axions
DESCRIPTION
Georg G. Raffelt, Max-Planck-Institut f ür Physik, München. Axions. Axions. Motivation , Cosmological Role and Astrophysical Limits. 4 th Schrödinger Lecture, Universit ät Wien, 24 May 2011. CP Violation in Particle Physics. Discrete symmetries in particle physics - PowerPoint PPT PresentationTRANSCRIPT
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
AxionsGeorg G. Raffelt, Max-Planck-Institut für Physik, München
AxionsMotivation, Cosmological Roleand Astrophysical Limits
4th Schrödinger Lecture, Universität Wien, 24 May 2011
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
CP Violation in Particle Physics
Physics Nobel Prize 2008
Discrete symmetries in particle physicsC – Charge conjugation, transforms particles to antiparticles violated by weak interactionsP – Parity, changes left-handedness to right-handedness violated by weak interactionsT – Time reversal, changes direction of motion (forward to backward)CPT – exactly conserved in quantum field theoryCP – conserved by all gauge interactions violated by three-flavor quark mixing matrix
M. Kobayashi T. Maskawa
All measured CP-violating effects derive from a single phase in the quark mass matrix (Kobayashi-Maskawa phase), i.e. from complex Yukawa couplings Cosmic matter-antimatter asymmetry requires new ingredients
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Measurements of CKM Unitarity Triangle
CKMfitter Grouphttp://ckmfitter.in2p3.fr
UTfit Collaborationhttp://www.utfit.org
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Kobayashi and Maskawa
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
The CP Problem of Strong Interactions
ℒQCD=∑𝑞𝜓𝑞( i𝐷−𝑚𝑞𝑒
i 𝜃𝑞 )𝜓𝑞−14𝐺𝜇𝜈𝑎𝐺𝑎
𝜇𝜈−Θ𝛼 s8𝜋 𝐺𝜇𝜈 𝑎
~𝐺𝑎𝜇𝜈
𝜓𝑞→𝑒❑−𝑖𝛾 5𝜃𝑞 /2𝜓𝑞
ℒQCD=∑𝑞𝜓𝑞 (i𝐷−𝑚𝑞)𝜓𝑞−
14𝐺𝐺− (Θ− arg det𝑀𝑞)⏟
−𝜋 ≤Θ≤+𝜋
𝛼s8𝜋 𝐺
~𝐺
Real quarkmass
Phase fromYukawa coupling
Anglevariable
CP-oddquantity
Remove phase of mass term by chiral transformation of quark fields
can be traded between quark phases and term No physical impact if at least one Induces a large neutron electric dipole moment (a T-violating quantity)
Experimental limits: Why so small?
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Neutron Electric Dipole Moment
Violates time reversal (T) andspace reflection (P) symmetries
Natural scale𝑒
2𝑚𝑁=1.06×10−14𝑒cm
Experimental limit|𝑑|=0.63×10− 25𝑒 cm
Limit on coefficient
Θ𝑚𝑞
𝑚𝑁≲10−11
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Dynamical SolutionPeccei & Quinn 1977, Wilczek 1978, Weinberg 1978
• Re-interpret as a dynamical variable (scalar field)
is pseudoscalar axion field, axion decay constant (Peccei-Quinn scale)
ℒCP=−𝛼 s8𝜋 ΘTr (𝐺~𝐺 )→−
𝛼 s8𝜋
𝑎(𝑥)𝑓 𝑎
Tr (𝐺~𝐺 )
• Axions generically couple to two gluons and mix with, , , mesons, inducing a mass (potential) for
𝑚𝑎 𝑓 𝑎=√𝑚𝑢𝑚𝑑
𝑚𝑢+𝑚𝑑𝑚𝜋 𝑓 𝜋 (A xion mass
& couplings )∼ ( Pion mass& couplings)×
𝑓 𝜋𝑓 𝑎
𝑎
𝑉 (𝑎)
Θ=0
• Potential (mass term) induced by drives to CP-conserving minimum
CP-symmetry dynamicallyrestored
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
The Pool Table Analogy (Pierre Sikivie 1996)
GravitySymmetricrelativeto gravity
Pool table
New degree of freedom Axion
𝚯
(Weinberg 1978, Wilczek 1978)
Axis
Symmetrydynamicallyrestored
(Peccei & Quinn 1977)
Symmetrybroken
Floor inclined
fa
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
33 Years of Axions
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
The Cleansing Axion
Frank Wilczek
“I named them after a laundry detergent, since they clean up
a problem with an axial current.” (Nobel lecture 2004)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion Bounds
