The talk will cover electronic processes in hot atomic matter giving rise to spectroscopic signatures, and present examples of astrophysical and laboratory observations of those.
Observations of neutrino oscillations have unambiguously proven that neutrinos have non-zero masses. Precision measurements of beta-decay kinematics represent the most promising model-independent approach to probing the extremely small absolute neutrino mass scale in a laboratory experiment.
Direct neutrino mass experiments have a long history dating back to the late 40s, and the development of experimental techniques has allowed to push the sensitivity to the level of 2 eV. Given this limit, all direct searches up to now have yielded values for mν2which are compatible with zero. Moreover, with most best-fit estimates for the measured quantity mν2lying in the unphysical range mν2 < 0 eV2, the best practice for analysing data and interpreting the results is not always obvious.
This talk will give an introduction to the measurement principle of beta-decay spectroscopy and expand on the statistical peculiarities connected to a physical parameter boundary. A brief review of past experiments and their approach in identifying systematic effects and treating statistical errors is given. Finally, a status update on the KArlsruhe TRitium Neutrino experiment is presented, which aims to push the neutrino mass sensitivity into the sub-eV regime by improving the statistical and systematic sensitivity of this measurement technique by two orders of magnitude.
Some remarkably universal empirical formulas are used to characterize the slow dynamics of disordered materials and imperfect crystals. Stretched-exponential relaxation is used for time-dependent response, non-classical critical scaling is used for temperature-dependent behavior, and 1/f noise is used for frequency-dependent fluctuations. I will describe a common physical foundation for all of these formulas. The behavior may be attributed to strict adherence to the laws of thermodynamics: energy is conserved using Hill’s subdivision potential for nonlinear terms, entropy is maximized using a local thermal bath, and similar states are treated using the statistics of indistinguishable particles. Alternatively, the mechanism may be interpreted using information theory for reversible fluctuations. I will emphasize how specific models based on these principles yield the empirical formulas, plus deviations from the formulas that often match the measured behavior.
