Fundamental physics with CMB: anomalies, new particles, primordial - - PowerPoint PPT Presentation

Fundamental physics with CMB: anomalies, new particles, primordial black holes

Rishi Khatri

In collaboration with Sandeep Kumar Acharya Subhajit Ghosh Tuhin S. Roy

The year 2020 marks the 100 years since the great debate between Harlow Shapley and Heber Curtis

https://apod.nasa.gov/diamond_jubilee/debate20.html Andromeda Image credit: GALEX/NASA/JPL/Caltech 1924: Hubble resolved ’Cepheid variable stars’ in Andromeda

The year 2020 marks the 100 years since the great debate between Harlow Shapley and Heber Curtis

https://apod.nasa.gov/diamond_jubilee/debate20.html Andromeda Image credit: GALEX/NASA/JPL/Caltech 1924: Hubble resolved ’Cepheid variable stars’ in Andromeda 1922-1924: Friedmann - Expanding Universe 1927: Lemaitre - connection to Slipher’s velocities of galaxies 1929: Hubble - distances to galaxies using Cepheids, Hubble diagram Trimble 2013, arXiv:1307.2289

Tremendous progress in CMB anisotropies after COBE CMB spectrum experiment is long overdue

1948: Prediction of 5K thermal radiation by Alpher and Herman following up on the idea of Gamow 1965: Discovery of CMB 1960s-1990s: Numerous ground based and rocket based attempts to measure CMB spectrum and anisotropies 1990: COBE measures spectrum (blackbody) and anisotropies almost simultaneous measurement of blackbody spectrum by Canadian rocket experiment COBRA 2000-2015: WMAP,Planck,SPT,ACT,Boomerang... etc - tremendous increase in precision Bicep2,SPT,ACT - First measurements of (lensing) B-mode polarization 2030:Primordial B-modes ? CMB spectrum ?

The culmination of observational and theoretical efforts

• f last 100 years is the standard ΛCDM cosmological

model

Standard ΛCDM = Standard model of particle physics + general relativity + cosmological principle + flatness + single field inflation (2 parameters) + cold dark matter (1 parameter) + cosmological constant (1 parameter) + baryogenesis (2 additional parameters: Hubble constant and optical depth to reionization can be fixed from other observations) The 6-parameter model may fail in future as precision improves − → anomalies or inconsistencies between different cosmological datasets → discovery of new physics

CMB is directly affected by new physics at z 2×106

Picture of Universe @ 380000 Years

The extreme simplicity of the early Universe before recombination and very weak interaction of the CMB photons with matter after recombination make precision science with CMB possible. Planck Collaboration 2015

Decompose the observed CMB blackbody intensity on the sphere into spherical harmonics

Fluctuations about average CMB with intensity from ¯ T = 2.725 K Θ(θ,φ) ≡ ∆T(θ,φ) ¯ T = ∑

ℓm

aℓmYℓm(θ,φ), Cℓ = ∑

m

aℓma∗

ℓm

Decompose the observed CMB blackbody intensity on the sphere into spherical harmonics

Fluctuations about average CMB with intensity from ¯ T = 2.725 K Θ(θ,φ) ≡ ∆T(θ,φ) ¯ T = ∑

ℓm

aℓmYℓm(θ,φ), Cℓ = ∑

m

aℓma∗

ℓm

Amplitude of each Fourier mode Θ0 in tightly coupled photon-baryon plasma satisfies a forced damped harmonic oscillator equation

Average CMB temperature fluctuation at point in space-time, Θ0(k,η) = (1/4)∆ρ/ρ d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

R = 3 4 ρb ργ , cs =

• 1

3(1+R) cs =Sound speed , φ,ψ=gravitational potentials Baryon loading (R) damps the oscillations, Gravity from all components of the Universe modifies the oscillations

Amplitude of each Fourier mode Θ0 in tightly coupled photon-baryon plasma satisfies a forced damped harmonic oscillator equation

Average CMB temperature fluctuation at point in space-time, Θ0(k,η) = (1/4)∆ρ/ρ d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

R = 3 4 ρb ργ , cs =

• 1

3(1+R) The amplitude of each Fourier mode oscillates. Adiabatic boundary conditions → Θ0 ∝ cos(kcsη)eik.x → standing sound waves with temporal frequency ω = kcs (sine mode absent)

Numerous ways for new physics to modify each of the terms

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Change in Hubble expansion or R modifies the damping term: e.g. charged dark matter will contribute to R.

