Search

Sonic crystal acoustic screens have been in progressive research and development in the last two decades as a technical solution for mitigating traffic noise. Their behaviour is quite different from that observed in classical barriers, with the latter being based on physically blocking the direct sound propagation path (only allowing diffracted noise to reach sensible receivers), and sonic crystals providing attenuation efficiency based on the creation of band-gaps at specific frequency ranges, due to the Bragg's interference phenomenon. The distinct physical mechanisms of these two types of noise barriers complicates the use of classical simplified or even numerical models developed for traditional barriers to simulate and predict the attenuation performance of a sonic crystal, and alternative methods become thus required. In the acoustics scientific literature, several authors have proposed estimation and simulation methods based on different numerical tools to predict the sound insulation provided by these new noise abatement solutions. This paper presents a comparative evaluation of some of these methods, with emphasis to the assessment of their accuracy versus memory usage in order to determine which one is the most suitable for optimization methodologies in the design of new devices with improved acoustic performance., Comment: 18 pages, 4 figures

In this work we present an integrated photogrammetric-acoustic technique that, together with the construction of a scaled wind tunnel, allows us to experimentally analyze the permeability behavior of a new type of acoustic screens based on a material called sonic crystal. Acoustic screens are devices used to reduce the noise, mostly due to the communication infrastructures, in its transmission phase from the source to the receiver. The main constructive difference between these new screens and the classic ones is that the first ones are formed by arrays of acoustic scatterers while the second ones are formed by continuous walls. This implies that, due to their geometry, screens based on sonic crystals are permeable to wind and water, unlike the classic ones. This fact may allow the use of these new screens in sandy soils, where sand would pass through the screen avoiding the formation of sand dunes that are formed in classic screens and drastically reduce their acoustic performance. In this work, the movement of the sand and the resulting acoustic attenuation in these new screens are analyzed qualitatively comparing the results with those obtained with the classic ones, obtaining interesting results under the acoustic point of view, Comment: 17 pages, 8 figures

The correction of transcranial focused ultrasound aberrations is a relevant topic for enhancing various non-invasive medical treatments. Nowadays, the most widely accepted method to improve focusing is the emission through multi-element phased arrays; however, a new disruptive technology, based on 3D printed holographic acoustic lenses, has recently been proposed overcoming the spatial limitations of phased arrays due to the submillimetric precision of the latest generation of 3D printers. This works aims to optimize this recent solution; particularly, the preferred acoustic properties of the polymers used for printing the lens are systematically analyzed, paying special attention to the effect of p-wave speed and its relationship to the achievable voxel size of 3D printers. Results from simulations and experiments clearly show that there are optimal ranges for lens thickness and p-wave speed, fairly independent of the emitted frequency, the transducer aperture, or the transducer-target distance, given a particular voxel size, Comment: 24 pages, 9 figures

Cold dark matter axions produced in the post-inflationary Peccei-Quinn symmetry breaking scenario serve as clear targets for their experimental detection, since it is in principle possible to give a sharp prediction for their mass once we understand precisely how they are produced from the decay of global cosmic strings in the early Universe. In this paper, we perform a dedicated analysis of the spectrum of axions radiated from strings based on large scale numerical simulations of the cosmological evolution of the Peccei-Quinn field on a static lattice. Making full use of the massively parallel code and computing resources, we executed the simulations with up to $11264^3$ lattice sites, which allows us to improve our understanding of the dependence on the parameter controlling the string tension and thus give a more accurate extrapolation of the numerical results. We found that there are several systematic effects that have been overlooked in previous works, such as the dependence on the initial conditions, contaminations due to oscillations in the spectrum, and discretisation effects, some of which could explain the discrepancy in the literature. We confirmed the trend that the spectral index of the axion emission spectrum increases with the string tension, but did not find a clear evidence of whether it continues to increase or saturates to a constant at larger values of the string tension due to the severe discretisation effects. Taking this uncertainty into account and performing the extrapolation with a simple power law assumption on the spectrum, we find that the dark matter mass is predicted in the range of $m_a \approx 95$-$450\,\mu\mathrm{eV}$., Comment: 52 pages, 46 figures; revised version of the manuscript, accepted for publication in JCAP

