This Week’s Hype

The June issue of Discover magazine has an article entitled The Fall and Rise of String Theory (sorry it’s behind a paywall).

I had added this as an update to the last posting, but just looked at it more carefully and realized that it’s squarely in the “string theory predictions” tradition covered by editions of “This Week’s Hype”. In particular, the article claims:

The upcoming Evolved Laser Interferometer Space Antenna could help verify string theory’s predictions of gravity waves. Three spacecraft will orbit around the sun and measure tiny ripples in space-time via sensitive lasers.

The article starts off by explaining the history of string theory this way:

String theory was once the hottest thing in physics…

Strominger knew, even in the euphoric ’80s, that such assertions were overblown. And, sure enough, skepticism has seeped in over the years. No one has yet conceived of an experiment that could definitively verify or refute string theory. The backlash may have peaked in 2006, when several high-profile books and articles attacked the theory. But while string theory has receded from the spotlight, it has not gone away. “The theory is still evolving and getting better — and better understood,” maintains Juan Maldacena of the Institute for Advanced Study at Princeton University….

Emerging from this diverse work is a new consensus: String theory may not be the fabled theory of everything, Strominger says, “but it is definitely a theory of something.”

The article’s main selling point for string theory is that it led Strominger to think about something else, ideas about the conformal symmetry of black hole solutions.

Strominger subsequently realized that the presence of this symmetry, which hadn’t been recognized before, could be used to support a range of predictions. For example, he and his collaborators are currently trying to calculate the intensity of electromagnetic radiation emanating from the vicinity of a black hole. In a few years, Strominger says, once the worldwide network known as the Event Horizon Telescope comes online, astronomers can test those radiation estimates through direct measurements.

Using similar techniques originally inspired by string theory, Strominger’s group has computed the spectrum of gravitational waves emitted when compact objects like stars fall into giant black holes — predictions that could be verified by the future Evolved Laser Interferometer Space Antenna, planned to launch in two decades (or maybe sooner). Strominger also believes that evidence of conformal symmetry might emerge from the Laser Interferometer Gravitational-Wave Observatory, which spotted gravitational waves for the first time earlier this year. Soon, he says, astronomers may be drowning in data that they cannot fully interpret. “We’d like to use ideas from string theory to shed some light on corners of this.”

From now on, I guess use of conformal symmetry in physics now likely to be sold as a “prediction of string theory”.

The article goes on to a different area of string theory hype, that of AdS/CMT. According to Andrew Green of University College, London, string theory is “the new calculus”, and according to the piece’s author “Strominger agrees.” It’s hard to come up with appropriate words to characterize this level of hype.