Miscellany

So I’ve been busy, but with good reason. Long ago I mentioned some research I have been doing with Jennie Chen, a grad student here, on the arrow of time. And finally the paper is done! We have just submitted the manuscript to the online e-print server at http://arxiv.org/archive/hep-th, where it should appear Thursday evening. (Update: here it is!) Some day we’ll even submit it to a journal, although that seems so twentieth-century to me.

As a reward to all our faithful readers at Preposterous Universe, here is the paper itself, revealed a full twenty-four hours before ordinary physicists get to see it! Getting in on the cosmological ground floor, as it were. The paper is available as a postscript file or as a pdf file; unfortunately the pdf version will look crappy on your screen, but it should print okay.

We have a grandiose-sounding goal: to explain the century-old puzzle of why the entropy of the universe was low in the past. The entropy, of course, is a measure of how “disorderly” a system is; more properly, how “generic” or “random” it is. Low-entropy states are suspiciously orderly; the classic example is a box of gas in which all of the gas just happens to be located in one corner. This is a perfectly acceptable configuration, but a statistically very unlikely one; if you let it go, the gas will quickly evolve to fill the room. This is the celebrated Second Law of Thermodynamics — in closed systems, entropy tends to increase (or stay constant). Long ago Boltzmann developed a mathematical understanding of this phenomenon, by showing how entropy measured the number of equivalent ways we could re-arrange the elements of the system to give a state that was macroscopically indistinguishable. For the box of gas, there aren’t that many ways we could re-arrange the molecules to keep them in one corner, but there are many ways we could re-arrange them smoothly throughout the box. It is therefore very natural to evolve from a low-entropy state to a high-entropy state, simply because there are so many more high-entropy states to evolve to.

The fact that entropy increases defines the arrow of time. It is a statistical phenomenon, valid for large systems, and the Second Law looks very different from the “microscopic” laws of physics, which are generally don’t care which direction time is running in. Of course, the only reason we see that entropy increases is because it used to be small in the past. Once the gas fills the box, it essentially stays there forever (apart from rare fluctuations).

So, as cosmologists, we have an issue to address — why was the entropy of our early universe so small? If high-entropy states are “natural,” why don’t we live in one? You might think to appeal to the dreaded anthropic principle, and argue that life couldn’t exist in a state with really high entropy. But that turns out not to be good enough; the entropy of our universe is much much lower than it needs to be to support the existence of life. So we are faced with the “arrow of time problem.”

Although there isn’t a consensus view of the solution to this problem, most cosmologists would guess that it has something to do with inflation. The idea of inflation states that the very early universe went through a period of incredible acceleration, which smoothed out the bumps and wiggles and gave us the big smooth universe we observe today. If it works, inflation tends to wipe out any pre-existing features and leave us with a universe similar to what we observe today.

But there’s a problem — even though cosmologists think that it’s quite natural for inflation to start and leave us with the universe we see, very few would think it was quite natural for a collapsing universe to smooth itself out and anti-inflate; that is, to undergo a process that is the time-reversed version of inflation. So secretly, the very idea of inflation has some time-asymmetry built into it; it makes sense forward but not backward. Therefore it doesn’t really count as a solution to the arrow of time problem. We need to explain how the conditions for inflation to start in the first place could naturally arise.

Jennie and I do the following thought experiment — if it weren’t for inflation, what would be a “natural” state for the universe to be in? Different people have addressed this question, with different answers; Roger Penrose, for example, has suggested that it would be a lumpy universe full of black holes. Our answer is almost exactly the opposite — the only natural state is empty space. This is basically because gravity makes everything unstable, and the entropy of any given configuration can always be increased by just expanding the universe by a huge factor. Sure, black holes will form, but they will ultimately evaporate away. If you let the universe evolve forever, it will ultimately get emptier and emptier (generically).

But we now know that even empty space has energy — vacuum energy. (Or at least some sort of dark energy.) So when we evolve to “empty space,” there is still some energy pushing the universe around; the resulting spacetime is called “de Sitter space.” Along with this energy comes a small nonzero temperature, which keeps all the fields in the universe gently fluctuating. Gentle or not, however, if we wait long enough we will find a really big fluctuation — one that is large enough to make inflation spontaneously begin. In other words, we are suggesting (although it’s not original with us) that de Sitter space is unstable; it doesn’t last forever, but eventually starts inflating here and there. These little inflationary patches will ultimately convert into ordinary matter and radiation, leaving behind universes just like our own.

And here is the fun part: this story can be told either forward or backward in time. In other words, you give me some state of the universe, chosen however you like. (Maybe you calculated the wavefunction of the universe, who knows.) I evolve it using the laws of physics. If Jennie and I are correct, it first empties out into a cold de Sitter space, dominated by a tiny shred of dark energy. But eventually we get lucky, and a small patch of inflating universe is born within this de Sitter background. This will happen at different places and times, give rise to a fractal distribution of spacetime geometry in the far future. And I can do the same thing going backwards in time from the initial state you gave me; the generic evolution is the same. It will empty out, and eventually begin to spontaneously inflate. So in the super-far past of our universe, before our “Big Bang” (which is nothing special in this picture), we will find other Big Bangs for which the arrow of time is running in the opposite direction. On the very largest scales, the entire universe is symmetric with respect to time.