A consequence of QCD axion dark matter being born after inflation is the emergence of small-scale substructures known as miniclusters. Although miniclusters merge to form minihalos, this intrinsic granularity is expected to remain imprinted on small scales in our galaxy, leading to potentially damaging consequences for the campaign to detect axions directly on Earth. This picture, however, is modified when one takes into account the fact that encounters with stars will tidally strip mass from the miniclusters, creating pc-long tidal streams that act to refill the dark matter distribution. Here we ask whether or not this stripping rescues experimental prospects from the worst-case scenario in which the majority of axions remain bound up in unobservably small miniclusters. We find that the density sampled by terrestrial experiment on mpc-scales will be, on average, around 70--90\% of the average local DM density, and at a typical point in the solar neighbourhood, we expect most of the dark matter to be comprised of debris from $\mathcal{O}(10^2$--$10^3)$ overlapping streams. If haloscopes can measure the axion signal with high-enough frequency resolution, then these streams are revealed in the form of an intrinsically spiky lineshape, in stark contrast with the standard assumption of a smooth, featureless Maxwellian distribution -- a unique prediction that constitutes a way for experiments to distinguish between pre and post-inflationary axion cosmologies., Comment: 5 + 9 pages, matches journal version

The properties of axion miniclusters and of the voids between them can have very strong implications for the discovery of axions and the dark matter of the Universe. These properties can be strongly affected by axion dynamics in the early Universe, such as the axion string network and the non-linear dynamics around the QCD phase transition. Recently, improvements in numerical simulation techniques have allowed us to calculate the dark matter axion field from axion strings and QCD effects using different methods: directly with low-tension strings but high resolution, directly with effective high-tension strings, or indirectly by extrapolating an attractor solution. In this work, we study the properties of miniclusters in the different approaches used in the literature. We find that, while there are substantial differences in the mass distribution and internal density profiles, globally there is a similar energy distribution between minicluster halos and voids., Comment: 17 pages, 6 figures

In the scenario in which QCD axion dark matter is produced after inflation, the Universe is populated by large inhomogeneities on very small scales. Eventually, these fluctuations will collapse gravitationally to form dense axion miniclusters that trap up to $\sim$75% of the dark matter within asteroid-mass clumps. Axion miniclusters are physically tiny however, so haloscope experiments searching for axions directly on Earth are much more likely to be probing ``minivoids'' -- the space in between miniclusters. This scenario seems like it ought to spell doom for haloscopes, but while these minivoids might be underdense, they are not totally devoid of axions. Using Schr\"odinger-Poisson and N-body simulations to evolve from realistic initial field configurations, we quantify the extent to which the local ambient dark matter density is suppressed in the post-inflationary scenario. We find that a typical experimental measurement will sample an axion density that is only around 10% of the expected galactic dark matter density. Our results also have implications for experimental campaigns lasting longer than a few years, as well as broadband haloscopes that have sensitivity to transient signatures. We show that for a $\mathcal{O}$(year)-long integration times, the measured dark matter density should be expected to vary by 20--30%., Comment: 11 pages + appendix, 10 figures. Version accepted by PRD

The Peak-Patch algorithm is used to identify the densest minicluster seeds in the initial axion density field simulated from string decay. The fate of these dense seeds is found by tracking the subsequent gravitational collapse in cosmological $N$-body simulations. We find that miniclusters at late times are well described by NFW profiles, although for around 80\% of simulated miniclusters a single power-law density profile of $r^{-2.9}$ is an equally good fit due to the unresolved scale radius. Under the assumption that all miniclusters with an unresolved scale radius are described by a power-law plus axion star density profile, we identify a significant number of miniclusters that might be dense enough to give rise to gravitational microlensing if the axion mass is $0.2 \,\mathrm{meV}\lesssim m_a \lesssim 3\,\mathrm{meV}$. Higher resolution simulations resolving the inner structure and axion star formation are necessary to explore this possibility further., Comment: 10+8 pages, 15 figures, v2 further comments on density profile fits, matches version accepted in Phys Rev D

