Possibilities for separation of scalar and vector characteristics of acoustic scatterer in tomographic polychromatic regime

Abstract The inverse wave problem of tomographic type is considered. It consists in reconstruction of several scatterer’s characteristics in the form of spatial distributions for sound speed, medium density, absorption coefficient and power index of its frequency dependence, as well as vector of flow velocity. In the form of a survey material (based on several publications), a sequence of steps is discussed that leads to reconstruction of each individual spatial distribution in the presence of different combinations of the mentioned characteristics. The minimum number of frequencies required for reconstruction is discussed when the complete set of scattering data is available at each of the frequencies. For the first time, two possible approaches to reconstruct the scatterer characteristics in the presence of inhomogeneous spatial distributions of the density and the flow velocity vector are compared, and attention is drawn to the perspectives of reconstruction by functional algorithms in this case. The possibility of separating the sought spatial distributions during the inverse problem solution is illustrated by numerical modeling.</jats:p

GCOS - The Global Cosmic Ray Observatory

International audienceNature is providing particles with energies exceeding 100 EeV. Their existence imposes immediate questions: Are they ordinary particles, accelerated in extreme astrophysical environments, or are they annihilation or decay products of super-heavy dark matter or other exotic objects? If the particles are accelerated in extreme astrophysical environments, are their sources related to those of high-energy neutrinos, gamma rays, and/or gravitational waves, such as the recently observed mergers of compact objects? The particles can also be used to study physics processes at extreme energies; is Lorentz invariance still valid? Are the particles interacting according to the Standard Model or are there new physics processes? The particles can be used to study hadronic interactions (QCD) in the kinematic forward direction; what is the cross section of protons at center-of-mass energies $\sqrt{s} > 100$~TeV?These questions are addressed at present by installations like the Telescope Array and the Pierre Auger Observatory. After the year 2030, a next-generation observatory will be needed to study the physics and properties of the highest-energy particles in Nature, building on the knowledge harvested from the existing observatories. It should have an aperture at least an order of magnitude bigger than the existing observatories. Recently, more than 200 scientists from around the world came together to discuss the future of the field of multi-messenger astroparticle physics beyond the year 2030. Ideas have been discussed towards the physics case and possible scenarios for detection concepts of theGlobal Cosmic Ray Observatory - GCOS.A synopsis of the key results discussed during the brainstorming workshop will be presented