Directsearches
Too muchcold dark matter (classic)
TelescopeExperiments
Globular clusters(a-g-coupling)
Too manyevents
Too muchenergy loss
SN 1987A (a-N-coupling)
Too muchhot dark matter
CAST ADMXCARRACK
Classicregion
Anthropicregion
103 106 109 1012 [GeV] fa
eVkeV meV meVmaneV
1015
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Supernova 1987A Energy-Loss Argument
SN 1987A neutrino signal Neutrinosphere
Neutrino
diffusion
Volume emission of novel particles
Late-time signal most sensitive observable
Emission of very weakly interactingparticles would “steal” energy from theneutrino burst and shorten it.(Early neutrino burst powered by accretion, not sensitive to volume energy loss.)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Diffuse Supernova Axion Background (DSAB)
Raffelt, Redondo & Viauxwork in progress (2011)
• Neutrinos from all core-collapse SNe comparable to photons from all stars• Diffuse Supernova Neutrino Background (DSNB) similar energy density as extra-galactic background light (EBL), approx 10% of CMB energy density • DSNB probably next astro neutrinos to be measured
• Axions with near SN 1987A energy-loss limit• Provide DSAB with compable energy density as DSNB and EBL• No obvious detection channel
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Do White Dwarfs Need Axion Cooling?
Isern, Catalán, García-Berro & TorresarXiv:0812.3043
White dwarf luminosity function(number of WDs per brightness interval)No axions
With axion cooling( near SN1987A limit)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion as a Nambu-Goldstone Boson
• New U(1) symmetry, spontaneously broken at a large scale • Axion is “phase” of new Higgs field: angular variable • By construction couples to term with strength , e.g. triangle loop with new heavy quark (KSVZ model)• Mixes with -- mesons• Axion mass (vanishes if or )
𝑚𝑎=√𝑚𝑢𝑚𝑑
𝑚𝑢+𝑚𝑑
𝑚𝜋
𝑓 𝜋 𝑓 𝑎
ℒCP=𝛼𝑠8𝜋 Θ𝐺𝑎
~𝐺𝑎→α s8π (Θ− 𝑎(𝑥)𝑓 𝑎 )⏟
𝐺𝑎~𝐺𝑎
Periodic variable (angle)
Φ=𝑓 𝑎+𝜌 (𝑥 )
√2𝑒𝑖𝑎 (𝑥 )𝑓 𝑎
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Creation of Cosmological Axions (very early universe)
• UPQ(1) spontaneously broken• Higgs field settles in “Mexican hat”• Axion field sits fixed at
𝑎
𝑉 (𝑎)
𝑎
𝑉 (𝑎)
Θ=0
( eV)• Axion mass turns on quickly by thermal instanton gas• Field starts oscillating when • Classical field oscillations (axions at rest)
Axions are born as nonrelativistic, classical field oscillationsVery small mass, yet cold dark matter
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion Cosmology in PLB 120 (1983)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Killing Two Birds With One Stone
Peccei-Quinn mechanism• Solves strong CP problem• May provide dark matter in the form of axions
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Cosmic Axion DensityModern values for QCD parameters and temperature-dependent axion massimply (Bae, Huh & Kim, arXiv:0806.0497)
If axions provide the cold dark matter:
• implies GeV and meV (“classic window”)
• GeV (GUT scale) or larger (string inspired) requires (“anthropic window”)
Ω𝑎h2=0.195Θi
2( 𝑓 𝑎1012GeV )
1.184
=0.105Θi2( 10𝜇eV𝑚𝑎 )
1.184
Θi=0.75( 1012GeV𝑓 𝑎 )
0.592
=1.0 ( 𝑚𝑎
10𝜇eV )0.592
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Cold Axion PopulationsCase 2:Reheating restores PQ symmetry
• Cosmic strings of broken UPQ(1) form by Kibble mechanism• Radiate long-wavelength axions• independent of initial conditions• or else domain wall problem
Inhomogeneities of axion field large,self-couplings lead to formation of mini-clustersTypical properties• Mass • Radius cm• Mass fraction up to several 10%
