Author: Sean Carroll

  • Apparently Astronomy is Un-American

    John McCain has a twitter account. Yes, that’s horrifying enough, but then there’s the actual content of what he writes. At least he is using in creative and productive ways! No, he isn’t. Yesterday he announced:

    Tmr I am gonna tweet the TOP TEN PORKIEST PROJECTS in theOmnibus Spending bill the Congress is about to pass

    Love it when Senators play cool. Love it. So today is the big list, and guess what comes in at number two?

    #2. $2 million “for the promotion of astronomy” in Hawaii – because nothing says new jobs for average Americans like investing in astronomy

    Sure, earmarks are dumb, and it would be nice to have a rational way to decide how best to prioritize federal spending. But don’t deny the obvious: when Republicans hear “science,” they think “something to be mocked in the service of burnishing our just-folks credentials.” Ask Bobby Jindal. Or, for that matter, John McCain.

  • Dark Forces Revisited

    I have a new paper out with Sonny Mantry and Michael Ramsey-Musolf, following up on our earlier paper with Chris Stubbs. The original idea was to imagine a new long-range force that couples directly to dark matter, but not to ordinary visible matter. (A simple scalar force, which is universally attractive between any two objects, as opposed to all the messy complications of a dark electromagnetic force.) Due to the magic of quantum mechanics, such a force will couple indirectly to ordinary matter via virtual particles. So in the first paper we studied how you could use fifth-force searches in ordinary matter to look for such dark forces.

    In this paper we are a little more systematic, and we follow Jo Bovy and Glennys Farrar in also considering consequences for direct dark matter detection experiments, as well as dark matter searches at colliders. Here is the (somewhat lengthy) abstract:

    Implications of a Scalar Dark Force for Terrestrial Experiments
    Authors: Sean M. Carroll, Sonny Mantry, Michael J. Ramsey-Musolf

    Abstract: A long range Weak Equivalence Principle (WEP) violating force between Dark Matter (DM) particles, mediated by an ultralight scalar, is tightly constrained by galactic dynamics and large scale structure formation. We examine the implications of such a “dark force” for several terrestrial experiments, including Eotvos tests of the WEP, direct-detection DM searches, and collider studies. The presence of a dark force implies a non-vanishing effect in Eotvos tests that could be probed by current and future experiments depending on the DM model. For scalar singlet DM scenarios, a dark force of astrophysically relevant magnitude is ruled out in large regions of parameter space by the DM relic density and WEP constraints. WEP tests also imply constraints on the Higgs-exchange contributions to the spin-independent (SI) DM-nucleus direct detection cross-section. For WIMP scenarios, these considerations constrain Higgs-exchange contributions to the SI cross-section to be subleading compared to gauge-boson mediated contributions. In multicomponent DM scenarios, a dark force would preclude large shifts in the rate for Higgs decay to two photons associated with DM-multiplet loops that might otherwise lead to measurable deviations at the LHC or a future linear collider. The combination of observations from galactic dynamics, large scale structure formation, Eotvos experiments, DM-direct-detection experiments, and colliders can further constrain the size of new long range forces in the dark sector.

    The looming problem with this whole game is that a long-range scalar force is unnatural. A scalar field should, by all rights, have a large mass, and that kind of mass drastically limits the range of the corresponding force. (That’s why the weak interactions are negligible compared to electromagnetism for everyday purposes; the W and Z bosons have a large mass, while the photon is massless.) You can keep scalar fields light by imposing symmetries, but that also tends to squelch any interesting interactions. But okay, it’s also unnatural for the Higgs boson to have a mass less than the Planck scale, or for the cosmological constant to be much less than the Planck scale. Unnatural things happen in the real world, so it’s not crazy to try to understand how they would manifest themselves.

    The question is, once you’ve allowed yourself some unnaturalness, where do you stop? In this paper we’ve tried hard to minimize the number of parameters we unnaturally tuned to small values. We’ve tuned things to keep the scalar field light while not messing up the mass of the ordinary Higgs field, but tried not to tune anything else. In that case there should be mixing of the new scalar with the Higgs, and that mixing plays an important role in the phenomenology. In particular, there are implications for ground-based experiments; thus the title! It’s a long paper, but if you read one paper on the implications of a scalar dark force for terrestrial experiments this week, it should definitely be this one.

