David J. E. Marsh - 京都大学hideo.kodama/UTQuestWS5/TalkFiles/DJ… · David J. E. Marsh...
Transcript of David J. E. Marsh - 京都大学hideo.kodama/UTQuestWS5/TalkFiles/DJ… · David J. E. Marsh...
David J. E. Marsh
David J. E. Marsh Phys. Rep. 643, 1 (2016)
Axion Cosmology, and the Lightest Possible Dark Matter Candidate
David J. E. Marsh
David J. E. Marsh
Initial Conditions and Relic Density
Symmetry Breaking and Inflation
David J. E. Marsh
Cold condensate from SSB.
The axion is born:
Vacuum Realignment
David J. E. Marsh
Axion acquires mass*, evolves according to Klein-Gordon:
(* I am ignoring T-dependence and
h i iti )
Axion is “frozen” by Hubble friction term.
Light axions are “DE-like”
Vacuum Realignment
David J. E. Marsh
Axion acquires mass*, evolves according to Klein-Gordon:
(* I am ignoring T-dependence and
h i iti )
Field oscillates & damps. WKB (or exact)
Osc. scalar ~ matter
David J. E. Marsh
Relic Density of Cold Axions
David J. E. Marsh
Ultralight axions: • Relic abundance
natural for GUT scale decay constants!
• SSB occurs before/during inflation.
Universe is one θ patch.
CMB B-pol BICEP/Planck (2014)
Scales of Interest
David J. E. Marsh
Non-thermal compare mass to Hubble (not T).
Physics: Hubble:
[eV]
Non-linear
Linear perts: LSS and the CMB
Size of dSph
“Fuzzy DM”, v. non-linear. Solitons in galaxies. ν<<1 Hz
Galaxy formation, halo model.
“WDM-like”
Equality
“DM-like” “DE/ν-like”
BBN
UV physics? Non-thermal epoch? Miniclusters?
Today
Field frozen: behave as Λ
Rough DM lower bound Precision DM cosmology
Precision Cosmology: Perturbations and Linear
Observables
CMB download: github.com/dgrin1/axionCAMB Cosmosis module coming soon…
Axion DM is “Fuzzy”
David J. E. Marsh
Clustering suppressed relative to CDM on small scales. Heuristically: de Broglie wavelength from Hubble flow.
Uncertainty in position: Recession veocity:
Q: how far away does cosmic DM have to be for r>λ?
Parametrically, this is borne out in cosmological PT…
The Axion Jeans Scale
David J. E. Marsh
Gradient energy scalar DM has effective sound
speed:
pressure gravity
WKB approx, e.g. Park et al (2012)
Exact solutions possible in axion-dominated Universe. e.g. DJEM (2016)
Fits for “transfer function” relative to CDM. Hu et al (2000)
The Axion Jeans Scale
David J. E. Marsh
Numerical solution* in Boltzmann code axionCAMB.
Fig. Hlozek, DJEM et al (2014)
(*un-normalized)
CMB Temperature Power
David J. E. Marsh
DM-like axions change during rad. dom. epoch acoustic peak
heights.
DE-like axions change angular scale and
evolution of Φ. SW
effect. Hlozek, DJEM et al (2014)
Physics: early w=-1 evolution changes expansion rate.
Constraints from Planck TT
David J. E. Marsh Hlozek, DJEM et al (2014)
Marginalised constraints via nested sampling with MultiNest.
Constraints from Planck TT
David J. E. Marsh Hlozek, DJEM et al (2014)
Interpretation as constraints on decay constant if φi~fa.
The Future: CMB-S4
David J. E. Marsh Hlozek, DJEM et al (2016)
Array of ground based telescopes for ~2020*. Advantage over Planck for DM: high-l lensing power.
CMB-S4 Science Book
S4 forecast
Axi
on D
M F
raction
Planck “forecast”
Axi
on D
M F
raction Improve lower bound on DM
particle mass by 102.
