|Oct19-05, 11:18 AM||#1|
Lawrence Krauss new book
A new book by Lawrence Krauss is scheduled to appear in bookstores tomorrow. Has anybody here seen an advanced copy?
Peter Woit has a review of the book
One of the perks of having a popular blog website seems to be that publishers send you reviewer copies of new books, before they hit the stores and go on amazon.
Here is the amazon page
It has a bunch of shorter reviews and the usual amazon info.
Krauss has written a number of general audience physics and cosmology books, including for instance a popular one called The Physics of Star Trek
This new one has the intriguing title:
HIDING IN THE MIRROR: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond
Part of the idea of the book is to explore mankind's age-old fascination with the notion of unseen extra dimensions.
|Oct19-05, 12:48 PM||#2|
Having read "Beyond Star Trek: From Alien Invasions to the End of Time" and "The Physics of Star Trek", Lawrence Krauss reveals some of the mistakes that come up throughout the popular television series. Although not in a negative way, in fact I’ve learnt a bit from those two books. If they’re anything to judge by, I would say this new book is worth the read also. Of particular interest is the connection between extra dimensions and an age old cultural fascinations with the idea.
|Oct19-05, 02:42 PM||#3|
I just preordered the new Krauss book, based on what I read on Woit's site. It was interesting to read some of the comments there on the comparison of Krauss's version of brane worlds to Lisa Randall's treatment in her new book Warped Passages. I thought that Lubos' comment that Krauss has never done any work in that field, whereas Randall has her name on a major initiative, does have some merit, although it was expressed in Lubos' usual over-the-top in-your-face style. I'm planning to go to a talk Randall is giving in Appleton next January, and if she is signing copies of her book I wil buy it then.
BTW, Hiding in the Mirror and Warped Passages sound like new volumes in some Sword and Sorcery series by Robert Jordan or Terry Goodkind!
|Oct26-05, 05:25 PM||#4|
Lawrence Krauss new book
Here is an interview with Krauss in the Cleveland Plain Dealer
if that link doesnt work try
the MSNBC inhouse blog that provided part of this information is run by
Alan Boyle and is called COSMIC LOG
it might be something to check out from time to time. While reading about Larry Krauss book I happened on a beautiful picture of a black hole gobbling up stars and a link to this ESO press release:
You may have seen this picture elsewhere. the article is called
Feeding the Monster
New VLT Images Reveal the Surroundings of a Super-massive Black Hole
kind of telescope photo that hooks one into a lifelong love-affair with astronomy
|Oct26-05, 05:39 PM||#5|
I don't know why they were privileged, but my local Barnes and Nobles has had Hiding in the Mirror for a week. I was able to read comparable sections from it and Warped Passages last Thursday. Just as advertised, Kraus is more succinct, Randall more discursive, but both of them taught me things I didn't know. When my bank account will stand it I will buy both. Well actually I'm waiting to see if Randall is selling her book at her talks (she's on tour now). If so I will buy Passages when she comes to Appleton in January.
|Oct27-05, 12:35 PM||#6|
|Oct27-05, 01:12 PM||#7|
I used to live in lowereastside, 12th st.
know the unionsquare neighborhood and those bookstores somewhat
|Nov14-05, 02:04 PM||#8|
Lawrence Krauss, whose new book is out, has been invited by the group blog COSMIC VARIANCE to be their guest blogger.
this just happened today, he wrote a short essay to start the thread---about string theory, about aesthetics and hype-vs-empiricism issues, about the current science/religion skirmishing.
AFAIK the guest blog just went up and there are some half a dozen comments. Nothing special so far but to keep an eye on.
|Nov14-05, 02:17 PM||#9|
Here is the amazon page for Krauss HIDING IN THE MIRROR
Before the book came out, Peter Woit did a very helpful job of sifting out some key quotations
---------quotes from Krauss and others exerpted in Peter Woit's review------
But in the ever-optimistic string worldview, there are no embarassments… For these ‘true believers’, every new development provides an opportunity to confirm one’s expectations that these ideas ultimately reflect reality.
… string theory might instead do for observational cosmology what it has thus far done for experimental elementary particle physics: namely, nothing.
In short, the as-of-yet hypothetical world of hidden extra dimensions had, for many who called themselved physicists, ultimately become more compelling than the world of our experience.
This embarassment is solved in the way other similar confusing aspects of string theory and M-theory are sometimes dealt with: Namely, it is assumed that when we fully understand the ultimate theory, everything will become clear.
Over the past five years, hundreds if not thousands, of scientific papers have been written considering cosmological possibilities that might be associated with Braneworld scenarios. One cannot do justice to all of them, but the greatest justice I could probably do to many of them is to not mention them here.
