response to Pandurang nayak's blogpost on Greene's "elegant universe"

http://pandunayak.blogspot.com/2007/05/elegant-universe.html

Hmm ... "string theory", maybe it should be classified under meta-physics?

I haven't read Brain Greene's book. But I have been hearing about strings since about 1988, from people of the likes of Gary Horowitz (with whom I did a postdoc later), Ed Witten, David Gross, Strominger etc.

Early strings: In relativity, the action (which is later extremized to find the equations governing its motion) for a free particle is simply the path integral of the infinitesimal distance ds. So Nambu-Gottu proposed that the action governing the motion of a string is its surface area. Now if you just extremize this the solutin would lead to the collapse of the string to a point, so you add in a linear tension term. The resulting solutions to the Eqn of Motion have the usual oscillatory modes etc.

Now, fundamental theories are field theories and particles are thier quanta. So far so good. But when you put in interacting fields (EM field (photons) and Dirac field (charged particles)) and quantize them you can't do it exactly. So you do perturbations about the 0 interaction, or the vaccuum. It turns out that even QED is perturbatively "non-renormalizable", sort of like a divergent series. However, unlike a divergent series, it turns out that removing certain infinities and adding the perturbation term by term does lead to converging answers that agree with experiment to astounding degree of 10^-12 etc!

So why are interacting particle field theories singular? Hand waving, it goes like this, any paricle interaction involves a node in spacetime (the "collision" or disassociation) where 3 worldlines come together. Now this is no longer a "line" and leads to trouble. Also, there are (solved) causality problems and reference frame problems for multiple interactions. However, a string interaction is visualized as a smooth manifold, the trousers topology - imagine two circles coming closer and merging to form one: while the sequence of two dimensional slices of this event appear to have a singularity (non-hausdorff ness or a cusp formation) the spacetime manifold (surface) is smooth!

So lots of excitement, particularly for string field theory. Claims and expectations:

1. string interactions are just smooth 2 dimensional surfaces
2. lack of point interactions means should be renormalizable
3. critical dimensions for string FT to be consistent, either 26 or 10, lots of yummy math, extra dimensions are compact manifolds, could be beautiful Calabi-Yau manifolds, topological invariants etc.
4. Then things got even better, solutions to string field equations (which themselves arise from requiring SFT to be “perturbatively renormalizable”) include general relativity with matter, physical matter field equations etc. Hence the claim it a TOE – Theory of everything!
5. Lots of connections between different areas of math discovered, by Witten and others.
   However,

1. No 2D surface admits a non-singular, non-degenerate Lorentzian metric everywhere. Metric = infinitesimal distance tensor, which is the geometry of the manifold. Lorentzian means one spacelike and one timelike dimension, I.e, one positive and one negative eigenvalue. In other words, somewhere on that trouser there is a singularity. This is not very important.
2. “renormalizable” means “perturbatively renormalizable”. What this means is one that the background spacetime in which the strings live is flat (why should that be so?) and this flat metric is used to setup a measure of distance for the perturbative expansions. Now: no one has actually done any perturbative calculations in full string theory, unlike in QED. Two, assuming a flat background spacetime is senseless for a self-proclaimed TOE (either GR is assumed and hence the string tension will cause curvature, or the background metric is a parameter whose value should be determined by the string EOM – see later. Three, a TOE should be exact, not perturbative, about some again arbitrarily chosen homogeneous solution.
3. In the perturbative expansion, in order for the first order term to be finite, certain conditions have to be met. These are the string field equations. One solution to the string field eqn is that the background metric used satisfy Einstein's field eqn for the metric, G mu nu = 8 Pi Tmu nu. However, there are other solutions, how many (not “countably how many”, rather how many dimensions and are these countable)? One doesn't even know the structure of the solution space. Other than knowing that GR is right, there is no way to pick that particular solution and hence claim that GR arises from string theory. Also, all this can only take place in 26 (or 10 or 11) dimensions of the background spacetime. Then one is left with explaining the apparent 4 dimensionality of the physical world – how do the extra dimensions compactify, why are they small and not say large. Note that the extra dimensions are physical (like a very tightly rolled up sheet of paper appears to be 1D but is actually 2D on the small scale), not extra dimensions in the fibre-bundle sense (where the extra dimension is just a property holder, say e.g. a sphere to represent the spin of a point particle).
4. See above. So string theory is not just a TOE, it is a TOEPUCI+ – Theory Of Everything Possible U Can Imagine and then some.To counter this and patrt of the previous criticism, let me make an analogy: suppose that immediately after Maxwell's EM and the Lorentz transformations somebody (the analog of a string theorist) said I have this wonderful theory of a thing called a metric that explains everything, I have an action principle (very important in physics then and now), I extremize it, the eqn says the ricci curvature of this metric thing is 0. A solution is that the world is flat! See, I have proved the world is flat. The analog of Lee or myself (in a very small way) or Woit would say, wait a minute, but there are numerous other solutions to your “metric equation” which say the metric is curved (what we now call the weyl curvature can be non-zero), how do you pick your flat metric from all the other solutions without knowing in advance that the world is flat? The answer is that you can't, the world is not flat and the metric theory is correct! So might String theory!
5. There have been a series of String bandwagons, all but the most recent few started by Ed Witten: matrix theory, conformal field theory, String BHs (most notably the CGHS black hole - a 2 D mini-micro nanomodel and symmetry reduction of string theory then with the sign of the exponent in the potential term arbitrarily reversed because everything else is too hard to solve), M-theory, membrane theory, Maldacena etc. The lifetime of each of these (as measured by publications) is about 5-6 years. Every two years there is a big string conference, some major breakthrough is announced, stringers dance the macarena in the aisles, the fever subsides, it proves a physics dead end and one moves on.
6. Now, contrary to Voit's claim that ST is “not even wrong”, a Weyl-square theorist whose seminar I attended in 1996 pointed out that string theory does actually make one very concrete testable prediction, and that never in the history of science has a theory been so wrong! Roughly speaking, in a non-perturbatively quantized ST, the string tension (actually stress) would be quantized, its quanta would be the planck tension (appropriate dimensional combination of G, c and h), which will also be the leading contributor to the cosmological constant (which is an energy density and has the same dimensions as tension/ area). There are strong astrophysical observational upper limits on the value of the CC, the planck tension is greater by about 40 orders of magnitude!
   Now, I have written much less than I could write, but already much more than you are interested in reading, so I'll just sto     