Is this scenario correct? Interesting? Important? We’re not sure yet. This is certainly not one of those brilliant flashes of insight, like the original discovery of inflation was. Rather, it’s a concatenation of several intriguing ideas, most of which had already been suggested by someone or another. And there are a million questions remaining to be answered, especially about the onset of inflation in an empty background spacetime. But I like how the whole picture hangs together, and wouldn’t be surprised if something like it eventually came to be accepted as a reasonable picture of the universe on the very largest scales.

Honestly, I think it’s a dead heat — a statistical tie, too close to call, too uncertain to prognosticate. And wishful thinking is a powerful drug. But I’m not too proud to take heart in this graph, from Andrea Moro at the University of Minnesota.

Here’s a homework assignment for you folks out there in internet-land. As my own assignment as a member of the Kavli Institute for Cosmological Physics here at Chicago, I’ve written a Cosmology Primer meant to explain the basic features of the universe to people on the street. It’s very much in rough draft form at present, but has nevertheless gone live. I’d be very interested in what people think — not about stylistic questions, since the look and feel will undoubtedly evolve, but whether the level is appropriate, and if the important questions are addressed, and if so if the answers make sense. Let me know.

Nobody with any pretensions to originality would quote Fafblog. It’s just too cheap and easy. But downright irresistible.

Some other candidates say they are steady but are they really? Or are they just suspiciously french an ketchupy? “Sacre bleu, vive le France,” say some other candidates. “Ceci n’est pas une pipe.”

Indeed.

By Heather McHugh. I’ve had this one linked to my home page for a while, but I’m not above recycling.

We were supposed to do a job in Italy

and, full of our feeling for

ourselves (our sense of being

Poets from America) we went

from Rome to Fano, met

the mayor, mulled

a couple matters over (what’s

a cheap date, they asked us; what’s

flat drink). Among Italian literati

we could recognize our counterparts:

the academic, the apologist,

the arrogant, the amorous,

the brazen and the glib — and there was one

administrator (the conservative), in suit

of regulation gray, who like a good tour guide

with measured pace and uninflected tone narrated

sights and histories the hired van hauled us past.

Of all, he was most politic and least poetic,

so it seemed. Our last few days in Rome

(when all but three of the New World Bards had flown)

I found a book of poems this

unprepossessing one had written: it was there

in the pensione room (a room he’d recommended)

where it must have been abandoned by

the German visitor (was there a bus of them?)

to whom he had inscribed and dated it a month before.

I couldn’t read Italian, either, so I put the book

back into the wardrobe’s dark. We last Americans

were due to leave tomorrow. For our parting evening then

our host chose something in a family restaurant, and there

we sat and chatted, sat and chewed,

till, sensible it was our last

big chance to be poetic, make

our mark, one of us asked

                     “What’s poetry?

Is it the fruits and vegetables and

marketplace of Campo dei Fiori, or

the statue there?” Because I was

the glib one, I identified the answer

instantly, I didn’t have to think — “The truth

is both, it’s both,” I blurted out. But that

was easy. That was easiest to say. What followed

taught me something about difficulty,

for our underestimated host spoke out,

all of a sudden, with a rising passion, and he said:

The statue represents Giordano Bruno,

brought to be burned in the public square

because of his offense against

authority, which is to say

the Church. His crime was his belief

the universe does not revolve around

the human being: God is no

fixed point or central government, but rather is

poured in waves through all things. All things

move. “If God is not the soul itself, He is

the soul of the soul of the world.” Such was

his heresy. The day they brought him

forth to die, they feared he might

incite the crowd (the man was famous

for his eloquence). And so his captors

placed upon his face

an iron mask, in which

he could not speak. That’s

how they burned him. That is how

he died: without a word, in front

of everyone.

               And poetry —

                              (we’d all

put down our forks by now, to listen to

the man in gray; he went on

softly) —

               poetry is what

he thought, but did not say.

Normally I pride myself on being more of an idea person than a man of action. Action can be exhausting, after all. But sometimes circumstances force you to move against your natural inclinations. So, recently Chris Lackner and I combined two of our favorite activities — poker and Bush-bashing — into a small but rewarding fundraising event for the Kerry campaign. We held a No-Limit Texas Hold’Em tournament, with proceeds going to the campaigns in Midwest battleground states.

Physicists constituted a minority of the participants — only four of the sixteen — but dominated in the late stages, including three of the top four finishers. Must be that special combination of mathematical wizardry and deep psychological insight that makes people successful in both science and poker. In a tense showdown stretching into the late hours of the evening, string theorist Jeff Harvey defeated cosmologist Risa Wechsler to take first place. (And they say that string theorists are disconnected from the real world.)

