quantum gravity

Physics / Quantum Mechanics / Relativity / etc.

The Holometer

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You may have heard the buzz about the holometer, shown in figure 1, before. It’s a giant laser interferometer, much like those used to search for gravitational waves, designed to detect quantum fluctuations in the fabric of spacetime. At least, that’s the claim. The holometer just released a preprint of their first science paper. And of course,  a Fermilab press release appears in Symmetry Magazine. The article is good, and I recommend you read it. And the holometer experiment is good, interesting science. But I have to say, I’m extremely annoyed by how much the holometer team is overselling their

Astrophysics / Geometry / Mathematics / etc.

Speculative Sunday: Can a Black Hole Explode?

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Cassiopeia A Spitzer Image

Nothing can escape the gravitational pull of a black hole, not even light. That’s why they’re, well, black. (Of course, as I’ve described before, black holes can glow very brightly, thanks to all the in-falling matter. Sometimes they even produce gamma rays. I’m also ignoring the negligible amount of Hawking radiation that black holes theoretically produce.) Once you pass the event horizon of a black hole, you cannot ever escape. Escape is simply forbidden by the laws of physics. That is, of course…if there actually is an event horizon, not just something that looks like one. Carlo Rovelli ,

Condensed Matter / cosmology / Physics / etc.

BICEP2, Primordial Gravity Waves, and Cosmic Inflation

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“Like the microscopic strands of DNA that predetermine the identity of a macroscopic species and the unique properties of its members, the modern look and feel of the cosmos was writ in the fabric of its earliest moments, and carried relentlessly through time and space. We feel it when we look up. We feel it when we look down. We feel it when we look within.” ~Niel Degrasse Tyson There was some very big news today! If you haven’t already heard, the BICEP2 research group at Harvard has found evidence of ancient gravitational waves in the sky. A lot

cosmology / Discrete Math / Geometry / etc.

Quantum Geometry: Causal Dynamical Triangulations

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An example causal triangulation

A “quantum gravity expert” is presumably someone well acquainted with the details of our immense ignorance of the subject. I suppose I count. ~John Baez I long ago promised that I would discuss some of my own research. Here’s the first post that makes good on that promise. Today I’ll discuss a theory of quantum gravity. Why Quantum Gravity? Without a doubt, the two greatest advances in physics in the last 120 years were the advent of general relativity and quantum mechanics. These two amazing theories have totally changed the way we see the world. Quantum mechanics describes the

Geometry / Mathematics / Physics / etc.

You Can’t Get There From Here: Dimension, Fractional Dimension, and the Quantum Universe

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You can’t get there from here. ~Maine saying My father once quoted a saying from Maine, where he spent some of his youth: “You can’t get there from here.” It refers to Maine’s winding road system, which often prevents a traveller from taking a direct route between two places. In physics and math terms, we might say that Maine’s road system is of fractional dimension: Less than two-dimensional, but more than one-dimensional. Integer Dimensionality Traditionally, we define the dimensionality of a space as the number of directions one can move in. For instance, a ski lift lives in a