# New Directions in Foundations of Physics 2008

On Friday afternoon, John Norton and I packed our bags and headed East to Washington, D.C., for the annual New Directions in Foundations of Physics conference. Here’s a little taste of my experience.

My late registration for the conference actually prevented me from joining everyone on the first day, so I spent Friday wandering around D.C. with my Hawking & Ellis text. This was just fine, as I needed to straighten a few things about the uniqueness of geodesics for one of my latest projects (which I promise to write about soon). And anyway, that evening, Jeff Bub very kindly hosted a reception for everyone at his house. So for me the conference began — as all good conferences should — with a glass of wine and plenty of friendly faces.

SATURDAY

The next morning, I pulled the car up to the hotel and piled it full of philosophers of physics. Paul Teller skillfully navigated us to the conference site, all the while deftly deflecting the good-natured heckling of John Norton and Richard Healey. We arrived, tanked up on coffee and bagels, and everything began.

When you first encounter quantum mechanics, you’re often inclined to ask, “Yes yes, but what’s really going on?” The non-intuitiveness of the quantum world often leads one to feel that there might be more a intuitive mechanism behind quantum theory, which (one hopes) would still give rise its successful predictions. A feeling like this that seemed to be lurking behind each of the day’s lectures.

What I learned by the end of the day is that there are many different ways that this upset-feeling can be appeased, if you work hard enough. Each of the four talks presented some new mechanism capable of modeling certain quantum phenomena. You might try to describe some correlations using classical theory and restricted notion of randomness, or using game theory. Or perhaps there is a graphical trick, or category theoretic method (or a combination of the two) that allows one to describe the theory in different terms. But the thesis of each of the talks had the rough form, “Here’s another way to describe the quantum phenomenon X.”

Rather than run through each of them, here’s a taste of what the first talk was like. It was given by Nicolas Gisan, a wily Swiss physicist whom I had the pleasure of meeting at Jeff’s party the night before. He had found a clever way to describe quantum correlations using what he called “non-local boxes.” The trick was to imagine two (classical) binary inputs that go into a randomizing box, and come out as binary outputs, up to some particular relation that the box guarantees. For example, one type of box, which he called a “PR Box,” guaranteed that

input1 * input2 = output1 + output2.

Each of Gisin’s crisp, clear explanations and carefully analyzed experiments were delivered with the punctual precision of the Swiss old school. In the end, he related his new conceptual tool to the Hamiltonian formalism. You won’t find it in nature, but it teaches you something interesting about the physics.

The difficulty, which many of the day’s talks shared, is saying precisely what that “something” is. Bill Unruh (a physics-hero of mine, whom I was delighted to find sitting a few seats to my left) pointed his out in the following way. A calculation that requires an ornate, often complicated conceptual apparatus on the new account, can be calculated in one line using quantum mechanics. So in what sense do the these new accounts improve our understanding?

To me, how you answer Bill’s question depends on how bothered you are by the “upset-feeling” I described above. Should we provide a “more fundamental” account of quantum phenomena than quantum mechanics? If so, you might find new conceptual apparatuses appealing, no matter how complicated they may seem. But if you take the apparatus provided by quantum mechanics to be both necessary and sufficient, it’s not clear how these new accounts help us to understand the world.

SUNDAY

We returned to the conference site the next day, again with the help of Paul Teller’s now-legendary navigating abilities. As the talks got going, I couldn’t help but notice Charles Misner, another one of my physics-heros, sitting right next to me.

The first talk, delivered by Laura Ruetsche, was the type of argument that only a philosopher of physics could give. Laura had drawn a very creative connection between the way in which we think about laws of nature, and the problem of unitarily inequivalent representations. Through a colorful but precise series of definitions and constructions, Laura argued that the traditional of laws as timeless and necessary has led us into unnecessary confusion when it comes to interpreting quantum field theory.

Laura was followed by Wayne Myrvold, who was worried about the following intriguing question: what’s the essence of the distinction between classical and quantum theory? Wayne’s suggestion was, the “non-narrativity” recently suggested by David Albert is not enough.

Both talks fit well into the atmosphere of a conference that was light-hearted, open-minded and fun. I must say that I enjoyed meeting, eating, and drinking with the members of this community as much as I enjoyed the content of the talks. Everyone was extremely kind and hospitable, above all Jeff and Robin. It was a successful conference by all accounts, and one I look forward to returning to next year.

Soul Physics is authored by Bryan W. Roberts. Thanks for subscribing.
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