What the notion of large or possibly infinite extra dimensions has done is borrow some of the facets of string theory while ignoring the bulk of the theory (forgive the pun), about which, as I have explained, we have only the vaguest notions. It seems to me to be a very big long shot that an apparently ad hoc choice of what to keep and what to ignore will capture the essential physics of our universe.
This [the Landscape] has resulted in yet another fascinating sociological metamorphosis of the theory, with warts becoming beauty marks.
… the anthropic principle is something that physicists play around with when they don’t have any fundamental theory to work with, and they drop it like a hot potato if they find one.
This finally brings up back to M-theory. Faced with the prospect that the theory may ultimately predict a virtually uncountable set of possible universes, some string theorists did a 180-degree about-face. Instead of heralding a unique Theory of Everything that could produce calculable predictions, they are now resorting to what even a decade ago they may have called the last refuge of scoundrels. But, when string theorists take a position, they do it with flair.
…if the landscape turns out to be the main physical implication of the grand edifice of string theory or M-theory… we might be left with the mere suggestion that anything goes. What was touted twenty years ago as a Theory of Everything would then instead have turned quite literally into a Theory of Nothing.
Krauss ends his book with an epilogue describing conversations with Gross, Wilczek and Witten about string theory. Wilczek is a skeptic, annoyed by the excessive claims made for the theory. Witten is quoted as saying that string theory “is a remarkably simple way of getting a rough draft of particle physics unified with gravity. There are, however, uncomfortably many ways to reach such a rough draft, and it is frustratingly difficult to get a second draft.” He justifies work on string theory partly through progress it has led to in the understanding of strongly coupled gauge theories.
Gross is described as convinced "that the theory is simply too beautiful not to be true”, an attitude that strikes Krauss “as sounding like religion more than science.” With this, Krauss ends his book by quoting Hermann Weyl:
"My work always tried to unite the true and the beautiful, but when I had to choose one or the other, I usually chose the beautiful."
So it is that mathematicians, poets, writers, and artists almost always choose beauty over truth. Scientists, alas, do not have this luxury, and can only hope that we do not have to make this choice.
-----end quote from Woit's review----
|Nov14-05, 08:33 PM||#10|
|Nov17-05, 10:33 PM||#11|
there are now over 133 comments on the thread, #133 is again by Smolin
the poster called Moshe has responded once to Smolin, that i could find, which was #50. It may be that what Lee means by "thanks for your last remark" was this Moshe post #50-----I couldnt find anything else it could refer to.
What impresses me here? Carefullness of statement and courtesy of address. Smolin is clearly trying to see if it is possible to have a constructive and substantitive discussion in public where non-experts can "look over the players' shoulders" or listen in. but there is a lot of distraction. If there COULD be an open constructive polite public discussion, where non-experts could listen, that would be great. Smolin said something about that as a goal. he's obviously interested in having that. However my impression is it's "noisy" at Cosmic Variance. Actually, in my humble opinion, there'v been quieter more substantive discussions between Smolin and other string experts over at Woit's Not Even Wrong blog.
Come to think of it, since Peter woit is not a partisan of either Loop or String he may preside over a better blog for really educational discussions. At Cosmic Variance the management is potentially more biased because involved in string research (and NOT in loop)----whereas Peter is involved in neither. But we just have to keep an open mind and see how this occasion turns out.
Anyway what we have at the moment is a small give and take exchange (around 3 or 4 posts in the midst of over 100) about a key issue----almost lost amongst other discussion---the other discussion could be enlightening as well. But this issue is really a key one. in what sense, if at all, does the string framework reproduce gravity in a mutable background---where space geometry changes with time
I wonder if Moshe will post a reply any time soon? If he does I will copy it here and we can take a look
|Nov18-05, 12:40 AM||#12|
indeed the poster at Cosmic Variance called Moshe did reply quite promptly and at considerable length. I will copy his response in full
137. Moshe on Nov 18th, 2005 at 12:28 am
Hi Lee, thanks for your last comment, it is certainly a pleasure talking physics!
(and apologies for the technical level of this stream of comments, but this is the most efficient way to resolve technical issues).
So, here is my understanding of the situation. The issue is that of classical stability, whether or not the spectrum of linearized fluctuations around specific background has tachyons. Now if space is exactly flat, the bosonic string has a tachyon with string scale mass, which means instability with string timescale. With worldsheet SUSY this disaster is avoided, one gets spectrum with no (classical linearized) instabilities.