Numerous ways for new physics to modify each of the terms

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Interactions of dark matter or dark radiation with baryons or photons will modify the sound speed

Numerous ways for new physics to modify each of the terms

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Any physics that modified the perturbations in any fluid affects CMB gravitationally through the forcing term e.g. stopping neutrino free streaming by introducing new interaction between neutrino and dark matter

Gravity of dark matter, baryons, neutrinos modifies the acoustic oscillations

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Dark matter: Constant gravity(F) - shift the zero of oscillations Θ0 ∝ cos(kcsη)−ψ Observed anisotropy: Θ0 +ψ ∝ cos(kcsη) ψ =gravitational redshift

Gravity of dark matter, baryons, neutrinos modifies the acoustic oscillations

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Baryons: Resonant forcing term - amplification of oscillations

Gravity of dark matter, baryons, neutrinos modifies the acoustic oscillations

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Dark matter + Baryons: small shift in zero of oscillations → Asymmetry in odd-even peaks Θ0 +ψ ≈ [Θ0(0)+ψ(0)(1+R)]cos(kcsη)−ψR

Gravity of decaying Neutrinos perturbations introduces phase-shift

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Neutrinos are free streaming at speed of light

Gravity of decaying Neutrinos perturbations introduces phase-shift

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

At time η, they erase perturbations on scales λ/2π η,k 1/η i.e. a mode decays on entering the horizon

Gravity of decaying Neutrinos perturbations introduces phase-shift

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Perturbations in neutrinos decay faster than plasma can respond (sound speed) → fast step function like contribution to F → phase shift in acoustic oscillations Θ0 +ψ ∝ cos(krs +φν),rs =

η

0 dηcs(η)

Gravity of decaying Neutrinos perturbations introduces phase-shift

d2Θ0 dη2 + 1 a da dη R 1+R dΘ0 dη +k2c2

sΘ0 = F(φ,ψ,R)

Perturbations in neutrinos decay faster than plasma can respond (sound speed) → fast step function like contribution to F → phase shift in acoustic oscillations Θ0 +ψ ∝ cos(krs +φν),rs =

η

0 dηcs(η)

We observe this pattern of oscillations as it exists at the time of recombination.

We observe a 2-D spherical projection of the 3-D CMB field at recombination: rs = r∗,z = z∗ ≈ 1100

Cℓ ∼ 2

π

dk k2P

A(k)j2 ℓ [k(η0 −η∗)][Θ0(k,η∗)+ψ(k,η∗)]2

Spherical Bessel projects mode k to ℓ ≈ k(η0 −η∗) ≡ kDA

CMB peak positions are sensitive to the Hubble constant

Acoustic peaks correspond to extrema of cos(kr∗ +φν) → kr∗ +φν = mπ,m ∈ Integers, m ≥ 1 ℓpeak ≈ kpeakDA = (mπ −φν)DA r∗ angular diameter distance to lss DA =

z∗

0 dz

1 H(z) sound horizon at recombination r∗ =

∞

z∗

dzcs(z) H(z) Hubble parameter H(z) = H0

• Ωr(1+z)4 +Ωm(1+z)+ΩΛ

(Friedmann equation)

H0 measured by CMB is in tension with local measurement

CMB :67.5±0.6 kms−1Mpc−1 Planck Collaboration 2018 SH0ES: 74.03±1.42 kms−1Mpc−1 Riess et al, 2019

H0 measured by CMB is in tension with local measurement

CMB :67.5±0.6 kms−1Mpc−1 Planck Collaboration 2018 SH0ES: 74.03±1.42 kms−1Mpc−1 Riess et al, 2019 ∼ 4σ discrepancy

Increasing the H0 while keeping energy densities in matter and radiation fixed gives a constant change in H(z)

Ghosh,Khatri,Roy 2019 Keeping fixed the physical densities of matter and radiation ΩrH2

0 and

ΩmH2

0 along with flatness (Ωr +Ωm +ΩΛ = 1) we want to increase H0

H2

0 → H2 0 +δ(H2 0)

⇒ H(z)2 → H(z)2 +δ(H2

0)

