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#1




Cosmological Problems
There have been recent cosmological experimental disclosures
represented in part by the following: The 7Be(n,p)7Li reaction and the Cosmological Lithium Problem: measurement of the cross section in a wide energy range at n\_TOF (CERN) https://arxiv.org/abs/1806.03050 "The new estimate of the 7Be destruction rate based on the new results yields a decrease of the predicted cosmological Lithium abundance of âˆ¼10%, insufficient to provide a viable solution to the Cosmological Lithium Problem." What is the resolution to the Lithium problem? No WIMPS have been found in reference to the dark matter problem. What are the dark matter alternatives? Collective Effects in Nuclear Collisions: Experimental Overview https://arxiv.org/abs/1810.06978 Viscosity plays an important role in measured LHC RHIC nuclear dynamics Does this viscosity experimental result influence BBN gas phased mechanisms? MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 = 67.4 km/s/Mpc is based on CMB. The reported H0 = 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? The universe increased expanding rate is an expression of dark energy measured by supernovae type II events. What is dark energy? The cosmological constant problem or the vacuum catastrophe indicates a vacuum energy theory differing from experiment by 120 orders of magnitude. What is the vacuum energy? Is there a common theoretical mechanistic thread connecting these experimental dots? Richard D Saam 
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#2




Cosmological Problems
In article ,=20
"Richard D. Saam" writes: There have been recent cosmological experimental disclosures represented in part by the following: =20 The 7Be(n,p)7Li reaction and the Cosmological Lithium Problem:=20 measurement of the cross section in a wide energy range at n\_TOF (CERN) https://arxiv.org/abs/1806.03050 "The new estimate of the 7Be destruction rate based on the new results=20 yields a decrease of the predicted cosmological Lithium abundance of=20 ~10%, insufficient to provide a viable solution to the Cosmological=20 Lithium Problem." What is the resolution to the Lithium problem? I, personally, don't know. Note, however, that the observations are not=20 easy. No WIMPS have been found in reference to the dark matter problem. What are the dark matter alternatives? Primordial black holes are still viable. Also, absence of evidence is=20 not evidence of absence. Even though we knew the sources and how many=20 were produced, it still took a long time before neutrinos were=20 discovered. Since practically nothing is known about WIMPs, there are=20 no robust predictions for cross sections and hence reaction rates. Collective Effects in Nuclear Collisions: Experimental Overview https://arxiv.org/abs/1810.06978 Viscosity plays an important role in measured LHC RHIC nuclear dynamics Does this viscosity experimental result influence BBN gas phased mechanisms? Do you have reason to think so? BBN seems reasonably successful. MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND=20 APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 =3D 67.4 km/s/Mpc is based on CMB. The reported H0 =3D 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? Add the error bars and you have a threesigma difference. Most would=20 consider it irresponsible to base a detection on three sigma, so why=20 base a tension on it. The universe increased expanding rate is an expression of dark energy measured by supernovae type II events. What is dark energy? Observationally, it is indistinguishable from a cosmological constant. =20 Theoretically, there is no reason it is not the cosmological constant. =20 There is no problem. The cosmological constant problem or the vacuum catastrophe indicates a vacuum energy theory differing from experiment by 120 orders of magnitude. What is the vacuum energy? It is clear from quantum field theory what it is. Why the observed=20 cosmological constant is much smaller is not completely clear, but 40=20 years ago Weinberg came up with an anthropic explanation, which noone=20 has refuted. Also, look for the paper by Bianchi and Rovelli. This is=20 probably another nonproblem. Is there a common theoretical mechanistic thread connecting these experimental dots? Probably not. To prove that there is, one would have to construct such=20 a theory. 
#3




