What's new inPhysics in ManySheeted SpaceTimeNote: Newest contributions are at the top! 
Year 2015 
Quantum fluctuations in geometry as a new kind of noise?Bee told in rather critical tone about an article titled "Search for SpaceTime Correlations from the Planck Scale with the Fermilab Holometer" reporting Fermilab experiment. The claim of Craig Hogan, who leads the experimental group, is that that the experiment is able to demonstrate the absence of quantum gravity effects. The claim is based on a dimensional estimate for transversal fluctuations of distances between mirrors reflecting light. The fluctuations of the distances between mirrors would be visible as a variation of interference pattern and the correlations of fluctuations between distant mirrors could be interpreted as correlations forced by gravitational holography. No correlations were detected and the brave conclusion was that predicted quantum gravitational effects are absent. Although no quantitative theory for the effect exists, the effect is expected to be extremely small and nondetectable. Hogan has however different opinion based on his view about gravitational holography not shared by workers in the field (such as Lenny Susskind). Argument seems to go like follows (I am not a specialist so that there might be inaccuracies). One has volume size R and the area of of its surface gives bound on entanglement entropy implying that fluctuations must be correlated. A very naive dimensional order of magnitude estimate would suggest that the transversal fluctuation of distance between mirrors (due to the fluctuations of spacetime metric) would be given by ⟨ Δ x^{2} ⟩ ∼ (R/l_{P}) ×l_{P}^{2}. For macroscopic R this could be measurable number. This estimate is of course ad hoc, involves very special view about holography, and also Planck length scale mysticism is involved. There is no theory behind it as Bee correctly emphasizes. Therefore the correct conclusion of the experiments would have been that the formula used is very probably wrong. Why I saw the trouble of writing about this was that I want to try to understand what is involved and maybe make some progress in understanding TGD based holography to the GRT inspired holography.
The difference between TGD based and GRT inspired holographies is forced by the new view about spacetime allowing also Euclidian spacetime regions and from new new view about General Coordinate Invariance implying SH. This brings in a natural identification of the 2surfaces serving as holograms. In GRT framework these surfaces are identified in ad hoc manner as outer surfaces of arbtrarily chosen 3volume. For details see the article Quantum fluctuations in geometry as a new kind of noise? or the chapter More about TGD inspired cosmology.

About congruence subgroupsStephen Crowley made a very interesting observation about Gaussian Mersennes in the comment section of the posting Pion of M_{G,79} hadron physics at LHC?. I glue the comment below. Matti, why Low Gaussian primes? Your list of primes is a subset of the factors of the dimension of the friendly giant group. The monster group was investigated in the 1970s by mathematicians JeanPierre Serre, Andrew Ogg and John G. Thompson; they studied the quotient of the hyperbolic plane by subgroups of SL2(R), particularly, the normalizer Γ_{0}(p)_{+} of Γ_{0}(p) in SL(2,R). They found that the Riemann surface resulting from taking the quotient of the hyperbolic plane by Γ_{0}(p)_{+} has genus zero if and only if p is 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 41, 47, 59 or 71. When Ogg heard about the monster group later on, and noticed that these were precisely the prime factors of the size of Monster, he published a paper offering a bottle of Jack Daniel's whiskey to anyone who could explain this fact (Ogg (1974)). I must first try to clarify to myself some definitions so that I have some idea about what I am talking about.

Does the rate of cosmic expansion oscillate?H. I. Ringermacher and L. R. Mead have written a very nice article with title "Observation of discrete oscillations in a modelindependent plot of cosmological scale factor versus lookback time and scalar field model". In the article Does the rate of cosmic expansion oscillate? I summarize the contents of the article as I understand it. After that I consider TGD inspired model for the findings based on the assumption that dark matter corresponds to phase with gigantic values of effective Planck constant. Appendix contains summary about Gaussian Mersennes which predict correctly both cosmological, astrophysical, biological, nuclear physics, length scales and predict new important length scales in particle physics. For details see the chapter More about TGD inspired cosmology or the article Does the rate of cosmic expansion oscillate?.

