Search results for "microwave"
showing 10 items of 693 documents
Test of the generation of High-Frequency Gravitational Waves by irradiating a dielectric film in a resonant cavity
2004
A recent proposal for generating High Frequency Gravitational Waves (HFGW) is based on the conversion of electromagnetic waves into gravitational waves by irradiating a dielectric film in the extreme conditions of a high vacuum and a strong magnetic field. These HFGWs can be tested using an electron paramagnetic resonant spectrometer (EPRS). This device contains all the necessary ingredients: a vacuum chamber, microwave generator, a strong magnetic field, and a resonant cavity where the substance to be analysed is introduced. The EPR spectrum of a very small paramagnetic core in a substance is the graph of the absorption of the paramagnetic core as a function of the strong magnetic field B.…
Second harmonic generation by an isolated spin
1970
Abstract The second harmonic generation at microwave frequency by a spin S = 1 2 in a cavity has been studied as a function of the external magnetic field using a resolvent technique, and the average transition rates to states with an increased number of double-frequency photons has been calculated. In spite of the crudeness of the model, a good qualitative agreement has been found between the predictions of the present theory and recent experimental results on non-linear behaviour of paramagnetic spin systems in a microwave field.
Most constraining cosmological neutrino mass bounds
2021
We present here up-to-date neutrino mass limits exploiting the most recent cosmological data sets. By making use of the cosmic microwave background temperature fluctuation and polarization measurements, supernovae Ia luminosity distances, baryon acoustic oscillation observations and determinations of the growth rate parameter, we are able to set the most constraining bound to date, $\ensuremath{\sum}{m}_{\ensuremath{\nu}}l0.09\text{ }\text{ }\mathrm{eV}$ at 95% C.L. This very tight limit is obtained without the assumption of any prior on the value of the Hubble constant and highly compromises the viability of the inverted mass ordering as the underlying neutrino mass pattern in nature. The …
Invisible neutrino decay in precision cosmology
2021
We revisit the topic of invisible neutrino decay in the precision cosmological context, via a first-principles approach to understanding the cosmic microwave background and large-scale structure phenomenology of such a non-standard physics scenario. Assuming an effective Lagrangian in which a heavier standard-model neutrino $\nu_H$ couples to a lighter one $\nu_l$ and a massless scalar particle $\phi$ via a Yukawa interaction, we derive from first principles the complete set of Boltzmann equations, at both the spatially homogeneous and the first-order inhomogeneous levels, for the phase space densities of $\nu_H$, $\nu_l$, and $\phi$ in the presence of the relevant decay and inverse decay p…
The present and future of the most favoured inflationary models after $Planck$ 2015
2015
The value of the tensor-to-scalar ratio $r$ in the region allowed by the latest $Planck$ 2015 measurements can be associated to a large variety of inflationary models. We discuss here the potential of future Cosmic Microwave Background cosmological observations in disentangling among the possible theoretical scenarios allowed by our analyses of current $Planck$ temperature and polarization data. Rather than focusing only on $r$, we focus as well on the running of the primordial power spectrum, $\alpha_s$ and the running of thereof, $\beta_s$. Our Fisher matrix method benefits from a detailed and realistic appraisal of the expected foregrounds. Future cosmological probes, as the COrE mission…
Can interacting dark energy solve the $H_0$ tension?
2017
The answer is Yes! We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant $H_0$ between the Cosmic Microwave Background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two datasets points towards an evidence for a non-zero dark matter-dark energy coupling $\xi$ at more than two standard deviations, with $\xi=-0.26_{-0.12}^{+0.16}$ at $95\%$ CL. However the $H_0$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantom-like equation of state $w=-1.184\pm0.…
Is it mixed dark matter or neutrino masses?
2018
In this paper, we explore a scenario where the dark matter is a mixture of interacting and non interacting species. Assuming dark matter-photon interactions for the interacting species, we find that the suppression of the matter power spectrum in this scenario can mimic that expected in the case of massive neutrinos. Our numerical studies include present limits from Planck Cosmic Microwave Background data, which render the strength of the dark matter photon interaction unconstrained when the fraction of interacting dark matter is small. Despite the large entangling between mixed dark matter and neutrino masses, we show that future measurements from the Dark Energy Instrument (DESI) could he…
New Methods of Scalar Dark Matter Detection
2017
In this chapter, I consider new mechanisms for the induction of a cosmological evolution of the fundamental constants (such as the electromagnetic fine-structure constant \(\alpha \) and the particle masses) by dark matter. By investigating the effects of “slow drifts” and oscillating variations of the fundamental constants due to dark matter in astrophysical phenomena, including Big Bang nucleosynthesis and cosmic microwave background radiation measurements, and laboratory clock-comparison experiments, I derive new limits on certain interactions of dark matter with ordinary matter that improve on previous limits by up to 15 orders of magnitude, as well as the first ever limits on several o…
A CMB search for the neutrino mass mechanism and its relation to the Hubble tension
2020
AbstractThe majoron, a pseudo-Goldstone boson arising from the spontaneous breaking of global lepton number, is a generic feature of many models intended to explain the origin of the small neutrino masses. In this work, we investigate potential imprints in the cosmic microwave background (CMB) arising from massive majorons, should they thermalize with neutrinos after Big Bang Nucleosynthesis via inverse neutrino decays. We show that measurements of the CMB are currently sensitive to neutrino-majoron couplings as small as $$\lambda \sim 10^{-13}$$λ∼10-13, which if interpreted in the context of the type-I seesaw mechanism correspond to a lepton number symmetry breaking scale $$v_L \sim {\math…
Dark Radiation and Inflationary Freedom after Planck 2015
2016
The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale-invariant. It has been shown, however, that the low-multipole spectrum of the CMB anisotropies may hint the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this non-standard PPS with the neutrino anisotropies, the neutrino masses, the effective number of relativistic species and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a non-standard PPS w…