Jan 25, 2022 06:20 PM
Physicists detect mysterious X particles in 'primordial soup' for the first time
https://www.sciencealert.com/for-the-fir...uon-plasma
EXCERPTS: A mysterious particle thought to have existed briefly just after the Big Bang has now been detected for the first time in the 'primordial soup'.
Specifically, in a medium called the quark-gluon plasma, generated in the Large Hadron Collider by colliding lead ions. There, amid the trillions of particles produced by these collisions, physicists managed to tease out 100 of the exotic motes known as X particles.
[...] Mere moments after the Big Bang, the very early Universe wasn't made of the same stuff we see floating around today. Instead, for a few millionths of a second, it was filled with plasma superheated to trillions of degrees, consisting of elementary particles called quarks and gluons. That's the quark-gluon plasma.
In less time than it takes to blink, the plasma cooled and the particles came together to form the protons and neutrons of which normal matter is constructed today. But in that very brief twitch of time, the particles in the quark-gluon plasma collided, stuck together, and came apart again in different configurations.
One of those configurations is a particle so mysterious, we don't even know how it's put together. This is the X particle, and it's only been seen very rarely and briefly in particle colliders – too briefly to be probed.
[...] Protons and neutrons are each made up of three quarks. Physicists believe that X particles may be made of four – either an exotic, tightly bound particle known as a tetraquark, or a new kind of loosely bound particle made from two mesons, each of which contain two quarks. If it's the former, because it's more tightly bound, it will decay more slowly than the latter... (MORE - missing details)
How infinite series reveal the unity of mathematics
https://www.quantamagazine.org/how-infin...-20220124/
INTRO: For sheer brilliance, it was hard to beat John von Neumann. An architect of the modern computer and inventor of game theory, von Neumann was legendary, above all, for his lightning-fast mental calculations.
The story goes that one day somebody challenged him with a puzzle. Two bicyclists start at opposite ends of a road 20 miles long. Each cyclist travels toward the other at 10 miles per hour. When they begin, a fly sitting on the front wheel of one of the bikes takes off and races at 15 miles per hour toward the other bike. As soon as it gets there, it instantly turns around and zips back toward the first bike, then back to the second, and so on. It keeps flying back and forth until it’s finally squished between their front tires when the bikes collide. How far did the fly travel, in total, before it was squished?
It sounds hard. The fly’s back-and-forth journey consists of infinitely many parts, each shorter than the one preceding it. Adding them up seems like a daunting task.
But the problem becomes easy if you think about the bicyclists, not the fly. On a road that’s 20 miles long, two cyclists approaching each other at 10 miles per hour will meet in the middle after 1 hour. And during that hour, no matter what path the fly takes, it must have traveled 15 miles, since it was going 15 miles an hour.
When von Neumann heard the puzzle, he instantly replied, “15 miles.” His disappointed questioner said, “Oh, you saw the trick.” “What trick?” said von Neumann. “I just summed the infinite series.”
Infinite series — the sum of infinitely many numbers, variables or functions that follow a certain rule — are bit players in the great drama of calculus. While derivatives and integrals rightly steal the show, infinite series modestly stand off to the side. When they do make an appearance it’s near the end of the course, as everyone’s dragging themselves across the finish line.
A regular column in which top researchers explore the process of discovery. This month’s columnist, Steven Strogatz, is a highly accomplished mathematician and author, and is the host of The Joy of x, a podcast for Quanta Magazine.
So why study them? Infinite series are helpful for finding approximate solutions to difficult problems, and for illustrating subtle points of mathematical rigor. But unless you’re an aspiring scientist, that’s all a big yawn. Plus, infinite series are often presented without any real-world applications. The few that do appear — annuities, mortgages, the design of chemotherapy regimens — can seem remote to a teenage audience.
The most compelling reason for learning about infinite series (or so I tell my students) is that they’re stunning connectors. They reveal ties between different areas of mathematics, unexpected links between everything that came before. It’s only when you get to this part of calculus that the true structure of math — all of math — finally starts to emerge.
