Search

Fuzzy dark matter (FDM), comprised of ultralight (⁠|$m \sim 10^{-22}\,{\rm eV}$|⁠) boson particles, has received significant attention as a viable alternative to cold dark matter (CDM), as it approximates CDM on large scales (⁠|${\gtrsim}1$|  Mpc) while potentially resolving some of its small-scale problems via kiloparsec-scale quantum interference. However, the most basic FDM model, with one free parameter (the boson mass), is subject to a tension: small boson masses yield the desired cores of dwarf galaxies but underpredict structure in the Lyman-α forest, while large boson masses render FDM effectively identical to CDM. This Catch-22 problem may be alleviated by considering an axion-like particle with attractive particle self-interactions. We simulate an idealized FDM halo with self-interactions parametrized by an energy decay constant |$f \sim 10^{15}~\rm {GeV}$| related to the axion symmetry-breaking conjectured to solve the strong-CP problem in particle physics. We observe solitons, a hallmark of FDM, condensing within a broader halo envelope, and find that the density profile and soliton mass depend on self-interaction strength. We propose generalized formulae to extend those from previous works to include self-interactions. We also investigate a critical mass threshold predicted for strong interactions at which the soliton collapses into a compact, unresolved state. We find that the collapse happens quickly, and its effects are initially contained to the central region of the halo. [ABSTRACT FROM AUTHOR]

Exploring the mysterious dark matter is a key quest in modern physics. Currently, detecting axions, a hypothetical particle proposed as a primary component of dark matter, remains a significant challenge due to their weakly interacting nature. Here we show at quantum level that in a cavity permeated by a magnetic field, the single axion-photon conversion rate is enhanced by the cavity quality factor and is quantitatively larger than the classical result by π/2. The axion cavity can be considered a quantum device emitting single photons with temporal separations. This differs from the classical picture and reveals a possibility for the axion cavity experiment to handle the signal sensitivity at the quantum level, e.g., a dual path quantum interferometry with cross-power and second-order correlation measurements. This scheme would greatly reduce the signal scanning time and improve the sensitivity of the axion-photon coupling, potentially leading to the direct observation of axions. Axions are the top contenders for explaining the enigmatic dark matter in the Universe. The authors present the inaugural quantum-level validation of a cavity's resonant boost to the conversion of axions into photons, thus employing a dual-path interferometry method can greatly enhance the signal-to-noise ratio in the experiments, enabling swifter scans and a better detection sensitivity for the evasive axion dark matter. [ABSTRACT FROM AUTHOR]

The axion anti-quark nugget (A Q ¯ N) model was developed to explain in a natural way the asymmetry between matter and antimatter in Universe. In this hypothesis, a similitude between the dark and the visible components exists. The lack of observability of any type of dark matter up to now, in particular A Q ¯ Ns, requires finding new ways of detecting these particles, if they exist. In spite of strong interaction with visible matter, for such objects a very small ratio of cross section to mass is expected and thus huge detector systems are necessary. This paper presents a new idea for the direct detection of the A Q ¯ Ns using minerals as natural rock deposits acting as paleo-detectors, where the latent signals of luminescence produced by interactions of A Q ¯ Ns are registered and can be identified as an increased and symmetrical deposited dose. The estimates were made for minerals widely distributed on Earth, for which the thermoluminescence (TL) signal is intense and if the thermal conditions are constant and with low temperatures, the lifetime of the latent signals is kept for geological time scales. [ABSTRACT FROM AUTHOR]

The cavity haloscope is among the most widely adopted experimental platforms designed to detect dark matter axions with its principle relying on the conversion of axions into microwave photons in the presence of a strong magnetic field. The Josephson parametric amplifier (JPA), known for its quantum-limited noise characteristics, has been incorporated into the detection system to capture the weakly interacting axion signals. However, the performance of the JPA can be influenced by its environment, leading to the potential unreliability of a predefined parameter set obtained in a specific laboratory setting. Furthermore, conducting a broadband search requires the consecutive characterization of the amplifier across different tuning frequencies. To ensure more reliable measurements, we utilize the Nelder–Mead technique as a numerical search method to dynamically determine the optimal operating conditions. This heuristic search algorithm explores the multidimensional parameter space of the JPA, optimizing critical characteristics such as gain and noise temperature to maximize signal-to-noise ratios for a given experimental setup. Our study presents a comprehensive analysis of the properties of a flux-driven JPA to demonstrate the effectiveness of the algorithm. This approach contributes to ongoing efforts in axion dark matter research by offering an efficient method to enhance axion detection sensitivity through the optimized utilization of JPAs. [ABSTRACT FROM AUTHOR]

I propose a unified model of particle physic and cosmology based on both a new extension of the standard particle model and the fundamental principle of the standard cosmology. Beyond the standard model, I introduce several species of dark fields with the dark symmetry of Z 2 ⊗ Z 2 ′ , the inflation field, cold dark matter (CDM) and dark energy (DE) are of course included among them. The model can coherently and completely describe the origin and evolution of the universe from the primordial inflation to the reheating, to the baryogenesis, to the current CDM and DE, and also the neutrino mass generation mechanism. For the energy evolution of each phase, I give its dynamical system of equations, and solve them by some special techniques. The numerical results can clearly show how each evolution is successfully implemented, furthermore, the model demonstrates that the DE genesis is purely from the CDM condensation, which is essentially a reverse process of the primordial slow-roll inflation, there is not the so-called "cosmological constant energy". By use of fewer input parameters, the model not only exactly reproduces the measured inflationary data and the current energy density budget, but also finely predicts such important values as the tensor-to-scalar ratio r 0. 0 5 ≈ 1. 6 8 × 1 0 − 6 , the inflaton mass M Φ ≈ 5. 0 5 × 1 0 1 0 GeV, the reheating temperature T r e ≈ 8. 2 9 × 1 0 1 0 GeV, the CDM mass M S ≈ 2 5 6 GeV, η B ≈ 6. 1 4 × 1 0 − 1 0 and h ≈ 0. 7 3 , in particular, the model smoothly clarifies and eliminates the "Hubble tension". In short, the unified model newly establishes the deeper and closer relations between particle physics and cosmology, therefore we expect the ongoing and future experiments to test the model. [ABSTRACT FROM AUTHOR]