Axions and axion-like particles (ALPs) are some of the most popular candidates for dark matter, with several viable production scenarios that make different predictions. In the scenario in which the axion is born after inflation, its field develops significant inhomogeneity and evolves in a highly nonlinear fashion. Understanding the eventual abundance and distribution of axionic dark matter in this scenario therefore requires dedicated numerical simulations. So far the community has focused its efforts on simulations of the QCD axion, a model that predicts a specific temperature dependence for the axion mass. Here, we go beyond the QCD axion, and perform a suite of simulations over a range of possible temperature dependencies labelled by a power-law index. We study the complex dynamics of the axion field, including the scaling of cosmic strings and domain walls, the spectrum of non-relativistic axions, the lifetime and internal structure of axitons, and the seeds of miniclusters. In particular, we quantify how much the string-wall network contributes to the dark matter abundance as a function of how quickly the axion mass grows. We find that a temperature-independent model produces 25\% more dark matter than the standard misalignment calculation. In contrast to this generic ALP, QCD axion models are almost six times less efficient at producing dark matter. Given the flourishing experimental campaign to search for ALPs, these results have potentially wide implications for direct and indirect searches., Comment: Version accepted by PRD, added small paragraph (section IIG) on the comparison with previous simulations. 19 pages, additional visualisations at https://www.youtube.com/channel/UCqosWwoOKrdmNKBbIwVUuGg

We study the gravitational collapse of axion dark matter fluctuations in the post-inflationary scenario, so-called axion miniclusters, with N-body simulations. Largely confirming theoretical expectations, overdensities begin to collapse in the radiation-dominated epoch and form an early distribution of miniclusters with masses up to $10^{-12}\,M_\odot$. After matter-radiation equality, ongoing mergers give rise to a steep power-law distribution of minicluster halo masses. The density profiles of well-resolved halos are NFW-like to good approximation. The fraction of axion dark matter in these bound structures is $\sim 0.75$ at redshift $z=100$., Comment: 8 pages, 6 figures, accepted by PRL

We explore finite size 3D effects in open axion haloscopes such as a dish antenna, a dielectric disk and a minimal dielectric haloscope consisting of a mirror and one dielectric disk. Particularly dielectric haloscopes are a promising new method for detecting dark matter axions in the mass range above $40\,\mu{\rm eV}$. By using two specialized independent approaches - based on finite element methods and Fourier optics - we compute the electromagnetic fields in these settings expected in the presence of an axion dark matter field. This allows us to study diffraction and near field effects for realistically sized experimental setups in contrast to earlier idealized 1D studies with infinitely extended mirrors and disks. We also study axion velocity effects and disk tiling. Diffraction effects are found to become less relevant towards larger axion masses and for the larger disk radii for example aimed at in full size dielectric haloscopes such as MADMAX. The insights of our study not only provide a foundation for a realistic modelling of open axion dark matter search experiments in general, they are in particular also the first results taking into account 3D effects for dielectric haloscopes., Comment: 41 pages, 20 figures; typos corrected, references updated

