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Category: physics – Page 179

Many people think that mathematics is a human invention. To this way of thinking, mathematics is like a language: it may describe real things in the world, but it doesn’t “exist” outside the minds of the people who use it.

But the Pythagorean school of thought in ancient Greece held a different view. Its proponents believed reality is fundamentally mathematical. More than 2,000 years later, philosophers and physicists are starting to take this idea seriously.

As I argue in a new paper, mathematics is an essential component of nature that gives structure to the physical world.

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This series is absolutely fantastic. Especially for Transhumanist non-astrophysicists like me!

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We routinely simulate the universe on all of its scales, from planets to large fractions of the cosmos. Today we’re going to see how it’s possible to build a universe in a computer — and see whether there’s a limit to what we can simulate.

Continue reading “How To Build The Universe in a Computer” | >

How many black holes are out there in the Universe? This is one of the most relevant and pressing questions in modern astrophysics and cosmology. The intriguing issue has recently been addressed by the SISSA Ph.D. student Alex Sicilia, supervised by Prof. Andrea Lapi and Dr. Lumen Boco, together with other collaborators from SISSA and from other national and international institutions. In a first paper of a series just published in The Astrophysical Journal, the authors have investigated the demographics of stellar mass black holes, which are black holes with masses between a few to some hundred solar masses, that originated at the end of the life of massive stars. According to the new research, a remarkable amount around 1% of the overall ordinary (baryonic) matter of the Universe is locked up in stellar mass black holes. Astonishingly, the researchers have found that the number of black holes within the observable Universe (a sphere of diameter around 90 billions light years) at present time is about 40 trillions, 40 billion billions (i.e., about 40 × 1018, i.e. 4 followed by 19 zeros!).

A new method to calculate the number of black holes

As the authors of the research explain: This important result has been obtained thanks to an original approach which combines the state-of-the-art stellar and binary evolution code SEVN developed by SISSA researcher Dr. Mario Spera to empirical prescriptions for relevant physical properties of galaxies, especially the rate of star formation, the amount of stellar mass and the metallicity of the interstellar medium (which are all important elements to define the number and the masses of stellar black holes). Exploiting these crucial ingredients in a self-consistent approach, thanks to their new computation approach, the researchers have then derived the number of stellar black holes and their mass distribution across the whole history of the Universe.

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Light-matter interactions form the basis of many important technologies, including lasers, light-emitting diodes (LEDs), and atomic clocks. However, usual computational approaches for modeling such interactions have limited usefulness and capability. Now, researchers from Japan have developed a technique that overcomes these limitations.

In a study published this month in The International Journal of High Performance Computing Applications, a research team led by the University of Tsukuba describes a highly efficient method for simulating light-matter interactions at the atomic scale.

What makes these interactions so difficult to simulate? One reason is that phenomena associated with the interactions encompass many areas of physics, involving both the propagation of light waves and the dynamics of electrons and ions in matter. Another reason is that such phenomena can cover a wide range of length and time scales.

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SciTechDaily.

Structure may reveal conditions needed for high-temperature superconductivity.

When two sheets of graphene are stacked atop each other at just the right angle, the layered structure morphs into an unconventional superconductor, allowing electric currents to pass through without resistance or wasted energy.

This “magic-angle” transformation in bilayer graphene was observed for the first time in 2018 in the group of Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT.

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While they don’t give the physical thrill of a real one, model roller coasters are always fun to watch. However, they actually make a poor analog of a full-sized ride, as gravitational force and aerodynamic drag don’t scale down in the same way, model roller coasters usually move way faster than the same design would in the real world. [Jon Mendenhall] fixed this deficiency by designing a model roller coaster that accurately simulates a full-sized ride.

The track and cart are all made of 3D printed pieces, which altogether took about 400 hours to print. The main trick to the system’s unique motion is that the cart is motorized: a brushless DC motor moves it along the track using a rack-and-pinion system. This means that technically this model isn’t a roller coaster, since the cart never makes a gravity-powered drop; it’s actually a small rack railway, powered by a lithium-ion battery carried on board the cart. An ESP32 drives the motor, receiving its commands through WiFi, while the complete setup is controlled by a Raspberry Pi that runs the cart through a predetermined sequence.

The design of the track was inspired by the Fury 325 roller coaster and simulated in NoLimits 2. [Jon] wrote his own software to generate all the pieces to be printed based on outputs from the simulator. This included all the track pieces as well as the large A-frames holding it up; some of these were too long to fit in [Jon]’s 3D printers and had to be built from smaller pieces. The physics simulation also provided the inputs to the controller in the form of a script that contains the proper speed and acceleration at each point along the track.

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