The axion haloscope is the currently most sensitive method to probe the vanishingly small coupling of this prominent Dark Matter candidate to photons. To scan a sizeable axion Dark Matter parameter space, the cavities that make up the haloscope need to be tuned efficiently. In this article, we describe a novel technique to tune axion haloscopes around 8.4 GHz in a purely mechanical manner without the use of dielectrics. We achieve tuning by introducing a gap along the cavity geometry. A quality factor reduction of less than 20% is achieved experimentally for a tuning range of around 600 MHz at room temperature and at cryogenic temperatures for around 300 MHz. A larger tuning range would require an improved alignments mechanism. We present the results of a corresponding prototype and outline prospects to further develop this technique. [ABSTRACT FROM AUTHOR]

We investigate the effects of an early cosmological period dominated by primordial 2-2-holes on axion dark matter. The 2-2-holes emerge as a new family of horizonless classical solutions for ultracompact matter distributions in quadratic gravity, a candidate theory of quantum gravity. Thermal 2-2-holes, sourced by relativistic thermal gas, exhibit Hawking-like radiation and fulfill the entropy-area law before they become remnants with almost no radiation. In this paper, we consider the remnant contribution to dark matter (DM) small and adopt the axion DM scenario by the misalignment mechanism. We show that a 2-2-hole domination phase in the evolution of the universe changes the axion mass window, obtained from the dark matter abundance constraints. The biggest effect occurs when the remnants have the Planck mass, which is the case for a strongly coupled quantum gravity. The change in abundance constraints for the Planck mass 2-2-hole remnants amounts to that of the primordial black hole (PBH) counterpart. Therefore, since we use the revised constraints from gravitational waves on the initial fraction of 2-2-holes, the results here can also be considered the updated version of the PBH case. As a result, the lower limit on the axion mass is found as ma ~ 10-9 eV. Furthermore, the domination scenario itself constrains the remnant mass Mmin considerably. Given that we focus on the pre-BBN domination scenario in order not to interfere with BBN (Big Bang nucleosynthesis) constraints, the remnant mass window becomes mPl ≲ Mmin ≲ 0.1 g. [ABSTRACT FROM AUTHOR]

Fuzzy dark matter (FDM), an attractive dark matter candidate comprising ultralight bosons (axions) with a particle mass ma ∼ 10−22 eV, is motivated by the small-scale challenges of cold dark matter and features a kpc-size de Broglie wavelength. Quantum wave interference inside an FDM halo gives rise to stochastically fluctuating density granulation; the resulting gravitational perturbations could drive significant disc thickening, providing a natural explanation for galactic thick discs. Here we present the first self-consistent simulations of FDM haloes and stellar discs, exploring ma  = 0.2–1.2 × 10−22 eV and halo masses M h = 0.7–2.8 × 1011 M⊙. Disc thickening is observed in all simulated systems. The disc heating rates are approximately constant in time and increase substantially with decreasing ma , reaching d h /d t ≃ 0.04 (0.4) kpc Gyr−1 and |${\rm d}\sigma _z^2/{\rm d}t \simeq 4$| (150) km2 s−2 Gyr−1 for ma  = 1.2 (0.2) × 10−22 eV and |$M_{\rm h}=7\times 10^{10} \, \rm {M}_{\odot }$|⁠ , where h is the disc scale height and σ z is the vertical velocity dispersion. These simulated heating rates agree within a factor of two with the theoretical estimates of Chiang et al. confirming that the rough estimate of Church et al. overpredicts the granulation-driven disc heating rate by two orders of magnitude. However, the simulation-inferred heating rates scale less steeply than the theoretically predicted relation |${\rm d}\sigma ^2_z/{\rm d}t \propto m_a^{-3}$|⁠. Finally, we examine the applicability of the Fokker–Planck approximation in FDM granulation modelling and the robustness of the ma exclusion bound derived from the Galactic disc kinematics. [ABSTRACT FROM AUTHOR]

A collaboration between CNRS-Grenoble and IBS-CAPP Daejeon plans to build a Sikivie's type haloscope for axion/ALPs dark matter search at the Dine-Fischler-Srednicki-Zhitnitskii sensitivity for the 300--600 MHz range. It will be based on the large-bore superconducting "outsert" coil of the Grenoble hybrid magnet, providing a central magnetic field up to 9 T in an 810-mm warm bore diameter. This magnet has recently been successfully powered up to 8.5 T, achieving the first step of the electrical commissioning phase. The design principles of the cryostat with its double dilution refrigerators to cool below 50 mK, the light Cu RF cavity of 700-mm diameter, and its tuning rod(s) and the first stages of the measurement chain are presented. Perspectives for the targeted sensitivity assuming less than a 2-year integration time are given. [ABSTRACT FROM AUTHOR]