Variation of Newston's constant and of length of dayJ. D. Anderson et al have published an article discussing the observations suggesting a periodic variation of the measured value of Newton constant and variation of length of day (LOD) (see also this). This article represents TGD based explanation of the observations in terms of a variation of Earth radius. The variation would be due to the pulsations of Earth coupling via gravitational interaction to a dark matter shell with mass about 1.3× 10^{4}M_{E} introduced to explain Flyby anomaly: the model would predict Δ G/G= 2Δ R/R and Δ LOD/LOD= 2Δ R_{E}/R_{E} with the variations pf G and length of day in opposite phases. The expermental finding Δ R_{E}/R_{E}= M_{D}/M_{E} is natural in this framework but should be deduced from first principles. The gravitational coupling would be in radial scaling degree of freedom and rigid body rotational degrees of freedom. In rotational degrees of freedom the model is in the lowest order approximation mathematically equivalent with Kepler model. The model for the formation of planets around Sun suggests that the dark matter shell has radius equal to that of Moon's orbit. This leads to a prediction for the oscillation period of Earth radius: the prediction is consistent with the observed 5.9 years period. The dark matter shell would correspond to n=1 Bohr orbit in the earlier model for quantum gravitational bound states based on large value of Planck constant. Also n>1 orbits are suggestive and their existence would provide additional support for TGD view about quantum gravitation. For details see the chapter Cosmology and Astrophysics in ManySheeted SpaceTime or the article Variation of Newston's constant and of length of day.

Planck 2013 bounds for cosmic string tensionPlanck 2013 gives bounds on the string tension of cosmic strings too. The bounds depend on the type of string considered: sone can consider NambuGoto strings, cosmic strings of gauge theories, string like objects of field theories, etcâ€¦ The upper bounds for TG are in the range 10^{6}10^{7} . One cannot of course directly compare these bounds to cosmic strings in TGD sense (not gauge theory strings but primordial 4D string like objects). In TGD framework the string tension characterizes the density of Kähler magnetic energy of 4D string like object with 2D string world sheet as Minkowski space projection. Cosmic string tension is inversely proportional to the square of CP_{2} length scale R and to Kähler coupling strength α_{K} for which the most recent estimate is as equal to fine structure constant: α_{K}≈ 1/137. The value of R is fixed by padic mass calculations from the conditions that electron mass comes out correctly. The velocity spectrum of distance stars in galaxy gives the same estimate if the gravitational field created by long cosmic string along which galaxies are located like pearls in string, gives an estimate consistent with this value. The estimate of cosmic string tension is TG= 6.9× 10^{7} and is therefore in the interval 10^{6}10^{7} , where the upper bounds for other string tensions reside. A comparison with string theory is in order. For NambuGoto strings the estimated upper bound for string tension is GT<1.5× 10^{7}  not a good news since the NambuGoto string tension should satisfy GT=1 in the original approach. The same holds true also for superstrings in the original sense of the word. Therefore the situation is not very promising for superstrings. In fact, it turned out very difficult to find anything concrete about the string tension of superstrings. I however found from web a ten year old estimate estimate TG= 1/3000 for superstring tension involving experimental input. Presumably the Planck 2013 results would lower this estimate by few orders of magnitude. For background see the chapter Cosmic Strings. 
Further progress in the understanding of dark matter and energy in TGD framework
At Thinking Allowed Original (thanks for Ulla!) there was an extremely interesting link to a popular article about a possible explanation of dark matter in terms of vacuum polarization associated with gravitation. The model can make sense only if the sign of the gravitational energy of antimatter is opposite to that of matter and whether this is the case is not known. Since the inertial energies of matter and antimatter are positive, one might expect that this is the case also for gravitational energies by Equivalence Principle but one might also consider alternative and also I have done this in TGD framework. The popular article lists four observations related to dark matter that neither cold dark matter (CMD) model nor modified gravitation model (MOND) can explain, and the claim is that the vacuum energy model is able to cope with them. Consider first the TGD based model.
For details see the chapter TGD and Astrophysics or the article Pioneer and Flyby anomalies for almost ten years later. 