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Mar
30
comment Cosmological constant
@zhermes, thank you for the participation, all the posts have been useful to me.
Mar
30
comment Cosmological constant
@zhermes, Einstein added the CC on the LHS of the equation AFTER finding out that his model leads to an expanding universe and he wanted it to be static. Then it was set to zero after Hubble’s discovery. Only later it was moved to RHS and given the modern interpretation. I thought this was common knowledge, but of course it is not essential.
Mar
30
comment Cosmological constant
@zhermes, I have already said that we make a lot of measurements indirectly, but this case is a bit different as summarized by Jerry Schirmer. Also, I said the technique is necessary for the case at hand. But I guess the wording is a bit confusing but not necessarily wrong because any other description might be cumbersome.
Mar
29
comment Cosmological constant
Please see my reply to lubos, and your own references are full of statements that support what I am saying. For example the list of problems in your second ref, this is not exhaustive. "Despite its success, the cosmological constant is not without problems (for further details on all the issues below see Weinberg (1989), Carroll (2001), and Padmanabhan (2003))."
Mar
29
comment Cosmological constant
@Cheeku, GR was modified to fit the observation of accelerated expansion.
Mar
29
comment Cosmological constant
But I am not against all that; we do what we have to, this is cosmology after all. I just thought either I am looking at it the wrong way, or a better characterization should be put forward to avoid confusion for the beginners.
Mar
29
comment Cosmological constant
The way then is to extract data from (CMB for example) by constructing various models to match data with formulas. Then we extract the value of CC for different models, this does not look like “measurement” in the usual sense. Typically we come up with theories via experimental results or use theory to explain experimental results. The models in this case are made based on the hypothesis that DE exists, and then DM was added to explain other observations, this I haven’t seen elsewhere.
Mar
29
comment Cosmological constant
@lubos, my reason for this question is to clarify the concept for myself, I have no other motives. Of course many measurements are done indirectly, but this case is a bit unusual, it goes too far. We are not measuring vacuum energy density directly (or indirectly) because we cannot measure such a low number and hence we are not even sure it is not zero. The theory that modifies GR to include CC itself is a bit ad-hoc, but never mind that (although other theories have been proposed, even some claim data contradict CC).
Mar
28
comment Cosmological constant
yes, both words are bad, but "measurement" sound worse. Maybe something like "hypothetically calculated".
Mar
27
asked Cosmological constant
Nov
18
comment What is the relativistic particle in a box?
Yes, all the papers are not equal in importance and rigor. But usually in science we do not do things because we like them. I had a need for it “as an idea”, then I discovered all these papers when I researched, so then I was wondering if other people had more information. But maybe this paper will help; it is from the prestigious Max Planck institute. arxiv.org/pdf/quant-ph/0701208v2.pdf. the first few paragraphs and the conclusion gives some hints.
Nov
18
comment What is the relativistic particle in a box?
Maybe it is useless to you, but the authors publish in well respected journals. and there are others. for example this paper is published in IOP.iopscience.iop.org/0143-0807/17/1/004 and this generalization adsabs.harvard.edu/abs/2011PhLA..375.1436A and this one cdsweb.cern.ch/record/1272071
Nov
16
comment How does relativity lead to multi particles in Dirac and QFT, exactly
Thanks.I alluded to the first paragraph in my OP. But I am not sure about the last sentence, can you please elaborate.
Nov
15
awarded  Commentator
Nov
15
comment What is the relativistic particle in a box?
thanks for going through the papers. What you are saying is of course textbook stuff. But my question( I reformulate) is why are they going about it i.e. how useful is it. and what is wrong with what is been proposed. Something along these lines.
Nov
15
comment How does relativity lead to multi particles in Dirac and QFT, exactly
Thanks Arnold, I am familiar with the standard answer, But I was really asking, what IS IT about relativity that produces the multi particle picture. I will come back to your analysis a bit later.
Nov
15
asked How does relativity lead to multi particles in Dirac and QFT, exactly
Nov
15
comment What is the relativistic particle in a box?
@DavidZaslavsky, Well, as you can see. Adler claims that there is no solution, Alhaidari finds a particular solution and Vidal Alonso finds a solution where mass is proportional to the width of the box, and there are others. So it is not clear to me what is going on. I usually try to ask questions related to fundamental issues that seem to be either glossed over or not well explained in the textbooks and literature.
Nov
15
comment What is the relativistic particle in a box?
@Prathyush , you right, but there are quite few physicists like I have listed that think otherwise. They seem to say That there is a solution as long as you don't go below certain distance or potential, not sure really.
Nov
15
comment Is it possible to recover the old Bohr-Sommerfeld model from the QM description of the atom by turning off some parameters?
Thanks, your answer is clearer now. But my problem is that you and lubos seems to say that the energy (=e^4m/h^2) is coincidental but not surprising. My view is that it looks coincidental but very surprising. It is not like we had a classical problem(it never was) and then we found an Ehrenfest's theorem to make the correspondence. It is ok though I can ponder it better now. Thank you all.