October 7th, 2019

лошадь, диаграмма, Фейнман

О распределении Брейта-Вигнера и кое-чем еще

Breit-Wigner distribution, quantum beats and GSI Anomaly: https://arxiv.org/abs/1704.05762

The relationship between Breit-Wigner distribution as an underlying basis for decaying unstable quantum systems and GSI experiment (anomaly) has not been addressed properly in the literatures. We show that quantum beats can be obtained using a superposition of two Breit-Wigner distributions. This modified distribution can explain the GSI time anomaly with quantum beats resulting from the existence of two energy levels of the decaying ion.
Comments: 7 pages, 2 Figure
Journal reference: Annals of Physics, Volume 410, November 2019, 167936
лошадь, диаграмма, Фейнман

К дискуссии об отрицательной температуре

Помнится, когда-то давно Игорь Иванов разбирался с этим на Элементах:
Настоящая температура не может быть отрицательной

Negative Absolute Temperatures: https://arxiv.org/abs/1910.01915

The concept of negative absolute temperature, introduced by Ramsey based on the study of a nuclear spin system by Purcell and Pound in 1951, has been subject to continued debate. According to a recent analysis by Struchtrup, the apparent negative temperature states are temperature unstable states for which no temperature-positive or negative-can be defined. Ramsey was aware of the potential problem with his treatment of the negative temperature by pointing it out that the apparent negative temperature states cannot be achieved via any reversible process. In this paper, we demonstrate that the existence of an upper limit in the allowed states of the system is not a sufficient condition, albeit a necessary condition, for the appearance of negative temperatures. A thermal system cannot move into any negative temperature state via reversible thermodynamic processes. Negative temperature of a system is a direct outcome of incorrectly applying thermodynamic functions to an irreversible process.
лошадь, диаграмма, Фейнман

Эффект Керкера в жизни растений

Насколько я понимаю, эффект Керкера - это резкая анизотропия в рассеянии света объектом, обладающим одновременно электрическим и магнитным дипольными моментами. И вот:

Kerker effect in Biomineral Calcium Carbonate Nanospherulites allows alpine plants from the Saxifraga genus to increase light collection efficiency

Being the polymorphs of calcium carbonate (CaCO3), vaterite and calcite have attracted a great deal of attention as promising biomaterials for drug delivery and tissue engineering. Furthermore, they are important biogenic minerals, enabling living organisms to reach specific functions. In nature, vaterite and calcite monocrystals typically form self-assembled polycrystal micro- and nano-particles, also referred to as spherulites. Here, we demonstrate that alpine plants belonging to the Saxifraga genus can use Kerker effect to improve light collection efficiency via producing CaCO3 polycrystal nanoparticles on the margins of their leaves. To provide clear physical background behind our concept, we study light scattering from artificially synthesized vaterite nanospherulites and reveal the phenomenon of directional light scattering. Dark-field spectroscopy measurements are supported by a comprehensive numerical analysis, accounting for the complex microstructure of particles. We demonstrate the generalized Kerker condition, where several higher order multipoles interfere constructively in the forward direction. As a result, highly directive forward light scattering from vaterite nanospherulites is observed in the entire visible range. Also, we present ex vivo study of microstructure and optical properties of leaves for the alpine plants Saxifraga "Southside Seedling" and Saxifraga Paniculata Ria and show performance of Kerker effect for these living organisms. Our results pave the way for a bioinspired strategy of efficient light collection by self-assembled polycrystal CaCO3 nanoparticles via engineering of light propagation directly to the photosynthetic tissue with minimized losses on backward scattering due to the generalized Kerker effect.

Кроме того, гуглеж привел вот к такой открытой статейке в Phys.Rev.X:

Optomechanical Kerker Effect: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.011008