The Standard Model (SM) of particle physics is a big success. However, it lacks explanations for cosmic inflation, the matter-anti-matter asymmetry of the Universe, dark matter, neutrino oscillations, and the feebleness of CP violation in the strong interactions. The latter may be explained by a complex scalar field charged under a spontaneously broken global U(1) Peccei-Quinn (PQ) symmetry. Moreover, the pseudo Nambu-Goldstone boson of this breaking -- the axion -- may play the role of the dark matter. Furthermore, the modulus of the PQ field is a candidate for driving inflation. If additionally three extra SM singlet neutrinos (whose mass is induced by the PQ field) are included, the five aforementioned problems can be addressed at once. We review the SM extension dubbed SMASH -for SM-Axion-Seesaw-Higgs portal inflation-, discuss its predictions and tests in astrophysics, cosmology, and laboratory experiments. Variants of SMASH are also considered and commented on., Comment: 29 pages, 11 figures, review article prepared for Frontiers

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 axion mass. We show that these oscillations are observable given realistic energy resolutions and can be used to determine the axion mass to within percent level accuracies. Using projections for the upcoming helioscope IAXO, we demonstrate that $>3\sigma$ sensitivity to a non-zero axion mass is possible between $3 \times 10^{-3}$ and $10^{-1}$ eV for both the Primakoff and axion-electron solar fluxes., Comment: 13 pages, 7 figures, matches published version, code available at http://cajohare.github.io/IAXOmass

We study the small scale structure of axion dark matter in the post-inflationary scenario, which predicts the formation of low-mass, high-density clumps of gravitationally bound axions called axion miniclusters. To this end, we follow numerically the cosmological evolution of the axion field and the network of strings and domain walls until the density contrast is frozen. Our simulations, comprising up to $8192^3$ points, are the largest studies of the axion field evolution in the non-linear regime presented so far. Axitons, pseudo-breathers of the Klein-Gordon equation, are observed to form in our simulation at late times. Studying their properties analytically and numerically, we observe that in particular, the earliest axitons contribute to density perturbations at the typical length scale of miniclusters. We analyse the small scale structure of the density field, giving the correlation length, power spectrum and the distribution of high-density regions that will collapse into axion miniclusters. The final density field of our simulations can be used to calculate the minicluster mass fraction in simulations including gravity. In particular, we find that typical minicluster progenitors are smaller than previously thought and only of moderate, $\mathcal{O}(1)$ overdensity. We expect these miniclusters to have a rich sub-structure, emerging from small-scale fluctuations produced in the collapse of the string-wall network and from axitons., Comment: 57 pages, 26 figures. Version v2 accepted for publication in JCAP

If the symmetry breaking leading to the origin of the axion dark matter field occurs after the end of inflation and is never restored, then overdensities in the axion field collapse to form dense objects known in the literature as axion miniclusters. The estimates of the typical minicluster mass and radius strongly depend on the details of the cosmology at which the onset of axion oscillations begin. In this work we study the properties and phenomenology of miniclusters in alternative cosmological histories and find that they can change by many orders of magnitude. Our findings have direct implications on current and future experimental searches and, in the case of discovery, could be used to learn something about the universe expansion prior to Big-Bang-Nucleosynthesis., Comment: 28 pages, 8 figures, 1 table. Matching published version. Significant improvements and new material covered over previous versions

We develop a formalism to describe extensions of existing axion haloscope designs to those that possess directional sensitivity to incoming dark matter axion velocities. The effects are measurable if experiments are designed to have dimensions that approach the typical coherence length for the local axion field. With directional sensitivity, axion detection experiments would have a greatly enhanced potential to probe the local dark matter velocity distribution. We develop our formalism generally, but apply it to specific experimental designs, namely resonant cavities and dielectric disk haloscopes. We demonstrate that these experiments are capable of measuring the daily modulation of the dark matter signal and using it to reconstruct the three-dimensional velocity distribution. This allows one to measure the Solar peculiar velocity, probe the anisotropy of the dark matter velocity ellipsoid and identify cold substructures such as the recently discovered streams near to Earth. Directional experiments can also identify features over much shorter timescales, potentially facilitating the mapping of debris from axion miniclusters., Comment: 62 pages, 13 figures