Ultralight axion (ULA) can be one of the potential candidates for dark matter. The extremely low mass of the ULA can lead to a de Broglie wavelength the size of galaxies which results in a suppression of the growth of structure on small scales. In this work, we forecast the constraint on the ULA particle mass m a and relative fraction to dark matter f a = Ωa/Ωd for the forthcoming Stage IV space-based optical survey equipment CSST (China Space Station Telescope). We focus on the CSST cosmic shear and galaxy clustering photometric surveys, and forecast the measurements of shear, galaxy, and galaxy–galaxy lensing power spectra (i.e. 3 × 2 pt). The effects of neutrino, baryonic feedback, and uncertainties of intrinsic alignment, shear calibration, galaxy bias, and photometric redshift are also included in the analysis. After performing a joint constraint on all the cosmological and systematical parameters based on the simulated data from the theoretical prediction, we obtain a lower limit of the ULA particle mass log10 (m a/eV) ≥ −22.5 and an upper limit of the ULA fraction f a ≤ 0.83 at 95 per cent confidence level, and log10 (m a/eV) ≥ −21.9 with f a ≤ 0.77 when ignoring the baryonic feedback. We find that the CSST photometric surveys can improve the constraint on the ULA mass by about one order of magnitude, compared to the current constraints using the same kind of observational data. [ABSTRACT FROM AUTHOR]

It has been recently claimed that the axion coupling to fermions is responsible for an oscillating electric dipole moment (EDM) in the background of axion dark matter. In this work, we re-examine the derivation of this effect. Contrary to previous studies, we point out the physical relevance of an axion boundary term, which is crucial in restoring the axion shift symmetry and drastically affects the EDM phenomenology. To describe the latter, we introduce the notion of a time-averaged effective axion EDM, which encodes the boundary term and whose magnitude depends on the oscillation regime. For slow oscillations, the boundary term washes out the standard oscillating EDM, resulting in an exact cancellation in the static limit. Conversely, during fast oscillations, the boundary term amplifies the effective EDM relatively to the standard EDM contribution. This observable is especially interesting in the case of the electron EDM. For an O (1) axion-electron coupling, the overall size of the effective EDM in the regime of intermediate or fast oscillations is comparable to the present static EDM limit. [ABSTRACT FROM AUTHOR]

In a recent study, we proposed an axion-electrodynamics model that consistently incorporates a lepton Dirac field into the gauge-invariant Lagrangian of a closed physical system. Our investigation delved toward potential applications of the model, with a focus on its implications in the realm of Dark Matter axions interacting with leptons in a nonlinear electrodynamics background. In the present work, we introduce an extended axion-electrodynamics model wherein the Bianchi identities are modified by the axion field. This leads to a modification of the energy conservation law for the fields: the Poynting theorem in a source-free region, in which the axion field is involved. By implementing a quantization scheme, our model can offer a novel approach for addressing the problem of axion production/conversion in the presence of electromagnetic and Dirac fields. [ABSTRACT FROM AUTHOR]

The Standard Model of electroweak interactions is based on the fundamental SU(2)weak × U(1)elect representation. It assumes massless neutrinos and purely left-handed massive W ± and Z0 bosons to which one should add the massless photon. The existence, verified experimentally, of neutrino oscillations poses a challenge to this scheme, since the oscillations take place between at least three massive neutrinos belonging to a mass hierarchy still to be determined. One should also take into account the possible existence of sterile neutrino species. In a somehow different context, the fundamental nature of the strong interaction component of the forces in nature is described by the, until now, extremely successful representation based on the SU(3)strong group which, together with the confining rule, give a description of massive hadrons in terms of quarks and gluons. To this is added the minimal U(1) Higgs group to give mass to the otherwise massless generators. This representation may also be challenged by the existence of both dark matter and dark energy, of still unknown composition. In this note, we shall discuss a possible connection between these questions, namely the need to extend the SU(3)strong × SU(2)weak × U(1)elect to account for massive neutrinos and dark matter. The main point of it is related to the role of axions, as postulated by Roberto Peccei and Helen Quinn. The existence of neutral pseudo-scalar bosons, that is, the axions, has been proposed long ago by Peccei and Quinn to explain the suppression of the electric dipole moment of the neutron. The associated U(1)PQ symmetry breaks at very high energy, and it guarantees that the interaction of other particles with axions is very weak. We shall review the axion properties in connection with the apparently different contexts of neutrino and dark matter physics. [ABSTRACT FROM AUTHOR]

We study the time evolution of magnetic fields in various configurations of spatially inhomogeneous pseudoscalar fields that are a coherent superposition of axions. For such systems, we derive a new induction equation for the magnetic field, which takes this inhomogeneity into account. Based on this equation, we study the evolution of a pair of Chern–Simons waves interacting with a linearly decreasing pseudoscalar field. The nonzero gradient of the pseudoscalar field leads to the mixing of these waves. We then consider the problem in a compact domain in the case where the initial Chern–Simons wave is mirror symmetric. The pseudoscalar field inhomogeneity then leads to an effective change in the dynamo parameter. Thus, the influence of a spatially inhomogeneous pseudoscalar field on the magnetic field evolution bears a strong dependence on the system geometry. [ABSTRACT FROM AUTHOR]

The axion offers a well-motivated solution to two fundamental questions in modern physics: the strong CP problem and the dark matter mystery. Cavity haloscopes, exploiting resonant enhancement of photon signals, provide the most sensitive searches for axion dark matter in the microwave region. However, current experimental sensitivities are limited to the O(100) µeV range, while recent theoretical predictions for the axion mass favor up to O(10²) µeV, suggesting the need of new experimental approaches that are suitable for higher mass regions. CAPP has developed/proposed several haloscopes effective for high-mass axion searches based on new cavity concepts and practical tuning mechanisms. They are characterized by large detection volumes and/or high quality factors at high frequencies, achieved by partitioning a single cavity into multiple cells, exploiting higher-order resonant modes, and constructing dielectric photonic crystal structures. Improving on the dish antenna haloscope scheme, a horn antenna array has also been proposed for volume-efficient broadband search in the THz region. We review these haloscope designs for sensitive search in the high-mass regions and discuss their impacts on future experiments. [ABSTRACT FROM AUTHOR]

