Searching for High Frequency Gravitational Waves with Phonons

The gravitational wave (GW) spectrum at frequencies above a kHz is a largely unexplored frontier. We show that detectors with sensitivity to single-phonon excitations in crystal targets can search for GWs with frequencies, $\mathrm{THz} \lesssim f \lesssim 100 \, \mathrm{THz}$, corresponding to the range of optical phonon energies, $\mathrm{meV} \lesssim \omega \lesssim 100 \, \mathrm{meV}$. Such detectors are already being built to search for light dark matter (DM), and therefore sensitivity to high-frequency GWs will be achieved as a byproduct. We begin by deriving the absorption rate of a general GW signal into single phonons. We then focus on carefully defining the detector sensitivity to monochromatic and chirp signals, and compute the detector sensitivity for many proposed light DM detection targets. The detector sensitivity is then compared to the signal strength of candidate high-frequency GW sources, e.g., superradiant annihilation and black hole inspiral, as well as other recent detector proposals in the $\mathrm{MHz} \lesssim f \lesssim 100 \, \mathrm{THz}$ frequency range. With a judicious choice of target materials, a collection of detectors could optimistically achieve sensitivities to monochromatic signals with $h_0 \sim 10^{-23} - 10^{-25}$ over $\mathrm{THz} \lesssim f \lesssim 100 \, \mathrm{THz}$.Comment: 32 pages, 4 figure

Axion detection with phonon-polaritons revisited

In the presence of a background magnetic field, axion dark matter induces an electric field and can thus excite phonon-polaritons in suitable materials. We revisit the calculation of the axion-photon conversion power output from such materials, accounting for finite volume effects, and material losses. Our calculation shows how phonon-polaritons can be converted to propagating photons at the material boundary, offering a route to detecting the signal. Using the dielectric functions of GaAs, Al$_2$O$_3$, and SiO$_2$, a fit to our loss model leads to a signal of lower magnitude than previous calculations. We demonstrate how knowledge of resonances in the dielectric function can directly be used to calculate the sensitivity of any material to axion dark matter. We argue that a combination of low losses encountered at $\mathcal{O}(1)$ K temperatures and near future improvements in detector dark count allow one to probe the QCD axion in the mass range $m_a\approx 100$ meV. This provides further impetus to examine novel materials and further develop detectors in the THz regime. We also discuss possible tuning methods to scan the axion mass.Comment: 13 pages, 2 figures, 1 table, comments welcom

Treating asthma: is there a place for leukotriene receptor antagonists?

SummaryAsthma is a chronic disorder, characterized by airway hyperresponsiveness (AHR), airway inflammation and airway remodelling. Evidence has been provided for a relationship between pathophysiology, airway inflammation and remodelling. Moreover, these asthma features have been shown to respond to anti-inflammatory therapy. According to current guidelines, monitoring of asthma is predominantly based on symptoms and lung function data. However, these parameters appeared as poor indices for asthma control. Alternatively, asthma control relates well to exacerbations and (anamnestic) surrogate biomarkers of airway inflammation. Hence, appropriate treatment of asthma should primarily target the airway inflammation.According to current guidelines for asthma management, anti-inflammatory therapy with inhaled corticosteroids (ICS) is the cornerstone in the treatment of persistent asthma. To further optimize asthma control, add-on therapy with long-acting β2-agonists (LABA) or leukotriene receptor antagonists (LTRA) should be combined with low to high doses of ICS. While the first combination focuses on optimal control of symptoms and lung function, the second provides a more complete suppression of the airway inflammation.In this paper we discuss treatment of asthma according to current guidelines versus new insights, addressing practical issues

Prospects for direct detection of black hole formation in neutron star mergers with next-generation gravitational-wave detectors

A direct detection of black hole formation in neutron star mergers would provide invaluable information about matter in neutron star cores and finite temperature effects on the nuclear equation of state. We study black hole formation in neutron star mergers using a set of 190 numerical relativity simulations consisting of long-lived and black-hole-forming remnants. The postmerger gravitational-wave spectrum of a long-lived remnant has greatly reduced power at a frequency f greater than f peak , for f ≳ 4     kHz , with f peak ∈ [ 2.5 , 4 ]     kHz . On the other hand, black-hole-forming remnants exhibit excess power in the same large f region and manifest exponential damping in the time domain characteristic of a quasinormal mode. We demonstrate that the gravitational-wave signal from a collapsed remnant is indeed a quasinormal ringing. We report on the opportunity for direct detections of black hole formation with next-generation gravitational-wave detectors such as Cosmic Explorer and Einstein Telescope and set forth the tantalizing prospect of such observations up to a distance of 100 Mpc for an optimally oriented and located source with an SNR of 4

Axion quasiparticles for axion dark matter detection

It has been suggested that certain antiferromagnetic topological insulators contain axion quasiparticles (AQs), and that such materials could be used to detect axion dark matter (DM). The AQ is a longitudinal antiferromagnetic spin fluctuation coupled to the electromagnetic Chern-Simons term, which, in the presence of an applied magnetic field, leads to mass mixing between the AQ and the electric field. The electromagnetic boundary conditions and transmission and reflection coefficients are computed. A model for including losses into this system is presented, and the resulting linewidth is computed. It is shown how transmission spectroscopy can be used to measure the resonant frequencies and damping coefficients of the material, and demonstrate conclusively the existence of the AQ. The dispersion relation and boundary conditions permit resonant conversion of axion DM into THz photons in a material volume that is independent of the resonant frequency, which is tuneable via an applied magnetic field. A parameter study for axion DM detection is performed, computing boost amplitudes and bandwidths using realistic material properties including loss. The proposal could allow for detection of axion DM in the mass range between 1 and 10 meV using current and near future technology