The correction of the aberration of transcranial focused ultrasounds is a relevant issue for enhancing various non-invasive medical treatments. Emission through multi-element phased arrays has been the most widely accepted method to reduce aberrations in recent years; however, a new disruptive technology, based on 3D printed acoustic lenses, has recently been proposed with lower cost and comparable accuracy. The number and size of transducers in phased array configurations was a bottleneck limiting the focusing accuracy, but once the submillimeter precision of the latest generation 3D printers has overcome this limitation, the challenge is now to improve the accuracy of the numerical simulations needed to design the lens. This study introduces and evaluates two improvements to the numerical model applied in previous works that proposed 3D lenses, which consist in the direct calculation of the phase pattern from the propagation of oscillating magnitudes in complex form, and in the introduction of the absorption phenomenon into the set of equations that describe the dynamics of the wave in both fluid and solid media. Numerical experiments are performed analysing the quality of the aberrated-corrected focus in different configurations. The results obtained show that the inclusion of absorption significantly improves focusing, especially where the thickness of the skull is more irregular., Comment: This document is a continuation of the previously published work (in Spanish) http://www.sea-acustica.es/fileadmin/Coruna17/ULT-0%20002.pdf where the use of 3D printed lenses was proposed for the correction of the aberrations in transcranial focused ultrasounds

We propose, design and construct a variant of the conventional axion haloscope concept that could be competitive in the search for dark matter axions of masses in the decade 10-100 $\mu$eV. Theses masses are located somewhat above the mass range in which existing experiments have reached sensitivity to benchmark QCD axion models. Our haloscope consists of an array of small microwave cavities connected by rectangular irises, in an arrangement commonly used in radio-frequency filters. The size of the unit cavity determines the main resonant frequency, while the possibility to connect a {large} number of cavities allows to reach large detection volumes. We develop the theoretical framework of the detection concept, and present design prescriptions to optimize detection capabilities. We describe the design and realization of a first small-scale prototype of this concept, called Relic Axion Detector Exploratory Setup (RADES). It consists of a copper-coated stainless steel five-cavities microwave filter with the detecting mode operating at around 8.4 GHz. This structure has been electromagnetically characterized at 2 K and 298 K, and it is now placed in ultra-high vacuum in one of the twin-bores of the 9 T CAST dipole magnet at CERN. We describe the data acquisition system developed for relic axion detection, and present preliminary results of the electromagnetic properties of the microwave filter, which show the potential of filters to reach QCD axion window sensitivity at X-band frequencies., Comment: approved for publication in JCAP, version after referee comments

Axions and other very light axion-like particles appear in many extensions of the Standard Model, and are leading candidates to compose part or all of the missing matter of the Universe. They also appear in models of inflation, dark radiation, or even dark energy, and could solve some long-standing astrophysical anomalies. The physics case of these particles has been considerably developed in recent years, and there are now useful guidelines and powerful motivations to attempt experimental detection. Admittedly, the lack of positive signal of new physics at the high energy frontier, and in underground detectors searching for weakly interacting massive particles, is also contributing to the increase of the interest in axion searches. The experimental landscape is rapidly evolving, with many novel detection concepts and new experiments being proposed lately. An updated account of those initiatives is lacking in the literature. In this review we attempt to provide such a review. We will focus on the new experimental approaches and their complementarity, but will also review the most relevant recent results from the consolidated strategies and the prospects of new generation experiments under consideration in the field. We will also briefly review the latest developments of the theory, cosmology and astrophysics of axions and we will discuss the prospects to probe a large fraction of relevant parameter space in the coming decade., Comment: To be published in Progress in Particle and Nuclear Physics 2018. 2nd version after referee comments, and with many suggestions received after our first version

Axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. Depending on the value of the field amplitude at the core $|\theta_0| \equiv |\theta(r=0)|$, the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. Starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of $|\theta_0|$. For small $|\theta_0| \lesssim 1$, we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. We compare qualitative analytical results with a numerical calculation. For large amplitudes $|\theta_0| \gtrsim 1$, the axion field probes the full non-harmonic QCD chiral potential and the axion star enters the {\it dense} branch. Our numerical solutions show that in this latter regime the axions are relativistic, and that one should not use a single frequency approximation, as previously applied in the literature. We employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. We interpret the solutions in the dense regime as pseudo-breathers, and show that the life-time of such configurations is much smaller than any cosmological time scale., Comment: 11 pages, 4 figures. v2: added references, matches published version

The neutrino flux at Earth is dominated in the keV energy range by the neutrinos produced in the Sun through thermal processes, namely photo production, bremsstrahlung, plasmon decay, and emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. Such a component of the neutrino flux is conspicuously absent from popular analyses of the all-sources spectrum at Earth, whereas if detected it could be a source of information about solar physics. Moreover, it would be the relevant background for keV-mass sterile neutrino dark matter direct searches., Comment: Comments added. 5 pages, 3 figures. Prepared for the proceedings of the conference TAUP 2017

There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu--Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -- the hypothetical pseudo Nambu--Goldstone boson predicted by the Peccei--Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -- the fifth force experiment ARIADNE and the helioscope IAXO -- can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter., Comment: 32 pages, 5 figures

We calculate the solar neutrino and antineutrino flux in the keV energy range. The dominant thermal source processes are photoproduction ($\gamma e\to e \nu\bar\nu$), bremsstrahlung ($e+Ze\to Ze+e+\nu\bar\nu$), plasmon decay ($\gamma\to\nu\bar\nu$), and $\nu\bar\nu$ emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. These latter processes dominate in the energy range of a few keV and thus carry information about the solar metallicity. To calculate their rate we use libraries of monochromatic photon radiative opacities in analogy to a previous calculation of solar axion emission. Our overall flux spectrum and many details differ significantly from previous works. While this low-energy flux is not measurable with present-day technology, it could become a significant background for future direct searches for keV-mass sterile neutrino dark matter., Comment: 32 pages, 23 figures. Added several references, a new figure and minor changes to match published version

We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass ($40-400~\mu$eV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics., Comment: 36 pages, 16 figures; v3: typos and a small sign error corrected as in the erratum published as JCAP 05 (2018) E02

We study the underlying theory of dielectric haloscopes, a new way to detect dark matter axions. When an interface between different dielectric media is inside a magnetic field, the oscillating axion field acts as a source of electromagnetic waves, which emerge in both directions perpendicular to the surface. The emission rate can be boosted by multiple layers judiciously placed to achieve constructive interference and by a large transverse area. Starting from the axion-modified Maxwell equations, we calculate the efficiency of this new dielectric haloscope approach. This technique could potentially search the unexplored high-frequency range of 10--100 GHz (axion mass 40--400 $\mu$eV), where traditional cavity resonators have difficulties reaching the required volume., Comment: 71 pages, 34 figures; v2: minor changes, typo in (4.13) corrected, matches published version

We propose a new strategy to search for dark matter axions in the mass range of 40--400 $\mu$eV by introducing dielectric haloscopes, which consist of dielectric disks placed in a magnetic field. The changing dielectric media cause discontinuities in the axion-induced electric field, leading to the generation of propagating electromagnetic waves to satisfy the continuity requirements at the interfaces. Large-area disks with adjustable distances boost the microwave signal (10--100 GHz) to an observable level and allow one to scan over a broad axion mass range. A sensitivity to QCD axion models is conceivable with 80 disks of 1 m$^2$ area contained in a $10$ Tesla field., Comment: 6 pages, 3 figures. v2: minor changes to align with published version

