tag:blogger.com,1999:blog-22973357.post5888498022087915145..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Post-empirical science is an oxymoron.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger141125tag:blogger.com,1999:blog-22973357.post-13916228747524789772017-02-26T19:53:39.592-05:002017-02-26T19:53:39.592-05:00Science is science because it's empirical. Th...Science is science because it's empirical. This is what differentiates it from mathematics, philosophy and theology. At best, if you can't test a hypothesis empirically, it's simply incomplete science, at worst it starts to take on a religious air.<br /><br />I'm afraid the trend towards secularism and the uncritical reverence towards science has not escaped the power of the Scientisthttps://www.blogger.com/profile/07084024240366738724noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73629667413190033932014-12-18T07:54:47.819-05:002014-12-18T07:54:47.819-05:00Physicists who are contributing to cancer therapy ...Physicists who are contributing to cancer therapy are frequently asked by patients about the safe or unsafe nature of radiation treatment. I was asked by a patient if a Higgs Boson would be generated during therapy. So I wonder how patients would react when word gets out that physics doesn't depend on data to check it's theories. The beauty and consistency of a theory is not a convincing Anonymoushttps://www.blogger.com/profile/05791476706162666857noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1340888005276799932014-08-20T08:55:18.559-04:002014-08-20T08:55:18.559-04:00Lee,
there is one more remark I should add in ord...Lee,<br /><br />there is one more remark I should add in order to alleviate your worries that NEC is a deadly threat to diversity in physics. This is the following: NAA is based on the observation that, despite serious attempts to do so, no alternatives to theory X have been found. If no-one looks for alternatives, the fact that none show up obviously tells nothing about the actual spectrum of richard.dawidhttps://www.blogger.com/profile/04438489790330841473noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31010884164109809282014-08-19T09:39:28.001-04:002014-08-19T09:39:28.001-04:00Dear Lee,
Several issues you raise have been addre...Dear Lee,<br />Several issues you raise have been addressed already in other entries of mine in this blog. Maybe it’s time to wind down our exchange after this, before repetition fully takes over. I think our differences are clearly spelled out by now. Anyway, here are my answers.<br /><br />As you point out once again, you take it to be one of NEC’s most serious problems that it can support richard.dawidhttps://www.blogger.com/profile/04438489790330841473noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1913927592808399312014-08-16T12:51:42.195-04:002014-08-16T12:51:42.195-04:00
Dear Giotis,
I never claimed LQG is equivalent t...<br />Dear Giotis,<br /><br />I never claimed LQG is equivalent to string theory in requiring unification-and in fact I agree that that is string theories most attractive feature. But I do claim LQG contains natural routes to unification. There arise from the simplest possible extensions of LQG and hence constitute instances of Dawid’s criteria of “The argument of unexpected explanatory Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5209874273306153792014-08-16T12:36:26.865-04:002014-08-16T12:36:26.865-04:00Dear Richard,
Many thanks. I read your July 16 p...Dear Richard,<br /><br />Many thanks. I read your July 16 post and it just makes me more confused as to exactly what you are advocating. <br /><br /><br />As I mentioned above, a lot comes down to your use of the term “viable,” You said above, “ I use a stronger notion of viability: a theory is viable if it agrees with the empirical data in a given empirical regime.” In your July 16 comment Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2636037807433683252014-08-16T04:05:05.671-04:002014-08-16T04:05:05.671-04:00Hello,
