Saturday, July 23, 2016

LUX

LUX looked for WIMPs using liquid Xenon. Their presentation is here.

Summary: they didn't find any, and put even stronger limits on their presence than ever before. (No, I have no idea what that 8B point on the figure means.) In the figure below, they say anything below the dark line at the bottom is still possible, but above it--not likely.

I don't mean that kind of WIMP. We've strong evidence for dark matter--stuff that doesn't interact strongly with normal matter, has to be uncharged, etc. One easy model proposes that dark matter is made of massive particles that don't interact strongly, but still do interact. WeaklyInteractingMassiveParticles. Since they interact weakly, maybe they interact via the Weak Interaction? If so, every now and then one of these WIMPs streaming through space should kick a nucleus, just as every now and then a neutrino does.

Several experiments have looked for them. LUX is the best so far in this regime--their curve is lower than everybody else's, including their own earlier (less data) work.


They lucked out, I suppose. The "Brazil" bands of yellow and green (named because of a resemblence to the flag of--guess) represent where they thought their sensitivity would be--they did even better, presumably thanks to some statistical fluctuation.

In one sense, there's still plenty of room for WIMPs to exist: you can always add another decade to the bottom of the log plot and make it look like there's more space. And, though it isn't so obvious, there are some assumptions shared by all the experiments shown involving the expected density of dark matter at this radius of the galaxy. If those estimates are badly wrong the raw numbers on the plot change. (The curves stay the same relative to each other, though.)

Long ago they ruled out interpreting the DAMA (or DAMA/Libra) results as WIMPs.

DAMA assumed that our solar system's orbit in the galaxy intersects a stream of dark matter flowing at some speed and direction. So long as it isn't at right angles to the Earth's rotation around the Sun, the Earth (and detectors flying aboard it) should intersect this stream with different speeds at different points in the Earth's orbit. If dark matter interacts at all with nuclei, never mind how, there should be an annual modulation in the interaction rate according as we hit the dark matter faster or slower. They see an annual modulation. They think it is dark matter. Most people don't, anymore.

So, where is the dark matter? If it doesn't interact at all (besides gravitationally) with normal matter, how in the world did the big bang manage to evolve two different types of matter? MACHOs, anyone?

I tend to favor a model in which the dark matter interacts only with neutrinos. Unfortunately, there's almost no way to test this. A successor to IceCube might be able to do it eventually, but first you have to have a good handle on extra-galactic neutrino sources, good enough to predict what rates ought to be and look for shortfalls--and that won't be good enough for years yet. Or you can hope for a conveniently placed supernova or three.

Robots in finance

Meiji Yasuda Life Insurance Co. has announced plans to deploy 100 Pepper robots, made by SoftBank Group Corp., at its 80 branches in October. Pepper will explain insurance products and services, and accompany sales people on their rounds.

This will give Meiji Yasuda the highest number of humanoid robots deployed in the financial industry.

A colleague points out that in Japan robots are more often seen as friendly helpers than threats. Still--a robot insurance salesman never gets tired, never gives up, never takes a hint.

And something about that phrase "highest number of humanoid robots deployed in the financial industry" suggests deep secrets somewhere. Do you welcome our new robot overlords, comrade?

mosquito repellent

Everybody has probably already read that chicken odor seems to reduce the presence of malaria-capable mosquitoes. I was told years ago that mosquitoes home in on CO2 and a few other chemicals--maybe something confuses them too.

But notice: it just reduces the number. And...

I was almost never bitten by mosquitoes in a room with a mosquito coil burning. Whether they drove mosquitoes out I never knew, but the incense drove me out. Chickens running around the house...

Friday, July 22, 2016

Paleo diet, adapted

The "paleo diet" was all the rage not too long ago--I still find relics of the fashion here and there. I was otherwise occupied--studying how to keep blood sugar low seemed more fruitful.

I gather the gist was to eat as your ancestors did.

I don't know about yours, but my ancestors ate lots of preserved food. Preserved beans may not have the same texture and crunch as those fresh off the vine, but it turns out they're available during winter. Were the originators of the paleo diet from California, perhaps? Hmm. Nope, Voegtlin was from Seattle--winters are not exactly cold there, but they're not good for growing.

So my ancestral diet would be fresh food in season, and preserved stuff the rest of the year. Meat as available ("Before food waste, let belly burst"), bread, fish as available... Today: Fresh food is in the fresh food section of the grocery store, fresh meat is in the meat section, and preserved food makes up a lot of the rest. Just what the doctor ordered! Beef jerky and a loaf of bread and a helping of preserved green beans (from a can)--eat like your ancestors did. I'll bet they fixed up things like this. OK, without the potatoes--maybe oats.