Axions can be considered as good dark matter candidates. The detection of such light particles can be achieved by observing axion-induced atomic excitations. The target is in a magnetic field so that the m-degeneracy is removed, and the energy levels can be suitably adjusted. Using an axion-electron coupling indicated by the limit obtained by the Borexino experiment, which is quite stringent, reasonable axion absorption rates have been obtained for various atomic targets The obtained results depend, of course, on the atom considered through the parameters ϵ (the spin−orbit splitting) as well as δ (the energy splitting due to the magnetic moment interaction). This assumption allows axion masses in the tens of μ eV if the transition occurs between members of the same multiplet, i.e., | J 1 , M 1 = − J 1 〉 → | J 1 , M 1 = − J + 1 〉 , J 1 ≠ 0 , and axion masses in the range 1 meV–1 eV for transitions of the spin−orbit splitting type | J 1 , M = − J 1 〉 → | J 2 , M 2 = − J 1 + q 〉 , q = − 1 , 0 , 1 , i.e., three types of transition. The axion mass that can be detected is very close to the excitation energy involved, which can vary by adjusting the magnetic field. Furthermore, since the axion is absorbed by the atom, the calculated cross-section exhibits the behavior of a resonance, which can be exploited by experiments to minimize any background events. [ABSTRACT FROM AUTHOR]

In this paper, we report the use of a superconducting transmon qubit in a 3D cavity for quantum machine learning and photon counting applications. We first describe the realization and characterization of a transmon qubit coupled to a 3D resonator, providing a detailed description of the simulation framework and of the experimental measurement of important parameters, such as the dispersive shift and the qubit anharmonicity. We then report on a Quantum Machine Learning application implemented on a single-qubit device to fit the u-quark parton distribution function of the proton. In the final section of the manuscript, we present a new microwave photon detection scheme based on two qubits coupled to the same 3D resonator. This could in principle decrease the dark count rate, favoring applications like axion dark matter searches. [ABSTRACT FROM AUTHOR]

Within the framework of the extended Einstein–aether–axion theory, we studied the model of a two-level aetheric control over the evolution of a spatially isotropic homogeneous Universe filled with axionic dark matter. Two guiding functions are introduced, which depend on the expansion scalar of the aether flow being equal to the tripled Hubble function. The guiding function of the first type enters the aetheric effective metric, which modifies the kinetic term of the axionic system; the guiding function of the second type predetermines the structure of the potential axion field. We obtained new exact solutions to the total set of master equations in the model (with and without cosmological constant), and studied four analytically solvable submodels in detail, for which both guiding functions are reconstructed and illustrations of their behavior are presented. [ABSTRACT FROM AUTHOR]

The axion is a long-postulated boson that can simultaneously solve two fundamental problems of modern physics: the charge–parity symmetry problem in the strong interaction and the enigma of dark matter. In this work, we estimate, by means of Monte Carlo simulations, the sensitivity of the Dark-photons & Axion-Like particles Interferometer (DALI), a new-generation Fabry–Pérot haloscope proposed to probe axion dark matter in the 25–250 μ eV band. [ABSTRACT FROM AUTHOR]

We analyze the Axion Electrodynamics in a two-dimensional slab of finite width L containing a homogeneous and isotropic dielectric medium with constant permittivity and permeability. We start from the known decomposition of modes in the nonaxion case and then solve perturbatively the governing equations for the electromagnetic fields to which the axions are also coupled. This is a natural approach, since the finiteness of L destroys the spatial invariance of the theory in the z-direction normal to the plates. In this way, we derive the value of the axion-generated rotation angle of the electric and magnetic fields after their passage through the slab, and use the obtained results to calculate the Casimir force between the two conducting plates. Our calculations make use of the same method as previously outlined by [J. S. Høye and I. Brevik, Eur. Phys. J. Plus 135, 271 (2020)] for the case of Casimir calculations in chiral media and extend former results on the Casimir force in Axion Electrodynamics. [ABSTRACT FROM AUTHOR]

Recent advances in photon detectors have provided exceptional sensitivities to dark matter with high angular resolution. Motivated by this, we present a detailed study of photon flux from dark matter decay in dwarf spheroidal galaxies (dSphs) by focusing on the detectors with arcsecond-level field of view and/or angular resolution. We propose to use differential D -factors since such detectors are sensitive to their dark matter distributions. We carefully estimate the differential D -factors of 35 dSphs. By using the differential D -factors, it turns out that the resulting signal flux can have a more than O (1–10) enhancement compared to conventional estimations. Based on this analysis, we find that the Infrared Camera and Spectrograph (IRCS) installed on the 8.2 m Subaru Telescope can be an excellent dark matter detector for the mass in the eV range, particularly axion-like particles (ALPs). Observing the Draco or Ursa Major II dSphs with the IRCS for O (1) night will enable us to place the most stringent bound for the ALP dark matter in the mass range of 1 eV ≲ m a ≲ 2 eV. [ABSTRACT FROM AUTHOR]