As was already mentioned, String theory is...Hello,<br /><br />As was already mentioned, String theory is not just a theory of QG but a unified framework of all fundamental fields(content and interactions) and of all fundamental physical principles and concepts.<br /><br />In that respect the fact that LQG does not constitute an alternative to String theory as a unified framework is acknowledged by LQG theorists themselves. So I don’t see Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72197286789888076982014-08-16T00:20:08.341-04:002014-08-16T00:20:08.341-04:00Giotis, Lee, Richard:
I will be traveling the nex...Giotis, Lee, Richard:<br /><br />I will be traveling the next weeks and not sure how much I come around to check my blog. I've increased the no-moderation window to 6 weeks, so your comments should now go through again without my okay.<br /><br />Lee: Sorry for missing your comment, I've found it in the spam queue, it should have appeared now. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53769318460981306622014-08-15T16:06:23.719-04:002014-08-15T16:06:23.719-04:00Dear Lee,
Much of what I’d have to answer to your ...Dear Lee,<br />Much of what I’d have to answer to your conceptual questions I’ve said already elsewhere on this blog. Therefore, in order not to get overly repetitive, let me refer back in particular to my entry from July 16 where I try to clarify my position with respect to my understanding of the relation between empirical and non-empirical confirmation and the issue of sociology.<br />With richard.dawidhttps://www.blogger.com/profile/04438489790330841473noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47177312582617185442014-08-15T10:33:07.766-04:002014-08-15T10:33:07.766-04:00Dear Giotis,
Well, surely you know that spin foam...Dear Giotis,<br /><br />Well, surely you know that spin foam models are ultraviolet finite. And there are recent results that show that in the presence of a cosmological constant they are infrared finite as well. But there is as yet no full blown description of an AdS/CFT correspondence in LQG.<br /><br /><br />Anyway, what I find remarkable is that, with respect to string theory, we are havingAnonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77666833018823845712014-08-15T01:19:05.431-04:002014-08-15T01:19:05.431-04:00Giotis:
I have comment moderation on for posts ol...Giotis:<br /><br />I have comment moderation on for posts older than 2 weeks. Almost all submissions on older posts are spam. If I turn it off, I have to go by hand through all the pages that collected spam over night and that costs me more time than I want to waste every morning. <br /><br />I normally check the moderation queue every morning unless traveling. Your comments are stuck in the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71224459821277407142014-08-14T15:39:10.127-04:002014-08-14T15:39:10.127-04:00Just to correct something:
I meant to say “and t...Just to correct something: <br /><br />I meant to say “and thus to test more efficiently the correspondence beyond BPS”.<br /><br />BTW Sabine, can you please turn off the moderation at least temporarily? <br />I write a comment and it appears after one or two daysGiotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-60113398360817869132014-08-14T14:45:01.776-04:002014-08-14T14:45:01.776-04:00Hello,
Sorry I never said that “quantize Strings ...Hello,<br /><br />Sorry I never said that “quantize Strings on AdS backgrounds” would give a background independent definition of the theory, or even a BLBI theory. Why I would say such thing?<br /><br />I mentioned this (together with the lack of an independent non perturbative definition of the theory) only to highlight the reason why it is generally difficult to do calculations on the bulk Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9624803165423627782014-08-14T11:05:45.063-04:002014-08-14T11:05:45.063-04:00Dear Giotis,
continuing...