Don't get the wrong impression: I'm surrounded by very good cooks and I no longer rely on "bachelor hash." But you can find cuisines in this country based on what you can fix out of cans and dried foods, and they seem as worthy the title of "ancestral style" as anything else. Only the rich get to eat fresh all the time.

Thursday, July 21, 2016

Disappointment alloyed?

"Russian track and field athletes will remain banned from the Olympics following claims the country ran a state-sponsored doping programme.(sic)"

Given the dangers from political violence and health risks I wonder if there's a little relief mixed in with the disappointment. The disappointments are huge--most athletes have very few chances at the Olympics, and missing this will mean that some will be too old/injured to compete next time. But I wonder how many have been having second thoughts about swimming/boating in a sewer, or relying on Brazilian security forces to keep terror attackers away.

Wednesday, July 20, 2016

The sales reps don't explain things well

We hired a new storage engineer the other month, and shortly thereafter lost him when he got an offer he couldn't refuse. In the meantime he helped commission an addition to our biggest lustre filesystem; a new Compellent system. Folklore says lustre likes its component filesystems to be roughly the same size, so this was divvied up into RAID6 virtual arrays. 160 disks *4TB/each *.9 to get TiB = 576TiB. 32TiB is a nice number, close to the size of the other arrays in the lustre system, so he configured 18 of them.

If you know storage you just went "rookie mistake: he forgot about the parity disks(*); you can really only make 15 arrays of that size, not 18." Yep, and usually that kind of mistake doesn't matter--when you try to do something like that the system does the arithmetic for you and you find out pretty quickly.

But the Compellents are clever. They were designed for a business model where you supply disk storage to 1000 machines, each with its own .5TB storage. If you look the machine you're browsing from, you notice there's a lot of "wasted" space; you don't use all .5TB. I certainly don't. So suppose your storage server pretended that it really had 800TB instead. That way your business can supply disk storage to 1500 machines. The space is over-committed, but just like airlines over-booking, most of the time it doesn't matter. If only a handful of users really need that full .5TB, they can get it without any intervention, and the rest don't know the difference. Nice and clever. (The Compellent is even more clever than that: it divides up space in virtual arrays that reflect your preferences for virtual disk sizes and does other cute tricks that we have absolutely no use for.)

We, on the other hand, want to fill up all the space with data, in one giant chunk. So the upshot was that the system pretended to have 25% more space than it really did. We set about filling it all up.

You can see that this is not going to end well.

It got worse. The system supports RAID6 (higher density) virtual storage, RAID10-dual striped (high read/write performance), or a dynamic combination in which the system accepts writes as high performance RAID10, and at some configurable after-hours time spends some time translating the fat RAID10 down to slow RAID6. That's 3 different modes. For the last mode (balance) you can either set a time or rely on a default that looks to be once a week or so (in hindsight).

With that in mind: imagine that you use the defaults--balance (write fat, translate to thin later) and once a week it does translation.

Now start filling it up slowly. All looked OK, no stability problems, so we let her rip.

Um. With maybe 300TiB already aboard, we now loaded about 70TiB in a few days. The clever machine turned this 70TiB input into 210TiB high performance dual-striped RAID10. Now it had no space left to do translations, and decided the safest thing to do was become readonly.

Down went the lustre filesystem. The only guy left on the team who had been learning lustre is still in the north woods with no cell phone coverage. Away went the weekend. We kept 3 pairs of eyes on everything as we learned as we went along.

We spent a lot of time with Dell engineers Monday. One was able to cobble together an array out of the spare disks to start a very slow translation job, while we try to drain one of the logical arrays so we can delete it and make the space to do fast translations. (Goosing that along is the reason I'm still awake right now. I spent a fair bit of today trying to clean up corrupted files.)

It was our configuration screw-up, and we're grateful for Dell pulling out chestnuts out of the fire. But we're going to change some procedures...


(*) RAID5 uses N data and 1 parity disk. If a disk fails (believe me, they do), you haven't lost any data. You can pop a spare in and rebuild the array. Problem: the rebuilding is pretty I/O intensive, and disks from the same family often have similar lifetimes. If you lose another disk during the rebuilding process, you've lost all the data in the array. Hence RAID6: N data and 2 parity disks. So if you have 10 4TB disks, by the time you're done putting it together in a safe array you have only 8 effective disks: 32TB instead of 40TB.