“When the Doctor no longer looks like You, White Boy.”

When the Doctor Doesn’t Look Like You

The full column should have been titled “When the Doctor no longer looks like You, White Boy.”. Women and non-white people have long contended with doctors who don’t look like them. What is more, white male doctors have long dismissed symptoms, in American women and African-American patients, which the doctors take seriously enough for white male patients.

Other than the overt racism and sexism inherent in patients and colleagues discriminating against non white male doctors, there is the covert racism and sexism in taking this issue seriously only when the affected patients are white males (as the title of the full column implies).

Re "What Makes Chechen Women So Dangerous?" (NYT, Op-Ed, March 31)

To The Editor, 

Re "What Makes Chechen Women So Dangerous?" (Op-Ed, March 31): While purporting to be an explanation of terrorism by Chechens, the article is nothing more than a barely disguised effort to criticize Israel and the simple desire of Jews everywhere to have a safe place to live and have families. One has only to replace "Chechnya" with "West Bank" - which the authors themselves seem to suggest- and "Moscow" with "Jerusalem", to see the clear anti-Semitic nature of the article. With the New York Times publishing such excuses for terrorism in its Op-Ed pages, does Israel have no friends left anywhere?

Gratuitous sexism alive and well amongst MDs in 21st century

Tara Parker Pope's blog on health on the NYT, 8 feb 2010, on the retraction of Lancet article linking MMR vaccine and autism:

http://well.blogs.nytimes.com/2010/02/08/did-the-media-inflame-the-vaccine-autism-link/#comment-476425

Comment #3 : In psychiatry long enough to have seen diagnostic fads come and go. Strongly suspect there’s a large subset of children diagnosed as autistic who merely suffer from a lack of maternal attention from busy working mothers and too much day care.

— MARK KLEIN, M.D. My response: In response to #3 Mark Klein’ s time-travelling email from the 1950’s:

“lack of maternal attention from busy working mothers”!
Lets try and rephrase that for the 21st century: “lack of parental attention from busy working parents”.
So how come so many of the kids diagnosed with autism seem to be children of white suburban full-time moms?

Anything else you want to blame it on: Rising illegal immigration; Increasing number of ignorant M.D.s?

— Ranjeet Tate

In response to Andrew Sullivan's article

Thanks Chris for bringing this to my attention.

AS brings up in his article something I have been feeling over the last two days listening to various right wing bloviators (e.g.on On Point with Tom Ashbrook (?)) argue against a fed trial - the elephant in the room that they fail to mention - they are afraid that most evidence will be thrown out or it be ruled a mistrial because of TORTURE. As someone arguing in favor of a fed trial pointed out, those on the right who want the trial to take place in the deeply flawed, ineffective and inexperienced US Military court (3 terror cases tried in 8 years, Vs. ~ few hundred in fed courts with a 93% conviction rate) are simply afraid that KSM could walk free. They want a trial that will guarantee conviction, but that is nothing other than a kangaroo court - you might as well just lynch KSM on the Glenn Beck show.

The other nonsense spouted on On Point, that went unchallenged, was that somehow the trial would damage the federal court system and that it would set a dangerous precedent. This was repeated numerous times, without any other explanation of why or how the fed system would or could be damaged nor any clarification of what exactly the precedent was going to be. Then there is the national security issue, "We will have to disclose various unconventional classified "information-gathering" techniques (probably illegal!) and hence they will become ineffective, because the "terrorists" will train themselves to withstand them (which is why KSM was water-boarded 183 times - "Oh it didn't work a 182 times, let's do it again" - this is the mark of what?), and also we will be stopped from using them, not that we did ever did use anything of the sort."