Cosmological Problems
On 10/25/18 12:15 PM, Phillip Helbig (undress to reply) wrote:
In article ,=20 "Richard D. Saam" writes: There have been recent cosmological experimental disclosures represented in part by the following: The 7Be(n,p)7Li reaction and the Cosmological Lithium Problem:=20 measurement of the cross section in a wide energy range at n\_TOF (CERN) https://arxiv.org/abs/1806.03050 "The new estimate of the 7Be destruction rate based on the new results yields a decrease of the predicted cosmological Lithium abundance of ~10%, insufficient to provide a viable solution to the Cosmological Lithium Problem." What is the resolution to the Lithium problem? I, personally, don't know. Note, however, that the observations are not easy. something amiss with BBN? No WIMPS have been found in reference to the dark matter problem. What are the dark matter alternatives? Primordial black holes are still viable. but there are arguments against black holes as dark matter https://arxiv.org/abs/1808.05910 Also, absence of evidence is not evidence of absence. Even though we knew the sources and how many were produced, it still took a long time before neutrinos were discovered. Since practically nothing is known about WIMPs, there are no robust predictions for cross sections and hence reaction rates. Collective Effects in Nuclear Collisions: Experimental Overview https://arxiv.org/abs/1810.06978 Viscosity plays an important role in measured LHC RHIC nuclear dynamics Does this viscosity experimental result influence BBN gas phased mechanisms? Do you have reason to think so? BBN seems reasonably successful. Yes, observed BBN expressions are reasonably successful (except for the Lithium problem), but the realm of fluid viscosity is different the gas kinematics. It implies that we are looking at gas phase BBN and there also exists a viscous BBN, something like looking at the steam but knowing the presence of water somewhere. MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 =3D 67.4 km/s/Mpc is based on CMB. The reported H0 =3D 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? Add the error bars and you have a threesigma difference. Most would consider it irresponsible to base a detection on three sigma, so why base a tension on it. The paper reports a 96.5% confidence level for the difference in the HOs 67.4 and 73.24 km/s/Mpc: 'The bestfit distance scale is 1.006 =C2=B1 0.033 , relative to the scale from Riess et al. (2016) with H0 = 73.24 km s1 Mpc1 used to predict the parallaxes photometrically, and is inconsistent with the scale needed to match the Planck 2016 CMB data combined with =CE=9BCDM at the 2.9\sigma confidence level (99.6%). At 96.5% confidence we find that the formal DR2 errors may be underestimated as indicated.' The universe increased expanding rate is an expression of dark energy measured by supernovae type II events. What is dark energy? Observationally, it is indistinguishable from a cosmological constant. Theoretically, there is no reason it is not the cosmological constant. There is no problem. Here are some Weinberg's thoughts on the problem: http://supernova.lbl.gov/~evlinder/weinberg.pdf 'The problem of the dark energy is also central to today's physics. Our best attempts at a fundamental theory suggest the presence of a cosmological constant that is many (perhaps as many as 120) orders of magnitude greater than the upper bound set by astronomical observations.Until it is solved, the problem of the dark energy will be a roadblock on our path to a comprehensive fundamental physical theory.' The cosmological constant problem or the vacuum catastrophe indicates a vacuum energy theory differing from experiment by 120 orders of magnitude. What is the vacuum energy? It is clear from quantum field theory what it is. Why the observed cosmological constant is much smaller is not completely clear, but years ago Weinberg came up with an anthropic explanation, which noone has refuted. Also, look for the paper by Bianchi and Rovelli. This is probably another nonproblem. ditto Weinberg's thoughts from above Is there a common theoretical mechanistic thread connecting these experimental dots? Probably not. To prove that there is, one would have to construct such a theory. Maybe the mechanism as simple as recognizing an entirely different phase analogous to liquid and gas relationships. Then observational cosmology and associated theories are not eliminated but complemented. 
#4