The axion is an intriguing dark matter candidate emerging from the Peccei-Quinn solution to the strong CP problem. Current experimental searches for axion dark matter focus on the axion mass range below 40 $\mu$eV. However, if the Peccei-Quinn symmetry is restored after inflation the observed dark matter density points to an axion mass around 100 $\mu$eV. A new project based on axion-photon conversion at the transition between different dielectric media is presented. By using $\sim 80$ dielectric discs, the emitted power could be enhanced by a factor of $\sim 10^5$ over that from a single mirror (flat dish antenna). Within a 10 T magnetic field, this could be enough to detect $\sim 100 \mu$eV axions with HEMT linear amplifiers. The design for an experiment is proposed. Results from noise, transmissivity and reflectivity measurements obtained in a prototype setup are presented. The expected sensitivity is shown., Comment: Contributed to the 12th Patras Workshop on Axions, WIMPs and WISPs, Jeju Island, South Korea, June 20 to 26, 2016

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos $N_i$, a new color triplet $Q$ and a complex SM-singlet scalar $\sigma$, whose vacuum expectation value $v_\sigma \sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of $\sigma$ and the SM Higgs, and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model - Axion - seesaw - Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments., Comment: v2. Version accepted for publication at JCAP

A minimal extension of the Standard Model (SM) with a single new mass scale and providing a complete and consistent picture of particle physics and cosmology up to the Planck scale is presented. We add to the SM three right-handed SM-singlet neutrinos, a new vector-like color triplet fermion and a complex SM singlet scalar $\sigma$ that stabilises the Higgs potential and whose vacuum expectation value at $\sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously. Primordial inflation is produced by a combination of $\sigma$ (non-minimally coupled to the scalar curvature) and the SM Higgs. Baryogenesis proceeds via thermal leptogenesis. At low energies, the model reduces to the SM, augmented by seesaw-generated neutrino masses, plus the axion, which solves the strong CP problem and accounts for the dark matter in the Universe. The model predicts a minimum value of the tensor-to-scalar ratio $r\simeq 0.004$, running of the scalar spectral index $\alpha\simeq - 7\times 10^{-4}$, the axion mass $m_A\sim 100\,\mu{\rm eV}$ and cosmic axion background radiation corresponding to an increase of the effective number of relativistic neutrinos of $\sim 0.03$. It can be probed decisively by the next generation of cosmic microwave background and axion dark matter experiments., Comment: 7 pages, 2 figures

We discuss the Aharonov-Bohm effect in the presence of hidden photons kinetically mixed with the ordinary electromagnetic photons. The hidden photon field causes a slight phase shift in the observable interference pattern. It is then shown how the limited sensitivity of this experiment can be largely improved. The key observation is that the hidden photon field causes a leakage of the ordinary magnetic field into the supposedly field-free region. The direct measurement of this magnetic field can provide a sensitive experiment with a good discovery potential, particularly below the $\sim$ meV mass range for hidden photons., Comment: 10 pages, 8 figures

QCD axions with meV mass can be behind some stellar cooling anomalies and form all or part of the cold dark matter of the universe. We discuss on a proposed experiment to discover the solar flux of meV mass axions: the International AXion Observatory: IAXO., Comment: 6 pages, 4 figures, Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs, Zaragoza, June 22 to 26, 2015

Several stellar systems (white dwarfs, red giants, horizontal branch stars and possibly the neutron star in the supernova remnant Cassiopeia A) show a mild preference for a non-standard cooling mechanism when compared with theoretical models. This exotic cooling could be provided by Weakly Interacting Slim Particles (WISPs), produced in the hot cores and abandoning the star unimpeded, contributing directly to the energy loss. Taken individually, these excesses do not show a strong statistical weight. However, if one mechanism could consistently explain several of them, the hint could be significant. We analyze the hints in terms of neutrino anomalous magnetic moments, minicharged particles, hidden photons and axion-like particles (ALPs). Among them, the ALP or a massless HP represent the best solution. Interestingly, the hinted ALP parameter space is accessible to the next generation proposed ALP searches, such as ALPS II and IAXO and the massless HP requires a multi TeV energy scale of new physics that might be accessible at the LHC., Comment: Minor corrections. Expanded presentation of new physics. Added discussion about massless hidden photons. 21 pages, 6 figures