Increasing the H0 while keeping energy densities in matter and radiation fixed gives a constant change in H(z)

Ghosh,Khatri,Roy 2019 Keeping fixed the physical densities of matter and radiation ΩrH2

0 and

ΩmH2

0 along with flatness (Ωr +Ωm +ΩΛ = 1) we want to increase H0

H2

0 → H2 0 +δ(H2 0)

⇒ H(z)2 → H(z)2 +δ(H2

0)

H(z) is larger at higher redshifts. So importance of constant shift decreases at large z

Increasing the H0 while keeping energy densities in matter and radiation fixed gives a constant change in H(z)

Ghosh,Khatri,Roy 2019 Keeping fixed the physical densities of matter and radiation ΩrH2

0 and

ΩmH2

0 along with flatness (Ωr +Ωm +ΩΛ = 1) we want to increase H0

H2

0 → H2 0 +δ(H2 0)

⇒ H(z)2 → H(z)2 +δ(H2

0)

DA → DA +δDA, δDA < 0, r∗ remains unchanged.

Increasing the H0 while keeping energy densities in matter and radiation fixed gives a constant change in H(z)

Ghosh,Khatri,Roy 2019 Keeping fixed the physical densities of matter and radiation ΩrH2

0 and

ΩmH2

0 along with flatness (Ωr +Ωm +ΩΛ = 1) we want to increase H0

H2

0 → H2 0 +δ(H2 0)

⇒ H(z)2 → H(z)2 +δ(H2

0)

Peak positions shift to smaller ℓ contradicting CMB observations, ℓpeak ≈ (mπ −φν)DA

r∗

Solution: undo the decrease in DA, or decrease r∗ to compensate or modify φν to compensate

Ghosh,Khatri,Roy 2019 For compensation by phase shift, φν, δℓpeak = δDA DA − δφm mπ −φ = 0 δφm ≈ mπ δDA DA

Solution: undo the decrease in DA, or decrease r∗ to compensate or modify φν to compensate

Ghosh,Khatri,Roy 2019 For compensation by phase shift, φν, δℓpeak = δDA DA − δφm mπ −φ = 0 δφm ≈ mπ δDA DA If we stop neutrinos from free streaming we get almost the right δφm, scale (m) dependent phase-shift

Implement by introducing a new interaction of neutrinos with a fraction of dark matter

Ghosh,Khatri,Roy 2019

MCMC analysis including galaxy power spectrum from WiggleZ survey shows reduction in tension to 2.1σ

Ghosh,Khatri,Roy 2019 u = σνχ

σT 100 GeV mχ

f = fraction of interacting dark matter W1 - k ≤ 0.1hMpc−1

Joint analysis with SH0ES shows improvement in χ2 for

• ne additional effective parameter (f = 10−3)

Ghosh,Khatri,Roy 2019

Predict enhancement of B-mode power spectrum and matter power spectrum testable by future experiments

Ghosh,Khatri,Roy 2018, Ghosh,Khatri,Roy 2019

We may have discovered a new dark interaction (non-standard behaviour) of neutrinos in Hubble tension

Looking for anomalies in CMB spectrum

Standard model predicts distortions other than Sunyaev-Zeldovich effect at the level of 10−8 and SZ effect at level of 10−6

No deviations from a Planck spectrum at ∼ 10−4

Fixsen et al. 1996, Fixsen and Mather 2002

50 100 150 200 250 300 350 400 100 200 300 400 500 600 Iν MJ/Sr, Error bars kJ/Sr ν (GHz) 2.725 K

• 60
• 30

30 60 100 200 300 400 500 600 Residuals kJ/Sr ν (GHz)

Planck spectrum Iν = 2hν3 c2 1 ehν/(kBT) −1 Relativistic invariant occupation number/phase space density n(ν) ≡ c2 2hν3Iν n(x) = 1 ex −1 , x = hν kBT

y-type (Sunyaev-Zeldovich effect) from clusters/reionization

yγ ≪ 1 , Te ∼ 104 y = (τreionization) kBTe mec2 ∼ (0.06)(1.6×10−6) ∼ 10−7

10

−19

10

−18

0.1 1 10 10 100 1000 Iν (Wm

−2

Hz

−1

Sr

−1

) x Frequency (GHz) Blackbody y−distortion

T=2.725K

e e e e e e e e e e

Efficiency of energy exchange between electrons and photons

Recoil: yγ =

dtcσTne

kBTγ mec2,

Tγ = 2.725(1+z) Doppler effect: ye =

• dtcσTne

kBTe mec2 In early Universe yγ ≈ ye y: Amplitude of distortion y =

• dtcσTne

kB

• Te −Tγ
• mec2

Efficiency of energy exchange between electrons and photons

Recoil: yγ =

dtcσTne

kBTγ mec2,

Tγ = 2.725(1+z)

