Audible Axions

Conventional approaches to probing axions and axion-like particles (ALPs) typically rely on a coupling to photons. However, if this coupling is extremely weak, ALPs become invisible and are effectively decoupled from the Standard Model. Here we show that such invisible axions, which are viable candidates for dark matter, can produce a stochastic gravitational wave background in the early universe. This signal is generated in models where the invisible axion couples to a dark gauge boson that experiences a tachyonic instability when the axion begins to oscillate. Incidentally, the same mechanism also widens the viable parameter space for axion dark matter. Quantum fluctuations amplified by the exponentially growing gauge boson modes source chiral gravitational waves. For axion decay constants $f \gtrsim 10^{17}$ GeV, this signal is detectable by either pulsar timing arrays or space/ground-based gravitational wave detectors for a broad range of axion masses, thus providing a new window to probe invisible axion models.Comment: 8 pages, 4 figures. References added, version submitted to JHE

One μ\mu to rule them all: CMB spectral distortions can probe domain walls, cosmic strings and low scale phase transitions

We present a new probe of purely gravitationally coupled sectors with large anisotropies. These anisotropies are damped via gravitational interactions with the baryon-photon fluid, which is heated up in the process. The injected heat causes measurable distortions of the cosmic microwave background spectrum. We give analytic estimates for the size of the distortions and outline how to calculate them from first principles. These methods are applied to anisotropies in the form of a domain wall/cosmic string network or caused by a first order phase transition or scalar field dynamics. We find that this method can potentially probe large regions of previously unconstrained parameter space and is very much complementary to up-coming searches of gravitational waves caused by such dark sectors

Preferential Amplification of CD8 Effector-T Cells after Transcutaneous Application of an Inactivated Influenza Vaccine: A Randomized Phase I Trial

Background: Current conventional vaccination approaches do not induce potent CD8 T-cell responses for fighting mostly variable viral diseases such as influenza, avian influenza viruses or HIV. Following our recent study on vaccine penetration by targeting of vaccine to human hair follicular ducts surrounded by Langerhans cells, we tested in the first randomized Phase-Ia trial based on hair follicle penetration (namely transcutaneous route) the induction of virus-specific CD8 T cell responses. Methods and Findings: We chose the inactivated influenza vaccine – a conventional licensed tetanus/influenza (TETAGRIP®) vaccine – to compare the safety and immunogenicity of transcutaneous (TC) versus IM immunization in two randomized controlled, multi-center Phase I trials including 24 healthy-volunteers and 12 HIV-infected patients. Vaccination was performed by application of inactivated influenza vaccine according to a standard protocol allowing the opening of the hair duct for the TC route or needle-injection for the IM route. We demonstrated that the safety of the two routes was similar. We showed the superiority of TC application, but not the IM route, to induce a significant increase in influenza-specific CD8 cytokine-producing cells in healthy-volunteers and in HIV-infected patients. However, these routes did not differ significantly for the induction of influenza-specific CD4 responses, and neutralizing antibodies were induced only by the IM route. The CD8 cell response is thus the major immune response observed after TC vaccination. Conclusions: This Phase Ia clinical trial (Manon05) testing an anti-influenza vaccine demonstrated that vaccines designed for antibody induction by the IM route, generate vaccine-specific CD8 T cells when administered transcutaneously. These results underline the necessity of adapting vaccination strategies to control complex infectious diseases when CD8 cellular responses are crucial. Our work opens up a key area for the development of preventive and therapeutic vaccines for diseases in which CD8 cells play a crucial role

Ultra-high frequency gravitational waves: where to next ?

