Category Archives: Science

Planck Speaks: Bad News for Primordial Gravitational Waves?

Ever since we all heard the exciting news that the BICEP2 experiment had detected “B-mode” polarization in the cosmic microwave background — just the kind we would expect to be produced by cosmic inflation at a high energy scale — … Continue reading

Posted in arxiv, Science | 52 Comments

How Much Cosmic Inflation Probably Occurred?

Nothing focuses the mind like a hanging, and nothing focuses the science like an unexpected experimental result. The BICEP2 claimed discovery of gravitational waves in the cosmic microwave background — although we still don’t know whether it will hold up … Continue reading

Posted in arxiv, Science | 15 Comments

Cosmological Attractors

I want to tell you about a paper I recently wrote with grad student Grant Remmen, about how much inflation we should expect to have occurred in the early universe. But that paper leans heavily on an earlier one that … Continue reading

Posted in arxiv, Science | 18 Comments

Effective Field Theory MOOC from MIT

Faithful readers are well aware of the importance of effective field theory in modern physics. EFT provides, in a nutshell, the best way we have to think about the fundamental dynamics of the universe, from the physics underlying everyday life … Continue reading

Posted in Academia, Science | 15 Comments

Single Superfield Inflation: The Trailer

This is amazing. (Via Bob McNees and Michael Nielsen on Twitter.) Backstory for the puzzled: here is a nice paper that came out last month, on inflation in supergravity. Inflation in Supergravity with a Single Chiral Superfield Sergei V. Ketov, … Continue reading

Posted in arxiv, Humor, Science | 28 Comments

Quantum Foundations of a Classical Universe

Greetings from sunny (for the moment) Yorktown Heights, NY, home of IBM’s Watson Research Center. I’m behind on respectable blogging (although it’s been nice to see some substantive conversation on the last couple of comment threads), and I’m at a … Continue reading

Posted in Science | 26 Comments

Quantum Sleeping Beauty and the Multiverse

Hidden in my papers with Chip Sebens on Everettian quantum mechanics is a simple solution to a fun philosophical problem with potential implications for cosmology: the quantum version of the Sleeping Beauty Problem. It’s a classic example of self-locating uncertainty: … Continue reading

Posted in Philosophy, Science | 245 Comments

Why Probability in Quantum Mechanics is Given by the Wave Function Squared

One of the most profound and mysterious principles in all of physics is the Born Rule, named after Max Born. In quantum mechanics, particles don’t have classical properties like “position” or “momentum”; rather, there is a wave function that assigns … Continue reading

Posted in arxiv, Philosophy, Science | 96 Comments

Galaxies That Are Too Big To Fail, But Fail Anyway

Dark matter exists, but there is still a lot we don’t know about it. Presumably it’s some kind of particle, but we don’t know how massive it is, what forces it interacts with, or how it was produced. On the … Continue reading

Posted in arxiv, Science | 22 Comments

Why the Many-Worlds Formulation of Quantum Mechanics Is Probably Correct

I have often talked about the Many-Worlds or Everett approach to quantum mechanics — here’s an explanatory video, an excerpt from From Eternity to Here, and slides from a talk. But I don’t think I’ve ever explained as persuasively as … Continue reading

Posted in Philosophy, Science | 237 Comments