

/ΩB0' 6.1 for

LCDM model.

GCH bestfit: ΩB0= 0.079 ± 0.025, ΩC0

/ΩB0' 3.6.

TS prediction ΩB0= 0.080+0.021

−0.013, ΩC0/ΩB0

= 3.1+1.8−1.3 with

match to WMAP5 sound horizon within 4% and no 7Lianomaly.

NZIP Conference, Wellington, 18 October 2011 – p.16/??

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Redshift time drift (Sandage–Loeb test)

–3

–2.5

–2

–1.5

–1

–0.5

01 2 3 4 5 6

(iii)

(i)

(ii)

z

H−1

0

dz

dτfor the timescape model with fv0 = 0.762 (solid line) is compared to three

spatially flat ΛCDM models with the same values of (ΩM0

, ΩΛ0

) as in previous figures.

Measurement is extremely challenging. May be feasibleover a 10–20 year period by precision measurements ofthe Lyman-α forest over redshift 2 < z < 5 with nextgeneration of Extremely Large Telescopes

NZIP Conference, Wellington, 18 October 2011 – p.17/??

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Apparent Hubble flow variance

NZIP Conference, Wellington, 18 October 2011 – p.18/??

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Apparent Hubble flow variance

As voids occupy largest volume of space expect tomeasure higher average Hubble constant locally untilthe global average relative volumes of walls and voidsare sampled at scale of homogeneity; thus expectmaximum H

0value for isotropic average on scale of

dominant void diameter, 30h−1Mpc, then decreasing tillevelling out by 100h−1Mpc.

Consistent with a Hubble bubble feature (Jha, Riess,Kirshner ApJ 659, 122 (2007)); or “large scale flows”with certain characteristics (cf Watkins et al).

Expected maximum “bulk dipole velocity”

vpec = (32H0 − H

0)30

hMpc = 510+210

−260 km/s

NZIP Conference, Wellington, 18 October 2011 – p.19/??

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N. Li & D. Schwarz, arxiv:0710.5073v1–2

-0.05

0

0.05

0.1

0.15

0.2

40 60 80 100 120 140 160 180

(HD

-H0)

/H0

r (Mpc)NZIP Conference, Wellington, 18 October 2011 – p.20/??

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PR Smale + DLW, in preparation

NZIP Conference, Wellington, 18 October 2011 – p.21/??

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The value of H0

Value of H0

= 74.2 ± 3.6 km/s/Mpc of SH0ES survey (Riess

et al., 2009) calibrated by NGC4258 maser distance at 7.5Mpc is a challenge for the timescape model. BUT

Expect variance in Hubble flow below scale ofhomogeneity with typical higher valueHvw0

= 72.3 km/s/Mpc at 30h−1 Mpc scale

H0

determinations independent of local distance ladder:

WiggleZ FLRW BAO value (Beutler et al,arXiv:1106.3366): H

0= 67 ± 3.2 km/s/Mpc

Quasar strong lensing time delays; e.g., (Courbin et al,1009.1473): H

0= 62+6

−4 km/s/Mpc

Megamaser distance of UGC3789 H0

= 66.6 ± 11.4

km/s/Mpc, (69 ± 11 km/s/Mpc with“flow modeling”).

NZIP Conference, Wellington, 18 October 2011 – p.22/??

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SummaryApparent cosmic acceleration can be understood purelywithin general relativity; by (i) treating geometry ofuniverse more realistically; (ii) understandingfundamental aspects of general relativity of statisticaldescription of general relativity which have not beenfully explored – quasi–local gravitational energy,of gradients in spatial curvature etc.

Extra ingredients – regional averages etc – go beyondconventional applications of general relativity

Description of spacetime as a causal relationalstructure – retains principles consistent with GR

Many details – averaging scheme etc – may change,but fundamental questions remain in any approach

NZIP Conference, Wellington, 18 October 2011 – p.23/??

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OutlookOther work

Several observational tests (Alcock-Paczynski test,Clarkson, Bassett and Lu test, redshift time drift etc)discussed in PRD 80 (2009) 123512

Work in progress

Adapting Korzynski’s “covariant coarse-graining”approach to more rigorously define regional averages(with James Duley)

Analysis of variance of Hubble flow in style of Li andSchwarz on large datasets (with Peter Smale)

Full analysis of CMB anisotropy spectrum in timescapemodel (with Ahsan Nazer)

NZIP Conference, Wellington, 18 October 2011 – p.24/??