Eigentlich habe ich reine Physik satt, will ich nichts mehr damit zu tun haben. Neurowissenschaften, Lebensprozesse als Informationsverarbeitung, damit kann man mich noch anfixen. Physik? Nein Danke.

Aber ich habe zu viele Freunde, die promovieren, zu viele Menschen um mich, die immer noch begeistert sind. Und manchmal finden die noch etwas, dass alte Neugier zurückkommen lässt. So zum Beispiel folgendes Paper:

Rigol et al.: Thermalization and its mechanism for generic isolated quantum systems

Für die Nichtphysiker: warum ist das so toll? Unsere Beschreibung der kleinsten Dinge ist dergestalt, daß diese kleinsten Dinge entsetzlich stabile Zustände haben. Wenn man irgendwelche Elementarteilchen, z.B. Elektronen brav irgendwo aufreiht (man nennt das: ihren Spin ausrichtet) dann bleiben die in diesem ‘präparierten’ (Quanten-)Zustand. Für alle Zeit.

Unsere Beschreibung der Systeme, die aus abermilliarden von kleinsten Teilchen aufgebaut sind, ist wiederum so, daß zunehmende Unordnung (’Entropie’) eine zwangsläufige Konsequenz des Vergehens der Zeit ist. Das kollidiert natürlich mit dem ewigen Zustand des präparierten Systems. Der Ausweg ist ein häßliches Konzept, das man Bad-System Kopplung nennt: für die Unordnung (die Zerstörung des Quantenzustandes) ist eine Störung von “aussen”, dem Bad, auf das System nötig. Diese Störung hat nun ganz merkwürdige Eigenschaften wie z.B. sie ist extrem klein, führt aber auf endlichen Zeitskalen zu Unordnung; außerdem darf man sie auf magische Weise in allen Rechnungen weglassen. Mit anderen Worten: das Konzept ist unbefriedigend.

Das obige Paper ersetzt dieses Konzept durch ein anderes, besseres Konzept. Es ist nur noch nicht ganz klar, wie es genau funktioniert, deshalb kann ich es nicht in einfache Worte fassen. Aber wenn diese Hypothese sich bewahrheiten sollte, wird sie die Grundlage der Thermodynamik (die sogenannte Ergodenhypothese), ein Kerngebiet der Physik, ganz neu definieren.

Disclaimer: I know, I know. This is about a piece of software for Windows. It’s not like I enjoy using Windows or that I even have it installed on any of my personal machines (I don’t). Read further, and you’ll see why I have to use Windows in my situation for a month or so.  And if you’re reading this on Fedora Planet or something, please don’t post something like “Don’t put Windows stuff on Fedora Planet”.  We’re all about Freedom, right?

So I started this internship doing medical physics theory at MUSC in Charleston, SC. I’m doing work in Radiology, and I’m required to use a program called CALDose_X to calculate radiation fractions imparted to patients.  The program is closed source and maintained by a nuclear physics theory lab in Portugal.  It can be found at http://www.grupodoin.com.

The program is useful for its purpose, but it’s otherwise kind of clumsy.  Exceptions aren’t handled very well, several features seem to be inconsistent with each other, and something is screwed up with how is recognizes the presence of a .NET framework on your machine (which is one reason that I couldn’t get it working under Wine).

The program is made for doctors to do single examinations with, but I’m using it to find trends in data.  Since it takes a while to fill out their little GUI form, I was finding it very tiresome to compute simulations for different values.  And since it was closed source with poor documentation, I couldn’t readily write any scripts to interface with it.

That’s when I had the idea to write a macro.  There are several macro recorder programs available for a fee for Windows, but I found something even better: AutoHotKey.  It’s free and open-source, and has an extensively documented scripting language that lets you interact directly with GUI elements (not just relying on screen coordinates).  Additionally, you can compile AHK scripts into Windows executables for use on any machine.  It also includes a window inspector to reveal the IDs of GUI elements so that you can interact with them in your scripts.

All-in-all, I was very pleased with this program.  I can’t stress how well it was documented. Writing a perl script to interface with some open source code – or at least some APIs – would have been nice, but this is a great solution for when that’s not available under Windows.

