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Posts Tagged ‘particle physics

“Bohr was inconsistent, unclear, willfully obscure, and right. Einstein was consistent, clear, down-to-earth, and wrong.”*…

The founders of quantum mechanics understood it to be deeply, profoundly weird. Albert Einstein, for one, went to his grave convinced that the theory had to be just a steppingstone to a more complete description of nature, one that would do away with the disturbing quirks of the quantum.

Then in 1964, John Stewart Bell proved a theorem that would test whether quantum theory was obscuring a full description of reality, as Einstein claimed. Experimenters have since used Bell’s theorem to rule out the possibility that beneath all the apparent quantum craziness — the randomness and the spooky action at a distance — is a hidden deterministic reality that obeys the laws of relativity.

Now a new theorem has taken Bell’s work a step further. The theorem makes some reasonable-sounding assumptions about physical reality. It then shows that if a certain experiment were carried out — one that is, to be fair, extravagantly complicated — the expected results according to the rules of quantum theory would force us to reject one of those assumptions.

According to Matthew Leifer, a quantum physicist at Chapman University who did not participate in the research, the new work focuses attention on a class of interpretations of quantum mechanics that until now have managed to escape serious scrutiny from similar “no-go” theorems.

Broadly speaking, these interpretations argue that quantum states reflect our own knowledge of physical reality, rather than being faithful representations of something that exists out in the world. The exemplar of this group of ideas is the Copenhagen interpretation, the textbook version of quantum theory, which is most popularly understood to suggest that particles don’t have definite properties until those properties are measured. Other Copenhagen-like quantum interpretations go even further, characterizing quantum states as subjective to each observer…

… which has, as you will see as you read on in the piece excerpted above, some pretty profoundly weird implications. Either the rules of quantum mechanics don’t always apply, or at least one basic assumption about reality must be wrong: “A New Theorem Maps Out the Limits of Quantum Physics.”

See also “Reality is that which, when you stop believing in it, doesn’t go away.”

* John Stewart Bell

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As we pity Schrödinger’s cat, we might we might send penetrating birthday greetings to Henry Way Kendall; he was born on this date in 1926. A particle physicist, he shared the Nobel Prize in Physics in 1990 (with Jerome Isaac Friedman and Richard E. Taylor) “for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics.”

In 1969, Kendall helped found the Union of Concerned Scientists. In 1997, in connection with the Kyoto Climate Summit, he helped produce a statement signed by 2,000 scientists calling for action on global warming.

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“Blessed be you, mighty matter”*…

 

anyon

The existence of anyons was inferred from quantum topology — the novel properties of shapes made by quantum systems

 

Every particle in the universe — from a cosmic ray to a quark — is either a fermion or a boson. These categories divide the building blocks of nature into two distinct kingdoms… or so we thought.  Now researchers have discovered the first examples of a third particle kingdom…

Anyons, as they’re known, don’t behave like either fermions or bosons; instead, their behavior is somewhere in the middle. In a recent paper published in Science, physicists have found the first experimental evidence that these particles don’t fit into either kingdom. “We had bosons and fermions, and now we’ve got this third kingdom,” said Frank Wilczek, a Nobel prize–winning physicist at the Massachusetts Institute of Technology. “It’s absolutely a milestone.”…

Rethinking the substance of reality…  More on these newly-identified building blocks at “‘Milestone’ Evidence for Anyons, a Third Kingdom of Particles.”

* “Blessed be you, mighty matter, irresistible march of evolution, reality ever newborn; you who, by constantly shattering our mental categories, force us to go ever further and further in our pursuit of the truth.”   — Pierre Teilhard de Chardin, Hymn of the Universe

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As we examine existence, we might spare a thought for Roger Bacon; he died on this date in 1292.  A philosopher and Franciscan friar, Bacon was one of the first to propose mathematics and experimentation as appropriate methods of science.  Working in mathematics, astronomy, physics, alchemy, and languages, he was particularly impactful in optics: he elucidated the principles of refraction, reflection, and spherical aberration, and described spectacles, which soon thereafter came into use.  He developed many mathematical results concerning lenses, proposed mechanically propelled ships, carriages, and flying machines, and used a camera obscura to observe eclipses of the Sun.  And he was the first European give a detailed description of the process of making gunpowder.

He began his career at Oxford, then lectured for a time at Paris, where his skills as a pedagogue earned him the title Doctor Mirabilis, or “wonderful teacher.”  He stopped teaching when he became a Franciscan.  But his scientific work continued, despite his Order’s restrictions on activity and publication, as Bacon enjoyed the protection and patronage of Pope Clement…  until, on Clement’s death, he was placed under house arrest in Oxford, where he continued his studies, but was unable to publish and communicate with fellow investigators.

Statue of Roger Bacon in the Oxford University Museum

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Written by LW

June 11, 2020 at 1:01 am

“All is Number… Number rules the universe”*…

 

Threes

 

The universe has cooked up all sorts of bizarre and beautiful forms of matter, from blazing stars to purring cats, out of just three basic ingredients. Electrons and two types of quarks, dubbed “up” and “down,” mix in various ways to produce every atom in existence.

