Search

The axion is a hypothetical particle motivated to address the strong CP problem, and is one of the appealing dark matter candidates. Numerous experimental searches for dark matter axions have been proposed relying on their coupling with photons. The classical equations of motion for the axion-photon coupling are well known but need to be fully computed for complex experimental setups. The partial differential equations of axion electrodynamics can be numerically solved using finite element methods. In this work, we simulate axion electrodynamics using COMSOL Multiphyics, a commercially available simulation software, for various experimental schemes, including the dish antenna haloscope, cavity haloscope, dielectric haloscope, and axion-photon regeneration. We show that the numerical results are in good agreement with the analytical solutions., Comment: 6 pages, 2 figures

In the search for axion dark matter, the cavity-based haloscope offers the most sensitive approach to the theoretically interesting models in the microwave region. However, experimental searches have been limited to relatively low masses up to a few tens of $\mu$eV, benefiting from large detection volumes and high quality factors for a given experimental setup. We propose a new cavity design suitable for axion searches in higher mass regions with enhanced performance. The design features a periodic arrangement of dielectric material in a conventional conducting cavity where the resonant frequency is determined by the interspace. This photonic crystal haloscope can make full use of a given volume even at high frequencies while substantially improving the cavity quality factor. An auxetic structure is considered to deploy the array for two-dimensional frequency tuning. We present the characteristics of this haloscope design and demonstrate its feasibility for high-mass axion searches., Comment: 7 pages, 9 figures

The cavity haloscope provides a highly sensitive method to search for dark matter axions in the microwave regime. Experimental attempts to enhance the sensitivity have focused on improving major aspects, such as producing strong magnetic fields, increasing cavity quality factors, and achieving lowest possible noise temperatures. Minor details, however, also need to be carefully considered in realistic experimental designs. They are associated with non-uniform magnetic fields over the detection volume, noise propagation under attenuation and temperature gradients, and thermal disequilibrium in the cavity system. We take analytical approaches to these topics and offer optimal treatments for improved performance., Comment: 17 pages, 8 figures

We present the first results of a search for invisible axion dark matter using a multiple-cell cavity haloscope. This cavity concept was proposed to provide a highly efficient approach to high mass regions compared to the conventional multiple-cavity design, with larger detection volume, simpler detector setup, and unique phase-matching mechanism. Searches with a double-cell cavity superseded previous reports for the axion-photon coupling over the mass range between 13.0 and 13.9$\,\mu$eV. This result not only demonstrates the novelty of the cavity concept for high-mass axion searches, but also suggests it can make considerable contributions to the next-generation experiments., Comment: 6 pages, 5 figures

In multiple inflation scenario having two inflations with an intermediate matter-dominated phase, the power spectrum is estimated to be enhanced on scales smaller than the horizon size at the beginning of the second inflation, $k > k_{\rm b}$. We require $k_{\rm b} > 10 {\rm Mpc}^{-1}$ to make sure that the enhanced power spectrum is consistent with large scale observation of cosmic microwave background (CMB). We consider the CMB spectral distortions generated by the dissipation of acoustic waves to constrain the power spectrum. The $\mu$-distortion value can be $10$ times larger than the expectation of the standard $\Lambda$CDM model ($\mu_{\Lambda\mathrm{CDM}} \simeq 2 \times 10^{-8}$) for $ k_{\rm b} \lesssim 10^3 {\rm Mpc}^{-1}$, while the $y$-distortion is hardly affected by the enhancement of the power spectrum., Comment: 16 pages, 5 figures