Case 1:Inflation after PQ symmetry breaking
Homogeneous mode oscillates after Dependence on initial misalignmentangle
• Isocurvature fluctuations from large quantum fluctuations of massless axion field created during inflation• Strong CMB bounds on isocurvature fluctuations• Scale of inflation required to be small
Dark matter density a cosmic randomnumber (“environmental parameter”)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Inflation, Axions, and Anthropic SelectionIf PQ symmetry is not restored after inflation• Axion density determined by initial random number • Different in different patches of the universe• Our visible universe, after inflation, from a single patch• Axion/photon ratio a cosmic random number, chosen by spontaneous symmetry breaking process
Allows for small and thus for at the GUT or string scale• Is this “unlikely” or “unnatural” or “fine tuned”?• Should one design experiments for very small-mass axion dark matter?
Difficult to form baryonic structures if baryon/dark matter density is too low,
posterior probability for small not necessarily small
• Linde, “Inflation and axion cosmology,” PLB 201:437, 1988• Tegmark, Aguirre, Rees & Wilczek, “Dimensionless constants, cosmology and other dark matters,” PRD 73:023505, 2006 [astro-ph/0511774]
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Lee-Weinberg Curve for Neutrinos and Axions
log (Ω𝑎)
log (𝑚𝑎)
Ω𝑀
10 eV 10 meV
CDM HDM
Axions Thermal RelicsNon-ThermalRelics
10 eV
CDMHDM
10 GeV
Neutrinos& WIMPs
Thermal Relicslog (Ω𝑎)
Ω𝑀
log (𝑚𝜈)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Neutrino and Axion Hot Dark Matter Limits
Marginalizing over neutrinohot dark matter component
eV (95% CL)
Assuming no axions
eV (95% CL)
Credible regions for neutrino plusaxion hot dark matter(WMAP-7, SDSS, HST)Hannestad, Mirizzi, Raffelt & Wong[arXiv:1004.0695]
95%68%
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion Bounds
Directsearches
Too muchcold dark matter (classic)
TelescopeExperiments
Globular clusters(a-g-coupling)
Too manyevents
Too muchenergy loss
SN 1987A (a-N-coupling)
Too muchhot dark matter
CAST ADMXCARRACK
Classicregion
Anthropicregion
103 106 109 1012 [GeV] fa
eVkeV meV meVmaneV
1015
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
New BBN limits on sub-MeV mass axions
Cadamuro, Hannestad, Raffelt & Redondo, arXiv:1011.3694 (JCAP)
• Axions essentially in thermal equilibrium throughout BBN• e+e- annihilation partly heats axions missing photons• Reduced photon/baryon fraction during BBN• Reduced deuterium abundance, using WMAP baryon fraction
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Creation of Adiabatic vs. Isocurvature PerturbationsInflaton field Axion field
Slow roll
Reheating
De Sitter expansion imprintsscale invariant fluctuations
Inflaton decay matter & radiationBoth fluctuate the same:Adiabatic fluctuations
Inflaton decay radiationAxion field oscillates late matterMatter fluctuates relative to radiation:Entropy fluctuations
De Sitter expansion imprintsscale invariant fluctuations
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Power Spectrum of CMB Temperature Fluctuations
Acoustic Peaks
Sky map of CMBR temperaturefluctuations
Multipole expansion
Angular power spectrum
Δ (𝜃 ,𝜑 )=𝑇 (𝜃 ,𝜑 )− ⟨𝑇 ⟩⟨ 𝑇 ⟩
Δ (𝜃 ,𝜑 )=∑ℓ=0
∞
∑𝑚=−ℓ
ℓ
𝑎ℓ𝑚𝑌 ℓ𝑚 (𝜃 ,𝜑 )
𝐶ℓ= ⟨𝑎ℓ𝑚∗ 𝑎ℓ𝑚⟩= 12ℓ+1 ∑
𝑚=−ℓ
ℓ
𝑎ℓ𝑚∗ 𝑎ℓ𝑚
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
CMB Angular Power Spectrum
Purely adiabatic
Purely isocurvature