PS: Do we have anything like this under Linux? (Not that there would be as much use for it when everything can be so elegantly linked…)

For most of my adult life, I’ve had a pretty handy way, when I’m asleep—and my dream is getting a bit too scary or unpleasant—of figuring out whether or not I’m probably just dreaming: I try to notice anything going on that is strange, highly improbable, or impossible.

I might, for example, notice that:

• I’ve fallen off a cliff and have only scratches
• I can fly
• I continue to be conscious even after undergoing something that should have killed me
• Someone who has already died is hanging out with me

In other words, something odd or highly unlikely—or either physically or logically impossible—is happening—and that cues me that I’m probably dreaming. Perhaps you’ve noticed similar cues in your own dreams that have suggested to you, while sleeping, that yes, in fact, you are likely to be dreaming.

But wait.

It’s dawned on me recently that my criteria for deciding whether I’m dreaming are only superficially reliable. Indeed, to put it bluntly, they’re deeply flawed. The reason I say this is that, by my very same criteria, what I take to be reality may also be a dream. Here’s some examples:

• Yesterday, Farrah Fawcett and Michael Jackson died on the same day. I realize I’m starting off with a lame example, but it’s something most people wouldn’t expect, and it happened, didn’t it?
• A few months back, a commercial airliner crashed into the Hudson River and nobody died. Once again, this is highly improbable, although I also admit that it is not logically impossible. But still, it’s something that, if I were sleeping, and trying to break the spell of a dream, might arouse my suspicions that yes, in fact, I’m dreaming.

Now you might say that both of these examples are spectacularly poor ones and easily explained. Such things, in a dream, might be no more than the beginning hints of something that is not quite right. But let’s take another example that brings us just a bit further along into doubt about whether you and I are dreaming right now:

• I take it as impossible (as I’m sure that you do) that a human standing on a sidewalk should simply begin to float in the air. But I also notice when I step outside that the sun, the moon, and the stars are in the sky, and that they’re not falling. When you think about it, that’s pretty trippy too. Thomas Jefferson famously said, on first hearing of people claiming to have seen rocks that had fallen out of the sky, that they must be lying, for rocks do not fall to earth from the sky. But meteors do fall to earth, don’t they? How odd to be in a system where some rocks fly and others fall. 

Now I know what you’re thinking. Any physicist could explain this seeming contradiction in a snap via the basic principles of gravity and the laws of motion. But here’s what’s interesting: Our dreams are predominantly lawful also. We touch things and they mostly move in predictable ways. Only some of the things in dreams seem out of the ordinary. In other words, most things that happen in dreams are physically impossible only in terms of what we deem to be “normal” in our waking states. But many of the things that are normal in our waking states, when you think about it, are as trippy and utterly contingent as our dreams. The universe didn’t have to have floating suns and moons and some rocks that fall from the sky. But it does. It is true that we have explanations for them, but these explanations are, ultimately, forms of rabbit-chasing question begging. In other words, the “explanation” may be in the dream too. The trippy question is why  things should be the way that they are at all, or move in accord with laws, or why there should be any laws in the first place. Laws don’t have to be. And floating suns, moons, and stars don’t have to be. But they are. In short, the universe that you imagine yourself to be awake in is as strange as anything in your dreams. You just think of your dreams as stranger than your waking states because they don’t match your waking states. But your waking states are simply a strangeness of a different kind, not of a different order.   

Here’s another example: Dinosaurs. Two hundred years ago people started digging in the earth and finding dinosaurs. Prior to that moment, nobody dreamed that there were such creatures buried in the ground. It’s like in a dream, where you’re suddenly being chased by a monster, or you suddenly find yourself floating. Who would have thought it? But what are your criteria for taking the latter as signifying a dream and the former as signifying reality? Aren’t these kinds of trippy and unexpected “real” discoveries a characteristic of dreams? The same applies to the first time it dawned on people that the earth is not only not flat, but it’s a spinning teensy ball zipping through space at the edge of a galaxy that is just one of a gazillion other galaxies in a universe that may itself be part of a gigantic multiverse.

