Manifestations of Dark Matter and Variations of the Fundamental Constants in Atoms and Astrophysical Phenomena

Abstract

We present an overview of recent developments in the detection of light bosonic dark matter, including axion, pseudoscalar axion-like and scalar dark matter, which form either a coherently oscillating classical field or topological defects (solitons). We emphasise new high-precision laboratory and astrophysical measurements, in which the sought effects are linear in the underlying interaction strength between dark matter and ordinary matter, in contrast to traditional detection schemes for dark matter, where the effects are quadratic or higher order in the underlying interaction parameters and are extremely small. New terrestrial experiments include measurements with atomic clocks, spectroscopy, atomic and solid-state magnetometry, torsion pendula, ultracold neutrons, and laser interferometry. New astrophysical observations include pulsar timing, cosmic radiation lensing, Big Bang nucleosynthesis and cosmic microwave background measurements. We also discuss various recently proposed mechanisms for the induction of slow 'drifts', oscillating variations and transient-in-time variations of the fundamental constants of Nature by dark matter, which offer a more natural means of producing a cosmological evolution of the fundamental constants compared with traditional dark energy-type theories, which invoke a (nearly) massless underlying field. Thus, measurements of variation of the fundamental constants gives us a new tool in dark matter searches.

Search for Axionlike Dark Matter through Nuclear Spin Precession in Electric and Magnetic Fields

“…where G andG are the gluonic field tensor and its dual, b = 1, 2, ..., 8 is the color index, g 2 /4π is the color coupling constant, N andN = N † γ 0 are the nucleon field and its Dirac adjoint, f a is the axion decay constant, and C G and C N are model-dependent dimensionless parameters. Astrophysical constraints on the axion-gluon coupling in (1) come from Big Bang nucleosynthesis [36][37][38]: m 1/4 a f a /C G 10 10 GeV 5/4 for m a 10 −16 eV and m a f a /C G 10 −9 GeV 2 for m a 10 −16 eV, assuming that axions saturate the presentday DM energy density, and from supernova energyloss bounds [35,39]: f a /C G 10 6 GeV for m a 3 × 10 7 eV. Astrophysical constraints on the axion-nucleon coupling in (1) come from supernova energy-loss bounds [39,40]: f a /C N 10 9 GeV for m a 3 × 10 7 eV, while existing laboratory constraints come from magnetometry searches for new spin-dependent forces mediated by axion exchange [41]: f a /C N 1 × 10 4 GeV for m a 10 −7 eV.…”

Exploring the ultra-light to sub-MeV dark matter window with atomic clocks and co-magnetometers

“…Moving to the 'ultra-light' regime requires yet a new battery of techniques (including relaxing the energy threshold by studying absorption, and not only scattering, of DM), e.g. [22,[40][41][42][43][44][45][46][47][48]. For both light and ultra-light dark matter, a key idea is to use very precise set-ups that may be sensitive to small or even vanishing momentum transfer.…”

“…Atomic clocks have already been used to, or suggested to, constrain ultra-light DM candidates [40][41][42][43] and other models beyond the SM [49]. In [40][41][42][43], the DM is assumed to be a massive scalar field that couples non-minimally to the SM fields. In these models, the scalar field oscillates at a frequency equal to the DM mass and/or is composed of finite size topological features that pass by the Earth.…”

Search for Axionlike Dark Matter with a Liquid-State Nuclear Spin Comagnetometer

“…1(b). We can ne-glect the Earth's orbital motion to leading order since the Earth moves around the Sun with a much smaller velocity of about 10 −4 c. The direction of the expected average velocity of the axion wind in celestial coordinates is thus (δ, η) ≈ (-48 • , 138 • ), where δ is the declination and η is the right ascension [19,31,51,52]. The z direction in laboratory coordinates should be rewritten in celestial coordinates as well.…”

“…The large parameter space of axion has motivated many experimental searches based on three possible types of non-gravitational interactions (couplings) between axions and standard model particles: the axion-photon coupling, which can interconvert axions and photons in a magnetic field [12]; the axion-gluon coupling, which can generate oscillating electric dipole moments (EDMs) in nuclei, atoms, and molecules [13][14][15][16]; the axion-fermion (wind) coupling, which can induce spin-dependent en-ergy shifts and spin precession in fermions [16][17][18][19][20]. The axion-photon coupling has been searched for in numerous experiments, many of which give constraints for axions with masses heavier than 10 −6 eV [21][22][23][24][25][26][27].…”