Cosmological Problems
In article , "Richard D.
Saam" writes: No WIMPS have been found in reference to the dark matter problem. What are the dark matter alternatives? Primordial black holes are still viable. but there are arguments against black holes as dark matter https://arxiv.org/abs/1808.05910 First, note that the title contains "clustered". So it is addressing only the question of clustered primordial black holes. Second, apparently this hasn't been accepted by any journal, perhaps not even submitted, so there might have been no external check. Note also that they write "Throughout this letter we have assumed a monochromatic initial PBH mass distribution." They do cite Carr, Kühnel, and Sandstad. Read that paper. It has almost 300 references. Read them as well. Those folks have done their homework. As luck would have it, just a few days ago I heard a talk on this topic by Florian Kühnel. He pointed out that many constraints are too strong because they are derived based on wrong or flawed assumptions. At https://indico.cern.ch/event/736594/...ew=nicecompact you can download his presentation (first talk after lunch on Tuesday 23 October). [[Mod. note  The presentation in question seems to be in Apple "keynote" format. At least on my computer, Libreoffice (v6.0.2.2.1) was unable to read it.  jt]] Collective Effects in Nuclear Collisions: Experimental Overview https://arxiv.org/abs/1810.06978 Viscosity plays an important role in measured LHC RHIC nuclear dynamics Does this viscosity experimental result influence BBN gas phased mechanisms? Do you have reason to think so? BBN seems reasonably successful. Yes, observed BBN expressions are reasonably successful (except for the Lithium problem), but the realm of fluid viscosity is different the gas kinematics. It implies that we are looking at gas phase BBN and there also exists a viscous BBN, something like looking at the steam but knowing the presence of water somewhere. If you can show that some sort of viscous BBN solves the lithium problem, fine, but merely juxtaposing various words with another might not even indicate a problem, much less a solution. MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 = 67.4 km/s/Mpc is based on CMB. The reported H0 = 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? Add the error bars and you have a threesigma difference. Most would consider it irresponsible to base a detection on three sigma, so why base a tension on it. The paper reports a 96.5% confidence level for the difference in the HOs 67.4 and 73.24 km/s/Mpc: 'The bestfit distance scale is 1.006 ± 0.033 , relative to the scale from Riess et al. (2016) with H0 = 73.24 km/s/Mpc used to predict the parallaxes photometrically, and is inconsistent with the scale needed to match the Planck 2016 CMB data combined with LambdaCDM at the 2.9\sigma confidence level (99.6%). At 96.5% confidence we find that the formal DR2 errors may be underestimated as indicated.' So only 2.9 sigma. Again, a claimed detection at 2.9 sigma would be deemed overconfident, so the same rules should apply for a claimed tension. In both cases, there might be something interesting, but one is far from being able to claim that something is seriously wrong. Note that not long ago there were claims that the Hubble constant was as low as 30 or as high as 100, with about 20% errors. Did any "new physics" come of that? No. Probably something similar will happen here. The universe increased expanding rate is an expression of dark energy measured by supernovae type II events. What is dark energy? Observationally, it is indistinguishable from a cosmological constant. Theoretically, there is no reason it is not the cosmological constant. There is no problem. Here are some Weinberg's thoughts on the problem: http://supernova.lbl.gov/~evlinder/weinberg.pdf 'The problem of the dark energy is also central to today's physics. Our best attempts at a fundamental theory suggest the presence of a cosmological constant that is many (perhaps as many as 120) orders of magnitude greater than the upper bound set by astronomical observations.Until it is solved, the problem of the dark energy will be a roadblock on our path to a comprehensive fundamental physical theory.' Weinberg presented an anthropic argument for the observed value of the cosmological constant, and many believe that there is no better explanation. It is not a FUNDAMENTAL explanation, but then there might not be one. There is no FUNDAMENTAL explanation for the distance of the Earth from the Sun, but there is an easily understood anthropic effect. The cosmological constant problem or the vacuum catastrophe indicates a vacuum energy theory differing from experiment by 120 orders of magnitude. What is the vacuum energy? It is clear from quantum field theory what it is. Why the observed cosmological constant is much smaller is not completely clear, but years ago Weinberg came up with an anthropic explanation, which noone has refuted. Also, look for the paper by Bianchi and Rovelli. This is probably another nonproblem. ditto Weinberg's thoughts from above The point is that Bianchi and Rovelli explicitly address the concerns of Weinberg but not vice versa. No progress can be made by just quoting someone who supports one's own point of view and ignoring others, especially if the latter explicitly address issues raised by the former. Is there a common theoretical mechanistic thread connecting these experimental dots? Probably not. To prove that there is, one would have to construct such a theory. Maybe the mechanism as simple as recognizing an entirely different phase analogous to liquid and gas relationships. Then observational cosmology and associated theories are not eliminated but complemented. Without some quantitative results, this is just a collection of buzzwords. If you think that this idea can somehow solve some problems, then present some quantitative results. 
#5