Calibration of nuclear‐magnetic‐resonance‐based searches for axion‐like dark matter can be performed by free induction decay (FID) measurements. This manu‐ script describes FID experiments on several solid materials, motivated by the Cosmic Axion Spin Precession Experiment (CASPEr) program. Experiments with207Pb nuclear spins in ferroelectrics, lead magnesium niobate‐lead titanate (PbMg1/3Nb2/3O3)2/3−${}_{2/3}-$ (PbTiO3)1/3 (PMN‐PT) and lead zirconium titante PbZr0.52Ti0.48O3 (PZT) are directly relevant to the CASPEr‐electric search for the electric dipole moment interaction of axion‐like dark matter. Experiments with 31P nuclear spins in gadolinium‐doped hydroxypyromorphite Pb4.95Gd0.05(PO4)3OH (HPM:Gd) are used for apparatus calibration. The measurements characterized the nuclear spin ensemble coherence time and the magnetic resonance detection sensitivity for these samples. Calibration is performed using small tip‐angle pulses. [ABSTRACT FROM AUTHOR]

In this paper, the time evolution of signals in axion dark matter experiments is considered from a quantum perspective. The aim is to illuminate the specific case of axion experiments and not to contribute new results to the general discussion of the quantum/classical connection. Classically, one expects a signal oscillating with a frequency equal to the axion mass whose amplitude is slowly rising due to the tiny interaction of the axions with ordinary matter. Quantum mechanically the latter time‐scale arises from the small splitting in the energy levels induced by the interaction between the axions and the experiment. It is always present in suitable, sensitive experiments. Signals that oscillate with the axion mass arise from processes changing the axion number. For certain observables such oscillations are absent for special initial quantum states of the axions. Examples are shown where these special states can be affected by the experiment such that a signal oscillating with the axion mass re‐appears. Suitable correlators that feature an oscillation with the axion mass are discussed, and comments on the connection to the classical treatment are provided. Explicitly, the Cosmic Axion Spin Precession Experiment (CASPEr) is studied, but these findings are expected to be adaptable to other axion dark matter searches. [ABSTRACT FROM AUTHOR]

Galactic dark matter may consist of axionlike particles (ALPs) that can be described as an "ultralight bosonic field" oscillating at the ALP Compton frequency. The ALP field can be searched for using nuclear magnetic resonance (NMR), where resonant precession of spins of a polarized sample can be sensitively detected. The ALP mass to which the experiment is sensitive is scanned by sweeping the bias magnetic field. The scanning either results in detection of ALP dark matter or rules out ALP dark matter with sufficiently strong couplings to nuclear spins over the range of ALP masses corresponding to the covered span of Larmor frequencies. In this work, scanning strategies are analyzed with the goal of optimizing the parameter‐space coverage via a proper choice of experimental parameters (e.g., the effective transverse relaxation time). [ABSTRACT FROM AUTHOR]

The low energy interactions between axions and electromagnetic fields that arise in models with heavy dyons charged under a spontaneously broken global axial U(1) symmetry are derived using the path integral approach. Hence, generic axion‐Maxwell equations relevant for experimental searches are obtained. It is found that the structure of the axion Maxwell equations can be significantly different compared to what is normally assumed in the literature, as the derived equations feature new axion‐dependent terms including CP‐violating ones. The new terms can reconcile the Peccei–Quinn solution to the strong CP problem with astrophysical axion hints, as well as give unique signatures in light‐shining‐through‐wall and haloscope experiments. Moreover, via the latter signatures, these experiments can indirectly probe the existence of heavy dyons. [ABSTRACT FROM AUTHOR]

Numerous observations suggest that there exist undiscovered beyond‐the‐standard‐model particles and fields. Because of their unknown nature, these exotic particles and fields could interact with standard model particles in many different ways and assume a variety of possible configurations. Here, an overview of the global network of optical magnetometers for exotic physics searches (GNOME), the ongoing experimental program designed to test a wide range of exotic physics scenarios, is presented. The GNOME experiment utilizes a worldwide network of shielded atomic magnetometers (and, more recently, comagnetometers) to search for spatially and temporally correlated signals due to torques on atomic spins from exotic fields of astrophysical origin. The temporal characteristics of a variety of possible signals currently under investigation such as those from topological defect dark matter (axion‐like particle domain walls), axion‐like particle stars, solitons of complex‐valued scalar fields (Q‐balls), stochastic fluctuations of bosonic dark matter fields, a solar axion‐like particle halo, and bursts of ultralight bosonic fields produced by cataclysmic astrophysical events such as binary black hole mergers are surveyed. [ABSTRACT FROM AUTHOR]

Axions are a well‐motivated dark matter candidate, with a host of experiments around the world searching for direct evidence of their existence. The ORGAN Experiment is a type of axion detector known as an axion haloscope, which takes the form of a cryogenic resonant cavity embedded in a strong magnetic field. ORGAN recently completed Phase 1a, a scan for axions ≈65 µeV, and placed the most stringent limits to date on the dark matter axion–photon coupling in this region, |gaγγ|≤3×10−12${|g_{a\gamma \gamma }|}\le 3\times 10^{-12}$. It has been shown that axion haloscopes such as ORGAN are automatically sensitive to other kinds of dark matter candidates, such as dark photons, scalar field/dilaton dark matter, and exotic axion–electromagnetic couplings motivated by quantum electromagnetodynamics. The exclusion limits placed on these various dark matter candidates are computed by ORGAN 1a, and sensitivity for some future ORGAN phases are projected. In particular, the dark photon limits are the most sensitive to date in some regions of the parameter space. [ABSTRACT FROM AUTHOR]

