tag:blogger.com,1999:blog-22973357.post4528292742363556624..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Researchers propose experiment to measure the gravitational force of milli-gram objects, reaching almost into the quantum realm.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger28125tag:blogger.com,1999:blog-22973357.post-40094383302769563672016-03-21T05:20:25.455-04:002016-03-21T05:20:25.455-04:00Maurice,
The sentence you quote from me that you ...Maurice,<br /><br />The sentence you quote from me that you think is "wrong in your opinion" was explicitly referring to the MWI. Just that you left out this part of the quote. I hope that this misquote was an accident and not deliberate.<br /><br />If you read it again you might note that I didn't and don't disagree with the point about the MWI that Giotis and Kiefer were Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42381148118920836052016-03-21T04:49:10.219-04:002016-03-21T04:49:10.219-04:00I checked out your "lecture" on Page &am...I checked out your "lecture" on Page & Geilker from Jan. 2012. You called their experiment a laughing matter and then Giotis made you aware of the fact that your lecture is in contradiction to Kiefer's Intro because he takes the experiment quite seriously. Now that's serious because it means that either Kiefer or you have misunderstood some very elementary concept, right? I Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62282595802976655312016-03-19T23:26:57.039-04:002016-03-19T23:26:57.039-04:00Wow, this is exciting stuff. We're only three ...Wow, this is exciting stuff. We're only three (or so) orders of magnitude off which is pretty amazing.Kaleberghttps://www.blogger.com/profile/05283840743310507878noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12745653578737751832016-03-18T13:49:22.603-04:002016-03-18T13:49:22.603-04:00Maurice,
Yes, it's embarrassing indeed that y...Maurice,<br /><br />Yes, it's embarrassing indeed that you cannot answer my questions after you've made such a lot of noise in pretending you know more about qg pheno than I. It is also astonishing that you seem to assume I know neither Page & Geilker's experiment (which I have both written about on my blog and have also covered in those QG 101 lectures you didn't attend) nor Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31809412916133409322016-03-18T12:01:27.984-04:002016-03-18T12:01:27.984-04:00"Tell me how you want to bring the gravitatio..."Tell me how you want to bring the gravitational field into a quantum superposition without at least pertubatively quantizing it." By assumption. Why would this assumption require that gravitons exist? "And then tell me what about Page and Geilker's experiment you cannot explain in the semi-classical treatment." That's becoming embarrassing. Page & Geilker's Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67218579326484230202016-03-18T11:05:18.878-04:002016-03-18T11:05:18.878-04:00Maurice,
Tell me how you want to bring the gravit...Maurice,<br /><br />Tell me how you want to bring the gravitational field into a quantum superposition without at least perturbatively quantizing it. And then tell me what about Page and Geilker's experiment you cannot explain in the semi-classical treatment. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33117273173227041942016-03-18T10:04:57.811-04:002016-03-18T10:04:57.811-04:00Sorry Sabine, apparently you really do not underst...Sorry Sabine, apparently you really do not understand Page/Geilker. I recommend Kiefer's discussion of their experiment in the Intro p.17-18 of his textbook (edition 2006), which concludes, quote: "This experiment [Page/Geilker] ... demonstrates convincingly that (1.34) [semi-classical expression with expectation value of stress-energy tensor] cannot fundamentally be true." Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39237866725517169882016-03-18T08:44:11.222-04:002016-03-18T08:44:11.222-04:00Maurice,
Sorry, I don't know what you mean ab...Maurice,<br /><br />Sorry, I don't know what you mean about the Page/Geilker experiment. To test quantum gravity, they were assuming that the quantum superpositions from some radioactive decay transfer over to massive balls. Clearly nobody in their right might would explect that. When I say quantum gravity, I here mean the perturbative quantization of quantum gravity. If you think that all I Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13300439942539527092016-03-18T07:20:47.640-04:002016-03-18T07:20:47.640-04:00"The Page/Geilker experiment presumes that he..."The Page/Geilker experiment presumes that heavy objects under question don't decohere."<br />No, it does not! Rather it presumes that decoherence of heavy objects is all that there is to wave-function collapse, i.e. that there is no explicit collapse mechanism extra to the usual formalism of QM. "As I explained above, you do not need to detect quanta of the gravitational fieldMauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50385336863927105742016-03-18T01:50:51.135-04:002016-03-18T01:50:51.135-04:00Maurice,