Cosmological Problems
In article ,
"Richard D. Saam" writes: What is the resolution to the Lithium problem? Subsequent to the Big Bang, lithium is created by cosmic rays and destroyed by stars. Are the yields known well enough to determine the BB abundance? No WIMPS have been found in reference to the dark matter problem. What are the dark matter alternatives? Massive particles that don't interact other than by gravitation (or have extremely low cross sections) come to mind. Theorists are creative, and no doubt there are a vast number of candidates. Collective Effects in Nuclear Collisions: Experimental Overview https://arxiv.org/abs/1810.06978 Viscosity plays an important role in measured LHC RHIC nuclear dynamics Does this viscosity experimental result influence BBN gas phased mechanisms? Someone else will have to answer that one. Only light nuclei matter, though. MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 = 67.4 km/s/Mpc is based on CMB. The reported H0 = 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? The difference is less than 3 sigma so may not be real. If there is a difference, timevariable dark energy would be one possibility. The Adam Riess colloquium I posted about earlier https://www.youtube.com/watch?v=eSPCyIJaPg is still relevant and easy to follow. The universe increased expanding rate is an expression of dark energy measured by supernovae type II events. I think you mean Type Ia SNe, but there are numerous other measurements that agree. What is dark energy? Nobody knows, but a cosmological constant is consistent with all data so far. The cosmological constant problem or the vacuum catastrophe indicates a vacuum energy theory differing from experiment by 120 orders of magnitude. So much for theory!  Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 6174957123 Cambridge, MA 02138 USA 
#6




Cosmological Problems
On 11/9/18 1:37 AM, Steve Willner wrote:
MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 = 67.4 km/s/Mpc is based on CMB. The reported H0 = 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? The difference is less than 3 sigma so may not be real. If there is a difference, timevariable dark energy would be one possibility. The Adam Riess colloquium I posted about earlier https://www.youtube.com/watch?v=eSPCyIJaPg is still relevant and easy to follow. Referencing a good summary article on the Ho tension: Measuring cosmic distances with standard sirens Physics Today, Dec 2018 universe expansion using supernovae Ho1 = 73.24 +/1.74 km s^1 Mpc^1 and Planck satellite's CMB fluctuations Ho2 = 67.74 +/.46 km s^1 Mpc^1 The hope is to resolve Ho tension with standard siren determination. There is one currently available measurement GW170817 with the hope of many more. rds 
#7




Cosmological Problems
In article , "Richard D.
Saam" writes: On 11/9/18 1:37 AM, Steve Willner wrote: MILKY WAY CEPHEID STANDARDS FOR MEASURING COSMIC DISTANCES AND APPLICATION TO Gaia DR2: IMPLICATIONS FOR THE HUBBLE CONSTANT https://arxiv.org/abs/1804.10655 The Planck H0 = 67.4 km/s/Mpc is based on CMB. The reported H0 = 73.24 km/s/Mpc is based on photometric parallaxes. What mechanism explains the difference? The difference is less than 3 sigma so may not be real. If there is a difference, timevariable dark energy would be one possibility. The Adam Riess colloquium I posted about earlier https://www.youtube.com/watch?v=eSPCyIJaPg is still relevant and easy to follow. Referencing a good summary article on the Ho tension: Measuring cosmic distances with standard sirens Physics Today, Dec 2018 universe expansion using supernovae Ho1 = 73.24 +/1.74 km s^1 Mpc^1 and Planck satellite's CMB fluctuations Ho2 = 67.74 +/.46 km s^1 Mpc^1 The hope is to resolve Ho tension with standard siren determination. There is one currently available measurement GW170817 with the hope of many more. I guess "standard sirens" mean "blackhole mergers detected by gravitational waves". As the song says, "two men say they're Jesus; one of them must be wrong". A third determination might disagree with both. Even if it agrees with one, that doesn't "resolve the tension". I also doubt whether the standardsiren technique will get the uncertainties down to a comparable level any time soon. My guess is that the errors have been overestimated. IIRC, H_0 is one area where WMAP and Planck don't agree well. So Planck is the odd man out, considering that most techniques favour a higher value (though with larger uncertainties). 
#8