• No. of scatterings

Doppler effect: ye =

• dtcσTne

kBTe mec2 In early Universe yγ ≈ ye y: Amplitude of distortion y =

• dtcσTne

kB

• Te −Tγ
• mec2

Efficiency of energy exchange between electrons and photons

Recoil: yγ =

dtcσTne

kBTγ mec2,

Tγ = 2.725(1+z)

• No. of scatterings

Energy transfer per scattering Doppler effect: ye =

• dtcσTne

kBTe mec2 In early Universe yγ ≈ ye y: Amplitude of distortion y =

• dtcσTne

kB

• Te −Tγ
• mec2

Intermediate-type distortions (Khatri and Sunyaev 2012b)

Solve Kompaneets equation with initial condition of y−type solution. ∂n ∂yγ = 1 x2 ∂ ∂xx4

• n+n2 + Te

T ∂n ∂x

• , Te

T =

(n+n2)x4dx

4

nx3dx

• 1.5
• 1
• 0.5

0.5 1 1.5 2 2.19 3.83 1 10 20 124 217 500 100

δIν (10-22Wm-2ster-1Hz-1) x=hν/(kBT) Observed Frequency (GHz) x0 xmin xmax y-type yγ=0.01 0.05 0.1 0.2 0.3 0.5 1 2 µ-type

y and i-type distortions are non-relativistic solutions

Many processes in the early Universe inject relativistic particles. So far these have been studied assuming non-relativistic y-type distortions. ◮ Particle decay: dQ

dz ∝ e

− 1+zdecay 1+z 2

(1+z)4 (Hu and Silk 1993, Chluba and Sunyaev 2012, Khatri and Sunyaev 2012a, 2012b) ◮ Cosmic strings: dQ dz ∝ constant Tashiro, Sabancilar, Vachaspati 2012 ◮ Primordial Black holes (PBH): Depends on the mass function Tashiro and Sugiyama 2008, Carr et al. 2010

→ non-trivial new physics during inflation to create O(1) fluctuations necessary to produce PBH

Particle cascades ⇒ Non-Thermal Relativistic Distortions

High Energye− e−e− γ e− e− e− γ γ γ e−e+ e− γ H H e− γ e− H H+ H+ H* e− γ γ γ γ γ γ γ γ Boosted CMB Photons Non−Thermal Relativistic Spectral Distortion Electromagnetic cascade Background

Photons lose energy slowly and must be evolved taking expansion into account

Photons injected at z = 1000.

10-3 10-2 10-1 100 101 102 103 104 105 102 103 104 105 106 107 108 109 101010111012 tH/tcool Photon energy(eV) Photo-ionization γ e- -> γ e- γ e-/H+/He++ -> e-e+ γ γCMB -> γ γ

Photons lose energy slowly and must be evolved taking expansion into account

Photons injected at z = 20000.

10-2 10-1 100 101 102 103 104 105 106 102 103 104 105 106 107 108 109 1010 1011 tH/tcool Photon energy(eV) γ e- -> γ e- γ e-/H+/He++ -> e-e+ γ γCMB -> γ γ

Electrons lose energy fast compared to the expansion of the Universe

100 102 104 106 108 1010 1012 100 101 102 103 104 105 106 107 tH/tcool Electron energy(eV) e-e- -> e-e-, z=1000 e-γ -> e-γ, z=1000 100 102 104 106 108 1010 1012 100 101 102 103 104 105 106 107 tH/tcool Electron energy(eV) e-e- -> e-e-, z=20000 e-γ -> e-γ, z=20000 e-e+ annh., z=20000