  • Why Isn’t This a Movie Yet?

    Following Scott Aaronson’s advice, I instructed the good folks at Amazon to send me a copy of The Princeton Companion to Mathematics. (In exchange for money, of course.) It’s sprinkled with gems like this, in the article on “Differential Topology” by my former professor Clifford Taubes:

    If you are with me so far, suppose now that an advanced alien en route from Arcturus to the galactic center kidnaps you and drops you into some unknown, 2n-dimensional manifold. You suspect that it is Sn x Sn, but you are not sure.

    Come on, the screenplay practically writes itself! I’m seeing Ewan McGregor, maybe Natalie Portman. Russell Crowe as the alien. SEEx could help with some of the mathy stuff. If any studio executives are reading this, call me, I’d be happy to bang out a treatment.

    Seriously, the book is great fun, and as Scott says it’s surprisingly readable. Not really a popularization; neither equations nor high-level abstractions are shied away from. (After months of jousting with the “grammar checker” in Microsoft Word, I now deploy sentence fragments and the passive voice out of sheer spite.) But put into the hands of the right ambitious high-school student, it could be life-changing.

    p.s. You haven’t really lived until you’ve seen Cliff Taubes do his little dance to illustrate the concept of “quantum fluctuations.”

  • The Coming Civil War

    Glenn Beck — who has a daily TV show on a popular cable news network and therefore must be taken more seriously in some quarters than scruffy people ranting on streetcorners — assembles his friends to war-game the coming civil war. Apparently a combination of 95% tax rates and a flood of unwashed Mexicans is going to provoke militias made of Bubbas to rise up against the U.S. government. Also, Obama is going to force states to accept stimulus money against their will.

    Beck follows up by explaining how God fits into all this. The answer is: God gave this country freedom, and God has a method of communicating to us when our freedoms are being taken away. That method, apparently, goes through the gut. Imminent threats to freedom are foreshadowed, if I understand correctly, by a mild sort of indigestion.

    You might think this is an isolated case, but here is Alan Keyes — who used to have a TV show, and was recruited by the Illinois Republican party to run for Senate, and therefore must be taken more seriously in some quarters than random fulminators on internet message boards — also warning darkly of the coming civil war.

    Indeed, it may have already begun. If I understand this article from HumanEvents.com correctly, several states have already declared sovereignty, paving the way to full-scale secession from the Union. Nobody wants this to happen, you understand; but if the Democrat party wants to undermine the Constitution and redistribute the wealth, the consequences are simply inevitable.

    Here at Cosmic Variance, we believe in always being prepared. The coming civil war isn’t going to be pretty. Don’t say you weren’t warned!

  • Wave of the Future

    In the progression from magazines to blogs to Twitter feeds, the tea leaves are clear. I think we need a new social network, on which updates will take the form of nothing more than a single “0” or “1”.

    We can call it “Bitter.”

  • Karl Rove is Following Me on Twitter

    Yeah, I got a Twitter account. Part of my continuing plan to take over all forms of modern social media. And besides, if I am struck by a deep thought while sitting in an airport waiting for a delayed flight, don’t you deserve to know about it right away? Of course you do.

    And emails like this make it all worthwhile:

    Hi, Sean Carroll (seanmcarroll).

    Karl Rove (KarlRove) is now following your updates on Twitter.

    Check out Karl Rove’s profile here:
    http://twitter.com/KarlRove

    Best,
    Twitter

    Now if I could get Shaq to follow me, I’d hit the big time.

    (Note that Rove has 13,373 followers, and is himself following 13,369 feeds. Clearly there are four Twitterers out there who really pissed him off.)

    p.s. I am a lagging indicator, so if you’re not already using Twitter, you are hopelessly backwards.

  • The Cathedral of Learning

    I just got back from Pittsburgh, a city famous for honoring football players along with Fathers of our country. Apparently they recently won some sort of sporting contest, so the citizens were generally in good spirits.