Axion direct detection in particle and condensed matter physics

The first part of this thesis investigates the direct detection of axions in particle physics. A generalized matrix formalism for describing axion-photon mixing in multi-layer systems to all orders in the axion-photon coupling is developed and applied for studying light shinning through a wall (LSW) experiments with and without dielectric layers. It is found that dielectric layers can be placed into two configurations - a transparent and a resonant one. For the transparent configuration, by tuning the distance between the dielectric layers, the experiment can be made to be more sensitive in specific relatively large axion mass ranges. For the ALPS II setup with dielectric layers it is possible to achieve a sensitivity enhancement for axion masses larger than $10^{-4}\,\text{eV}$. Dielectric layers in the resonant case could be used to replace cavities around the (re)generation regions of existing LSW experiments. Then we turn to open axion haloscopes, which aim to detect axions from the dark matter halo. Two methods for effectively calculating the emitted electromagnetic fields in 3D are presented. Both methods represent a significant improvement, as they are much more computationally efficient than a straight forward approach based on standard three dimensional finite element computations. We consider the upcoming MADMAX and BRASS axion haloscope experiments. For the BRASS haloscope we study how axion velocity effects could shift the emitted electromagnetic radiation pattern, while for MADMAX we investigate diffraction, disk tiling and waveguide surroundings. None of the studied 3D effects would be a show stopper for the MADMAX experiment. The second part of the thesis concerns axion quasiparticles (AQs) in topological magentic insulators (TMIs). By AQs we mean quasiparticles, which have the same interaction with the electromagnetic fields as axions from particle physics. AQs in TMIs have not been detected so far. For a future detection via THz transmission spectroscopy a detailed calculation of the expected signal is needed. We present such a calculation and demonstrate that by fitting the future measurements to our signal calculation important material parameters of the TMI can be determined. AQs in TMIs can also be used in order to detect dark matter axions (DAs) since they can resonantly mix with the AQs and photons in TMIs. We present a detailed signal calculation for a DA search with a TMI layer. The calculation takes into account appropriate interface conditions for the electromagnetic and axion field as well as material losses. Analytical expressions for the resonance width and peak values are presented. For a DA search TMI materials with a relatively small refractive index are advantageous. TMIs with a thickness of a few mm and a surface area of $A=1\,\text{m}^2$ can probe QCD axion models for DA masses between $0.7\,\text{meV}$ and $3.5\,\text{meV}$. Magnon and photon losses need to be less than $10^{-5}\,\text{meV}$ in order not to reduce the emitted signal significantly

Gravitational waves as a big bang thermometer

There is a guaranteed background of stochastic gravitational waves produced in the thermal plasma in the early universe. Its energy density per logarithmic frequency interval scales with the maximum temperature Tmax which the primordial plasma attained at the beginning of the standard hot big bang era. It peaks in the microwave range, at around 80 GHz [106.75/g*s(Tmax)]1/3, where g*s(Tmax) is the effective number of entropy degrees of freedom in the primordial plasma at Tmax. We present a state-of-the-art prediction of this Cosmic Gravitational Microwave Background (CGMB) for general models, and carry out calculations for the case of the Standard Model (SM) as well as for several of its extensions. On the side of minimal extensions we consider the Neutrino Minimal SM (νMSM) and the SM-Axion-Seesaw-Higgs portal inflation model (SMASH), which provide a complete and consistent cosmological history including inflation. As an example of a non-minimal extension of the SM we consider the Minimal Supersymmetric Standard Model (MSSM). Furthermore, we discuss the current upper limits and the prospects to detect the CGMB in laboratory experiments and thus measure the maximum temperature and the effective number of degrees of freedom at the beginning of the hot big bang

Freezing-In Gravitational Waves

The thermal plasma in the early universe produced a stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). In previous works only single graviton production processes that contribute to the CGMB have been considered. Here we also investigate graviton pair production processes and show that these can lead to a significant contribution if the maximum temperature of the universe in units of Planck mass divided by the internal coupling in the heat bath is large enough. As the dark matter freeze-in production mechanism is conceptually very similar to the GW production mechanism from the primordial thermal plasma, we refer to the latter as "GW freeze-in production". We also show that quantum gravity effects arising in single graviton production are smaller than the leading order result by a factor of the square of the ratio between the maximum temperature and the Planck mass. In our work we explicitly compute the CGMB spectrum within a scalar model with quartic interaction

Freezing-In Gravitational Waves

The thermal plasma in the early universe produced a stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). In previous works only single graviton production processes that contribute to the CGMB have been considered. Here we also investigate graviton pair production processes and show that these can lead to a significant contribution if the maximum temperature of the universe in units of Planck mass divided by the internal coupling in the heat bath is large enough. As the dark matter freeze-in production mechanism is conceptually very similar to the GW production mechanism from the primordial thermal plasma, we refer to the latter as "GW freeze-in production". We also show that quantum gravity effects arising in single graviton production are smaller than the leading order result by a factor of the square of the ratio between the maximum temperature and the Planck mass. In our work we explicitly compute the CGMB spectrum within a scalar model with quartic interaction