Future 21cm line observations
and new Physics	

Kazunori Kohri((郡和範))  

16/10/27

Theory Center, IPNS, KEK,
and Sokendai
Tsukuba, Japan	
Kaz Kohri, Kanazawa

Abstract	• Future	  precise	  cosmological	  21cm	  line	  observa6ons	  	  are	  planned,	  e.g.,	  such	  as	  SKA	  or	  Omniscope.	  
• By	  using	  data	  taken	  by	  those	  experiments,	  we	  can	  obtain	  unique	  informa6on	  for	  new	  physics	  such	  as	  i. Neutrino’s mass hierarchy (Hints of GUT)
ii. Time-evolution of dark energy (Quantum gravity)iii. Precise matter fluctuations (Hints of Inflation)
iv. ...
16/10/27

Kaz Kohri, Kanazawa

Review	  of cosmological	  21cm	  lines	

16/10/27

Kaz Kohri, Kanazawa

Spin	  temperature	  	  Ts	• Deﬁned	  by	  the	  ra6o	  of	  the	  occupa6on	  numbers	  in	  two	  states	  n upperg upper⎡ ΔE ⎤⎥=Exp ⎢ −⎢⎣ T S ⎥⎦nlower g lower

g i = degree of reedom for a level "i"
16/10/27

Kaz Kohri, Kanazawa

Cosmological	  21cm	  emission	  line	  emiJed	  at	  the	  reioniza6on	  epoch

T~0.003eV	

T~0.01eV	21cm line power spectrum P21(k,µ)
traces the baryon power spectrumµ: cosine with respect to line of sight 	

Detail of ionization history
gives us power spectrum

0.6 km2	

1 km2	

Why cosmological 21cm line observations
are so strong?
• Linear	  perturba6ons	  Much	  before	  	  galaxy	  forma6on	  (T	  >>	  0.001	  eV)	  	  • A	  lot	  	   of	  informa6on	  by	  tomography	  A	  lot	  of	  independent	  Fourier	  modes	  for	  broad	  z	  range	  (7	  <	  z	  <	  10)	  	  • Precise	  data	  independently-­‐diﬀerently	  from	  	  CMB	  	  Much	  aXer	  the	  recombina6on	  (T	  <<	  	  0.3	  eV)	  	  CMB	  polariza6on	  observa6ons• Obtaining	  useful	  informa6on	  for	  gravita6onal	  poten6al	  • Supplemental	  for	  the	  21cm	  line	  observa6ons

(KEK’s)	  Future	  CMB	  polariza6on	  observa6ons• POLARBEAR	  2	  (<2016)	  • Simons	  Array	  (<2020)	  • GroundBIRD	  • LiteBIRD	  (<2025	  for	  large	  scales)
LiteBIRD	Neutrinos	

16/10/27

Kaz Kohri, Kanazawa

Neutrino	  mass	  and	  #	  of	  species	  Nν	

From oscillation experiments	

∑=ν> 	 ∑=

ν> 	 From the current cosmological observations such as CMB + ..., 	

∑16/10/27)=ν)<(σ 	 ν ())
Kaz Kohri, Kanazawa=±σ 	 

Hot	  and/or	  warm	  thermal-­‐relic	  	  • Neutrino	  becomes	  non-­‐rela6vis6c	  at	  T nonrela ~ mν / 3
t nonrela ~Mpl

T2nonrela• Free-­‐streaming	  length	  during	  its	  rela6vis6c	  era	  λ`FS ~ 2t nonrela

16/10/27

T nonrela
T0⎛m ⎞~ 102 Mpc ⎜ DM ⎟⎜⎝ 1eV ⎟⎠−2⎛m ⎞3
MFS ~ ρm,0λFS~ 1018 M  ⎜ DM ⎟⎜⎝ 1eV ⎟⎠Kaz Kohri, Kanazawa−1note that M cluster < 1016M Mν = ∑ mν with m1 = m2 = m3i =1,2,3δm ∝ a

