### The light limit of the neutrino

Neutrinos are the most light particles in the universe, but we don't know your mass. In the current state of the research, the only thing that we can hope to do is find upper and lower limits. And in the previous weeks we have some interesting news about the upper limit.
In april Physics Review Letters published a paper in which a team of researcher have compared constraints from physically motivated neutrino mass models (i.e., ones respecting oscillation experiments) to those from models using standard cosmological approximations. They founded an upper limit about $0.26 \, eV$, almost 2 million times lighter than an electron.
Loureiro, A., Cuceu, A., Abdalla, F. B., Moraes, B., Whiteway, L., McLeod, M., ... & Rollins, R. P. (2019). Upper Bound of Neutrino Masses from Combined Cosmological Observations and Particle Physics Experiments. Physical review letters, 123(8), 081301. doi:10.1103/PhysRevLett.123.081301 (arXiv
In the meanwhile, just ten days ago, the KATRIN's team (KATRIN, Karlsruhe Trtitium Neutrino experiment) announced the new experimental upper limit: $1.1 \, eV$.
Aker, M., Altenmüller, K., Arenz, M., Babutzka, M., Barrett, J., Bauer, S., ... & Besserer, U. (2019). An improved upper limit on the neutrino mass from a direct kinematic method by KATRIN. arXiv:1909.06048.
The research of neutrino mass becomes more and more interesting: if the study of theoretical models combined with astronomical data gives us an idea of the range to look for, experiments will say the last word.
The hunt to the neutrino is still open!

### Maths in Europe: Lunar Arithmetic

One of the most popular expressions in Italy for giving strength to numbers is mathematics is not an opinion. The expression is exclusively Italian and mathematicians don't agree with this opinion, since they have fun inventing a large number of different mathematics. For example, a curious mathematics is what today called lunar arithmetic. In this kind of arithmetic, the sum between two digits gives the largest digit, while the product between two digits gives the smallest one. A particular consequence of the multiplication rule is the definition of prime numbers: in base 10 a lunar prime number is a number divisible only by itself and by 9, because the neutral element of lunar multiplication is 9.
Continue on Mathematics in Europe

### Updates from outer space: from Earth to K2-18 b

There are some interesting news about the research of exoplanets, but the first step starting from our planet, the Earth. Indeed, Evelyn Macdonald and Nicolas Cowan used the satellite Scicast to detect the transit spectrum of our planet. The idea is to deduce the atmosphere composition, obtaining the Earth's organic signature, and in this way data to confront with exoplanets transit spectrum.
Macdonald, E. J., & Cowan, N. B. (2019). An empirical infrared transit spectrum of Earth: opacity windows and biosignatures. Monthly Notices of the Royal Astronomical Society, 489(1), 196-204. doi:10.1093/mnras/stz2047
About two weeks after the pubblication of the previous paper, an international team of astronomers have discovered water vapor in the atmosphere of K2-18 b, an exoplanet that orbit in the habitable zone of the red dwarf K2-18. While it was initially considered a mini-Neptune on its 2015 discovery, the improved data on K2-18b has classified it as a super-Earth, although its size and density make it unlikely to be composed entirely of rocky iron and silicates.
Tsiaras A., Waldmann I. P., Tinetti G., Tennyson J., Yurchenko S. N. (2019). Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b. Nature Astronomy. doi:10.1038/s41550-019-0878-9

### Breakthrough Prize 2020: Physics and Mathematics

2020 Breakthrough Prize in Fundamental Physics to the Event Horizon Telescope Collaboration, for the first image of a supermassive black hole, taken by means of an Earth-sized alliance of telescopes.
Using eight sensitive radio telescopes strategically positioned around the world in Antarctica, Chile, Mexico, Hawaii, Arizona and Spain, a global collaboration of scientists at 60 institutions operating in 20 countries and regions captured an image of a black hole for the first time. By synchronizing each telescope using a network of atomic clocks, the team created a virtual telescope as large as the Earth, with a resolving power never before achieved from the surface of our planet. One of their first targets was the supermassive black hole at the center of the Messier 87 galaxy – its mass equivalent to 6.5 billion suns. After painstakingly analyzing the data with novel algorithms and techniques, the team produced an image of this galactic monster, silhouetted against hot gas swirling around the black hole, that matched expectations from Einstein's theory of gravity: a bright ring marking the point where light orbits the black hole, surrounding a dark region where light cannot escape the black hole's gravitational pull.
2020 Breakthrough Prize in Mathematics to Alex Eskin, for revolutionary discoveries in the dynamics and geometry of moduli spaces of Abelian differentials, including the proof of the "magic wand theorem" with Maryam Mirzakhani.
Eskin teamed with famed Iranian mathematician and Fields Medalist, Maryam Mirzakhni, to prove a theorem about dynamics on moduli spaces. Their tour de force, published in 2013 after five years of labor, is a result with many consequences. One addresses the longstanding problem: If a beam of light from a point source bounces around a mirrored room, will it eventually reach the entire room – or will some parts remain forever dark? After translating the problem to a highly abstract multi-dimensional setting, the two mathematicians were able to show that for polygonal rooms with angles which are fractions of whole numbers, only a finite number of points would remain unlit. Mirzakhani passed away in 2017, at age 40, after fighting breast cancer for several years.

via Breakthrough Prize