The Page/Geilker experiment presumes tha...Maurice,<br /><br />The Page/Geilker experiment presumes that heavy objects under question don't decohere. No, an experiment of the type I sketched here would not prove that gravitons exist. As I explained above, you do not need to detect quanta of the gravitational field to demonstrate that the field must be quantized. These are just two different things. That electron orbits are quantized Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24924387866805874822016-03-18T01:46:04.312-04:002016-03-18T01:46:04.312-04:00Robert,
Sorry, I don't know what you want to ...Robert,<br /><br />Sorry, I don't know what you want to measure. For what I can tell you are proposing to let an atom decay and then measure its gravitational field. Could you be somewhat more specific? If you take an ensemble of particles that decay which is not in a coherent state you get a stochastic contribution and as a result the net gravitational field is the same as in the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87855176872214346812016-03-17T17:21:50.279-04:002016-03-17T17:21:50.279-04:00This might be crazy, but consider this Quantum Zen...This might be crazy, but consider this Quantum Zeno effect experiment: http://phys.org/news/2015-10-zeno-effect-verifiedatoms-wont.html.<br /><br />I quote from the article directly:<br /><br />"Previous experiments have demonstrated the Zeno Effect with the "spins" of subatomic particles. "This is the first observation of the Quantum Zeno effect by real space measurement of PonderSeekDiscoverhttps://www.blogger.com/profile/00913503952284529871noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-45239375979574026532016-03-17T12:31:25.441-04:002016-03-17T12:31:25.441-04:00My attempt for an intelligible explanation: the pr...My attempt for an intelligible explanation: the proposal (apparently from Richard Feynman) is to test if the gravitational field can entangle a system with a second system that is in a spatially dis-localised state. To entangle the systems two different gravitational fields are needed: one for each quantum-mechanical state of the second system - one field that pulls a component of the first Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-88884211953421111382016-03-17T04:05:55.093-04:002016-03-17T04:05:55.093-04:00This means you have to be able to bring a "he...This means you have to be able to bring a "heavy" object into a superposition. <br /><br />I don't think this is a problem. Do the thing with the radioactive source. This creates a superposition of an object as heavy as you want. For this question, it does not matter, that its position will be entangled with all kinds of air molecules and soft photons. So decoherence does not affectRoberthttps://www.blogger.com/profile/06634377111195468947noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35984047922648905242016-03-17T02:13:13.822-04:002016-03-17T02:13:13.822-04:00Seem to me, that these kind of experiments may jus...Seem to me, that these kind of experiments may just be what the doctor order to get theoretical physics unstuck again.Anonymoushttps://www.blogger.com/profile/14479459346584756683noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50776054187742975252016-03-16T07:47:32.252-04:002016-03-16T07:47:32.252-04:00Robert,
I've tried for like a decade to come ...Robert,<br /><br />I've tried for like a decade to come up with any measurable inconsistency that this would result in and failed. Once you put in numbers, you always end up with something that's way smaller than anything that we could detect. Just try it... I have tried this in all kinds of scenarios, forwards and backwards, but the problem is always the same: to make this effect Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91338059951930602602016-03-16T07:37:08.122-04:002016-03-16T07:37:08.122-04:00Maurice,
