sage
发表文章数: 1125
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One comment on quantum gravity
Sal: 是啊， 额外的维度、 超对称、 无穷无尽的场 ...
these are not the assumptions of string theory. these are the predictions of string theory.
| 发表时间：2004-03-05, 00:03:34 |
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卢昌海
发表文章数: 1617
武功等级: 北冥神功
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Re: One comment on quantum gravity
This is Sal's way of expressing things, Prof Simp did say:
Simp: 超弦理论也有不少预言啊。
Sal: 比方说？
Simp: 比方说大的额外维度 (large extra dimension)、 超对称、 标准模型中不可能出现的反应。
And there will be more discussions on that in the later part of the article.
Thanks for the suggestion in the other post. There will be article(s) in favor of string theory on the site (Pochinski's lecture, however, is the type of material that whoever be able to understand will not need any translation :-) The current physics literature is already overwhelmingly favorable to string theory, this is why I translate this one first.
宠辱不惊，看庭前花开花落
去留无意，望天空云卷云舒
| 发表时间：2004-03-05, 08:46:55 |
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sage
发表文章数: 1125
武功等级: 天山六阳掌
(第六重)
内力值: 535/535
Re: One comment on quantum gravity
Large extra dimension is NOT a prediction of string theory. I don't know if the author deliberately trying to make string theorist sounds stupid.
Anyway, I think there must be some scientific american articles about string theory which might be easier for everybody to understand. there is one on loop quantum gravity by Smolin as well.
| 发表时间：2004-03-06, 23:59:57 |
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卢昌海
发表文章数: 1617
武功等级: 北冥神功
(第一重)
内力值: 602/602
Re: One comment on quantum gravity
For a theory that claims to have only one input, everything (except for that single input) must be either a prediction or a hidden assumption (or irrelevant). For now, large extra dimension may look like a model dependent input, just like the various string vacua theorists are studying. But eventually - as string theorists hoped - they (if really needed) should all come up as the result of string dynamics. In this sense, these (if really needed) ARE all predictions of the theory, and - as string theorists hoped - they should be, otherwise string theory is not as logically simple as they claimed (what's the difference between having 19 free parameters versus having one free parameter plus a whole free manifold?).
It is true that the author's knowledge on string theory is limited (sometimes even erroneous), and his view is highly biased (he is not a neutral person). But IMHO he does have some points that are worth reading - and these days, it's hard to hear any real theorist expression opinions agianst string theory as directly and frankly as he did. The balance I will pursue is to post counter-opinions sometime in the future. It's hard to make each single article un-biased, but easier to achieve the desired fairness with a collection of articles.
宠辱不惊，看庭前花开花落
去留无意，望天空云卷云舒
| 发表时间：2004-03-07, 09:14:18 |
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sage
发表文章数: 1125
武功等级: 天山六阳掌
(第六重)
内力值: 535/535
Re: One comment on quantum gravity
OK.
Actually I am not necessarily a big fan of string theory either. However, loop quantum gravity definitely should not have the status as a potential theory as string theory. Not even close.
It is amusing to see that they mention string theory does not have a model precisely reproduce the Standard Model as if loop quantum gravity can do even a similar job.
| 发表时间：2004-03-07, 20:59:07 |
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