Imaging quantum entanglement

The main object of a paper published a couple of days ago on Science is to find an answer to the following question:

what kind of imaging process could reveal a Bell inequality?

The experimental set-up used a $\beta$-Barium Borate crystal pumped by a (quasi-cotinuous) laser. The pairs of entagled photons generated are subsequently separated on a beam splitter and propagate into two distinct optical systems like LIGO interferometer.
The results is the production of some images that shots the Bell inequality violation, like the following image:

Moreover, our demonstration shows that one can detect the signature of a Bell-type behavior within a single image acquired by an imaging setup. By demonstrating that quantum imaging can generate high-dimensional images illustrating the presence of Bell-type entanglement, we benchmark quantum imaging techniques against the most fundamental test of quantum mechanics.

Moreau, P. A., Toninelli, E., Gregory, T., Aspden, R. S., Morris, P. A., & Padgett, M. J. (2019). Imaging Bell-type nonlocal behavior. Science Advances, 5(7), eaaw2563. doi:10.1126/sciadv.aaw2563

Murray Gell-Mann: Proposing quarks

In 1963, when I assigned the name "quark" to the fundamental constituents of the nucleon, I had the sound first, without the spelling, which could have been "kwork". Then, in one of my occasional perusals of Finnegans Wake, by James Joyce, I came across the word "quark" in the phrase "Three quarks for Muster Mark". Since "quark" (meaning, for one thing, the cry of the gull) was clearly intended to rhyme with "Mark", as well as "bark" and other such words, I had to find an excuse to pronounce it as "kwork". But the book represents the dream of a publican named Humphrey Chimpden Earwicker. Words in the text are typically drawn from several sources at once, like the "portmanteau" words in Through the Looking-Glass. From time to time, phrases occur in the book that are partially determined by calls for drinks at the bar. I argued, therefore, that perhaps one of the multiple sources of the cry "Three quarks for Muster Mark" might be "Three quarts for Mister Mark", in which case the pronunciation "kwork" would not be totally unjustified. In any case, the number three fitted perfectly the way quarks occur in nature.

- Murray Gell-Mann, The Quark and the Jaguar, 1995 - via en.wiki

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Quantum gravity without gravitons

Charles Choi writes on Scientific American:

In a paper recently accepted by the journal Classical and Quantum Gravity, however, astrophysicist Richard Lieu of the University of Alabama, Huntsville, argues that LIGO should already have detected gravitons if they carry as much energy as some current models of particle physics suggest. It might be that the graviton just packs less energy than expected, but Lieu suggests it might also mean the graviton does not exist.

But:

Loop quantum gravity does not use gravitons as building blocks.

The map of mathematics

The field of mathematics is massive, but a lot of people stop dealing with more complex maths after leaving university. Or, if you're not involved in an occupational field that needs mathematics, you might stop taking mathematics courses toward the end of high school. However, math is much bigger than most people realize. This creative map of mathematics made by Domain of Science puts the entirety of the field onto a single map.
The video traces the origins of math back to counting, which the video points out is not an exclusively human activity. It then quickly mentions how early civilizations tapped into counting and transformed it, most notably Arab scholars who created the first books on algebra. From there, mathematics and the sciences exploded during the Renaissance period.
After that point, the video starts to take off and diverge into a variety of mathematics we've come to know today. Maths diverged into two categories: pure maths and applied maths. Pure maths consists of the studies of numbers systems, structures (like algebra and group theory), spaces (goemetry and trigonometry) and more. Applied mathematics then taps into the application of pure maths. It includes the calculations that help determine how life functions, like mathematical chemistry or biomathematics. It also includes daily usage of math in economics, game theory, and statistics. By the end of the 11 minute video, viewers are left in awe (or simply overwhelmed) by all the possibilities that fall under the umbrella of "maths."
There were some mistakes made in the video that have since been corrected in the video's description. One of the biggest is that the video mistakenly mentions 1 as a prime number. However, prime numbers by definition are numbers bigger than 1 that can be divided evenly only by 1 or itself. The number must be greater than 1.