We give a brief update on the search for Hidden Photon Dark Matter with FUNK. The experiment uses a large spherical mirror, which, if Hidden Photon Dark Matter exists in the accessible mass and coupling parameter range, would yield an optical signal in the mirror's center in an otherwise dark environment. After a test run with a CCD, preparations for a run with a low-noise PMT are under way and described in this proceedings., Comment: Proceedings for PHOTON 2015, BINP Novosibirsk, Russia, June 15-19, 2015; 4 pages, 2 figures

If dark matter consists of hidden-sector photons which kinetically mix with regular photons, a tiny oscillating electric-field component is present wherever we have dark matter. In the surface of conducting materials this induces a small probability to emit single photons almost perpendicular to the surface, with the corresponding photon frequency matching the mass of the hidden photons. We report on a construction of an experimental setup with a large ~14 m2 spherical metallic mirror that will allow for searches of hidden-photon dark matter in the eV and sub-eV range by application of different electromagnetic radiation detectors. We discuss sensitivity and accessible regions in the dark matter parameter space., Comment: 9 pages, proceeding of the 34th International Cosmic Ray Conference (ICRC), July 30 - August 6, 2015, The Hague, The Netherlands

A time-domain numerical code based on the constitutive relations of nonlinear acoustics for simulating ultrasound propagation is presented. To model frequency power law attenuation, such as observed in biological media, multiple relaxation processes are included and relaxation parameters are fitted to both exact frequency power law attenuation and empirically measured attenuation of a variety of tissues that does not fit an exact power law. A computational technique based on artificial relaxation is included to correct the non-negligible numerical dispersion of the numerical method and to improve stability when shock waves are present. This technique avoids the use of high order finite difference schemes, leading to fast calculations. The numerical code is especially suitable to study high intensity and focused axisymmetric acoustic beams in tissue-like medium, as it is based on the full constitutive relations that overcomes the limitations of the parabolic approximations, while some specific effects not contemplated by the Westervelt equation can be also studied. The accuracy of the method is discussed by comparing the proposed simulation solutions to one-dimensional analytical ones, to $k$-space numerical solutions and also to experimental data from a focused beam propagating in a frequency power law attenuation media., Comment: arXiv admin note: substantial text overlap with arXiv:1401.6669

We discuss the impact of a hidden sector consisting of Minicharged Particles (MCPs) and massless hidden photons on the expansion history of our Universe. We present parameter scans for the amount of extra relativistic particles (Neff) and the abundance of light nuclei for fermionic MCPs with masses between ~100 keV and 10 GeV and minicharges in the range 10^(-11)-1. Current CMB and BBN data significantly constrain the available parameter space of MCPs. The shown results are a valuable indicator for future experimental searches and are presented in a flexible way so that more accurate results on Neff can be easily interpreted., Comment: Contributed to the 10th Patras Workshop on Axions, WIMPs and WISPs, CERN, June 29 to July 4, 2014

We present the results of a search for transversely polarised hidden photons (HPs) with $\sim 3$ eV energies emitted from the Sun. These hypothetical particles, known also as paraphotons or dark sector photons, are theoretically well motivated for example by string theory inspired extensions of the Standard Model. Solar HPs of sub-eV mass can convert into photons of the same energy (photon$\leftrightarrow$HP oscillations are similar to neutrino flavour oscillations). At SHIPS this would take place inside a long light-tight high-vacuum tube, which tracks the Sun. The generated photons would then be focused into a low-noise photomultiplier at the far end of the tube. Our analysis of 330 h of data (and {330 h} of background characterisation) reveals no signal of photons from solar hidden photon conversion. We estimate the rate of newly generated photons due to this conversion to be smaller than 25 mHz/m$^2$ at the 95$%$ C.L. Using this and a recent model of solar HP emission, we set stringent constraints on $\chi$, the coupling constant between HPs and photons, as a function of the HP mass.