Finally Read the LIGO Paper

I finally found some time to read the LIGO paper. A couple things that I thought were interesting:

  1. The peak power from gravitational waves was 200 solar masses per second. The power didn’t stay there for very long since a total of 3 solar masses was radiated away.
  2. The rate of false positives the size of the signal seen is one in tens of thousands of years, so this is a signal that is enormously above any known backgrounds.
  3. LIGO also uses some complicated template fitting routine where they compare the measured signal to a library of pre-calculated theoretical curves. This only gives approximate results for physics parameters, so they then have to supplement this with an actual fit.
  4. The next biggest event had a false positive rate of only one every few years

Debate Over Math Curriculum Resurfaces

The debate over primary & secondary school math curricula that was sparked in part by a New York Times editorial a couple years ago has come up again in the Chronicle of Higher Education.

The main argument now, as before, is that subjects beyond basic arithmetic are too hard for many students and should not be required for graduation nor seen as necessary for gaining entrance into colleges. This includes subjects like geometry and algebra.

The original article was met with widespread scorn, and this one, which includes an interview with the author of the old article, should too. Basically, there are a huge number of problems with eliminating a requirement that high school students take algebra or even discouraging students from taking classes like algebra, trigonometry, and calculus. For subjects involving math, these courses represent something more like grammar and composition than an advanced course in literary analysis. They are fundamental subjects that must be mastered before a student is capable of succeeding and not arbitrary barriers to success. Entering college without any knowledge of calculus puts students in many fields at a serious disadvantage compared to most of their peers. Without algebra, even introductory classes in many fields are inaccessible, and the corresponding majors become impossible to complete in less than five or even six years.

What Hacker, the author of the original article, suggests doing will effectively lock many students out fields like engineering, physics, chemistry, mathematics, computer science, statistics, and even many (most?) social sciences. All that will be left will be humanities and the arts (and even then some classes may be impossible to complete). He makes the claim that “coding is not based on mathematics,” yet the opposite is true. In many ways, computer science is a subfield of mathematics. There is more to computer science than just programming, but a programmer that knows no serious math will quickly find that their options are limited.

Furthermore, at many colleges, lower-level math classes (basically, anything below calculus) aren’t even considered college material. This is true of the schools that I attended. If students matriculate without being able to take at least calculus, they’ll be forced to waste a lot of time and money taking non-credit remedial courses to catch up.

Hacker’s arguments seem to be based on the assumption that mathematics beyond arithmetic is uniquely expendable out of all the basic primary and secondary school subjects. Somehow other fields like statistics (which is really just a form of applied math) can be taught independently of mathematics. Anyone who has actually studied a field that requires a decent amount of math knows how important a strong background in as many math topics as possible can be. Physics uses topics like group theory, complex analysis, ordinary and partial differential equations, differential geometry, linear algebra, and many others quite regularly. Students don’t typically see any of these until after several semesters of calculus.

I can’t help but think that Hacker sees math as nothing more than rote memorization of basic formulae (which maybe isn’t surprising for someone who has so much disdain for any math harder than arithmetic). Even if literary analysis is just as rigorous as mathematics, that doesn’t mean that we should get rid of mathematics. We should demand that all subjects be as rigorous as possible. Being able to solve complex mathematical problems can be just as important as being able to read complicated works of literature and write coherently about them.

Colbert & Brian Greene Discuss Gravitational Waves

Yesterday, Columbia professor Brian Greene was on Colbert’s show to talk about gravitational waves. Greene gives some nice explanations for laymen (with graphics!) about gravitational waves in general and about LIGO. He even brings out a Michelson interferometer to demonstrate how the LIGO setup works (though not with gravitational waves). Since Greene is a theorist, I would assume that someone else had to set up the interferometer for it to actually show some sensible results. You can find the video on Youtube here.

Antares Looks for Dark Matter Signals

The ANTARES neutrino telescope has a new result looking for “secluded” dark matter, where dark matter annihilation is mediated through some new mediator that then decays into Standard Model particles. They claim that this can explain the high energy bump in the positron/electron ratio and can also still be a thermal relic from the Big Bang.

They look at several different channels, including one where the mediator actually lives long enough to reach Earth and decay in the atmosphere, and others where neutrinos in the final state are measured.

For this model, the result is actually stronger than direct detection experiments for spin-dependent interactions and is stronger at very high masses in the spin-independent channel. While this result isn’t particularly groundbreaking, the paper mentions that it is the first search of this kind for this type of dark matter, and I think the model, which I hadn’t heard much of previously, sounds quite interesting.

DM-Ice Releases Results

The DM-Ice experiment has released their first results for a search for an annually modulating signal of dark matter. They’re currently about an order of magnitude off from the purported DAMA/LIBRA signal but hopefully will improve significantly in the future.

DM-Ice is a NaI(Tl)-based experiment looking for signals of dark matter in their scintillating crystals. The big purpose of DM-Ice is to test various theories for why the DAMA/LIBRA experiment, a NaI(Tl) experiment at Gran Sasso, has seen an annual modulation in its event rate for many years. Various people have proposed that maybe DAMA/LIBRA is just seeing a seasonal effect. DM-Ice is in Antarctica, so any seasonal effects will be very different. If DM-Ice sees the same modulation as DAMA/LIBRA, then that would rule out many of the proposed explanation, since dark matter will modulate in the same way no matter where the detector is but most other things will be location dependent.