Cosmological Problems
A few comments about just how one goes about measuring (estimating)
the Hubble constant with gravitationalwave "standard sirens"... The key physics underlying these measurements is that gravitationalwave (GW) observations of the final stages of the orbital decay and coalescence of a compactobject binary system allow it to be treated as a GW "standard siren". [In this context "compact" means compact enough so that we can ignore tidal effects, in practice this means the individual objects are black holes (BHs) or neutron stars (NSs).] [By analogy to the classic phrase "standard candle", such GW sources are called "standard sirens" (the precoalescence GW signal is roughly a sine wave which sweeps up in frequency an amplitude as the system gets closer to coalescence).] That is, assuming that general relativity can accurately model the system, from the GW observations alone we can calculate the distance  more precisely, the luminosity distance  to the source in meters. Unfortunately, the current GW observations don't give a very accurate sky position  the error ellipsoids have areas of tens of square degrees. This should decrease to a few square degrees when additional detectors come online 510 years from now. But that's still a substantial sky area, containing many many galaxies. In a classic 1986 paper (Nature 323, 310), Bernard Schutz worked out that there are two subcases for estimating the Hubble constant: The first subcase occurs if the coalescence produces a strong electromagnetic (EM) signal, which we use to accurately localize its sky position. In practice this (strong EM signal) is true for binary NS coalescences (which seem to produce a short gamma ray burst, with strong flux everywhere in the EM spectrum from radio to gamma rays). Given an accurate sky localization, then we can then use standard optical/infrared astronomy techniques to measure the redshift of the galaxy at that position. (We assume, as seems very likely, that the compact binary is in or nearby a galaxy.) Combining the measured redshift with the GW luminosity distance then gives an estimate of the Hubble constant. I don't recall the exact numbers, but I think a few dozen binaryNS coalescences observed with the current generation of GW detectors should yield an estimate of the Hubble constant good to a few km/sec/Mpc (i.e., good enough to be useful in discriminating between the supernovae and CMB estimates). The second subcase is if the coalescence does NOT produce a detectable EM signal. In practice this second subcase occurs for binaryBH coalescences. (We don't yet know whether BH/NS coalescences will produce a detectable EM signal  theoretical models suggest that it will, but there are a lot of uncertainties.) Schutz described a statistical procedure for estimating the Hubble constant from this type of observations (GW "standard siren" but no EM signal & no accurate sky localization), but this would require a larger number of observations, say on the order of 100 to a few hundered. The actual event rates for BH/BH, NS/NS, and BH/NS coalescences are rather uncertain. To date 7, 1, and 0 of these (respectively) have been observed (https://arxiv.org/abs/1811.12907), and with continued GWdetector tweaks and improvements) it seems likely that the detection rates will increase by a factor of 310 over the next decade.   "Jonathan Thornburg [remove animal to reply]" Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA "There was of course no way of knowing whether you were being watched at any given moment. How often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was even conceivable that they watched everybody all the time."  George Orwell, "1984" 
#9




Cosmological Problems
On 12/15/18 12:59 PM, Jonathan Thornburg [remove animal to reply] wrote:
The actual event rates for BH/BH, NS/NS, and BH/NS coalescences are rather uncertain. To date 7, 1, and 0 of these (respectively) have been observed (https://arxiv.org/abs/1811.12907), and with continued GWdetector tweaks and improvements) it seems likely that the detection rates will increase by a factor of 310 over the next decade. Looking beyond the decade And again referencing the Physics Today Dec 2018 article: The ESA Interferometer Space Antenna(LISA) to be launched in 2034 will operate in the milliHz range (1010,000 Hz range of ground based gw detectors) involving coalescence of black holes of 10^4  10^7 solar masses for distances corresponding to redshifts as large as 20 with accuracy to determine the source position accurately enough to pin down the galaxy cluster or even the galaxy hosting the event. Corresponding narrower Ho resolution is expected. Are there any anticipated Planck spacecraft replacements to verify its CMB based: Ho2 = 67.74 ±.46 km s^1 Mpc^1? The Webb infrared spacecraft will not apparently do it. Richard D Saam [Moderator's note: The James Webb Space Telescope is more like a traditional telescope in space, the successor to HST in some sense, but with more emphasis on the infrared. The CMB is observed at lower frequencies, with bolometers (which are also used in the far (lowerfrequency) infrared) and traditional radio receivers. As far as I know there is no CMB satellite in the works, but some groundbased stuff such as the Simons Observatory. P.H.] 
#10




Cosmological Problems
[Moderator's note: The James Webb Space Telescope is more like a
traditional telescope in space, the successor to HST in some sense, but with more emphasis on the infrared. JWST wavelength range is roughly 0.6 to 27 microns The CMB is observed at lower frequencies much longer wavelengths than JWST. As far as I know there is no CMB satellite in the works, same here but some groundbased stuff such as the Simons Observatory. P.H.] I think there's quite a lot of groundbased work. Most familiar to me is South Pole Telescope: https://pole.uchicago.edu/ There's also BLAST, a balloon telescope: https://sites.northwestern.edu/blast/ They've done CMB work in the past, but the upcoming flight seems to be Galactic objects. All groundbased and balloon telescopes study relatively high multipoles, i.e., relatively small angular scales. I think it's only the lower multipoles that carry information on H, but I may be wrong.  Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 6174957123 Cambridge, MA 02138 USA 

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