Category: Thermo/StatMech

One, Two, Many, Lots: Investigating the Start of Many-Body Physics

Part of Fig. 2 from the arxiv version of the paper by Wenz et al.

Two papers with a similar theme crossed my social media feeds in the last couple of days. You might think this is just a weird coincidence, but I’m choosing to take it as a sign to write about them for the blog. So, what are these papers, and what’s the theme? One is the final… Continue reading One, Two, Many, Lots: Investigating the Start of Many-Body Physics

Free, As In Energy

Via social media, John Novak cashes in a Nobel Betting Pool win from a while back, asking: Please explain to me the relationship between energy, entropy, and free energy. Like you would explain it to a two year old child. Why? There is a statistical algorithm called Expectation Maximization which is often explained in terms… Continue reading Free, As In Energy

When Is a Composite Object a Particle?

Interference pattern of single molecules, cropped from an image on the web page of the Arndt group in Vienna.

Through some kind of weird synchronicity, the title question came up twice yesterday, once in a comment to my TED@NYC talk post, and the second time on Twitter, in a conversation with a person whose account is protected, thus rendering it un-link-able. Trust me. The question is one of those things that you don’t necessarily… Continue reading When Is a Composite Object a Particle?

Things I’ve Never Quite Understood: Microscopic Picture of Blackbody Radiation

Spectrum of light reaching Earth from the Sun, from wikimedia.

I’m putting together slides for a TED audition talk in a couple of weeks, about how the history of quantum mechanics is like a crossword puzzle. This involves talking about black-body radiation, which is the problem that kicked off QM– to explain the spectrum of light emitted by hot objects, Max Planck had to resort… Continue reading Things I’ve Never Quite Understood: Microscopic Picture of Blackbody Radiation

Bose Condensation of Coffee?

Coffee and a notebook, from a fun Physics Stack Exchange discussion.

Writing up the evaporative cooling post on cold atom techniques, I used the standard analogy that people in the field use for describing the process: cooling an atomic vapor to BEC is like the cooling of a cup of coffee, where the hottest component particles manage to escape the system of interest, and what’s left… Continue reading Bose Condensation of Coffee?

Tools of the Cold-Atom Trade: Evaporative Cooling

The signature image of a cloud of rubidium atoms crossing the BEC transition, from the Nobel Prize site.

In our last installment of the cold-atom toolbox series, we talked about why you need magnetic traps to get to really ultra-cold samples– because the light scattering involved in laser cooling limits you to a temperature that’s too high for making Bose-Einstein condensation (BEC). This time out, we’ll talk about how you actually get to… Continue reading Tools of the Cold-Atom Trade: Evaporative Cooling

Few-Body Systems: Cooler Than You Might Think

Figure 2 from the arxiv version of the preparation paper.

Hey, dude? Yeah, what’s up? I’m not normally the one who initiates this, but I was wondering: When you were at DAMOP last week, did you see any really neat physics? Oh, sure, tons of stuff. It was a little thinner than some past meetings– a lot of the Usual Suspects didn’t make the trip–… Continue reading Few-Body Systems: Cooler Than You Might Think

How Good Is My Starbucks Cup?

Highly sophisticated experimental apparatus for testing the quality of my Starbucks cup.

It’s been a while since I’ve done a post over-analyzing some everyday situation, because I’ve been too busy to do any silly experiments. We’re on break this week, though, so I took a little time Monday to bring excessive technology to bear on the critically important scientific question: how good is my insulated Starbucks cup?… Continue reading How Good Is My Starbucks Cup?

Direct and Indirect Heating: Why Don’t Power Plants Change Local Climate?

This past weekend, I was at Boskone, where I appeared on a few science-y panels. One of these was on the possibility of beaming power down from space: Energy From Space Beam me down some juice, Scotty? Let’s talk about the possibilities — and practicalities — of really long-distance power transmission. Tom Easton (M), Jordin… Continue reading Direct and Indirect Heating: Why Don’t Power Plants Change Local Climate?

How Do You Make Negative Temperatures, Anyway?

Part of Figure 1 from the arxiv preprint of the paper discussed in the post.

Last week’s post talked about the general idea of negative temperature, with reference to this much-talked-about Science paper (which also comes in a free arxiv version from which the figures used here are taken). I didn’t go into the details of how they made a negative temperature gas, though, and as it’s both very clever… Continue reading How Do You Make Negative Temperatures, Anyway?