Before I explain, let’s look at another puzzle involving an infinite series... (MORE - details)
https://www.sciencealert.com/for-the-fir...uon-plasma
EXCERPTS: A mysterious particle thought to have existed briefly just after the Big Bang has now been detected for the first time in the 'primordial soup'.
Specifically, in a medium called the quark-gluon plasma, generated in the Large Hadron Collider by colliding lead ions. There, amid the trillions of particles produced by these collisions, physicists managed to tease out 100 of the exotic motes known as X particles.
[...] Mere moments after the Big Bang, the very early Universe wasn't made of the same stuff we see floating around today. Instead, for a few millionths of a second, it was filled with plasma superheated to trillions of degrees, consisting of elementary particles called quarks and gluons. That's the quark-gluon plasma.
In less time than it takes to blink, the plasma cooled and the particles came together to form the protons and neutrons of which normal matter is constructed today. But in that very brief twitch of time, the particles in the quark-gluon plasma collided, stuck together, and came apart again in different configurations.
One of those configurations is a particle so mysterious, we don't even know how it's put together. This is the X particle, and it's only been seen very rarely and briefly in particle colliders – too briefly to be probed.
[...] Protons and neutrons are each made up of three quarks. Physicists believe that X particles may be made of four – either an exotic, tightly bound particle known as a tetraquark, or a new kind of loosely bound particle made from two mesons, each of which contain two quarks. If it's the former, because it's more tightly bound, it will decay more slowly than the latter... (MORE - missing details)
How infinite series reveal the unity of mathematics
https://www.quantamagazine.org/how-infin...-20220124/
INTRO: For sheer brilliance, it was hard to beat John von Neumann. An architect of the modern computer and inventor of game theory, von Neumann was legendary, above all, for his lightning-fast mental calculations.
The story goes that one day somebody challenged him with a puzzle. Two bicyclists start at opposite ends of a road 20 miles long. Each cyclist travels toward the other at 10 miles per hour. When they begin, a fly sitting on the front wheel of one of the bikes takes off and races at 15 miles per hour toward the other bike. As soon as it gets there, it instantly turns around and zips back toward the first bike, then back to the second, and so on. It keeps flying back and forth until it’s finally squished between their front tires when the bikes collide. How far did the fly travel, in total, before it was squished?
It sounds hard. The fly’s back-and-forth journey consists of infinitely many parts, each shorter than the one preceding it. Adding them up seems like a daunting task.
But the problem becomes easy if you think about the bicyclists, not the fly. On a road that’s 20 miles long, two cyclists approaching each other at 10 miles per hour will meet in the middle after 1 hour. And during that hour, no matter what path the fly takes, it must have traveled 15 miles, since it was going 15 miles an hour.
When von Neumann heard the puzzle, he instantly replied, “15 miles.” His disappointed questioner said, “Oh, you saw the trick.” “What trick?” said von Neumann. “I just summed the infinite series.”
Infinite series — the sum of infinitely many numbers, variables or functions that follow a certain rule — are bit players in the great drama of calculus. While derivatives and integrals rightly steal the show, infinite series modestly stand off to the side. When they do make an appearance it’s near the end of the course, as everyone’s dragging themselves across the finish line.
A regular column in which top researchers explore the process of discovery. This month’s columnist, Steven Strogatz, is a highly accomplished mathematician and author, and is the host of The Joy of x, a podcast for Quanta Magazine.
So why study them? Infinite series are helpful for finding approximate solutions to difficult problems, and for illustrating subtle points of mathematical rigor. But unless you’re an aspiring scientist, that’s all a big yawn. Plus, infinite series are often presented without any real-world applications. The few that do appear — annuities, mortgages, the design of chemotherapy regimens — can seem remote to a teenage audience.
The most compelling reason for learning about infinite series (or so I tell my students) is that they’re stunning connectors. They reveal ties between different areas of mathematics, unexpected links between everything that came before. It’s only when you get to this part of calculus that the true structure of math — all of math — finally starts to emerge.
Before I explain, let’s look at another puzzle involving an infinite series... (MORE - details)