A plasma haloscope has recently been proposed as a feasible approach to extend the search for dark matter axions above 10 GHz (≈40 μ$\umu$eV), whereby the microwave cavity in a conventional axion haloscope is supplanted by a wire array metamaterial. Since the plasma frequency of a metamaterial is determined by its unit cell, and is thus a bulk property, a metamaterial resonator of any frequency can be made arbitrarily large, in contrast to a microwave cavity which incurs a steep penalty in volume with increasing frequency. To assess the actual potential of this concept as a practical dark matter haloscope, the basic properties of wire array metamaterials have been investigated through an extensive series of S21 measurements in the 10 GHz range. This report presents some new systematics of wire array metamaterials themselves including the approach to full plasmonic behavior, the applicability of the semianalytic theory of Belov, and estimates of the loss term which bode favorably for the plasmonic haloscope application. This present work constitutes the first precision test of the semianalytic theory of Belov et al., for which the predicted plasma frequency agrees with the experimental value at the 0.1% level. [ABSTRACT FROM AUTHOR]

It has been hypothesized that dark matter is comprised of ultra-light bosons whose collective phenomena can be described as a scalar field undergoing coherent oscillations. Examples include axion and fuzzy dark matter models. In this ultra-light dark matter (ULDM) scenario, the harmonic variation in the field's energy–momentum tensor sources an oscillating component of the gravitational potential that we show can resonantly excite stellar oscillations. A mathematical framework for predicting the amplitude of these oscillations is developed, which reveals that ULDM predominantly excites p-modes of degree l  = 1. An investigation of resonantly excited solar oscillations is presented, from which we conclude that dark matter induced oscillations of the Sun are likely undetectable. We discuss prospects for constraining ULDM using other stellar objects. [ABSTRACT FROM AUTHOR]

In the non-relativistic limit, two types of dark matter axion interactions with fermions are thought to dominate: one is induced by the spatial gradient of the axion field and called the axion wind, and the other by the time-derivative of the axion field, generating axioelectric effects. By generalizing Schiff theorem, it is demonstrated that this latter operator is actually strongly screened. For a neutral fermion, it can be entirely rotated away and is unobservable. For charged fermions, the only effect that can peek through the screening is an axion-induced electric dipole moment (EDM). These EDMs are not related to the axion coupling to gluons, represent a prediction of the Dirac theory analogous to the g = 2 magnetic moments, are not further screened by the original Schiff theorem, and are ultimately responsible for inducing the usual axioelectric ionization. The two main phenomenological consequences are then that first the axion-induced nucleon EDM could be significantly larger than expected from the axion gluonic coupling, and second, that the electron EDM could also become available, and could actually be highly sensitive to relic axions. [ABSTRACT FROM AUTHOR]

Axion Dark Matter (DM) is studied on the formation of SuperMassive Black Holes (SMBH) at high red shift z. It is shown that the attractive self-interaction of this DM may resolve the tension between the large mass with high angular momentum of SMBH and its early time formation. We consider the ultra-light axion DM around O (1 0 − 2 1) eV as its origin, which may also cause nano-Hz stochastic gravitational wave background recently observed. [ABSTRACT FROM AUTHOR]

The QCD (Quantum ChromoDynamics) axion emerged as one of the best-motivated dark matter candidates. In 2018, the Axion Dark Matter eXperiment (ADMX), one of the U.S. Department of Energy's "Gen 2" flagship dark-matter projects, demonstrated first sensitivity to the highly plausible "DFSZ" dark matter axion couplings over a small frequency range. We anticipate this development marks the first step in constructing yet more powerful experiments that can explore large swaths of the axion parameter space at high sensitivity and result in a discovery. But, realizing this requires advances in both our understanding of the theory and experiment design. Between 25 January and 27 January 2021, the "Axions Beyond Gen 2 Workshop" was held, where selected members of the community discussed our broad understanding of the QCD axion and charted a course for future experiments having sensitivity and mass reach well beyond the current "Gen 2" experiments. These proceedings are summaries of the topics presented and discussed. [ABSTRACT FROM AUTHOR]

The dynamics of spin in external electromagnetic, gravitational, and axion fields is analyzed in the framework of the gravitoelectromagnetism approach in Einstein's general relativity theory. We consistently extend the recent studies from the flat Minkowski geometry to the curved spacetime manifolds, contributing to the discussion of the possible new role of a precessing spin as an "axion antenna" that can be used to detect the hypothetical axion-like dark matter. The formalism developed helps to clarify the subtle influence of the gravitational/inertial and axion fields in the ultra-sensitive high-energy spin experiments with charged particles and neutrons at accelerators and storage rings devoted to testing fundamental physical symmetries, including attempts to establish the nature of dark matter in the Universe. [ABSTRACT FROM AUTHOR]

In the near future BabyIAXO will be the most powerful axion helioscope, relying on a custom‐made magnet of two bores of 70 cm diameter and 10 m long, with a total available magnetic volume of more than 7 m3. In this document, it proposes and describe the implementation of low‐frequency axion haloscope setups suitable for operation inside the BabyIAXO magnet. The RADES proposal has a potential sensitivity to the axion‐photon coupling gaγ$g_{a\gamma }$ down to values corresponding to the KSVZ model, in the (currently unexplored) mass range between 1 and 2 μ$\umu$ eV, after a total effective exposure of 440 days. This mass range is covered by the use of four differently dimensioned 5‐meter‐long cavities, equipped with a tuning mechanism based on inner turning plates. A setup like the one proposed will also allow an exploration of the same mass range for hidden photons coupled to photons. An additional complementary apparatus is proposed using LC circuits and exploring the low energy range (≈10−4−10−1μ$\approx \ 10^{-4}-10^{-1} \ \umu$ eV). The setup includes a cryostat and cooling system to cool down the BabyIAXO bore down to about 5 K, as well as an appropriate low‐noise signal amplification and detection chain. [ABSTRACT FROM AUTHOR]

