theoretical_physics (4)

Strange Metals...


A diagram showing different states of matter as a function of temperature, T, and interaction strength, U (normalized to the amplitude, t, of electrons hopping between sites). Strange metals emerge in a regime separating a metallic spin glass and a Fermi liquid. P. Cha et al./Proceedings of the National Academy of Sciences 2020

Topics: Black Holes, Modern Physics, Quantum Mechanics, Superconductors, Theoretical Physics

Even by the standards of quantum physicists, strange metals are just plain odd. The materials are related to high-temperature superconductors and have surprising connections to the properties of black holes. Electrons in strange metals dissipate energy as fast as they’re allowed to under the laws of quantum mechanics, and the electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.

Generating a theoretical understanding of strange metals is one of the biggest challenges in condensed matter physics. Now, using cutting-edge computational techniques, researchers from the Flatiron Institute in New York City and Cornell University have solved the first robust theoretical model of strange metals. The work reveals that strange metals are a new state of matter, the researchers report July 22 in the Proceedings of the National Academy of Sciences.

“The fact that we call them strange metals should tell you how well we understand them,” says study co-author Olivier Parcollet, a senior research scientist at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ). “Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics.”

Quantum Physicists Crack Mystery of ‘Strange Metals,’ a New State of Matter, Thomas Sumner, Simon Foundation

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Quantum Sound...

Credit: Getty Images


Topics: Modern Physics, Phonons, Quantum Mechanics, Theoretical Physics

Researchers have gained control of the elusive “particle” of sound, the phonon. Although phonons—the smallest units of the vibrational energy that makes up sound waves—are not matter, they can be considered particles the way photons are particles of light. Photons commonly store information in prototype quantum computers, which aim to harness quantum effects to achieve unprecedented processing power. Using sound instead may have advantages, although it would require manipulating phonons on very fine scales.

Until recently, scientists lacked this ability; just detecting an individual phonon destroyed it. Early methods involved converting phonons to electricity in quantum circuits called superconducting qubits. These circuits accept energy in specific amounts; if a phonon’s energy matches, the circuit can absorb it—destroying the phonon but giving an energy reading of its presence.

In a new study, scientists at JILA (a collaboration between the National Institute of Standards and Technology and the University of Colorado Boulder) tuned the energy units of their superconducting qubit so phonons would not be destroyed. Instead the phonons sped up the current in the circuit, thanks to a special material that created an electric field in response to vibrations. Experimenters could then detect how much change in current each phonon caused.

“There’s been a lot of recent and impressive successes using superconducting qubits to control the quantum states of light. And we were curious—what can you do with sound that you can’t with light?” says Lucas Sletten of U.C. Boulder, lead author of the study published in June in Physical Review X. One difference is speed: sound travels much slower than light. Sletten and his colleagues took advantage of this to coordinate circuit-phonon interactions that sped up the current. They trapped phonons of particular wavelengths (called modes) between two acoustic “mirrors,” which reflect sound, and the relatively long time sound takes to make a round trip allowed the precise coordination. The mirrors were a hair’s width apart—similar control of light would require mirrors separated by about 12 meters.


Trapping the Tiniest Sound, Leila Sloman, Scientific American

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Credit: Shutterstock


Topics: God Particle, Higgs Boson, Large Hadron Collider, Standard Model, Theoretical Physics

c. 1400, "having power to control fate, from weird (n.), from Old English wyrd "fate, chance, fortune; destiny; the Fates," literally "that which comes," from Proto-Germanic *wurthiz (source also of Old Saxon wurd, Old High German wurt "fate," Old Norse urðr "fate, one of the three Norns"), from PIE *wert- "to turn, to wind," (source also of German werden, Old English weorðan "to become"), from root *wer- (2) "to turn, bend." For sense development from "turning" to "becoming," compare phrase turn into "become."

Etymology online: Weird

We all know and love the Higgs boson — which to physicists' chagrin has been mistakenly tagged in the media as the "God particle" — a subatomic particle first spotted in the Large Hadron Collider (LHC) back in 2012. That particle is a piece of a field that permeates all of space-time; it interacts with many particles, like electrons and quarks, providing those particles with mass, which is pretty cool.

But the Higgs that we spotted was surprisingly lightweight. According to our best estimates, it should have been a lot heavier. This opens up an interesting question: Sure, we spotted a Higgs boson, but was that the only Higgs boson? Are there more floating around out there doing their own things?

But the Higgs that we spotted was surprisingly lightweight. According to our best estimates, it should have been a lot heavier. This opens up an interesting question: Sure, we spotted a Higgs boson, but was that the only Higgs boson? Are there more floating around out there doing their own things?

Physicists Search for Monstrous Higgs Particle. It Could Seal the Fate of the Universe.
Paul Sutter, Astrophysicist, Live Science

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In Finnegan's Wake...

Murray Gell-Mann won the 1969 Nobel Prize in Physics.Credit: Santa Fe Institute


Topics: Nobel Laureate, Nobel Prize, Particle Physics, Quarks, Standard Model, Theoretical Physics

The Nobel Prize in Physics 1969 was awarded to Murray Gell-Mann "for his contributions and discoveries concerning the classification of elementary particles and their interactions."

The Nobel Prize in Physics 1969. Nobel Media AB 2019. Wed. 29 May 2019. < >

Murray Gell-Mann, one of the founders of modern particle physics, died on 24 May, aged 89. Gell-Mann’s most influential contribution was to propose the theory of quarks — fundamental particles that make up most ordinary matter.

To bring order to a plethora of recently discovered subatomic particles, in 1961 Gell-Mann proposed a set of rules based on symmetries in the fundamental forces of nature. The rules classified subatomic particles called hadrons into eight groups, a scheme he named the eightfold way in a reference to Buddhist philosophy.

In 1964, he realized that such rules would naturally arise if the particles were composed of two, three or more fundamental particles, held together by the strong nuclear force. (US–Russian physicist George Zweig came to the same conclusion independently in the same year.) Protons and neutrons, for example, would be made up of three of these more fundamental particles, which Gell-Man named quarks, inspired by a quote — “Three quarks for Muster Mark!” — from James Joyce’s 1939 novel Finnegan's Wake. [1]

Quarks and Leptons are the building blocks which build up matter, i.e., they are seen as the "elementary particles". In the present standard model, there are six "flavors" of quarks. They can successfully account for all known mesons and baryons (over 200). The most familiar baryons are the proton and neutron, which are each constructed from up and down quarks. Quarks are observed to occur only in combinations of two quarks (mesons), three quarks (baryons). There was a recent claim of observation of particles with five quarks (pentaquark), but further experimentation has not borne it out. [2]


1. Murray Gell-Mann, father of quarks, dies - US physicist was one of the chief architects of the standard model of particle physics. Davide Castelvecchi, Nature
2. Hyperphysics: Quarks

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