Hamann, Hannestad, Raffelt & Wong, arXiv:0904.0647
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Parameter Degeneracies
Hamann, Hannestad, Raffelt & Wong, arXiv:0904.0647
WMAP-5WMAP-5 + LSSPlanck forecastCosmic VarianceLimited (CVL)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Isocurvature Forecast
Hubble scale during inflation
Axio
n de
cay
cons
tant
Hamann, Hannestad, Raffelt & Wong, arXiv:0904.0647
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Experimental Tests of Invisible Axions
Primakoff effect:
Axion-photon transition in externalstatic E or B field(Originally discussed for by Henri Primakoff 1951)
Pierre Sikivie:
Macroscopic B-field can provide alarge coherent transition rate overa big volume (low-mass axions)• Axion helioscope: Look at the Sun through a dipole magnet• Axion haloscope: Look for dark-matter axions with A microwave resonant cavity
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Search for Solar Axions
g a
Sun
Primakoff production
Axion Helioscope(Sikivie 1983)
gMagnet S
Na
Axion-Photon-Oscillation
Tokyo Axion Helioscope (“Sumico”) (Results since 1998, up again 2008) CERN Axion Solar Telescope (CAST) (Data since 2003)
Axion flux
Alternative technique: Bragg conversion in crystal Experimental limits on solar axion flux from dark-matter experiments (SOLAX, COSME, DAMA, CDMS ...)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Tokyo Axion Helioscope (“Sumico”)
Moriyama, Minowa, Namba, Inoue, Takasu & YamamotoPLB 434 (1998) 147Inoue, Akimoto, Ohta, Mizumoto, Yamamoto & MinowaPLB 668 (2008) 93
m
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
CAST at CERN
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Sun Spot on CCD with X-Rays
ROI
„suspicious pressure“
90 min tracking result
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion-Photon-Conversion
Stationary Klein-Gordon equationfor photons and axionsin external transverse B-field
−𝑖𝜕𝑧 (𝐴𝑎 )=[𝜔+ 12 ( 0 𝑔𝑎𝛾𝐵𝑔𝑎𝛾𝐵 𝑚𝑎
2 /𝜔)](𝐴𝑎 )
𝑚𝑎=0Conversion probability
𝑃 (𝑎→𝛾 )=(𝑔𝑎𝛾𝐵𝐿2sin (𝑥 )𝑥 )
2
𝑥=√(𝑚𝑎2
4𝜔 )2
+(𝑔𝑎𝛾𝐵𝐿2 )2
Saturation of at for sufficiently largemass eV for CAST)𝑳𝑩
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Helioscope Limits
CAST-I results: PRL 94:121301 (2005) and JCAP 0704 (2007) 010 CAST-II results (He-4 filling): JCAP 0902 (2009) 008
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Next Generation Axion Helioscope
• CAST has one of the best existing magnets that one could “recycle” for axion physics (LHC test magnet)
• Only way forward is building a new magnet, especially conceived for this purpose
• Work ongoing, but best option up to now is a toroidal configuration:
– Much bigger aperture than CAST: per bore – Lighter than a dipole (no iron yoke) – Bores at room temperature
I. Irastorza et al., “Towards a new generation axion helioscope”, arXiv:1103.5334
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Helioscope Prospects
SN 1987ALimits
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion-Like Particles (ALPs)Particles with two-photon vertex: Pseudoscalars: • Gravitons• Neutral pions ()• Axions and similar hypothetical particles
Two-photondecay
Γ 𝑎𝛾=𝑔𝑎𝛾2 𝑚𝑎
3
64𝜋
Primakoffeffect
BextStarGalaxy
Magnetically induced vacuumbirefringence
Bext Bext
Vacuum Cotton-Mouton effect
Gravitationallight deflection
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Recent “shining-light-through-a-wall” or vacuum birefringence experiments:• ALPS • BMV • BFRT• GammeV • LIPPS • OSQAR • PVLAS
Photon Regeneration Experiment at DESY (ALPS)Ehret et al. (ALPS Collaboration), arXiv:1004.1313