Dark matter (DM) can be composed of a collection of axions, or axion-like particles (ALPs), whose existence is due to the spontaneous breaking of the Peccei–Quinn U (1) symmetry, which is the most compelling solution of the strong C P -problem of quantum chromodynamics (QCD). Axions must be spin-0 particles with very small masses and extremely weak interactions with themselves as well as with the particles that constitute the Standard Model. In general, the physics of axions is detailed by a quantum field theory of a real scalar field, ϕ. Nevertheless, it is more convenient to implement a nonrelativistic effective field theory with a complex scalar field, ψ , to characterize the mentioned axions in the low-energy regime. A possible application of this equivalent description is for studying the collapse of cold dark matter into more complex structures. There have been a few derivations of effective Lagrangians for the complex field ψ , which were all equivalent after a nonlocal space transformation between ϕ and ψ was found, and some other corrections were introduced. Our contribution herein is to further provide higher-order corrections; in particular, we compute the effective field theory Lagrangian up to order (ψ * ψ) 5 , also incorporating the fast-oscillating field fluctuations into the dominant slowly varying nonrelativistic field. [ABSTRACT FROM AUTHOR]

If a light axion is present during inflation and becomes part of dark matter afterwards, its quantum fluctuations contribute to dark matter isocurvature. In this article, we introduce a whole new suite of cosmological observables for axion isocurvature, which could help test the presence of axions, as well as its coupling to the inflaton and other heavy spectator fields during inflation such as the radial mode of the Peccei-Quinn field. They include correlated clock signals in the curvature and isocurvature spectra, and mixed cosmological-collider non-Gaussianities involving both curvature and isocurvature fluctuations with shapes and running unconstrained by the current data analyses. Taking into account of the existing strong constraints on axion isocurvature fluctuations from the CMB, these novel signals could still be sizable and potentially observable. In some models, the signals, if observed, could even help us significantly narrow down the range of the inflationary Hubble scale, a crucial parameter difficult to be determined in general, independent of the tensor mode. [ABSTRACT FROM AUTHOR]

In this work, we study the autonomous dynamical system of different F (R) models in the formalism of holographic dark energy using the generalized Nojiri–Odintsov cut-off. We explicitly give the expression of the fixed points as functions of the infrared cut-off for vacuum F (R) gravity in flat and non-flat FRW background and for F (R) coupling axion dark matter. Each fixed point component can be taken as a condition on the cut-off and on the expression of F (R) , leading to physically interesting constraints on these functions. [ABSTRACT FROM AUTHOR]

Haloscopes, microwave resonant cavities utilized in detecting dark matter axions within powerful static magnetic fields, are pivotal in modern astrophysical research. This paper delves into the realm of cylindrical geometries, investigating techniques to augment volume and enhance compatibility with dipole or solenoid magnets. The study explores volume constraints in two categories of haloscope designs: those reliant on single cavities and those employing multicavities. In both categories, strategies to increase the expanse of elongated structures are elucidated. For multicavities, the optimization of space within magnets is explored through 1D configurations. Three subcavity stacking approaches are investigated, while the foray into 2D and 3D geometries lays the groundwork for future topological developments. The results underscore the efficacy of these methods, revealing substantial room for progress in cylindrical haloscope design. Notably, an elongated single cavity design attains a three-order magnitude increase in volume compared to a WC-109 standard waveguide-based single cavity. Diverse prototypes featuring single cavities, 1D, 2D, and 3D multicavities highlight the feasibility of leveraging these geometries to magnify the volume of tangible haloscope implementations. [ABSTRACT FROM AUTHOR]

The signal to noise ratio efficiency ϵSNR in axion dark matter searches has been estimated using large-statistic simulation data reflecting the background information and the expected axion signal power obtained from a real experiment. This usually requires a lot of computing time even with the assistance of powerful computing resources. Employing a Savitzky-Golay filter for background subtraction, in this work, we estimated a fully analytical ϵSNR without relying on large-statistic simulation data, but only with an arbitrary axion mass and the relevant signal shape information. Hence, our work can provide ϵSNR using minimal computing time and resources prior to the acquisition of experimental data, without the detailed information that has to be obtained from real experiments. Axion haloscope searches have been observing the coincidence that the frequency independent scale factor ξ is approximately consistent with the ϵSNR. This was confirmed analytically in this work, when the window length of the Savitzky-Golay filter is reasonably wide enough, i.e., at least 5 times the signal window. [ABSTRACT FROM AUTHOR]

Ignorance of the initial condition for the axion dynamics in the early Universe has led us to consider an O(1) valued initial amplitude, and that prefers the decay constant, Fa, of the QCD axion to be an intermediate scale such as 1012 GeV in order to explain the dark matter abundance. We explore a cosmological scenario of Fa being much larger than 1012 GeV by considering the axion and modulus dynamics during inflation to set the initial amplitude. We show that if the volume modulus (radion) of the extra-dimension is stabilized mainly by the QCD contribution to the modulus potential during inflation, the QCD axion with the string-scale decay constant obtains a mass around the inflationary Hubble parameter. This means that the axion rolls down to the θ = 0 minimum during the inflation realizing almost vanishing initial amplitude, and the inflationary quantum fluctuation can be the dominant source of the current number density of axions. We find natural parameter regions where the axion explains the cold dark matter of the Universe, while the constraint on the isocurvature perturbation is avoided. The presence of the axion miniclusters or axion stars are predicted in a wide range of parameters, including the one explains the Subaru-HCS microlensing event. [ABSTRACT FROM AUTHOR]