What balderdash, the CIA is capable only of grasping "micro-intelligence" (so-and-so is at a wedding party  let's do the predator kowabunga!, or evidence that some handshake somewhere took place or not) and is fundamentally incapable of seeing macro-intelligence on a societal or historic scale. So they can be trusted to big time EFF UP Pakistan!

In response to: Gamma-ray photon race ends in dead heat...

In response to:

ScientificBlogging Gamma-ray photon race ends in dead heat; Einstein wins this round. We'll get you yet, though, Al.

www.sciencecodex.com

Source: www.sciencecodex.com

Racing across the universe for the last 7.3 billion years, two gamma-ray photons arrived at NASA's orbiting Fermi Gamma-ray Space Telescope within nine-tenths of a second of one another. The dead-heat finish may stoke the fires of debate among physicists…

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Kevin D Wieland wrote:

How do you know they started at the exact same time and not 9/10th a second apart?

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Here are my collected comments:

The article itself says that the difference in arrival times is "… likely due to the detailed processes of the gamma-ray burst…", i.e. in the source of the γ rays.

Addressing Kevin’s question in more detail:

The telescope was looking at the same part of the sky, presumably small enough to contain only one source of γ s. A Gamma ray burst was observed (bunch of γ s with energies between the two extremes mentioned in the article.). Gamma ray bursts last on the order of a couple of seconds (See above article.). On a macroscopic scale, the photons traverse the same spatial trajectory and intervening objects, but one is a few seconds behind the other. Nothing changes cosmologically on a scale of two seconds - except of course for gamma bursts and supernovae, which weren't observed. Macroscopic dispersive effects (change in refractive index due to frequency) in large intervening nebulae etc. cannot in principle be ruled out, but what do I know about astrophysics? Presumably they carefully chose a very empty part of the sky.

So, in order to reject the null hypothesis (that there are no differences in the speeds of the photons of different energies) any observed difference has to be >~ 2 secs. If there are hypothesized physical processes that do predict larger differences in arrival times, the observed 0.9 sec difference will put very tight constraints on the viability of those theories.

Now, watch the string theorists squeeze themselves through those very tight constraints! They have had 30 + years of practise!

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Bo Asciu wrote:

Kevin good point, keen mind.

Space/Time can't be that "frothy" since the laws of the universe are so precise. Too much looseness and the whole thing falls apart.

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Briefly addressing Bo’s comments:

There is classical, deterministic chaos, there are classical uncertainties due to stochastic processes, and we haven't even got to talking about QM! -in terms of causing frothiness in spacetime.

The point is that there are viable and very precise theories - "laws of the universe" - that separately either hypothesize or predict a "frothy" universe on a scale somewhere between 10^-18m and the Planck scale (10^-35m). The observations discussed put presumably very tight constraints on the free parameters in the theories that distinguish them from Einsteinian General Relativity.

If say the two photons had arrived more than 8 secs apart, the observations would tell us precisely how "frothy" spacetime actually is – how big are the hyopothesized microstructures, on what time scales do they change, how do they interact with different photons.

Even Einstein's very beautiful, very precise etc etc General Theory of Relativity CANNOT rule out frothiness of the universe on some heretofore unobserved, untested scale, though very good arguments can be made that the GTR will break down at some scale > Planck. If frothiness is observed at some larger scale, it will put a lower bound on the domain of applicability of the GTR (Since it hypothesizes a smooth (or at least twice differentiable) geometry for spacetime, GTR is valid above but not below the scale at which those “violations” are observed.).

Letter to Tom Ashbrook and On Point on "Polanski"

In response to an interview with Henri-Levy and Ferraro:

I'd like to state that I am in favor of extraditing Polanski and making him stand trial. There are three points I would like to make:

1) Even though his victim has pardoned him, which she is welcome to do, she should no longer interfere with the criminal case. In India, bigamy is illegal for Hindus and it is a crime for Hindu men to have more than one wife. However, it can't be prosecuted and has almost never been prosecuted because only the injured party or someone with standing in the case can file a police complaint or file charges. In the case of bigamy, this translates into this responsibility being put on the first wife, who is all too often either submissive, subjugated or financially totally dependent on her husband.

2) Ferraro points out that Polanski's status should not affect the decision to prosecute or not. However, hypocrisy in prosecuting crimes or in access to justice is nothing new: when the Americans sign on to the International Criminal Court, and begin to prosecute those Americans who broke the law on torture (be they ex-Presidents or film-makers) and those soldiers and mercenaries who continue to commit crimes in Iraq and cooperate with international justice, perhaps it will then be easier for the Europeans to swallow the Americans' sanctimonius arguments about "no one is above the law".

3) Polanski should be tried not because "he is vile" but because he has broken the law. Judgments of character should not interfere with judgments of action - lest we fall into the fascist and hierarchical trap of letting the "good" people off the hook for their misdeeds - ranging from massacres during fascist Spain to rapes by high caste men against low caste women in rural India.