RAID10 is nice and fast and robust: each disk has a duplicate. Dual striped RAID10 is even more robust and fast: each disk has 2 spares. But that means that 2/3 of your space is "wasted."

Friday, July 15, 2016

Side effects

The UNMIL has had a large peacekeeping force in Liberia for a number of years now, and it is time to draw down.

When I was there I saw quite a few furniture stores. I was told this was part of a rehabilitation for former fighters--learn a trade and support yourself. Ah. And who buys the Western-style furniture? Oh, mostly foreigners, peacekeepers, and so on. And what happens when the peacekeepers leave and live somewhere else? We expect the economy to have picked up by then.

A lot of the troops' salaries probably went home to family, but some was spent locally and it was hard currency. Now that they're leaving, hard currency is drying up. Expect a jolt.

Blame slinging has already begun:

He said the CBL is, however, aware that there are some business executives who are reportedly hoarding large quantities of Liberian dollar at home instead of using the banking system.

He said these suspected hoarders have the tendency of using cash “hoards to adversely and artificially impact the exchange rate; actions that have the propensity to be interpreted as economic sabotage.”

People are blaming the CBL for printing too many Liberian dollars; he needs to point elsewhere. Still--claiming that executives are hoarding Liberian dollars in order to make them depreciate?

BTW, police aren't getting paid:

Delays in the payment of Liberia National Police officers after waiting for nearly three months yesterday took a different turn when pay checks in Liberian dollars could not be encashed at the bank.

After the checks were reportedly rejected due to lack of sufficient funds, LNP authorities under the supervision of the Police Support Unit (PSU) took over yesterday’s payment exercise, which was conducted in the basement of the LNP on Capitol Hill.

A Daily Observer investigation established that during the exercise, which brought together officers from the PSU, Liberian dollar checks that were destined to be cashed at one of the local banks, were discovered to have names of several “dead personnel and officers,” others who had traveled abroad and others dismissed and no longer in the employ of the LNP.

I don't think you can attribute that problem to the UNMIL drawdown, though.

Wednesday, July 13, 2016

Sunday, July 10, 2016

"Gen of Academia, I observe that you are very religious in all respects."

I've read several popular essays bemoaning the hypersensitive "precious snowflakes" afflicting our campuses, and wondering at the spinelessness of the administrators.

I don't believe it. I don't know any of these alleged snowflakes personally, but somehow I have trouble believing that a professor would need a fainting couch when a man wore the wrong shirt. If so, TV should have left her comatose.

This alleged sensitivity seems more like tithing dill and mint and cumin and carefully straining out all gnats from the camel soup.

Let me run with that model. Infidels and any who disagree with a denunciation are evil. Those who fail to commit to the full (and dynamic) list of regulations are, at best, failures who must be rebuked. The sensitivity is affectation, in a status struggle as they explore the ramifications of the principles of their religion.(*) If A can claim awareness of a new oppression, however small it may seem to outsiders, that proves that "ze" is holier than the others.

The faith is widely respected, even by school administrators who, since they often have real jobs, are not generally among the adepts. The adepts tell others what needs to change.

Hmm. The model seems to fit OK.

At least the old Syrian ascetics only flagellated themselves.

(*) The main articles of the faith seem to be that all human relationships are power-based, all people are equivalent and only distinguished by environment, and that identity is self-determined. And that inequality is proof that power has been misused.


Perhaps I should borrow a phrase from Andre Norton and start referring to people as "gentle-saps," suppressing the urge to use the short vowel sound instead of the long.

Sunday, July 03, 2016

July 3 fireworks

The temperature slowly dropped from the 70's to mid 60's as the evening darkened. We'd decided to skip the city fireworks display, which was scheduled for after the last midget race, which started at 10. We opted for a small fire in the firepit instead. We didn't miss much though--the fireflies were out in force (but not mosquitoes!), and neighbors 2 houses away had an hour and a half of cone fountains, rockets, and shells. I've no idea how they afford the display; maybe several families get together--I didn't recognize most of the people standing around when I went over to thank them. One of the big red 80' wide bursts went off 30 feet up (oops) and a small silver blue shell skittered down the street before exploding--but otherwise there were no mishaps in the amateur show.

Across the street in the other direction, in "Nature's Preserve Office Park" (*), another group fired off a shorter show; a block down our street somebody was setting off some lovely shells; there was another show two blocks in one direction and we could see another through the trees about 6 blocks away in yet another direction.