Axions provide a solution to the strong CP problem and are excellent dark matter candidates. The presence of additional sources of CP violation, for example to account for the matter/antimatter asymmetry of the universe, can lead to CP-violating interactions between axions and Standard Model fields. In case axions form a coherent dark matter background, this leads to time-oscillating fundamental constants such as the fine-structure constant and particle masses. In this work we compare the sensitivity of various searches for CP-odd axion interactions. These include fifth-force experiments, searches for time-oscillating constants induced by axion dark matter, and direct limits from electric dipole moment experiments. We show that searches for oscillating constants can outperform fifth-force experiments in the regime of small axion masses, but, in general, do not reach the sensitivity of electric dipole moment experiments. [ABSTRACT FROM AUTHOR]

We explore the axionic dark matter search sensitivity with a narrow-band detection scheme aimed at the axion-photon conversion by a static electric field inside a cylindrical capacitor. An alternating magnetic field signal is induced by effective currents as the axion dark matter wind flows perpendicularly through the electric field. At low axion masses, such as in a KKLT scenario, front-end narrow band filtering is provided by using LC resonance with a high Q factor, which enhances the detectability of the tiny magnetic field signal and leads to thermal noise as the major background that can be reduced under cryogenic conditions. We demonstrate that high g a γ sensitivity can be achieved by using a strong electric field E ∼ MVm - 1 . The QCD axion theoretical parameter space would require a high E ∼ GVm - 1 field strength. Using the static electric field scheme essentially avoids exposing the sensitive superconducting pickup to an applied laboratory magnetic field. [ABSTRACT FROM AUTHOR]

In this work, we studied the phase space of f (R) gravity in the presence of a misalignment axion, including parity violating Chern–Simons terms. We construct the autonomous dynamical system by using appropriate dimensionless variables and find the cosmological attractors of the phase space, which are basically the fixed points of the autonomous dynamical system. We focus on the R 2 model and the misalignment axion potential near the minimum. We demonstrate that the Chern–Simons terms have no effect on the phase space. We found four distinct, possibly unstable fixed points with physical significance. Specifically, we found two identical de Sitter fixed points, one radiation domination fixed point, and one dark matter dominated fixed point. Thus, in the presence of a kinetic misalignment axion, the vacuum f (R) gravity contains all of the cosmological fixed points that can characterize all of the known evolution eras of our universe. [ABSTRACT FROM AUTHOR]

We consider an isotropic homogeneous cosmological model with five interacting elements: first, the dynamic aether presented by a unit timelike vector field; second, the pseudoscalar field describing an axionic component of the dark matter; third, the cosmic dark energy, described by a rheologic fluid; fourth, the non-axionic dark matter coupled to the dark energy; and fifth, the gravity field. We show that the early evolution of the Universe described by this model can include two specific epochs: the first one can be characterized as a super-inflation epoch; the second epoch is associated with an oscillatory regime. The dynamic aether carries out a regulatory mission; the rheologic dark fluid provides the specific features of the spacetime evolution. The oscillations of the scale factor and of the Hubble function are shown to switch on the parametric (Floquet-type) mechanism of the axion number growth. [ABSTRACT FROM AUTHOR]

Ultralight axion-like particles are well-motivated relics that might compose the cosmological dark matter and source anomalous time-dependent magnetic fields. We report on terrestrial bounds from the Noble And Alkali Spin Detectors for Ultralight Coherent darK matter (NASDUCK) collaboration on the coupling of axion-like particles to neutrons and protons. The detector uses nuclei of noble-gas and alkali-metal atoms and operates in the Spin-Exchange Relaxation-Free (SERF) regime, achieving high sensitivity to axion-like dark matter fields. Conducting a month-long search, we cover the mass range of 1.4 × 10−12 eV/c2 to 2 × 10−10 eV/c2 and provide limits which supersede robust astrophysical bounds, and improve upon previous terrestrial constraints by over two orders of magnitude for many masses within this range for protons, and up to two orders of magnitude for neutrons. These are the sole reliable terrestrial bounds reported on the coupling of protons with axion-like dark matter, covering an unexplored terrain in its parameter space. Axions are hypothetical particles that constitute leading candidates for the identity of dark matter. Here, the authors improve previous exclusion bounds on axion-like particles in the range of 1.4–200 peV, and report direct terrestrial limits on the coupling of protons and neutrons with axion-like dark matter. [ABSTRACT FROM AUTHOR]

We investigate the correction to the potential that gives rise to the bound orbits and radiation from non-spinning inspiralling binary black holes in a dark matter environment consisting of axion-like particles and dark photons using the techniques of Worldline Effective Field Theory. We compute the conservative dynamics up to 1PN order for gravitational, electromagnetic, and Proca fields and up to 2PN order for the scalar field. The effect of axion-electromagnetic coupling (gaγγ) arises to the conservative dynamics at 2.5PN order and the kinetic mixing constant (γ) at 1PN order. Furthermore, we calculate the radiation due to the various fields present in our theory. We find that the contribution of gaγγ to the gravitational radiation appears at N(7)LO and to the scalar radiation appears at N(5)LO. We also find that these radiative corrections due to the coupling gaγγ vanishes for any orbit confined to a plane because of the existence of a binormal like term in effective radiative action but give rise to non-zero contributions for any orbit that lies in three dimensions. Last but not the least, γ contributes to the gravitational radiation at N(2)LO and N(4)LO. [ABSTRACT FROM AUTHOR]

We aim to search for axion-like particles in the eV mass range using a variable-angle stimulated resonance photon collider (SRPC) with three intense laser beams. By changing angle of incidence of the three beams, the center-of-mass-system collision energy can be varied and the eV mass range can be continuously searched for. In this paper, we present the design and construction of such a variable-angle three-beam SRPC ( t SRPC ), the verification of the variable-angle mechanism using a calibration laser, and realistic sensitivity projections for searches in the near future. [ABSTRACT FROM AUTHOR]