Weak equivalence principle violated in gravitational waves

Credit: Pixabay/CC0 Public Domain

The Weak equivalence principle (WEP) is a key aspect of classical physics. It states that when particles are in freefall, the trajectories they follow are entirely independent of their masses. However, it is not yet clear whether this property also applies within the more complex field of quantum mechanics. In new research published in EPJ C, James Quach at the University of Adelaide, Australia, proves theoretically that the WEP can be violated by quantum particles in gravitational waves—the ripples in spacetime caused by colossal events such as merging black holes.

As well as resolving a long-standing debate in quantum theory, Quach’s findings could lead to the development of advanced new materials, including fluids with infinite conductivity and zero viscosity. These could be used as advanced gravitational wave detectors and may even lead to devices which can mirror gravitational waves and harvest their energy. Quach based his approach around a principle named ‘Fisher information’—a way of measuring how much information an observable random variable carries about a particular unknown parameter. Here, the random variable describes the position of a quantum particle in a gravitational field, while the unknown parameter is its mass. If the WEP were obeyed, the Fisher information should be zero in this case.

Through his calculations, Quach rewrote an equation describing the WEP for freely falling quantum particles, to incorporate their Fisher information. He showed that while these particles obey the WEP in static gravitational fields, their trajectories can indeed give away information about their mass when they pass through gravitational waves. For the first time, the calculation precisely characterizes how the WEP can be violated by quantum particles, and provides key insights for future studies searching for the violation through real experiments.

How Einstein’s equivalence principle extends to the quantum world

More information:
James Q. Quach, Fisher information and the weak equivalence principle of a quantum particle in a gravitational wave, The European Physical Journal C (2020). DOI: 10.1140/epjc/s10052-020-08530-6

Weak equivalence principle violated in gravitational waves (2020, October 28)
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ASU journalism student sues, claiming university violated her First Amendment rights in fallout from controversial tweet

An Arizona State University journalism student is suing after she says she was removed from leading the student-run radio station over a controversial tweet.

a woman standing in front of a building: ASU's Walter Cronkite School of Journalism and Mass Communication in downtown Phoenix.

© The Republic
ASU’s Walter Cronkite School of Journalism and Mass Communication in downtown Phoenix.

The suit names the Arizona Board of Regents, ASU, the Walter Cronkite School of Journalism and Mass Communication and Kristin Gilger, Cronkite interim dean.

The lawsuit claims that the university violated Rae’Lee Klein’s First Amendment rights to free expression by refusing to allow her to continue as station manager of Blaze Radio because of her tweet.

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The university, in a statement to The Arizona Republic on Tuesday, refuted that claim, saying, “Klein’s conduct in the aftermath of the tweet — rather than the tweet itself — meant that she was no longer able to perform the job for which she was hired.”

a woman standing in a room: Rae'Lee Klein in the Blaze Radio studio at Arizona State University. Klein has sued the school in the aftermath of her controversial tweet.

© Courtesy of Rae’Lee Klein
Rae’Lee Klein in the Blaze Radio studio at Arizona State University. Klein has sued the school in the aftermath of her controversial tweet.

But Klein said she was first scolded about her tweet and later scolded for her media appearances and conversations with elected officials as her situation gained attention. 

“They were first upset by my free speech and now they’re upset that I’ve become this cause célèbre for free speech, so it’s just disappointing to see them keep taking the same stance and not want to work or correct the situation,” Klein told The Republic. 

Jack Wilenchik, Klein’s attorney, filed the complaint in U.S. District Court on Monday.

Klein faced swift backlash from within and outside her radio station after a tweet she posted in the aftermath of police shooting Jacob Blake in Kenosha, Wisconsin, on Aug. 23. Klein shared a New York Post article with graphic details from a police report accusing Blake of sexual assault.

The Aug. 29 tweet, deleted later, was captioned, “Always more to the story, folks. Please read this article to get the background of Jacob Blake’s warrant. You’ll be quite disgusted.”

Many interpreted her tweet as justifying or excusing police brutality against Black people. Klein defended it as sharing truthful information and an additional perspective, as journalists are taught.

The radio station board quickly voted to remove Klein, but Klein refused to step down. In the weeks of turmoil following, Klein said she was told that she could not stay on as station manager and was offered several other job alternatives.

The school has said Klein was not removed because of the views she expressed.

Klein: First Amendment violated

Klein’s lawsuit states that ASU is unlawfully preventing Klein from being station manager based on the content of her free speech. It asks the court to rule for her to remain in that position. 

Because ASU is an entity of state government, it cannot legally deny benefits — like a job at the radio station — on the basis of speech, according

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