Surely if you had dreamed such a thing six hundred years ago you’d wake up and say, “That was absurd! I knew I was dreaming!”

But you’re not dreaming, are you?

Are you?

Here’s my ringer (that we might, in fact, all be dreaming something together). It’s one thing to be suspicious about improbable and seemingly physically impossible things, but when something happens that we know  is logically impossible, then surely we must be dreaming, right?

Exhibit A: The universe’s existence. There are only three things that might explain the universe’s existence:

1. God made it;
2. it made itself; or
3. it has always been

That’s it. All three ”answers” are, at some level, either a form of question begging, or logically impossible. If, for example, God made the universe, who made God? The creator leads to an endless regression. And let’s look at the second “explanation” for the universe. If the universe made itself, then that means that there once was nothing and now there is something. That’s ridiculous. As King Lear says, “Nothing can come of nothing.” This leaves us with only one more option: The universe has always been. But that explanation for the universe sucks too. If the universe has just always been, how could that be? It’s crazy. As the poet A.R. Ammons has said: “The universe has no floor / but we walk the floor.”

That sounds like a dream to me.

So what if we are living in a dream? What does this mean? Well, one thing it means is that the boundary that you have set between you and everything else is flawed, for you are, in fact, the whole shebang. The universe is all in your head! All the cool and unexpected things that you hear or encounter are coming from you. You’re surprising yourself.

You do that in dreams too, don’t you? People say things or things happen that completely blow you away. You think that you couldn’t possibly have thought of that yourself, but you did, because it happened in your head.

You’re very smart, indeed!

But now my question is: Are you dreaming me, am I dreaming you, or is somebody else dreaming both of us?

And how would we know?

Here’s part of a scene I like in the film Magnolia. The sky starts to rain frogs. The part of this scene where a smart little boy watches the frogs fall and says to himself repeatedly—”This is something that happens!”—is not included here, but I hope you get the point. Weird things—like dinosaurs and physicists who claim we might live in a hologram—crop up periodically in our consciousnesses—and we incorporate them into what we call reality. In other words, we seem vested in a thesis that we live in a ”real world” when we might just as well be living in a kind of dream (the hint of which being all the weird shit that’s happening, and that we discover has happened, and that we nevertheless get used to somehow and then take for “normal”):

The other day I saw a fascinating NOVA program on PBS.  It is called Parallel Worlds, Parallel Lives and it focuses on Hugh Everett and his son Mark. On the surface the two seem completely different but they are actually linked in an interesting way. In the end, the life of the father explains the life of the son.

In the early 60’s Hugh was a physicist for the Pentagon working as a cold war scientist.  Frustrated with the prevailing views of quantum physics theory (which I will not even begin to explain) he started exploring other types of particle theories.  Eventually he came up with the Many World’s Theory.  As best as I can grasp this theory looked at particles  at their own level- not at how they created larger phenomenon.  According to the NOVA program this view broke with tradition and was the beginning of Everett’s theories.  Looking at the world on such a small level he noticed energy behaving differently.  (Like I said I am way out of my element in explaining this).  Here’s how NOVA explains it:

“Byrne: In order to demonstrate the consequence of this mathematically, Everett came up with a solution showing that the observer, the human being, correlates with every possible state that the gram of carbon, that pencil tip, could be in. So before the human being looks at the gram of carbon, the carbon is in all the millions or billions or trillions of possible states, and after the human looks at the gram of carbon, he or she is in one state. In Everett’s theory, what happens in between, as it were, when the human actually looks at the carbon—or a clock or any other object—is that he or she splits like an amoeba. (The act of looking, that interaction, is just exchanging energy. A person looking at a clock, for example, is an energetic interaction, with photons of light bouncing off the clock and going into the person’s eye.)

So, in Everett’s view, when the human correlates herself—that is, interacts, exchanging energy with the gram of carbon or a clock or whatever—she splits like an amoeba. She splits into copies of herself, one for each element in the superposition.

NOVA: And this split is what creates the “many worlds” of his theory?