Recursive solution to the evolution of particle cascades

Divide the energy range from 1eV to 10 GeV in logarithmic energy bins At each time step particles in the shower will cascade down from high energy to low energy bins ⇒ Recursive solution starting from lowest energy bins ∆Nβ

s =

∑

α=e−,e+,γ

• −∑

j<s

Pβα(Es,Ej)Nβ

s + ∑ j>s

Pαβ(Ej,Es)Nα

j +Sβ(Es)

• ,

Fraction of energy going into spectral distortions is a function of energy

0.2 0.4 0.6 0.8 1 104 105 106 107 108 109 1010 1011 Fraction of injected energy going to heat Electron energy(eV) heat x<=20 photons x>20 photons

At z 105 the shape of the CMB distortion depends on the spectrum of injected particles

Acharya and Khatri 2019a

• 6
• 4
• 2

2 4 6 8 10 1 10 100 1000 δIν(10-23Wm-2Hz-1ster-1) x ν(GHz) Kompaneets kernel y=5.88×10-6 10 MeV γ 100 MeV γ 1 GeV γ 10 GeV γ 10 MeV e-e+ pair

• 6
• 4
• 2

2 4 6 8 10 1 10 100 1000 δIν(10-23Wm-2Hz-1ster-1) x ν(GHz) Kompaneets kernel 100 MeV e-e+ pair 1 GeV e-e+ pair 10 GeV e-e+ pair

New COBE constraints on decaying dark matter: upto a factor of 5 correction

electron-positron channel Acharya and Khatri 2019b 10-4 10-3 104 105 DM ->e-e+ fX (95% limit) decay redshift (zX) y i m a p p r

• x

. 2me+3 MeV +20 GeV +20 keV + 3 M e V

New COBE constraints on decaying dark matter: upto a factor of 5 correction

photon channel Acharya and Khatri 2019b 10-4 10-3 104 105 DM ->γγ fX (95% limit) decay redshift (zX) y i m a p p r

• x

. 3 MeV 20 GeV 20 keV 30 MeV

CMB spectral distortions are sensitive to the mass of decaying particle as well as the lifetime

COBE Constraints Acharya and Khatri 2019b electron-positron channel photon channel

104 105 106 decay redshift (zX) 1011 1010 109 108 107 100 101 102 103 104 DM mass in MeV 10-4 10-3 10-2 10-1 fX 0.0001 0.0002 0.0003 0.0005 0.0008 0.003 0.008 0.03 lifetime τX(s) 104 105 106 decay redshift (zX) 1011 1010 109 108 107 10-1 100 101 102 103 104 DM mass in MeV 10-4 10-3 10-2 10-1 fX 0.0001 0.0001 0.0002 0.0003 0.0005 0.0008 0.003 0.008 0.03 lifetime τX(s)

Energy injection changes the recombination history/residual electron fraction after recombination

Acharya and Khatri 2019c Lifetime = 1014 s 0.0001 0.001 0.01 0.1 1 10 100 1000 xe redshift (z)

no DM 1 TeV γγ 100 MeV e-e+ 100 keV e-e+ 10 keV γγ 1 MeV γγ

polarization Hot Hot Cold Cold e− E B Scattering of quadrupole

CMB E-mode polarization is enhanced from extra scatterings

0.01 0.1 1 10 100 (ℓ(ℓ+1)Cℓ(EE))/(2π) (µK2) ℓ

no DM 1 TeV γγ 100 MeV e-e+ 100 keV e-e+ 10 keV γγ 1 MeV γγ

A fraction of energy injected before recombination survives until after recombination

Acharya and Khatri 2019c 200 GeV dark matter decaying to electron-positron pairs 1e-16 1e-14 1e-12 1e-10 1e-08 1e-06 0.0001 0.01 1 100 1000 fH,ion(z) redshift (z)

τ=1018 s (long decay) 1016 s(zX ≈ 14) 1014 s(≈300) 1013 s(zX≈1200) 1012 s(≈ 4500) 1011 s(≈15000)

CMB anisotropies give strongest constraints for energy injection upto z ≈ 10000!

Acharya and Khatri 2019c 10-12 10-10 10-8 10-6 10-4 10-2 100 1010 1012 1014 1016 1018 1020 1022 1024 104 103 102 10 fXfEM lifetime (τX) redshift (zX)

1 TeV e-e+ 100 MeV e-e+ 30 MeV e-e+ 100 keV e-e+ 1 TeV γ 1 GeV γ 1 MeV γ 10 keV γ spectral distortions

Big bang nucleosynthesis

Fields, Molaro and Sarkar 2019, Particle Data Group

High energy photons can dissociate light elements produced in the BBN

Acharya and Khatri 2019c

Strongest constraints come from deuterium destruction and He-3 over-production.

