The presence of a primordial magnetic field would have induced resonant conversions between photons and axion-like particles (ALPs) during the thermal history of the Universe. These conversions would have distorted the blackbody spectrum of the cosmic microwave background (CMB). In this context, we derive bounds on the photon-ALP resonant conversions using the high precision CMB spectral data collected by the FIRAS instrument on board of the Cosmic Background Explorer. We obtain upper limits on the product of the photon-ALP coupling constant g times the magnetic field strength B down to g B > 10^{-13} GeV^{-1} nG for ALP masses below the eV scale.
We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD $θ$ angle that redshifts in the early universe, increasing the neutron-proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of 4He during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for time-varying neutron EDMs. The QCD axion does not couple strongly enough to affect BBN.
We study in detail MSW-like resonant conversions of QCD axions into hidden axions, including cases where the adiabaticity condition is only marginally satisfied, and where anharmonic effects are non-negligible. When the resonant conversion is efficient, the QCD axion abundance is suppressed by the hidden and QCD axion mass ratio. We find that, when the resonant conversion is incomplete due to a weak violation of the adiabaticity, the CDM isocurvature perturbations can be significantly suppressed, while non-Gaussianity of the isocurvature perturbations generically remain unsuppressed. The isocu…
Axion dark matter can resonantly convert to photons in the magnetosphere of neutron stars, possibly giving rise to radio signals observable on Earth. This method for the indirect detection of axion dark matter has recently received significant attention in the literature. The calculation of the radio signal is complicated by a number of effects; most importantly, the gravitational infall of the axions onto the neutron star accelerates them to semi-relativistic speed, and the neutron star magnetosphere is highly anisotropic. Both of these factors complicate the calculation of the conversion of …
Axions seem ubiquitous in string theories and some of them may be produced non-thermally by heavy scalar decays, contributing to dark radiation. We study various cosmological effects of photons produced from the axionic dark radiation through axion-photon conversion in the presence of primordial magnetic fields, and derive tight constraints on the combination of the axion-photon coupling and the primordial magnetic field.
One of the fundamental results used in observational cosmology is the distance duality relation (DDR), which relates the luminosity distance, $D_L$, with angular diameter distance, $D_A$, at a given redshift $z$. We employ the observed limits of this relation to constrain the coupling of axion like particles (ALPs) with photons. With our detailed $3D$ ALP-photon mixing simulation in standard $Λ$CDM universe and latest DDR limits observed in Holand \& Barros (2016) we limit the coupling constant $g_ϕ\le 6 \times 10^{-13} GeV^{-1}\left(\frac{nG}{\langle B \rangle_{\rm Mpc}}\right)$ for ALPs of m…
We apply the axion-photon conversion mechanism to the 130 GeV $γ$-ray line observed by the Fermi satellite. Near the Galactic center, some astrophysical sources and/or particle dark matter can produce energetic axions (or axionlike particles), and the axions convert to $γ$ rays in Galactic magnetic fields along their flight to the Earth. Since continuum $γ$-ray and antiproton productions are sufficiently suppressed in axion production, the scenario fits the 130 GeV $γ$-ray line without conflicting with cosmic ray measurements. We derive the axion production cross section and the decay rate of …
Recently the EDGES experiment reported an enhanced 21cm absorption signal in the radio wave observation, which may be interpreted as either anomalous cooling of baryons or heating of cosmic microwave background photons. In this paper, we pursue the latter possibility. We point out that dark radiation consisting of axion-like particles can resonantly convert into photons under the intergalactic magnetic field, which can effectively heat up the radiation in the frequency range relevant for the EDGES experiment. This may explain the EDGES anomaly.