Byrne: Yes. And wild as it sounds—a person splitting into numerous copies of herself—Hugh Everett’s theory has not been shown to be mathematically incorrect. God knows, people have tried. They have found some mathematical gaps, but you can’t fault his basic mathematical logic, which made a powerful case that every time there is an interaction anywhere in the universe above a certain size, one of the systems splits in order to accommodate all of the elements and the superpositions that are contained in the wave mechanics function that describes the observed system. In other words, the basis for having multiple universes emerges from his solution of the measurement problem.”

In other words, on a particle level atoms present possible outcomes and in a way those possibilities continue on whether the human participates or not.  Using the example above if the person looks at the pencil or not, the particle energy around the action still exists.  This is why Everett called it the Many World theory.  On a particle level there are infinite numbers of worlds created every moment which all react in different ways.

This is where the son comes in. Like I said, on the surface Mark has nothing in common with his father.  He is  a front runner for an independent rock band called the Eels.  According to the NOVA program much of Mark’s music is dark, focusing on mental illness, abuse, and death.  To give you an idea one of their most famous songs is called “Novocaine for the Soul”. Apparently much of the darkness in the music came from a lonely childhood with a father obsessed with work and science.  On the program Mark tells the story of a conversation over the dishes he had with his father just before he passed away.  Of this simple chat he says “We joked around a little and I remember thinking that it was the most human, real conversation I’d ever had with him. He even told me a joke.”

Later the next day his father dies, and he is devastated by the missed opportunities.  Eventually Mark tries to put his feelings to music and as he struggles he realizes something about his father.  He learns they had a key similarity:

“I realized that I had been feeling that same thing he must have been feeling all those years when he couldn’t be bothered because he always had some crazy ideas he was trying to sort out in his head. You’re just about to crack the code and the kid wants to play baseball. I get it now. We’re both “idea men” and anything outside of these ideas is a distraction.”

With this understanding Mark begins to learn more about the ideas of his father.  Finally it occurs to him that their lives are the ultimate example of the Many World’s theory.  Two worlds co-existing independently of each other and yet intrinsically dependent on one another.   It’s like the show’s title describes: Parallel Worlds, Parallel Lives.  In the end, Mark understood his life better because of his father’s theories.  This to me is fascinating.  How often do we have answers staring at us in the face, yet we dismiss it as ordinary or familial? How often do we discount something because it is different, even offensive, and yet in that other world is the answer to our own happiness?

There are so many examples of parallel worlds, which if understood could enlighten both worlds.  Notice we aren’t talking about combining worlds.  They are inherently separate, but perhaps they could still teach us?  The NOVA program explores the worlds of father vs son, musician vs  scientist, and youth vs. age.  Religion would be another interesting subject for discussion.

Like I said, the science is a bit beyond me, so I hope I have done justice to the program.  If you get a chance, put it on your DVR or watch it on youtube.com . It kind of reminded me of a This American Life piece on television.- excellent and thought provoking. Check out the PBS website on the show for more information. http://www.pbs.org/wgbh/nova/manyworlds/.  On a final side note, this program would be great for teachers and homeschoolers who want to learn more about physics theory.  I know practically nothing and it explained complex concepts in ways even I understood.

To stretch a supply of salt generally means using it sparingly.

But researchers from Sandia National Laboratories and the University of Pittsburgh were startled when they found they had made the solid actually physically stretch.

“It’s not supposed to do that,” said Sandia principal investigator Jack Houston. “Unlike, say, gold, which is ductile and deforms under pressure, salt is brittle. Hit it with a hammer, it shatters like glass.”

That a block of salt can stretch rather than remain inert might affect world desalination efforts, which involve choosing particular sizes of nanometer-diameter pores to strain salts from brackish water. Understanding unexpected salt deformations also may lead to better understanding of sea salt aerosols, implicated in problems as broad as cloud nucleation, smog formation, ozone destruction and asthma triggers, the researchers write in their paper published in the May Nanoletters.