Anyway, what I find r...Dear Giotis,<br /><br />continuing...<br /><br />Anyway, what I find remarkable is that we are having the same debate we had in 2006 and could have had in 2000. This in itself shows why I disagree with Dawid’s claim to have given “ criteria that would allow someone to evaluate the viability of a theory even if empirical data are not available for the time being.” There has in fact been Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-45098695558765096242014-08-14T11:03:29.052-04:002014-08-14T11:03:29.052-04:00Dear Giotis,
You say, “I don’t have a clue why s...Dear Giotis,<br /><br /><br />You say, “I don’t have a clue why someone will argue that AdS/CFT is not background independent.” Can I help? The clue would be to read the definition I gave of background independence, which is the standard definition.<br /><br /><br /> “the definition of observable quantities does not depend on the specification of any fixed classical geometries or fields.” <br /Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85712136235675556972014-08-13T10:23:50.461-04:002014-08-13T10:23:50.461-04:00Everyone knows that besides AdS/CFT we don’t have ...Everyone knows that besides AdS/CFT we don’t have a non perturbative definition of String theory yet and everyone knows that it is notoriously difficult to quantize Strings on AdS backgrounds. <br /><br />This of course and the lack of an independent non perturbative definition of the theory is the reason you can’t test the correspondence beyond the semi-classical limit. The current view is that Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2173409218102355672014-08-12T11:39:25.089-04:002014-08-12T11:39:25.089-04:00Dear Richard,
Continuing to your remarks on backg...Dear Richard,<br /><br />Continuing to your remarks on background independence: “ST does not predict background dependent physics but merely has been developed from a starting point that does not make background independence explicit.”<br /><br />First, by background independent we usually mean that “the definition of observable quantities does not depend on the specification of any fixed Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64940037684929652332014-08-12T10:53:25.255-04:002014-08-12T10:53:25.255-04:003:51 AM, August 12, 2014
Dear Richard,
Many thank...3:51 AM, August 12, 2014<br />Dear Richard,<br /><br />Many thanks for your remarks. I agree this is a useful discussion.<br /><br /><br />A key assertion you make is, “What I try to argue for is that NEC does have significant epistemic value.” At this point I want to ask you for your general theory of how science works. Here is mine, which was presented in Chap 17 of TTWP: Science Anonymoushttps://www.blogger.com/profile/10548788662592180869noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66069613632030093662014-08-12T10:31:19.075-04:002014-08-12T10:31:19.075-04:00Giotis: Sure, I agree with that. The way you phras...Giotis: Sure, I agree with that. The way you phrased it though I thought you thought I said otherwise. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-4110284981819235442014-08-12T09:31:19.522-04:002014-08-12T09:31:19.522-04:00But then my comment holds i.e. you never know the ...But then my comment holds i.e. you never know the limits to what you can observe in the natural world. <br /><br />Maybe in the future you would be able to find detectable empirical signatures of QG theories but for this you need to continue the digging.Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-80206949470221567822014-08-12T09:10:39.018-04:002014-08-12T09:10:39.018-04:00As I explained in my post, I say "useless&quo...As I explained in my post, I say "useless" to mean "useless to describe the natural world". Neither LQG nor string theory describes anything we observe that could not also be described with GR and the standard model. (See above for my comments regarding AdS/CFT.) Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59085144603094398632014-08-12T09:06:48.630-04:002014-08-12T09:06:48.630-04:00Why are you saying that String theory and LQG are ...Why are you saying that String theory and LQG are useless then?Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56109891532370455792014-08-12T09:01:17.858-04:002014-08-12T09:01:17.858-04:00Giotis,
No, you misread me. I did not say that on...Giotis,<br /><br />No, you misread me. I did not say that one shouldn't think about black hole evaporation, entropy and so on, and I also didn't say that one should be content with the contradictions left within the classical theory. What I am saying is that without experimental evidence any consistent explanation is as good as the other. The black hole information loss problem is exactlySabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25937125302279698662014-08-12T08:50:48.360-04:002014-08-12T08:50:48.360-04:00Sabine’s comment about the black hole evaporation ...Sabine’s comment about the black hole evaporation etc. reminds me Freeman Dyson’s attitude towards the quantization of Gravity and gravitons i.e. that people should be content with the existing low energy effective description of Gravity by Einstein and not try to quantize it since we have zero chance of observing a graviton.<br /><br />I’m wondering what his reaction was when he heard the recentGiotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-29969874550350355142014-08-12T07:50:29.353-04:002014-08-12T07:50:29.353-04:00Dear Richard,
Sorry about that, I was being too b...Dear Richard,<br /><br />Sorry about that, I was being too brief. What I meant is what I already said above, to the extent that some assessment is non-empirical it's not useful and to the extent that it's useful it's not non-empirical. Sure, we are pretty certain black holes exist and so on, we have data on that (empirical), so your theory of quantum gravity better fits to that data. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com