In this paper we investigate the potential of current and upcoming cosmological surveys to constrain the mass and abundance of ultra-light axion (ULA) cosmologies with galaxy cluster number counts. ULAs, sometimes also referred to as Fuzzy Dark Matter, are well-motivated in many theories beyond the Standard Model and could potentially solve the $Λ$CDM small-scale crisis. Galaxy cluster counts provide a robust probe of the formation of structures in the Universe. Their distribution in mass and redshift is strongly sensitive to the underlying linear matter perturbations. In this forecast paper w…
We investigate the bounds on axionlike states from flavor-changing neutral current b->s decays, assuming the axion couples to the standard model through mixing with the Higgs sector. Such GeV-scale axions have received renewed attention in connection with observed cosmic ray excesses. We find that existing B->K l+ l- data impose stringent bounds on the axion decay constant in the multi-TeV range, relevant for constraining the "axion portal" model of dark matter. Such bounds also constrain light Higgs scenarios in the next-to-minimal supersymmetric standard model. These bounds can be improved b…
Axion helioscopes search for solar axions and axion-like particles via inverse Primakoff conversion in strong laboratory magnets pointed at the Sun. While helioscopes can always measure the axion coupling to photons, the conversion signal is independent of the mass for axions lighter than around 0.02 eV. Masses above this value on the other hand have suppressed signals due to axion-photon oscillations which destroy the coherence of the conversion along the magnet. However, the spectral oscillations present in the axion conversion signal between these two regimes are highly dependent on the axi…
Ultraviolet completions for axion-like particles (ALPs) lighter than the neutral pion generically induce ALP-neutral pion mixing, and are therefore sensitive to direct constraints on the mixing angle. For ALPs below the pion mass, we demonstrate that strong and novel bounds on the ALP-pion mixing angle can be extracted from existing rare pion decay data, measured by the PIENU and PIBETA experiments.
We study the conditions for the adiabatic resonant conversion of the cold dark matter (CDM) axions into photons in existence of the astrophysically sourced strong magnetic fields such as those in the neutron star magnetosphere. We demonstrate the possibility that the forthcoming radio telescopes such as the SKA (Square Kilometre Array) can probe those photon signals from the CDM axions.
We compute the photon-axion conversion probability in an external magnetic field with a strong transverse gradient in the eikonal approximation for plane waves. We find it typically smaller than a comparable uniform case. Some insights into the phenomenon of photon-axion splitting are given.
In the presence of an external magnetic field the axion and the photon mix. In particular, the dispersion relation of a longitudinal plasmon always crosses the dispersion relation of the axion (for small axion masses), thus leading to a resonant conversion. Using thermal field theory we concisely derive the axion emission rate, applying it to astrophysical and laboratory scenarios. For the Sun, depending on the magnetic field profile plasmon-axion conversion can dominate over Primakoff production at low energies ($\lesssim 200\,$eV). This both provides a new axion source for future helioscopes…
We consider recent progress in constraining the axion-nucleon coupling constants and the Yukawa-type corrections to Newtonian gravity from experiments on measuring the Casimir interaction. After a brief review of previously obtained constraints, we concentrate on the new Casimir-less experiment, which allows to strengthen the known results up to factors of 60 and 1000 for the axion-like particles and Yukawa-type corrections, respectively. We also discuss possibilities allowing to further strengthen the constraints on axion-nucleon coupling constants, and propose a new experiment aiming to achi…
Axion-photon conversion at dielectric interfaces, immersed in a near-homogeneous magnetic field, is the basis for the dielectric haloscope method to search for axion dark matter. In analogy to transition radiation, this process is possible because the photon wave function is modified by the dielectric layers ("Garibian wave function") and is no longer an eigenstate of momentum. A conventional first-order perturbative calculation of the transition probability between a quantized axion state and these distorted photon states provides the microwave production rate. It agrees with previous results…
We reconsider the conversion of the photon into axion in the external electromagnetic fields, namely in the static fields and in a periodic field of the wave guide. The total cross-sections for the conversion are evaluated in detail. The result shows that with strong strength of external electromagnetic fields, the cross-sections are large enough to measure the axion production. In the wave guide there exists the resonant conversion at the low energies, in which the value of cross-sections is much enhanced
We examine the resonant conversion of axion-like particle (ALP) or dark photon to the electromagnetic photon in the early Universe, which takes place due to the ALP-photon-dark photon oscillations in background dark photon gauge fields. It is noted that the corresponding conversion probability can have an unusual spectral feature which allows strong conversion at low frequency domain, but has negligible conversion at high frequencies above certain critical frequency which is determined by the ALP coupling to dark photon and the strength of background dark photon gauge field. We apply this sche…
We show that axion dark matter (DM) may be detectable through narrow radio lines emitted from neutron stars. The neutron star magnetosphere hosts a strong magnetic field and a plasma frequency that increases towards the neutron star surface. As the axions pass through the magnetosphere, they can resonantly convert into radio photons in a narrow region around the radius at which the plasma frequency equals the axion mass. The bandwidth of the signal is set by the small DM velocity dispersion far away from the neutron star. We solve the axion-photon mixing equations, including a full treatment o…
Photon - axion conversions in the resonant cavity with the lowest mode are considered in detail by the Feynman diagram method. The differential cross sections are presented and numerical evaluations are given. It is shown that there is a resonant conversion for the considered process, in which the conversion cross sections are much larger than those of the wave guide in the same conditions. Some estimates for experimental conditions are given from our results.