Acharya and Khatri 2019c 1e-06 1e-05 0.0001 0.001 0.01 0.1 10 100 1000 fXfEM Photon energy (MeV)

2H dissociation 3He production

CMB anisotropy, spectral distortions and BBN constraints on long lived unstable particles

Acharya and Khatri 2019c 10-12 10-10 10-8 10-6 10-4 10-2 100 106 108 1010 1012 1014 1016 1018 1020 1022 1024 106 105 104 103 102 10

COBE PIXIE 5 MeV 4 MeV 26 MeV 3 M e V C M B a n i s

• t

r

• p

y

fXfEM lifetime (τX) in seconds redshift (zX)

this work Slatyer et al. Poulin et al. BBN (this work) BBN (Poulin et al.)

Primordial black holes can emit all standard model particles if they are hot enough

Acharya and Khatri 2019d 1 10 1012 1013 1014 1015 1016 1017 0.001 0.01 0.1 1 10 f(MBH) MBH (g) TBH (GeV) γ+ν +e +µ +π0,π+,- +u+d+s+g +c+τ+b +W+Z+h+t

CMB and BBN constraints on primordial black holes

Acharya and Khatri 2019d 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 1010 1011 1012 1013 1014 1015 1016 1017 2×105 6000 100

COBE-FIRAS PIXIE

fBH MBH (g) zBH

this work Lucca et. al. Stocker et. al. Poulter et. al. BBN (Carr et. al.) BBN (this work)

10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 1010 1011 1012 1013 1014 1015 1016 1017 2×105 6000 100

COBE-FIRAS PIXIE

fBH MBH (g) zBH

21 cm global Gamma rays Cosmic rays Galactic 511 keV line

PBH constraints translate into constraints on primordial power spectrum

Probing 40 e-folds of inflation! 0.014 0.016 0.018 0.02 0.022 0.024 0.026 1014 1015 1016 1017 PR (k) k (Mpc-1)

CMB anisotropy BBN Spectral distortion (PIXIE) 21 cm 511 keV gamma rays

Injection of high energy neutrinos can change relative energy density of neutrinos and photons (Neff): constraints beyond z = 2×106

Neutrinos carry information from z 2×106 and hand it over to photons at z 2×106 Acharya& Khatri 2020 ∆Neff = Neff ∆ρν ρν − ∆ρCMB ρCMB

High energy photons produced in neutrino cascade can destroy BBN elements

The future: Falsifying ΛCDM

Next decade will see a deluge of data from CMB as well as large scale structure experiments, Confronting the standard cosmological model Vera Rubin Observatory https://www.lsst.org/

The future: Falsifying ΛCDM

Next decade will see a deluge of data from CMB as well as large scale structure experiments, Confronting the standard cosmological model Vera Rubin Observatory https://www.lsst.org/ New ways of measuring the Hubble constant will test Hubble anomaly and confirm or deny it Lensing time delay experiments H0LiCOW series of experiments Tip of the Red Giant Branch (TRGB) based calibration of Supernovae Freedman et al. 2019 - Carnegie-Chicago Hubble program

6

Discovery Precision measurement (of things already discovered) Primordial B-modes (Gravitons) Lensing B-modes Spectral Distortions E-modes Discovery Space for the next CMB mission Discovery 17 e-folds of inflation, Nature of Dark Sector, Primodial Black Holes, Topological Defects, New interactions, particles

CMB space mission proposals Low resolution Spectral distortions (Absolute Calibration) PIXIE (NASA) PRISTINE (ESA) LITEBIRD (JAXA) B-modes High resolution CORE (ESA) PICO (NASA) ECHO (ISRO) PRISM (ESA) ECHO (ISRO)?

Planck launch 2009 CMB-BHARAT mission presents an unique opportunity for India to take the lead on prized quests in fundamental science in a field that has proved to be a spectacular success, while simultaneously gaining valuable expertise in cutting-edge technology for space capability through global cooperation. Next (to next ?) Gen CMB mission ?

Edwin Hubble, The Realm of the Nebulae, 1936