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Pi stories: the Cyclometricus and other tales

Fifth period

It was 1621 when the Cyclometricus by Willebrord Snellius, a pupil of Ludolph van Ceulen, was published. Snellius proved that the perimeter of the inscribed polygon converges to the circumference twice than the circumscribed polygon. As a good pupil of van Ceulen, Snellius managed to get 7 decimal places for the $\pi$ by using a 96-sided polygon. His best result, however, was 35 decimal places, which improved his master's result, 32.
The next improvement is dated 1630 by Christoph Grienberger, the last mathematician to evaluate $\pi$ using the polygon method, while the first successful method change came out thanks to the british mathematician and astronomer Abraham Sharp who determined 72 decimal places of $\pi$, of which 71 correct, using a series of arctangents. A few years later, John Machin improved Sharp's result with the following formula and that allowed him to achieve the remarkable result of 100 decimal places! \[\frac{\pi}{4} = 4 \arctan \frac{1}{5} - \arctan \frac{1}{239}\] Machin's approach proved successful, so much so that the slovenian baron Jurij Vega improved on two occasions the above formula obtaining a greater number of decimal digits of $\pi$, the first time in 1789 with a formula similar to Euler's one \[\frac{\pi}{4} = 5 \arctan \frac{1}{7} + 2 \arctan \frac{3}{79}\] then in 1794 with a Hutton-like formula \[\frac{\pi}{4} = 2 \arctan \frac{1}{3} + \arctan \frac{1}{7}\] The arctangent era continued with William Rutherford \[\frac{\pi}{4} = 4 \arctan \frac{1}{5} - \arctan \frac{1}{70} + \arctan \frac{1}{99}\] and with Zacharias Dase \[\frac{\pi}{4} = \arctan \frac{1}{2} + \arctan \frac{1}{5} + \arctan \frac{1}{8}\] Finally comes the british William Shanks that pushing the full potential of the Machin's formula managed to get 707 decimal places, of which only 527 were correct after Ferguson's controls in 1946. Here, however, we are going in the era of mechanical calculation, prologue to computer era.

Women in physics

I would share some free ebooks from IOP about the contribution of women in physics:

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Women and Physics by Laura McCullough (pdf)

This book begins with an examination of the numbers of women in physics in English-speaking countries, moving on to examine factors that affect girls and their decision to continue in science, right through to education and on into the problems that women in physics careers face. Looking at all of these topics with one eye on the progress that the field has made in the past few years, and another on those things that we have yet to address, the book surveys the most current research as it tries to identify strategies and topics that have significant impact on issues that women have in the field.

Beyond Curie: Four women in physics and their remarkable discoveries, 1903 to 1963 by Scott Calvin (pdf)

In the 116 year history of the Nobel Prize in Physics, only two women have won the award; Marie Curie (1903) and Maria Mayer (1963). During the 60 years between those awards, several women did work of similar calibre. This book focuses on those women, providing biographies for each that discuss both how they made their discoveries and the gender-specific reception of those discoveries. It also discusses the Nobel process and how society and the scientific community's treatment of them were influenced by their gender.

After the War: Women in physics in the United States by Ruth H Howes, Caroline L Herzenberg (pdf)

This book examines the lives and contributions of American women physicists who were active in the years following World War II, during the middle decades of the 20th century. It covers the strategies they used to survive and thrive in a time where their gender was against them. The percentage of woman taking PhDs in physics has risen from 6% in 1983 to 20% in 2012 (an all-time high for women). By understanding the history of women in physics, these gains can continue.
It discusses two major classes of women physicists; those who worked on military projects, and those who worked in industrial laboratories and at universities largely in the late 1940s and 1950s. While it includes minimal discussion of physics and physicists in the 1960s and later, this book focuses on the challenges and successes of women physicists in the years immediately following World War II and before the eras of affirmative actions and the use of the personal computer.

The man who measured Mount Everest

Radhanath Sikdar was an Indian mathematician who, among many other things, calculated the height of Mount Everest in the Himalaya and showed it to be the tallest mountain above sea level.