Articles by David Appell
Phys.org / A new calculation of the electron's self-energy improves determination of fundamental constants
When quantum electrodynamics, the quantum field theory of electrons and photons, was being developed after World War II, one of the major challenges for theorists was calculating a value for the Lamb shift, the energy of ...
Phys.org / The future lifespan of plants just got extended
For now, the future of life on Earth is in human hands. But after the anthropocentric era, the situation starts to get dicey. The sun's luminosity is increasing over time, about 1% every 110 million years, so the Earth's ...
Phys.org / Scientists use machine learning to develop an opener for a molecular can
In an era of medical care that is increasingly aiming at more targeted medication therapies, more individual therapies and more effective therapies, doctors and scientists want to be able to introduce molecules to the biological ...
Phys.org / Numerical simulations show how the classical world might emerge from the many-worlds universes of quantum mechanics
Students learning quantum mechanics are taught the Schrodinger equation and how to solve it to obtain a wave function. But a crucial step is skipped because it has puzzled scientists since the earliest days—how does the real, ...
Phys.org / Latest gravitational wave observations conflict with expectations from stellar models
Almost 300 binary mergers have been detected so far, indicated by their passing gravitational waves. These measurements from the world's gravitational wave observatories put constraints on the masses and spins of the merging ...
Phys.org / Detecting the gravitational wave memory effect from core-collapse supernovae
Einstein's theory of gravity, general relativity, has passed all tests with predictions that are spot-on. One prediction that remains is "gravitational wave memory"—the prediction that a passing gravitational wave will permanently ...
Phys.org / How much permafrost will melt this century, and where will its carbon go?
Among the many things global warming will be melting this century—sea ice, land glaciers and tourist businesses in seaside towns across the world—is permafrost. Lying underneath 15% of the northern hemisphere, permafrost ...
Phys.org / A technosignature that could detect an extraterrestrial civilization's reliance on nuclear fusion
Extraterrestrial civilizations need a great deal of energy as they advance up the Kardashev scale. Fossil fuels are finite, wind and solar energy are carbon free but not as efficient as fossil fuels, and traditional nuclear ...
Phys.org / Cosmological model proposes dark matter production during pre-Big Bang inflation
As physicists continue their struggle to find and explain the origin of dark matter, the approximately 80% of the matter in the universe that we can't see and so far haven't been able to detect, researchers have now proposed ...
Medical Xpress / Assessing synchronized activity in the human brain through frequency-dependent covariance analysis
This year is the centennial anniversary of German psychiatrist Hans Berger's invention of electroencephalography (EEG), a way to record electrical activity in the brain, now called brainwaves or neural oscillations. Amazingly, ...
Phys.org / An unexpected delay in a standard quantum optical process generates pairs of photons
Since it was first demonstrated in the 1960s, spontaneous parametric down-conversion (SPDC) has been at the center of many quantum optics experiments that test the fundamental laws of physics in quantum mechanics, and in ...
Phys.org / Observing dark matter at cosmic dawn
After almost a century of speculation, proposals and searches for dark matter, physicists now know that it currently comprises about 27% of the universe's mass-energy, with an abundance over five times that of ordinary matter ...
Phys.org / Researchers find a possible solution to the cosmic ray muon puzzle
Scientists have a problem with cosmic rays—they produce too many muons at the Earth's surface. Cascades of muons are byproducts of high-energy cosmic rays as they collide with nuclei in the upper atmosphere, and scientists ...
Phys.org / Artificial intelligence finds previously undetected historical climate extremes
There are over 30,000 weather stations in the world, measuring temperature, precipitation and other indicators often on a daily basis. That's a massive amount of data for climate researchers to compile and analyze to produce ...
Phys.org / An improved quantification of the intergalactic medium and cosmic filaments
Much of the mass in the universe lies not in stars or galaxies, but in the space between them, known as the intergalactic medium. It is warm and even hot, and is called the "warm-hot intergalactic medium," or WHIM. It holds ...
