Probing Fundamental Physics with the Radio Sky
Amanda Weltman University of Cape Town & Institute for Advanced Study
Recontres de Moriond, La Thuile March 2017
Collaborators: B. Gaensler, Y-Z. Ma, A. Walters, X. Xu, A Witzemann. HIRAX collaboration Radio Astronomy
Discovered by Jansky in 1930’s to get rid of noise to improve telephones for Bell labs Extremely weak - Add them all up (except solar) - not enough to melt a snowflake! Low Frequencies, long wavelengths ~ 10 MHz —> 1 THz Large wavelengths - good because goes straight through dust (grains much smaller in ISM) Low energy —> hyperfine splitting ——> 21 cm HI line. Optical and radio - ground based. Atmosphere absorbs IR, UV, X-ray, Gamma-ray.
CMB, pulsars, quasars, radio galaxies, neutron stars, evidence for DM, indirect evidence for gravitational radiation, strong lensing, exoplanets ——- What is next? Radio Astronomy Parkes Observatory, Australia HARTRAO, South Africa FAST, China
Lovell Telecope, UK
Green Bank Telescope, USA SPT, Antarctica ACA/ALMA, Chile HIRAX Hydrogen Intensity and Real time Analysis eXperiment L. Newburgh, AW et.al 2016 • 1024 6 m dish array • 400 - 800 MHz radio interferometer • Intensity mapping of BAO at z ~ 0.8 - 2.5 • ideal to probe dark energy • constrain dynamical dark energy • constrain curvature • Transients - pulsars and fast radio bursts • FRBs - short (~ms), bright ( ~Jy), radio transients, likely cosmological • complementary to CHIME - South, lower RFI, no snow http://www.acru.ukzn.ac.za/~hirax MeerKAT Meerkats
KAT-7 HIRAX Hyrax/Dassies Intensity Mapping
Goal: measure baryon acoustic oscillations with HI intensity mapping How: observe unresolved sources via their redshifted 21 cm line What: produce maps of large scale structure to measure BAO Why: BAO are a preferential length scale 150 Mpc characterize the expansion history of the universe
dark energy
A Sunday on La Grande Jatte, Seurat, 1884 Forecasts
Preliminary Forecasts
Bull, Clarkson, Santos, AW & Witzemann - to appear 2017 Constraining the Multiverse
Curvature matters! Guth and Nomura, 2012 Kleban and Schillo, 2012
4 Measurement of positive curvature ⌦ < 10 k Eternally inflating multiverse is ruled out 4 Measurement of negative curvature ⌦k > 10
Bubble nucleation happened, excludes some pre-inflation histories 4 Measurement of curvature ⌦k > 10 | | Slow-roll eternal inflation ruled out
4 Cosmic variance bound ⌦k 10 Leonard, Bull & Allison ⇠ 2016 Improve bounds by order of magnitude. Close to absolute bound.
Break curvature dark energy degeneracy to improve these constraints. FRBs Walters, Gaensler, AW & Ma, To appear 2017 DM of the IGM is a function of cosmological parameters A catalogue of FRBs could thus distinguish z (z )(1 + z )dz
Preliminary Next Frontier
The SKA project is an array of radio telescopes - ostensibly Astronomy but in reality it can be a fundamental physics machine
• Curvature http://www.ska.ac.za/media/gigapans.php • Dark Energy • Dark Matter • Astroparticle physics • Pulsars • Pulsar timing arrays • Gravitational waves • Magnetism
• Early universe • Late universe • General Relativity • Primordial Non-Gaussianity • ALPS KAT-7 SKA South Africa Find BSM particles in the Radio?
Light Scalar fields are abundant in BSM and string theories.
Typically, gravitational strength, long range forces, coupled to everything … yet unobservable in the solar system?
Hide from our view - Screening mechanisms. Set the coupling to be small. By hand or environmentally small - e.g. Symmetron Allow the mass of the field to be environmentally dependent - Chameleon screening. All f(R) models. Consider a kinetic coupling - effectively reduces matter coupling - Vainshtein screening. DGP, massive gravity and galileons.
Rethink known observations and future ones Chameleon Gravity J. Khoury and AW 2004 J. Khoury and AW 2004 P.Brax, C v.d Bruck, A. Davis, J. Khoury and AW 2004 Reduced Planck Mass Coupling to photons Matter Fields
1/2 MPl =(8⇡G)
2 M e MPl S = d4xp g PlR (@ )2 V ( ) F µ⌫ F +S g(i), (i) 0 2 4 µ⌫ 1 m µ⌫ m Z ⇣ ⌘ @ A
g = detgµ⌫ (i) 2 i /MPl gµ⌫ = e gµ⌫
Einstein Frame Metric Potential is of the runaway form Conformally Coupled
This field couples to all matter types - and in a different way to regular gravity Effective Potential
3 24 3 ⇢E = 10g.cm ⇢g = 10 g.cm M Ve↵ ( )=V ( )+⇢e Pl
Environment dependent chameleon mass
4 M n V ( )=M 1+ n ⇣ ⌘ Ratra-Peebles mE mg E g ⌧ 1 m mm atm . M ~ meV to drive acceleration
1 4 m 10 10 AU solar . Lab tests constrain the parameters
26 orders of magnitude between mm 1 and Mpc mcosmos . Mpc Chameleons Far
Photon-Chameleon oscillations - polarisation changes, brightness altered - e.g. photon to chameleon conversion in SN + chameleon-photon mixing in the IGM —> supernovae brightening C. Burrage 2007
Screened vs unscreened - behaviour dependent on size of astrophysical objects - potentially observable deviations in dynamics of stars and galaxies - large halos screened, small halos unscreened - Voids defined by small galaxies appear larger than expected L. Hui et. al 2009 - e.g. unscreened stars -> greater gravitational field -> burn brighter, hotter, faster J. Sakstein, B. Jain and V. Vikram 2014
Break the equivalence between mass distribution inferred from non relativistic tracers and photons - signatures found by comparing dynamical and lensing masses - e.g. agree for large but not small galaxies L. Hui et. al 2009
Comparing screened vs unscreened components or tracers Chameleons Far
B. Jain, AW et. al 2013 Astrophysical and Cosmological Bounds
Old bound
B. Jain, AW et. al 2013 Parting thoughts
Change the way we think..... New ideas ...... New theories Change the way we test..... New ideas...... New experiments
Complementary experiments - High and low energy and intensity
Complementary observations - Cosmology, astrophysics and astronomy
Use experiment and observation to constrain theory and offer surprises
Cosmology must engage with particle physics
The Intensity Frontier must meet the Cosmic Frontier
Theorists, experimentalists and astronomers - converse
Exploring the Universe with the world’s largest radio telescope Fundamental Physics with the Square Kilometre Array
• May(1stD5th,(2017,(in(FlicDenDFlac,(MauriJus( • Topics( • Invited(speakers(include:( – Cosmology(&(Dark(Energy( – J.(Silk( ((–((C.(Boehm( – Cosmic(Dawn(&(ReionisaJon( – R.(Barkana (–((J.(Pritchard( – Dark(MaOer(&(AstroparJcle(Physics( – T.(Davis ( (–((P.(Bull( – Gravity(&(GravitaJonal(Waves( – F.(Pretorius (–((S.(Nissanke( ( ! !!www.skatelescope.ca/physics! La(Pirogue(