So we had a fine time sitting and watching the fire and the fireworks and the fireflies.

Rockets and shells are quite illegal, of course (this is Wisconsin), but I think the police know better than to try to interfere. Middle Daughter suggested they were probably very busy with drunk and disorderly.


(*) You can't make this stuff up.

Thursday, June 30, 2016

We need some new ideas

Sabine Hossenfelder writes
At the end of the LHC’s first run at high energies, both the CMS and ATLAS collaborations reported a particularly interesting “bump” in the diphoton channel. ... a bump of a particular size, width and energy could either indicate a completely new, fundamental, beyond-the-standard-model particle, the first of its kind – or a new standard model feature — or it could simply be statistical noise. Despite the fact that it would be the nightmare of most of my colleagues, I’m hoping the diphoton bump turns out to be nothing more than noise.
and
Since I entered physics, I’ve seen grand unified models proposed and falsified. I’ve seen loads of dark matter candidates not being found, followed by a ritual parameter adjustment to explain the lack of detection. I’ve seen supersymmetric particles being “predicted” with constantly increasing masses, from some GeV to some 100 GeV to LHC energies of some TeV. And now that it looks like the LHC isn’t going to see any superpartners either, my colleagues in particle physicists are more than willing to once again move the goalposts.

Yep. What she said. SuperSymmetry is a way to get the equations to please not give infinity as an answer, but somehow the predicted particles (one for each of the known particles) just never turn up. SuperCemetery of effort.

Perhaps more dramatically, Adam Frank wants to drag some theorists out of Laputa with a few postulates that used to be pretty standard wisdom: "There is only one universe." (a bas le multiverse!) "Time is real" (not emergent), and "Mathematics is selectively real" (the real world doesn't care how beautifully symmetric your equations are).

Two big complaints about string theory are that there's been no convergence on an actual theory that makes testable predictions within its framework(*), and that it predicts SuperSymmetry--which doesn't seem to exist.

I'll add my complaint that when you have to renormalize to get your sums to shake the infinities out of them, there's something seriously wrong with the paradigm of your calculation. I don't know how to fix it. (**)

And in a related vein, I'm pretty dubious of early Universe inflation: the universe expanded extra fast for a while just after the Big Bang. Why? Ummm.. Well, if it did expand that way then observations match theory, so let's assume it did and try to figure out how. And Dark Energy to make the Universe's expansion accelerate.

We need some new ideas.


(*)The assumptions that make up the framework seemed quite nice, though.


(**) UPDATE: I think what I want is a way of finding a problem dual to the type of things we do now, but that is more tractable even if it is less obvious how it connects to the physics.

Tuesday, June 28, 2016

In amber

A bird lost a wing-tip in amber. I've nothing to say, just go look. I didn't know amber sometimes had feathers, but this isn't the only sample.

Saturday, June 25, 2016

More proverbs

I spent a good chunk of the day resting my newly wrenched back(*) and reading the Expositors commentary on Ecclesiastes. (Wordy, and I think he missed fire a few times.) He cited some proverbs from the Talmud, and I looked them up. Some of the proverbs are familiar, and I gather they were a little reluctant to cite one source, but others aren't. Have a look.
The house which opens not to the poor will open to the physician.

Hospitality is an expression of Divine worship.

Truth is heavy, therefore few care to carry it.

The soldiers fight, and the kings are heroes.

Commit a sin twice and it will not seem to thee a crime.

Hold no man responsible for his utterances in times of grief.

All the blessings of a household come through the wife, therefore should her husband honour her.


(*) and walking around too, the way you're supposed to--but it's hard to read then.

Friday, June 24, 2016

Voting

BBC has a puff piece on youth response to the Brexit.
Other than anger, a common theme was frustration among 16- and 17-year-olds, who were not allowed to vote in the poll. Last year an initiative backed by Labour, the Lib Dems and SNP proposed lowering the voting age. However the government rejected the idea on the grounds of cost, and it was voted down.

"I love waking up to be completely terrified about something that's going to affect me yet i had no say in it," mused one teenager.

I completely forgot about that bit of nonsense: 16-year-old voters. Yikes.

I've a better idea: raise the voting age to 30, younger if you serve a couple of years in the military.

FWIW, I'm not British, and can really only guess at how I would have voted if I was. As an American, I'd vote for Brexit and damn the torpedoes. But I've no feel for what the problems and benefits and loyalties really would be like there, and apparently a lot of people there thought differently; Brexit won by only a small margin.