(DESY, using HERA dipole magnet) (Laboratoire National des Champs Magnétiques Intens, Toulouse) (Brookhaven, 1993) (Fermilab) (Jefferson Lab) (CERN, using LHC dipole magnets) (INFN Trieste)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Limits on Axion-Like Particles from Laser Experiments
Ehret et al. (ALPS Collaboration), arXiv:1004.1313
Limits on pseudoscalars, similar plot for scalars
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Search for Galactic Axions (Cold Dark Matter)
Power
Frequency ma
Axion Signal
Thermal noise of cavity & detector
Power of galactic axion signal
Microwave Energies (1 GHz 4 meV)
Dark matter axions Velocities in galaxy Energies therefore
ma = 1-100 meV
va 10-3 c
Ea (1 10-6) maAxion Haloscope (Sikivie 1983)
Bext 8 Tesla
Microwave ResonatorQ 105
Primakoff Conversionga
Bext
Cavityovercomesmomentummismatch
4×10−21W 𝑉0.22m3 ( 𝐵
8.5 T )2 𝑄105×( 𝑚a
2𝜋 GHz )( 𝜌𝑎5×10−25 g / cm 3 )
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Axion Dark Matter SearchesLimits/sensitivities, assuming axions are the galactic dark matter
1. Rochester-Brookhaven- Fermilab, PRD 40 (1989) 3153
2. University of Florida PRD 42 (1990) 1297
3. US Axion Search ApJL 571 (2002) L27
4. CARRACK I (Kyoto) hep-ph/0101200
4
123
5. ADMX (US) foreseen RMP 75 (2003) 777
5
6. New CARRACK (Kyoto) K.Imai (Panic 2008)
6
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
ADMX Hardware
Gianpaolo Carosi, Talk at Fermilab (May 2007)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
SQUID Microwave Amplifiers in ADMX
Gianpaolo Carosi, Talk at Fermilab (May 2007)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
ADMX phase I: First-year science data (2009)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
And if the axion be found? Karl van Bibberat IDM 2008
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Fine Structure in the Axion Spectrum• Axion distribution on a 3-dim sheet in 6-dim phase space• Is “folded up” by galaxy formation• Velocity distribution shows narrow peaks that can be resolved• More detectable information than local dark matter density
P.Sikivie& collaborators
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
CARRACK
Kenichi Imai
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
New CARRACK (Kyoto)
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
CARRACK Apparatus
Kenichi Imai
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Assume axions are galactic dark matter: 300 MeV/cm3
Independently of expect
Expect time-varying neutron EDM, MHz frequency for GeV
Experimental limit on static EDM
Use much larger electric fields within atoms, small energy shifts withinpolarized molecules: Molecular interferometry techniques may work,a factor 100 off at present. Best in kHz-MHz regime (anthropic window).
Searching for Axions in the Anthropic Window
Graham & Rajendran, arXiv:1101.2691
Georg Raffelt, MPI Physics, Munich 4th Schrödinger Lecture, University Vienna, 24 May 2011
Summary
• Peccei-Quinn dynamical CP symmetry restoration is better motivated than ever and provides an excellent CDM candidate• Realistic full-scale search in “classic window” (1-100 meV) is finally beginning (ADMX and New CARRACK)• Isocurvature fluctuations could still show up (Planck, future CVL probe)• CAST solar axion search almost complete and has crossed into hot dark matter region. No axions found, new limits.• Hint for additional cooling in white dwarfs by axions? Leads to significant diffuse supernova axion background (DSAB). Parameters testable with Next Generation Helioscope?