Now, let us talk about backgrounds that are almost flat, then just by continuity the only thing one has to worry about is the spectrum of modes that would have been zero modes in flat space. So my statement is that weakly curved solutions of string theory have tachyons if and only if the corresponding GR+matter solution is stable. So string theory at the classical level is as stable or unstable as the corresponding field theory it includes. On the classical level such instability is not such a disaster, one simply gets an unstable solution of Einstein equation, those are fine, they are not inconsistent (nor are they very interesting…)
The point about worlsheet SUSY is a red herring I believe. Generally worldsheet structures are invisible from the spacetime viewpoint, they are just mathematical tricks (it is unnecessarily confusing to think about string worldsheet as embedded in spacetime, as one has to sum over worldsheet metrics, where the induced metric from spacetime is only one of the metrics to be summed over). Worldsheet SUSY is that mathematical trick allowing spacetime fields to have spin. It turns out that in string theory it also projects out the bosonic string tachyon, leaving the situation I described in the last paragraph. So all the set of models we mentioned, orbifolds, cosets etc. are consistent backgrounds of classical string theory with no tachyons.
So to summarize,classically I think the statement that generic weakly curved solution of Einstein equation lifts to a classical solution of the full superstring theory, with no tachyons.
I keep adding the adjectives “classical” and “weakly coupled” to everything, and at that level I think what I said so far is correct, hopefully someone will correct me if I am wrong. Now once we add quantum corrections there are several disasters that can happen, for example w/o spacetime SUSY various massless modes will start getting sources, so static solutions of the classical equations will no longer stay static (which sometimes is referred to as “instability”). If you are not interested specifically in static solutions maybe this point is not such a concern.
More seriously for time dependent backgrounds, I think singularity theorems say that in many cases (generically?) time dependent backgrounds will tend to have spacelike singularity in the past or future, and then the background is no longer weakly curved everywhere. This manifest itself by certain singularities in string theory observables, also sometimes referred to as “instabilities” (one can detect certain lack of imagination…). As I said this is the reason why this is an interesting topic. It is certainly not clear that a generic classical solution of any theory, especially containing gravity, should lift to a full solution of the quantum theory. The question which do and which do not, and whether one can do it perturbatively or not, are very interesting open issues, not a lot is known about them currently.
|Nov20-05, 08:48 PM||#13|
the preceding post was Moshe's #137 over at cosmic variance.
Lee just replied (it was #154) and then Moshe again:
----quote from CV---
Lee Smolin on Nov 20th, 2005 at 6:13 pm
Thanks very much for your #137. This is helpful, but can I query you on one point, where you say that on “…backgrounds that are almost flat, then just by continuity the only thing one has to worry about is the spectrum of modes that would have been zero modes in flat space. So my statement is that weakly curved solutions of string theory have tachyons if and only if the corresponding GR+matter solution is stable. So string theory at the classical level is as stable or unstable as the corresponding field theory it includes.”
Can you fill in a few details of this argument? It seems to me that given that the cancellation of the tachyon involves a projection to a smaller state space (the GSO projection) and given that the projection implies spacetime supersymmetry which is broken as soon as there is any time dependence, you have to show that you can continue to impose a projection that eliminates a tachyon for any small non-supersymmetric deformation of the background geometry. Has this been done? If not, I don’t think you can use an effective field theory argument that assumes that the tachyon is absent from the deformed theory.
On a related point, you say, “It is certainly not clear that a generic classical solution of any theory, especially containing gravity, should lift to a full solution of the quantum theory.” But for the classical theory to be recovered as the low energy limit, must it not be that every solution to the classical theory that is weakly curved on the Planck scale must lift to a coherent state in the quantum theory?
Moshe on Nov 20th, 2005 at 6:38 pm
Back to physics, very theraputic…
The comment of continuity was just an intuitive comment, not really necessarily an EFT argument. Basically the spectrum of the string is continuous as a function of the background fields (w/o changing the GSO projection), so string scale tachyon cannot just pop up when you turn on arbitrarily small background fields. In any event, I assure you there are also more complete calculations, that was just an argument why this had to be the case. Incidentally, even for static backgrounds there are non-SUSY classically stable cases, but they are quantum mechanically unstable in the sense that they don’t stay static after including quantum corrections.
As for the last paragraph, I mentioned that in the context of backgrounds which develope singularities, and then we don’t have a criteria for judging which background lift to the full quantum theory. My bet is that weakly curved backgrounds should be fine, but one cannot know for sure yet. (incidentally, is it always true that for time dependent background singularity thm. dictate there generaically exists future or past singulairty?)
Moshe on Nov 20th, 2005 at 6:56 pm
Oh, one more point, the GSO projection by itself does not imply spacetime SUSY, it just allows for that possibility, if the background fields cooperate…
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