"I was hoping it should be obvious ...Maurice,<br /><br /><i>"I was hoping it should be obvious that "fully left" or "fully right" is a way to say it's in a quantum superposition of two locations." Sorry, your quoted sentence is incomprehensible, "fully left" means that there is no amplitude on the right, i.e. no superposition, isn't that correct?!</i><br /><br />I was hoping it should Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-68168744220514375532016-03-16T04:27:09.309-04:002016-03-16T04:27:09.309-04:00Hi,
I find it very hard to believe that the lower...Hi,<br /><br />I find it very hard to believe that the lower possibility in http://2.bp.blogspot.com/-YjhJRr_pgHg/VhkX-ooJe4I/AAAAAAAACyA/9SPZL0ykbBg/s1600/sneq.jpg could be realized as that would immediately conjure up all kinds of quantum inconsistencies. <br /><br />For example, you could send a particle been right through the center of the set up and investigate the gravitational pull on it. Roberthttps://www.blogger.com/profile/06634377111195468947noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87562125349144764272016-03-16T04:18:37.503-04:002016-03-16T04:18:37.503-04:00"I was hoping it should be obvious that "..."I was hoping it should be obvious that "fully left" or "fully right" is a way to say it's in a quantum superposition of two locations." Sorry, your quoted sentence is incomprehensible, "fully left" means that there is no amplitude on the right, i.e. no superposition, isn't that correct?! Can you please clear this up and then answer my last Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-58450738048565993972016-03-16T03:43:34.373-04:002016-03-16T03:43:34.373-04:00Another one on the arxiv just today:
Probing a Gr...Another one on the arxiv just today:<br /><br /><a href="http://arxiv.org/abs/1603.04430" rel="nofollow">Probing a Gravitational Cat State: Experimental Possibilities</a>Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55576429415920130912016-03-16T02:17:12.970-04:002016-03-16T02:17:12.970-04:00Uncle,
Indeed, they also point out in the paper t...Uncle,<br /><br />Indeed, they also point out in the paper that a sphere is not the most optimal geometry and that this is one way to improve the efficiency. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83790027790280046422016-03-16T02:15:31.495-04:002016-03-16T02:15:31.495-04:00Maurice,
There is no general technical discussion...Maurice,<br /><br />There is no general technical discussion of this, or at least I am not aware of it. As I said this is more or less a topic nobody even thought about until a few years ago. You find some elaboration on the difference in variances in <a href="http://arxiv.org/abs/1512.02083" rel="nofollow">this example</a>. I can just tell you that from various scenarios I've thought of, theSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27419357037649266902016-03-15T16:10:49.739-04:002016-03-15T16:10:49.739-04:00The spherical ball shape of the test masses is not...The spherical ball shape of the test masses is not optimal for maximizing surface gravitation at the gap. In 2-D, then rotate about the vertical symmetry axis for the test mass (derivation is 380 words),<br /><br />Sphere, r(theta) = 2Rcos(theta)<br />Shmoo, r(theta) = 5^(1/3)Rsqrt[cos(theta)]<br />(6/5)[(5/8)^(1/3)] = 2.6% better<br /><br />http://pages.physics.cornell.edu/~aalemi/random/Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-76571243667680168252016-03-15T14:44:42.986-04:002016-03-15T14:44:42.986-04:00"If you calculate the variance of the quantiz..."If you calculate the variance of the quantized system, it's characteristically different from the unquantized one, where the gravitational field cannot properly be "with" the object." Can you please point us to a technical discussion of this? The blog-post the figure is from does not supply such a discussion. The figure itself does not help me: why is the grav. field Mauricehttps://www.blogger.com/profile/16375058316648610565noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22065424388534407382016-03-15T14:07:21.337-04:002016-03-15T14:07:21.337-04:00Maurice,
A good question. Yes, the measurement wo...Maurice,<br /><br />A good question. Yes, the measurement would collapse the object (or at least decohere it to some extent, depending on what exactly you measure), but that doesn't mean that the measurement doesn't contain information about whether the state was in a quantum superposition. Basically, what you want to know is whether the gravitational field was "with" the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com