But puzzlingly, this family of matter particles—the up quark, down quark, and electron—is not the only one. Physicists have discovered that they make up the first of three successive “generations” of particles, each heavier than the last. The second- and third-generation particles transform into their lighter counterparts too quickly to form exotic cats, but they otherwise behave identically. It’s as if the laws of nature were composed in triplicate. “We don’t know why,” said Heather Logan, a particle physicist at Carleton University.

In the 1970s, when physicists first worked out the standard model of particle physics—the still reigning set of equations describing the known elementary particles and their interactions—they sought some deep principle that would explain why three generations of each type of matter particle exist. No one cracked the code, and the question was largely set aside. Now, though, the Nobel Prize–winning physicist Steven Weinberg, one of the architects of the standard model, has revived the old puzzle. Weinberg, who is 86 and a professor at the University of Texas, Austin, argued in a recent paper in the journal Physical Review D that an intriguing pattern in the particles’ masses could lead the way forward…

The laws of nature appear to have been composed in triplicate: “Why Do Matter Particles Come in Threes?

* Pythagoras

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As we study structure, we might recall that on this date in 1981, Nature set the world’s record for “Longest Scientific Name” when it published the systematic name for the deoxyribonucleic acid (DNA) of the human mitochondria; it contains 16,569 nucleotide residues and is thus about 207,000 letters long.

220px-Map_of_the_human_mitochondrial_genome.svg

The 16,569 bp long human mitochondrial genome with the protein-coding, ribosomal RNA, and transfer RNA genes

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Written by LW

April 9, 2020 at 1:01 am

“There is a size at which dignity begins”*…

 

neutrino1-800x533

The spectrometer for the KATRIN experiment, as it works its way through the German town of Eggenstein-Leopoldshafen in 2006 en route to the nearby Karlsruhe Institute of Technology

 

Isaac Asimov dubbed neutrinos “ghost particles.” John Updike immortalized them in verse. They’ve been the subject of several Nobel Prize citations, because these weird tiny particles just keep surprising physicists. And now we have a much better idea of the upper limit of what their rest mass could be, thanks to the first results from the Karlsruhe Tritium Neutrino experiment (KATRIN) in Germany. Leaders from the experiment announced their results last week at a scientific conference in Japan and posted a preprint to the physics arXiv.

“Knowing the mass of the neutrino will allow scientists to answer fundamental questions in cosmology, astrophysics, and particle physics, such as how the universe evolved or what physics exists beyond the Standard Model,” said Hamish Robertson, a KATRIN scientist and professor emeritus of physics at the University of Washington…

Physicists get small: “Weighing in: Physicists cut upper limit on neutrino’s mass in half.”

* Thomas Hardy, “Two on a Tower”

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As we step onto the scales, we might spare a thought for Max Karl Ernst Ludwig Planck; he died on this date in 1947.  A theoretical physicist, he is best remembered as the originator of quantum theory.  It was his discovery of energy quanta that won him the Nobel Prize in Physics in 1918.

220px-Max_Planck_1933 source

 

Written by LW

October 4, 2019 at 1:01 am

Adventures in Cosmology: Starting out Simply…

Why was entropy so low at the Big Bang? (source: Internet Encyclopedia of Philosophy)

Back in 2010, SUNY-Buffalo physics professor Dejan Stojkovic and colleagues made a simple– a radically simple– suggestion:  that the early universe — which exploded from a single point and was very, very small at first — was one-dimensional (like a straight line) before expanding to include two dimensions (like a plane) and then three (like the world in which we live today).

The core idea is that the dimensionality of space depends on the size of the space observed, with smaller spaces associated with fewer dimensions. That means that a fourth dimension will open up — if it hasn’t already — as the universe continues to expand.  (Interesting corollary: space has fewer dimensions at very high energies of the kind associated with the early, post-big bang universe.)

Stojkovic’s notion is challenging; but at the same time, it would help address a number of fundamental problems with the standard model of particle physics, from the incompatibility between quantum mechanics and general relativity to the mystery of the accelerating expansion of the universe.

But is it “true”?  There’s no way to know as yet.  But Stojkovic and his colleagues have devised a test using the Laser Interferometer Space Antenna (LISA), a planned international gravitational observatory, that could shed some definitive light on the question in just a few years.

Read the whole story in Science Daily, and read Stojkovic’s proposal for experimental proof in Physical Review Letters.

As we glance around for evidence of that fourth dimension, we might bid an indeterminate farewell to Ilya Prigogine, the Nobel Laureate whose work on dissipative structures, complex systems, and irreversibility led to the identification of self-organizing systems, and is seen by many as a bridge between the natural and social sciences.  He died at the Hospital Erasme in Brussels on this date in 2003.

Prigogine’s 1997 book, The End of Certainty, summarized his departure from the determinist thinking of Newton, Einstein, and Schrödinger in arguing for “the arrow of time”– and “complexity,” the ineluctable reality of irreversibility and instability.  “Unstable systems” like weather and biological life, he suggested, cannot be explained with standard deterministic models.  Rather, given their to sensitivity to initial conditions, unstable systems can only be explained statistically, probabilistically.

source: University of Texas

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