The QCD axion or axion-like particles are candidates of dark matter of the universe. On the other hand, axion-like excitations exist in certain condensed matter systems, which implies that there can be interactions of dark matter particles with condensed matter axions. We discuss the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level. The conversion rate of the light dark matter, such as the elementary particle axion or hidden photon, into the condensed matter axion is estimated for the discovery of the …
Axion-Like Particles (ALPs) are the focus of intense current research. We analyze photon-ALP conversion in the context of relativistic jet models of Active Galactic Nuclei (AGN) for more than 100 sources. Contrary to previous claims, we find that this process cannot occur above 100 GeV regardless of the actual AGN model and the values of ALP parameters. This result rules out a proposed strategy to bypass the cosmic opacity above 100 GeV, as apparently required by observations. We also show that for some AGN an observable effect can show up in the X and soft gamma-ray bands.
Ultra-light dark matter may consist of axion-like particles with masses below 10^(-19) eV. Two-photon interactions of these particles affect the polarization of radiation propagating through the dark matter. Coherent oscillations of the Bose condensate of the particles induce periodic changes in the plane of polarisation of emission passing through the condensate. We estimate this effect and analyze MOJAVE VLBA polarization observations of bright downstream features in the parsec-scale jets of active galaxies. Through the non-observation of periodic polarization changes, we are able to constra…
Stronger constraints on the pseudoscalar coupling constants of an axion to a proton and a neutron are obtained from an indirect measurement of the effective Casimir pressure between two Au-coated plates by means of micromechanical torsional oscillator. For this purpose, the additional effective pressure due to two-axion exchange is calculated. The role of boundary effects and the validity region of the proximity force approximation in application to forces of axion origin are determined. The obtained constraints are up to factors of 380 and 3.15 stronger than those found recently from other la…
Constraints on the Yukawa-type corrections to Newton's gravitational law and on the coupling constant of axionlike particles to nucleons obtained from different laboratory experiments are reviewed and compared. The constraints on non-Newtonian gravity under discussion cover the wide interaction range from nanometers to millimeters and follow from the experiments on neutron scattering, measuring the Casimir force and Cavendish-type experiments. The constraints on the axion-to-nucleon coupling constant following from the magnetometer measurements, Cavendish-type experiments, Casimir physics, and…
Magnetic fields mix axions with photons, allowing for the cyclotron process e -> e + a by virtue of an intermediate plasmon even if axions do not couple to electrons at tree level. The axion and longitudinal-plasmon dispersion relations always cross for a certain wave number, leading to a resonant enhancement of this process. Even then, however, it cannot quite compete with the usual nucleon processes in a supernova core. The well-known axion window 10^{-5} eV < m_a < 10^{-2} eV remains open and axions may still constitute the cosmic dark matter.