There has recently been an increased interest in electro-magnetic GW detectors, due to the first detections of GWs and the rapid evolution of the technology driven by searches for light dark matter. The question how to calculate the response of e.g. a cavity to a GW has been debated since the 80s and the current understanding is that the usage of a special frame, the proper detector frame, is necessary to get the correct result. This idea is however somewhat disturbing, since coordinate invariance lies at the heart of general relativity, and criticism of this approach is therefore as old as the approach itself. We hope to clarify some of the issues leading to this apparent contradiction

Axion fragmentation on the lattice

We analyze the phenomenon of axion fragmentation when an axion field rolls over many oscillations of a periodic potential. This is particularly relevant for the case of relaxion, in which fragmentation provides the necessary energy dissipation to stop the field evolution. We compare the results of a linear analysis with the ones obtained from a classical lattice simulation, finding an agreement in the stopping time of the zero mode between the two within an O(1) difference. We finally speculate on the generation of bubbles with different VEVs of the axion field, and discuss their cosmological consequences

Probing an ultralight QCD axion with electromagnetic quadratic interaction

The axion-gluon coupling is the defining feature of the QCD axion. This feature induces additional and qualitatively different interactions of the axion with standard model particles -- quadratic couplings. Previously, hadronic quadratic couplings have been studied and experimental implications have been explored especially in the context of atomic spectroscopy and interferometry. We investigate additional quadratic couplings to the electromagnetic field and electron mass. These electromagnetic quadratic couplings are generated at the loop level from threshold corrections and are expected to be present in the absence of fine-tuning. While they are generally loop-suppressed compared to the hadronic ones, they open up new ways to search for the QCD axion, for instance via optical atomic clocks. Moreover, due to the velocity spread of the dark matter field, the quadratic nature of the coupling leads to low-frequency fluctuations in any detector setup. These distinctive low-frequency fluctuations offer a way to search for heavier axions. We provide an analytic expression for the power spectral density of this low-frequency background and briefly discuss experimental strategies for a low-frequency background search

Primordial gravitational waves in the nano-Hertz regime and PTA data — towards solving the GW inverse problem

Abstract In recent years, several pulsar timing array collaborations have reported first hints for a stochastic gravitational wave background at nano-Hertz frequencies. Here we elaborate on the possibility that this signal comes from new physics that leads to the generation of a primordial stochastic gravitational wave background. We propose a set of simple but concrete models that can serve as benchmarks for gravitational waves sourced by cosmological phase transitions, domain wall networks, cosmic strings, axion dynamics, or large scalar fluctuations. These models are then confronted with pulsar timing data and with cosmological constraints. With only a limited number of free parameters per model, we are able to identify viable regions of parameter space and also make predictions for future astrophysical and laboratory tests that can help with model identification and discrimination

Successful intra-class switching among IL-17 antagonists: a multicentre, multinational, retrospective study

IL-17 blockers are among the newer anti-psoriatic treatment options and little is known about the interclass switching. We have thus initiated a multi-center, multi-national, retrospective study to assess the treatment response of patients who were switched from one IL-17 blocker to another. Analysis consisted of data from patients with moderate-to-severe psoriasis who did not respond satisfactorily to one of the available IL-17 blockers (secukinumab, ixekizumab, brodalumab) and were subsequently switched to another drug of this class. After 12 weeks of treatment, patients’ PASIs were evaluated. Treatment success was defined as reaching PASI 75 after 12 weeks. Topical treatment was allowed and used in all patients. 26 patients were included (13 male, 13 female) and 29 switches were evaluated. Overall, 29 switches in 21 patients were evaluated. 18 patients changed their therapy from secukinumab to ixekizumab, or in 7 cases to brodalumab. Brodalumab was used in 3 cases after failure of treatment with ixekizumab. Only in one case, non-response of brodalumab resulted in a therapy switch to secukinumab. In 15 (52%) cases, PASI 75 was reached. In 6 (20%) patients, the switch led to a PASI 50 response. No success of treatment was seen among 8 (28%) participants. When patients fail to respond or do not tolerate an IL-17 blocker, switching to another anti-IL-17A/RA is a promising viable option. Larger studies are needed to confirm our results