    I was visiting to Center for the Philosophy of Science at the University of Pittsburgh, to speak in their annual lecture series. The Center, along with the Department of History and Philosophy of Science, help make Pittsburgh one of the world’s leading institutions for studying philosophy of science.

    The Center is also a remarkably friendly place, and I had a great time during my visit. The highlight, predictably, was lunch with some of the graduate students, where we got to let our hair down and talk about big ideas concerning time and causality and determinism. (Almost all professional academics start out fascinated by big ideas, but the interest is gradually beaten out of them along the way by the demands of professionalism and career advancement. Grad school is probably the peak combination of background knowledge and willingness to confront the hard problems.) I also got to chat with Adolf Grünbaum, whose declamations concerning the Primordial Existential Question had impressed me a year and a half ago. And I got to meet some fellow bloggers in the flesh — the formidable Cosma Shalizi, who helped me understand how to augment the principle of indifference with conditionalizing over the past hypothesis, and Bryan Roberts of Soul Physics, who was one of the aforementioned grad students.

    Cathedral of Learning But if I’m really honest, my favorite part of the trip was probably the building. The Center for the Philosophy of Science is housed in the Cathedral of Learning, a looming structure on the University’s campus — the second-tallest academic building in the world, after one at Moscow State University. Despite my lack of religious sympathies, I love cathedrals — the looming structures, swooping curves, open spaces, all designed to elicit a certain emotional response going far beyond their direct practical purpose. (Not that different from the best casinos in Vegas, really.) And I love learning! So the Cathedral of Learning is pretty much the perfect building.

    And it really does work as a building. What everyone points to are the many Nationality Rooms scattered throughout the building — a series of 27 spaces decorated in the style of various different countries, often with the input (and financial assistance) of the respective governments, which work as display pieces but are also functioning classrooms. (I was told that prospective students are sometimes convinced to come to Pittsburgh by a visit to the room corresponding to their personal heritage.) But what I liked was the immense Commons Room (pictured), with impossibly high ceilings, which is just a place where people can sit down and read and talk and think. Such places are very precious, and the world should have a lot more of them.

    If Wikipedia is to be believed, the Cathedral grew out of a vision of Chancellor John Gabbert Bowman in the 1920’s. He insisted that the Commons Room be built on the principles of true Gothic architecture, with self-supporting arches. When told that these things cost money, he replied:

    “You cannot build a great University with fraud in it.”

    I’m not sure if that’s strictly true, but it’s an honorable principle to strive towards.

  • Grow Up, America

    Various things that have been piling up in the “Bloggable” folder. But together they tell their own story.

    Part of the stimulus package includes money for high-speed rail. That’s good — if the government is going to be spending piles of money in an attempt to kick-start the economy, it would be nice to get something of lasting value in return, and mass transportation connecting distant cities is certainly of lasting value. Of course opponents are playing politics with it, which is to be expected. And here is their fun strategy: to highlight on such proposed high-speed rail line, between Los Angeles and Las Vegas, and label it the “Sin Express.” Get it? Real Americans don’t travel between those two dens of iniquity, only shady reprobates who want to divert stimulus dollars from hard-working blue-collar Midwesterners who would never step foot inside a shiny Vegas casino.

    Unfortunately, it’s not even true — there is no money set aside for high-speed rail between LA and Vegas, and it’s not listed as a high priority on the Federal Railroad Administration’s list of officially designated high-speed rail corridors. Which is too bad, as I’ve driven along several of those hypothetical routes, and the one between LA and Vegas is certainly one of the more useful places to plunk down some high-speed rail.

    Read Jessica Valenti on “hook-up culture.” In case you don’t know what that is, it’s a catchphrase invented by cultural conservatives who would like you to believe that kids today are disrespecting America’s Puritan heritage by having sex with each other. And they may be right! I suspect that some kids are having sex with each other. Sex is fun. But it is also something to be careful about, with possible unintended consequences ranging from emotional pain to disease to unplanned pregnancies. So we might hope that responsible cultural conservatives would want to equip young men and women with the knowledge necessary to avoid those pitfalls while enjoying the fun parts of sex. But that agenda seems to be well-hidden under a campaign to shame people, under the theory that other people having sex is a dirty and disgusting thing.