Allow detection of 1% departures from CDM at 5σ. S4 can do precision tests
of the CDM paradigm! Ωa~fa
2 improve fa bound.
Challenge: modelling effects of non-linear clustering.
(*near term also “Simons array”)
Non-Linear Scales and Galaxy Formation
Fig: Schive et al (2014) Fig: Schwabe et al (2016)
Halo Model download: github com/DoddyPhysics/HMcode
Overview: Hui et al (2016)
The Halo Mass Function
David J. E. Marsh DJEM & Silk (2013), Du et al (2016)
Physics: pressure/λdB suppresses galaxy formation. Methodology: Press-Schechter and/or N-body sims. Physics: pressure/λdB suppresses galaxy formation. Methodology: Press-Schechter and/or N-body sims.
Corasaniti, DJEM et al (2016)
HUDF cumulative luminosity. Data: Bouwens et al (2014).
100%
50%
10-22eV
10-23eV 50%
CDM
High-z Galaxy Formation
David J. E. Marsh Bozek, DJEM et al (2015); Schive et
al (2015); Corasaniti, DJEM et al (2016)
Abundance matching: HMF UV luminosity. Less clustering later halo formation, fewer high-z
galaxies.
Bright Faint
JWST No
fainter galaxies
Different techniques (matching, SFR, HMF), different data (observations, redshifts, binning) all reach the same conclusions:
is consistent with the data.
Ionized fraction inc. astro. uncertainties.
CDM 10-22eV 10-21eV
Reionization and CMB τ
David J. E. Marsh Bozek, DJEM et al (2105)
High-z galaxies reionize the Universe optical depth. Fewer galaxies later reionization lower τ Planck.
CMB uncertain. But will improve with better EE & kSZ.
Ionized fraction inc. astro. uncertainties. Integrate…
tension
“Axion Stars” and Galaxy Cores
David J. E. Marsh Schive et al (2014+), Schwabe et al (2016+)
ULAs gravitationally condense on small scales inside halos.
David J. E. Marsh
“Axion Stars” and Galaxy Cores
Schive et al (2014+), Schwabe et al (2016+)
R>λdB NFW
Soliton core
• Cores are local ground state soliton soln.
• Cores size shrinks with increasing density.
• Scaling relationship: • Large scale
incoherence NFW.
• Parameterise density profile with transition.
simulation results…
The Cusp-Core Problem?
David J. E. Marsh Walker & Penarrubia (2011)
(e.g.) Slopes of Fornax & Sculptor density profiles:
Velocity dispersion at half-light measures enclosed mass. Two populations constrain slope of DM halo.
Pure
cusp
exc
lude
d >99%
Constraints From Cores
David J. E. Marsh Gonzalez-Morales, DJEM et al
(2016) DJEM & Pop (2015) Chen et al
Use of mock data shows that Jeans analysis is biased and cannot discriminate between models (β-degeneracy).
Slopes method + improved estimator is unbiased.
Jeans Slope
s New
0.4
x10
-22eV
Hig
h-z
gala
xies • All evidence points
to cores. • BUT axions (just)
too light c.f. WDM. • Assume negligible
baryonic feedback. • Testable in future
via (non-)universality.
Extra Topics
David J. E. Marsh
David J. E. Marsh
Let’s take a break...
m~10-22 eV appears special: Limit of our ignorance for DM. Possible source of dSph cores.
Can we ever detect such an axion?
Detecting ULAs with
nEDM: Paving the
Way for CASPEr
David J. E. Marsh
Fig: Harris (2007)
The neutron EDM Experiment
David J. E. Marsh
Ultracold neutrons spinning “in a jar” in E and B fields. Ran at RAL/ILL from 1998 giving best static nEDM limit:
Baker et al (2006); Pendlebury et al (2015)
Measures energy splitting relative to Larmour freq. of Hg:
Cycles: 130s; E-flips: hourly; “Run” measures dn every day.