How often do you get to see a picture of internationally renowned theoretical physicists staring each other down over a flop? The role of the button (indicating the dealer) was played by a small Albert Einstein action figure. Note also the abundance of alcoholic beverages — well-known to increase one’s poker skills.

So we raised a little money and had a lot of fun. These events are also good because they give people a feeling of being involved in the process; empirically, anyone who goes to a fundraiser is more likely to actually vote on Election Day. (Hopefully, even if they didn’t do well in the tournament.)

The 14th edition of Tangled Bank (just as fascinating as the 13th, if not officially as lucky) is now up at Prashant Mullick’s weblog. It involves a bacterium named Wigglesworthia, so you know it will be good.

Since choosing between presidential candidates can be hard, it’s often wise to turn to newspaper endorsements to decide how to vote. George W Bush’s landslide victory over Al Gore in 2000 can be largely attributed to his over 2-1 lead in newspaper endorsements (an amazing accomplishment for the liberal media, we must admit). This year looks less promising for the President, as John Kerry seems to be kicking his butt in the endorsement race. Even the President’s hometown paper would rather see him return to Crawford.

But we have to take into account quality, not just quantity. Before anyone makes any hasty decisions, keep in mind the keen judgment of these world opinion leaders who have looked carefully at the record and come out for Bush:

• Al-Quaeda is for Bush!
  

  The statement said Abu Hafs al-Masri needs what it called Bush’s “idiocy and religious fanaticism” because they would “wake up” the Islamic world.

  Can’t ask for a more clear-eyed policy analysis than that.

• Vladimir Putin (“Vladimir” to his friends) is for Bush!
  
  The courageous leader who has brought peace and democracy to a Russian nation still in the delicate stages of post-Communism understands what it takes to be resolute in the face of annoying international pressures.

• Iran’s National Security Council is for Bush!
  
  The mullahs understand that, loose talk about axes of evil notwithstanding, those Democrats tend to frown upon so-called “human rights violations,” which tends to get in the way of sensible realpolitik.

So I’m sure the President isn’t losing any sleep. Who needs the Albuquerque Tribune, anyway?

I noticed this striking image in this month’s University of Chicago Magazine — a rainy training session for the Sierra Leone Amputee Football Team. Captain M’byo Conteh is in the center.

I have to confess that I didn’t even know there was such a team, nor that there was a UK National Amputee Team for them to play against, as explained in this page at Polaris Images. (UofC alumnus Adam Nadel took the award-winning pictures.) The team formed a couple of years ago, in an attempt to look beyond the grinding poverty and constant war that plague the country. The UK tour was organized by charitable organization Action for Children in Conflict.

Amadu Kamara celebrates a goal. The team didn’t fare well against their British counterparts, but they were pleasantly surprised by the warmth with which they were greeted on the tour.

Two different views of the same event. The event being a Bush rally in Oregon, featuring a celebration of moral values and the expulsion of three local teachers with tickets to the event who were wearing T-shirts carrying the motto “Protect Our Civil Liberties.”

One article about the event seems to be derived almost exclusively from a Democratic Party press release.

Responding to the number of examples of American voters being turned away, or removed from George W. Bush’s visits to their cities and states, Democratic National Committee Chairman Terry McAuliffe hosted a national conference call with Oregon teachers who were kicked out of an Oct. 14 Medford Bush rally for wearing T-shirts saying, “Protect Our Civil Liberties.”

McAuliffe released the following statement Sunday:

“”The President has stripped his events of anyone who might disagree with him, which is completely un-American. It is dangerous for a President to be the bubble boy of American politics. But it might explain why the President can’t admit the problems of people without jobs, without health care, without prescription drugs, or trying to put their kids through college. He doesn’t know about them because he refuses to even see them.”

But those of us who think that people should be able to wear whatever T-shirts they like (although “protect our civil liberties” is pushing the irony envelope a little far, I must admit) have heard so many of these stories that it’s too exhausting to gather our outrage once more. And the President’s supporters are able to overlook little events like this. He is, after all, resolute in the face of threats, both real and imagined. And Kerry is a flip-flopper! If stifling a little dissent is the price we have to pay for security, so be it.

The interesting thing is the local paper’s pro-Bush take on the same event, sporting the title “Crowd lauds Bush for conviction, ‘his word’.” The story about the teachers is relegated to a passing mention in the second half of the article. It’s the pro-Bush story that is scarier to those of us who are on the anti-theocracy side of our great national debate.

Applegate Christian Fellowship pastor Rev. Peter John Courson gave an invocation, urging onlookers to pray for the president and to bless the troops.

“In Jesus’’ name, thank you for being here,” he said.

During the Pledge of Allegiance, the crowd emphasized the words “under God.”

Applegate resident Tustin Ellison, who said he’’s as conservative as “Attila the Hun,” said he doesn’’t agree with everything the president has done, but supports the invasion of Iraq.

[…]

Medford resident Rochelle Lovlin said she supported the president because he conveys a sense of morality.

“He knows how to quote scripture better than Kerry,” she said.

Who was it again who was famously able to quote scripture for his own purpose?