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Probing the Early and Late Universe with the Gravitational-Wave Background Alexander C. Jenkins GW4FP Workshop, Amsterdam 13 November 2019 The Stochastic Gravitational-Wave Background 1 Cosmic Strings 2 Compact Binary Coalescences 3

SLIDE 1

Probing the Early and Late Universe with the Gravitational-Wave Background

Alexander C. Jenkins GW4FP Workshop, Amsterdam 13 November 2019

SLIDE 2

The Stochastic Gravitational-Wave Background

Cosmic Strings

Compact Binary Coalescences

SLIDE 3

Stochastic gravitational-wave background (SGWB) faint/numerous sources astrophysical and cosmological incoherent, persistent, correlated GW density parameter: ΩGW(f ) = 1 ρcrit dρGW d(ln f )

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 1 / 16

SLIDE 4

LIGO upper limits (isotropic)

LIGO/Virgo ’19 PRD, arXiv:1903.02886

scales as ∼ 1/ √

bs time

(as well as number and sensitivity of detectors) note that ΩGW ≪ ΩCMB ≈ 10−5, so detection is hard

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 2 / 16

SLIDE 5

Angular power spectrum

Images: Planck collaboration

CMB Cℓ =

d2ˆ

nPℓ(cos θ) δT δTθ SGWB Cℓ =

d2ˆ

nPℓ(cos θ) δΩGWδΩGWθ

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 3 / 16

SLIDE 6

LIGO upper limits (directional)

LIGO/Virgo ’19 PRD, arXiv:1903.08844

results depend on GW frequency spectrum ΩGW = Ωref(f /fref)α

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 4 / 16

SLIDE 7

The Stochastic Gravitational-Wave Background

Cosmic Strings

Compact Binary Coalescences

SLIDE 8

Cosmic string network O(1) long string → many loops

ne parameter: string tension

Gµ = mass length ∼

new physics scale

Planck scale

generically produced in many BSM theories

Ringeval, Sakellariadou, & Bouchet ’07 JCAP, arXiv:astro-ph/0511646

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 5 / 16

SLIDE 9

GW bursts from loops Cusp Kink

−0.4 −0.2 0.0 0.2 0.4 t/s h(t) Cusp Kink

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 6 / 16

SLIDE 10

Did LIGO/Virgo just see its first cosmic string???

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 7 / 16

SLIDE 11

Cosmic string SGWB LIGO O2 constraint: Gµ 10−14 (109 TeV) with LISA/ET: Gµ 10−17(107.5 TeV) what does this mean for HEP?

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 8 / 16

SLIDE 12

Cosmic strings beyond ΛCDM SGWB spectrum depends on thermal history

Auclair+ (inc. ACJ) ’19, arXiv:1909.00819

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 9 / 16

SLIDE 13

Cosmic strings beyond ΛCDM SGWB spectrum depends on relativistic degrees of freedom

Auclair+ (inc. ACJ) ’19, arXiv:1909.00819

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 10 / 16

SLIDE 14

Anisotropies from cosmic strings stronger for smaller Gµ could this help detection?

ACJ & Sakellariadou ’18 PRD, arXiv:1802.06046

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 11 / 16

SLIDE 15

The Stochastic Gravitational-Wave Background

Cosmic Strings

Compact Binary Coalescences

SLIDE 16

Compact binary SGWB: a new probe of large-scale structure

Springel+ ’05 Nature, arXiv:astro-ph/0504097

CBCs expected to be loudest component of SGWB BHs and NSs live in galaxies ∴ galaxies trace out LSS

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 12 / 16

SLIDE 17

Simulating the compact binary SGWB

ACJ+ ’18 PRD, arXiv:1806.01718

get galaxies from Millennium N-body simulation compute rate for each galaxy superimpose → SGWB map

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 13 / 16

SLIDE 18

Probing LSS with LIGO/Virgo? will close the gap over time, and with more detectors signal could be larger if we find new populations (e.g. BHNS) can we boost the signal by cross-correlating with galaxy surveys? (see talk by Omar Contigiani)

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 14 / 16

SLIDE 19

Projection effects can enhance the signal at large scales

Bertacca+ (inc. ACJ) ’19, arXiv:1909.11627

alexander.jenkins@kcl.ac.uk Probing the Universe with the GW Background GW4FP, 13 November 2019 15 / 16

SLIDE 20

Summary the stochastic GW background will soon be a vital probe of cosmology and fundamental physics searches for new physics with GWs from cosmic strings new probe of large-scale structure with clustering of compact binaries