    You may have heard that Michael Phelps, former paragon of American purity and might and speediness in water, has been uncovered as a shocking moral degenerate. Apparently he intentionally inhaled the fumes from a slowly-burning psychoactive herb, funneled through some sort of device designed expressly for that purpose, while “chilling” with his “buds.” Now all of his recent success at the Beijing Olympics must be called into question — how do we know that his fantastic performances in competitive swimming weren’t artificially aided by “toking” on a “doobie” before hopping in the pool? Naturally, Phelps has been suspended from competition, stripped of lucrative sponsorship deals, and forced to wear a sackcloth and ashes while parading around the town square with a giant scarlet “M” hanging around his neck.

    Here is the letter Michael Phelps should have written. If only.

    Annette Obrestad This is Annette Obrestad from Norway, one of the best poker players in the world. She is also a young woman, and a great role model for girls in what has traditionally been a boy’s game. She burst on the scene when she was only 15 years old, winning online tournaments in Europe. At the age of 18 she proved that her prowess extended to live play, winning $2 million by taking first place at the World Series of Poker Europe Main Event.

    But Obrestad can’t legally play poker for money in the United States. She’s too young, and will have to wait another year until she turns 21. You can join the army, or vote, or sign multi-million-dollar basketball contracts if you are 20 years old, but you can’t play poker for money. (Michael Phelps participated in the 2000 Olympics at the age of 15.) America is afraid of poker. The Unlawful Internet Gambling Enforcement Act, smuggled through Congress in 2006, led many online poker sites to stop accepting money from U.S. players, no matter how old they are.

    I’m not sure what it is that makes America so puritanical, compared to Western Europe. (It’s also substantially more religious, but the direction of the causal arrows is not clear.) Hopefully we can scold the country into taking a more grown-up attitude toward sex, drugs, gambling — maybe even, someday, rock and roll. A few more blog posts like this one should do it.

  • The Race for the Higgs

    The Large Hadron Collider should be lurching back to life this year, but the Tevatron at Fermilab might yet have a last hurrah. While the LHC is still fixing itself after last fall’s explosions, the Tevatron has been collecting data like mad, and hopes to continue for another couple of years. At the American Association for the Advancement of Science meeting in Chicago, Fermilab scientists said they have quite a good shot at collecting “evidence for” (although not quite “discovery of”) the Higgs boson before all is said and done.

    Adam Yurkewicz at US/LHC Blogs has the scoop, and you should go there for more info. But this graph tells the basic story. It’s the probability that Fermilab will be able to find “three-sigma” evidence for the Higgs, depending on what its mass is, if the Tevatron gets to run through 2011.

    chance-of-higgs-discovery-at-tevatron-large.jpg

    Due to complicated background events, finding a particle like the Higgs isn’t just a matter of smacking together protons and antiprotons at higher and higher energies. Some possible values of the Higgs mass make it easier to find than others, since the reactions that produce it aren’t as swamped by boring known events. That’s why the Tevatron has a shot, even if LHC opens with substantially larger energies later this year. The BBC story portrays the whole thing as a race, which is fine, but to the rest of the world it’s more important to just find the darn thing than which continent gets there first. (Given that the Higgs is a boson, the smart money would seem to be on Europe.)

  • The Dark Sector @ Google

    Last November I gave a talk at the Google outpost in Santa Monica, on dark matter and dark energy. I covered a lot of ground pretty quickly, introducing the Standard Model and the basics of the Big Bang as well as some ideas about the dark sector.

    This was part of the Authors @ Google series, which features a plethora of great talks. Check out Salman Rushdie, Arianna Huffington, John Hodgman, Tyler Cowen, Anthony Bourdain, Steven Pinker, Lane Montgomery, and dozens more.

    I’ve collected various YouTube videos featuring my bad self, but I honestly can’t bear to watch any of them. Can’t stand to see myself speaking (although obviously I have no issues with other people listening raptly). So if any of these are actually Rickrolls, don’t blame me.