16/10/27

i31− fν
5fν = ρν / ρm

Kaz Kohri, Kanazawa

Lensed	  CMB	  B-­‐mode	  CℓBB	

16/10/27

Kaz Kohri, Kanazawa

Neutrinos with mν=O(0.01) eV become
non-relativistic at 3T=mν=O(0.01) eV 	
• Much	  aXer	  the	  recombina6on	  (3T	  <<	  0.3eV)	  • Much	  before	  	  galaxy	  forma6on	  (3T	  >>	  0.001eV)	  21cm line + CMB lensed B-mode
polarization should be the best tool toconstrain mass hierarchy with mν~0.05
eV 	

16/10/27

Kaz Kohri, Kanazawa

Future	  constraints	  on	  neutrino	  mass	  by	  21cm,	  CMB,	  and	  BAOOyama, Kohri, Hazumi (2015)	

Future	  constraints	  on	  neutrino	  hierarchy	  	  by	  21cm,	  CMB	  and	  BAOOyama, Kohri, Hazumi (2015)	

• Hierarchy	  parameterrν ≡m 3 − m1
Σmi⎧⎪ > 0 normal hierarchy=⎨⎪⎩ < 0 inverted hierarchy

Dark	  Energy

A	  parameteriza6on	  of	  models
w X (z ) = p (z ) / ρ (z ) =Current	  bounds
a s = 0.5, p = 1

Forecast	  in	  future	  experiments

Precise	  maJer	  power	  spectrum	  and	  inﬂa6on	  models	

16/10/27

Kaz Kohri, Kanazawa

Power	  spectrum	  of	  curvature	  perturba6on	
• Parameteriza6on	  16/10/27

Kaz Kohri, Kanazawa

Predictions and Observations• Planck2015 satellite reported;ε ≡ (V 'm pl /V )2 / 2
η ≡ V ''m 2pl /Vξ (2) ≡ V '''V 'm pl4 /V 2l

Power spectrum of density fluctuationm pl = Mp / 8πV−102Pζ ==(30.91±0.25)×10(1σ)~(ΔT/T)
24π 2m pl εlSpectral index
ns =ld lnPζ

+ 1 == 1 + 2η − 6ε = 0.9639 ± 0.0047 (1σ )dlnk
n s − 1 ~ −0.04

Running of spectral index
αs =ldnsd ln k= 24ε 2 − 16εη − 2ξ (2) = 0.009 ± 0.010 (1σ )Running of running~ -0.02 − 0.02 (1σ)

Forecasts	  of	  running	  and	  	  Running	  of	  Running

KK, Oyama, Sekiguchi, T.Takahashi (2013)	

αs ≡βs ≡d ln Pςd ln kdα sd ln k

Δα s <O(10−3 )Δn s <O(10−3 )Δα s <O(10−3 )Δβs <O(10−3 )Future	  Sensi6vi6es	  by	  	  21cm	  line	  and	  CMP	  polariza6ons

KK, Oyama, T.Takahashi, T.Sekiguchi, 2013	Predic6ons	  by	  Starobinsky-­‐type	  inﬂa6on	  models
Asaka, Iso, H.Kawai, KK, Noumi, Terada (2016)	

αs	

ポテンシャルエネルギー	r	

⎡m 2pl ⎛⎞⎤1b4223S = ∫ d x − g ⎢ − m pl R +R +R + ...⎟ ⎥⎜22⎢ 212m ⎝6m⎠⎥⎣⎦

対応するスカラー場の場の値	

ns	ns	

Summary	• Future	  cosmological	  21cm	  line	  observa6ons	  	  are	  planned,	  such	  as	  SKA	  or	  Omniscope.	  
• By	  using	  data	  of	  such	  future	  21cm	  line	  observa6ons	  with	  combining	   CMB,	  and	  BAO	  (large	  scale	  structure),	  we	  can	  obtain	  unique	  informa6on	  for	  new	  physics	  such	  as	  i. Neutrino’s mass hierarchy (Hints of GUT)
ii. Time-evolution of dark energy (Quantum gravity)iii. Precise matter fluctuations (Hints of Inflation)
iv. ...
16/10/27

Kaz Kohri, Kanazawa