Magnetic Turbulence Boosts Supernova Signals of Axion-Photon Conversion
Istituto Nazionale di Fisica Nucleare (INFN)（意大利国家核物理研究所）；Gran Sasso Science Institute (GSSI)（格兰萨索科学研究所）；Università degli Studi di Padova（帕多瓦大学）；Max-Planck-Institut für Physik（马克斯·普朗克物理研究所）
Axion couplings to photons could induce photon-axion conversion in the presence of magnetic fields in the Universe. This conversion could impact various cosmic distance measurements, such as luminosity distances to type Ia supernovae and angular distances to galaxy clusters, in different ways. In this paper we consider different combinations of the most up-to-date distance measurements to constrain the axion-photon coupling. Employing the conservative cell magnetic field model for the magnetic fields in the intergalactic medium (IGM) and ignoring the conversion in the intracluster medium (ICM)…
Recently it has been suggested that dark radiation in the form of axions produced during the decay of string theory moduli fields could be responsible for the soft x-ray excess in galaxy clusters. These soft X-ray photons come about due to the conversion of these axions into photons in the magnetic fields of the clusters. In this work we calculate the conversion of axionic dark radiation into X-ray photons in the magnetic field of our own Galaxy. We consider Delta N ~ 0.5 worth of dark radiation made up of axions with energy of order 0.1-1 keV. We show that it is possible, if a little optimist…
It is known that a coherently oscillating axion field is a candidate of the dark matter. In the presence of the oscillating axion, the photon can be resonantly produced through the parametric amplification. In the universe, there also exist cosmological magnetic fields which are coherent electromagnetic fields. In the presence of magnetic fields, an axion can be converted into a photon, and vice versa. Thus, it is interesting to investigate what happens for the axion-photon system in the presence of both the axion dark matter and the magnetic fields. This system can be regarded as a coupled sy…
The strongest constraints on the Yukawa-type corrections to Newton's gravitational law and on the coupling constants of axion-like particles to nucleons, following from recently performed experiments of the Casimir physics, are presented. Specifically, the constraints obtained from measurements of the lateral and normal Casimir forces between sinusoidally corrugated surfaces, and from the isoelectronic experiment are considered, and the ranges of their greatest strength are refined. Minor modifications in the experimental setups are proposed which allow strengthening the resultant constraints …
Axion dark matter (DM) may convert to radio-frequency electromagnetic radiation in the strong magnetic fields around neutron stars. The radio signature of such a process would be an ultra-narrow spectral peak at a frequency determined by the mass of the axion particle. We analyze data we collected from the Robert C. Byrd Green Bank Telescope in the L-band and the Effelsberg 100-m Telescope in the L-Band and S-band from a number of sources expected to produce bright signals of axion-photon conversion, including the Galactic Center of the Milky Way and the nearby isolated neutron stars RX J0720.…
Axions are well-motivated candidates for dark matter. Recently, much interest has focused on the detection of photons produced by the resonant conversion of axion dark matter in neutron star magnetospheres. Various groups have begun to obtain radio data to search for the signal, however, more work is needed to obtain a robust theory prediction for the corresponding radio lines. In this work we derive detailed properties for the signal, obtaining both the line shape and time-dependence. The principal physical effects are from refraction in the plasma as well as from gravitation which together l…
The light pseudoscalar particle, dubbed the axion, borne out of the Peccei-Quinn solution to the strong CP problem in QCD remains elusive. One avenue of inferring its existence is through its coupling to electromagnetic radiation. So far, laboratory experiments have dedicated all efforts to detect the axion in the mass range $10^{-6} < m_a < 10^{-3}$ eV with a photon-axion coupling strength $g_{aγγ} < 10^{-10}GeV^{-1}$, where the limits are derived from astrophysical considerations. In this study, we present a novel way of constraining $g_{aγγ}$ by looking at the level of linear polarization i…
Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle-dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resultin…
This article describes a search for low-mass axion-like particles (ALPs) at the Large Hadron Collider (LHC). If ALPs were produced at the LHC via gluon-gluon fusion and decayed to bosons, the energy dependence of the measured diboson cross-sections would differ from the Standard Model expectation. Measurements of $WW$ and $Zγ$ differential cross-sections by the ATLAS collaboration are interpreted to constrain ALP couplings to $W$-, $Z$-bosons and photons assuming gluon-gluon-fusion production.
The non-resonant conversion of Cosmic Microwave Background (CMB) photons into scalar as well as light pseudoscalar particles such as axion-like particles (ALPs) in the presence of turbulent magnetic fields can cause a unique, spatially fluctuating spectral distortion in the CMB. We use the publicly available Planck temperature maps for the frequency channels (70-545 GHz) to obtain the first ALP distortion map using $45\%$ clean part of the sky. The $95^{th}$ percentile upper limit on the RMS fluctuation of ALP distortions from the cleanest part of the CMB sky at $15$ arcmin angular resolution …
We point out that stars in the mass window ~ 8-12 Msun can serve as sensitive probes of the axion-photon interaction, g_{Aγγ}. Specifically, for these stars axion energy losses from the helium-burning core would shorten and eventually eliminate the blue loop phase of the evolution. This would contradict observational data, since the blue loops are required, e.g., to account for the existence of Cepheid stars. Using the MESA stellar evolution code, modified to include the extra cooling, we conservatively find g_{Aγγ} <~ 0.8 * 10^{-10} GeV^{-1}, which compares favorably with the existing bounds.