Sensitive to tiny energy shifts:
Q: can we use the time series to search for axions?
Axions and nEDM
David J. E. Marsh Graham & Rajendran (2013)
Ayres, Rawlik, DJEM et al (in prep.)
Graham & Rajendran: assumed no signal on cycle scales, and averaged. Published data not available for this. For m-1>run, ILL limit ~ 10 times worse than published:
(unpublished) cycle level PSI data + 4 years ILL:
David J. E. Marsh
nEDM (blinded)
Nicholas Ayres and Michal Rawlik for nEDM:
nEDM also sensitive to “axion wind”, but cannot beat SNe…
Numerical GR for Axion Stars
David J. E. Marsh
Fig: Helfer, DJEM et al (2016)
David J. E. Marsh
GRChombo, Clough et al (2015)
Katy Clough Thomas Helfer
(3+1) numerical GR with a scalar cosine potential (any V!).
Stability Solution Space
David J. E. Marsh
Core Collapse I: BHs
David J. E. Marsh Helfer, DJEM et al (2016)
• Above critical MADM and fa axion stars collapse to BHs.
• Appears hard to realise for axion stars from DM structure.
• Mergers and BH formation signals?
Core Collapse II: Axion Emission
David J. E. Marsh Helfer, DJEM et al (2016)
Fig: Levkov et al (2016)
• Below critical fa, quartic interactions axion
emission. • Destabilise galaxy cores
for fa<1015 GeV. CDM
HDM?
ULA Endgame: Can We Exclude 10-22 eV?
David J. E. Marsh
ULA Endgame: 21cm and 10-18 eV
David J. E. Marsh
Scale Mpc-1
CDM w/ vel CDM no vel
Sensitivity early LW
21cm
Pow
er S
pect
rum
z=2
0
Fig. Visbal et al (2012)
DM-baryon relative v modulates large scale 21cm power. Effect can be measured by e.g. LOFAR.
Tseliakhovich & Hirata (2010) Visbal et al (2012)
ULA Endgame: 21cm and 10-18 eV
David J. E. Marsh
Large scale 21cm power from baryon v coherence. Originates from small-scale P(k) effect absent for
ULAs.
Scale Mpc-1
CDM m<10-18 eV Sensitivity
early LW
21cm
Pow
er S
pect
rum
z=2
0
Fig. Visbal et al (2012)
DJEM (2015)
Problem: need to
understand SFR!
Caveats & Work in Progress
David J. E. Marsh
Anharmonic potentials: • Relic density lower fa. In prep w/ Diez-
Tejedor. • axionCAMB: modified perts. In prep w/ Leung. Iscourvature: precision CMB in prep w/ Hlozek.
Multiple axions? “Predicted” by string/M-theory. Can we do precision cosmology? In prep w/ Stott.
“Miniclusters”. Beyond the QCD axion
microlensing constraints. In prep w/ Quevillon.
Simulations with m~10-22 eV. More community input!
Direct detection: can it ever work at ultra-low frequency? Lyman-alpha forest: WTF? In prep w/ Bozek et al.
The Principle of Plenitude: “This best of all possible worlds will contain all possibilities, with our finite experience of eternity giving no reason to dispute nature’s perfection.”
Gottfried Leibniz (1646-1716), in Theodicee
Pangloss sometimes said to Candide: “There is a concatenation of events in this best of all possible worlds: for if you had not been kicked out of a magnificent castle for love of Miss Cunégonde–if you had not come under the Inquisition–if you had not walked over America–if you had not stabbed the Baron–if you had not lost all your sheep from the fine country of El Dorado– why, then, you would not be here, eating preserved citrons and pistachio-nuts.” “All that is very well,” answered Candide, “but let us cultivate our garden.”
Voltaire (1694-1778), in Candide
Quoted in “String Axiverse”