The serendipitous discovery came about as researchers were examining the mechanical properties of salt in the absence of water. They found unexpectedly that the brittle substance appeared malleable enough to distort over surprisingly long distances by clinging to a special microscope’s nanometer-sized tip as it left the surface of the salt.

More intense examination showed that surface salt molecules formed a kind of bubble — a ductile meniscus — with the exploratory tip as it withdrew from penetrating the cube. In this, it resembled the behavior of the surface of water when an object is withdrawn from it. But unlike water, the salt meniscus didn’t break from its own weight as the tip was withdrawn. Instead it followed the tip along, slip-sliding away (so to speak) as it thinned and elongated from 580 nanometers (nm) to 2,191 nm in shapes that resembled nanowires.

A possible explanation for salt molecules peeling off the salt block, said Houston, is that “surface molecules don’t have buddies.” That is, because there’s no atomic lattice above them, they’re more mobile than the internal body of salt molecules forming the salt block.

Salt showing signs of surface mobility at room temperatures was “totally surprising,” said Houston, who had initially intended to study more conventionally interesting characteristics of the one-fourth-inch square, one-eighth-inch-long salt block.

- via sciencedaily

At the very generous invitation of Louise Lerner from Argonne National Lab in the comments to our welcome post, we’ve decided to add another stop on our tour before heading south from Chicago. Between that and the grueling pace we set by adding Oak Ridge at the last minute, we’ve fallen behind both on our sleep and on our posting. But bear with us – we’ve got a few days of plain driving ahead of us, so should be able to catch up over the weekend.

Aside from everything else, I filled up both of my memory cards at Fermilab – 12 GB of photos!

-Nick

El protón está formado por tres quarks de valencia (uud), dos quarks up y uno down. El espín del protón debería ser 1/2 ya que los correspondientes a los quarks suman 1/2-1/2+1/2. Sin embargo, los experimentos de dispersión inelástica profunda indican que no es así. Más aún, los 3 quarks sólo aportan el 20-30% del espín total del protón. En realidad, el protón está formado por un “mar” de gluones y pares quark-antiquark virtuales. La interpretación teórica de los experimentos más recientes en el RHIC (Relativistic Heavy Ion Collider en Brookhaven, EEUU) indican que los gluones aportan muy poco al espín del protón, el 3-5% del total. ¿De qué depende el espín del protón? Nadie lo sabe realmente. Los cálculos teóricos mediante métodos numéricos son casi imposibles y los experimentos en el RHIC no tienen energía suficiente todavía. La hipótesis más barajada entre los especialistas es que dependen del momento angular orbital conjunto de quarks y gluones. Según los especialistas faltan muchos años para que podamos determinar experimentalmente esta contribución. Curioso lo mucho que sabemos de unas cosas y lo poco de otras.

Ya nos hablaron de este problema Madhusree Mukerjee, “Origen del espín del protón,” Investigación y Ciencia, Mayo 1994, y Schäfer Rith, “The Mystery of Nucleon Spin,” en Scientific American, July 1999. Que los gluones no lo explican apareció a finales del año pasado en muchos medios, como en Saeko Okada, “Gluons don’t explain the spin surprise,” en relación al artículo técnico De Florian, D., Sassot, R., Stratmann, M., Vogelsang, W. “Global analysis of helicity parton densities and their uncertainties,” Physical Review Letters 101: 072001, 2008, y el más reciente Daniel de Florian, “Next-to-leading order QCD corrections to hadron+jet production in pp collisions at RHIC,” Physical Review D 79: 114014, 15 June 2009.

RHIC animations and multimedia.

PS: Los interesados en detalles técnicos pero físicos en general pueden consultar el artículo de Steven D. Bass, “The proton spin puzzle: where are we today?,” Mod. Phys. Lett. A 24: 1087-1101, 2009 (ArXiv, Submitted on 28 May 2009). “The proton spin puzzle has challenged our understanding of QCD for the last 20 years. The proton spin puzzle seems to be telling us about the interplay of valence quarks with the complex vacuum structure of QCD.” [Visto en The Gauge Connection]. La entrada “PHENIX says gluons are not all the story,” también será de vuestro interés.