Dark energy weakens

Quanta Magazine post (see this) tells about the evidence, found by DESI collaboration, that dark energy is getting weaker. These findings challenge the very notion of dark energy, which is also theoretically problematic. There is the problem whether the dark energy corresponds to a modification of the gravitational part of the action obtained by replacing the curvature scalar by adding a volume term or a modification of the matter part of the action corresponding to exotic particles, quintessence, with a negative pressure.

In Big Think (see this) there is article discussing in detail the claim about the claimed weakening of dark energy (see this). The article describes in detail their constraints on the $\Lambda$CDM model. It becomes clear that standard cosmology is a good parametrization of huge amounts of data but has a lot of problems and that the notion of dark energy is far from being elegant. The basic empirical inputs are as follows.

1. Cosmic microwave background (CMB) provides information about the basic parameters of the standard cosmology such as its age, the value of Hubble constant characterizing the expansion rate, and density matter. This information allows us to identify several anomalies. For instance, the Hubble constant seems to have two slightly different values. It would seem that Hubble constant depends on length scale but the notion of scale is lacking from the standard cosmology.
2. The finding that the radiation from supernovae of type I is weaker than expected led to the conclusion that cosmic expansion is accelerating. Cosmological constant characterizing dark energy density would at least parametrix the acceleration expansion in the general relativistic framework.
3. Baryonic acoustic oscillations (BAO) provide information about the large scale structure of the Universe and BAO led in the recent study to the conclusion that dark energy is weakening. BAO has also led to the conclusion that the density of baryonic matter is decreasing: as if baryons were disappearing. Are these two phenomena different aspects of the same phenomenon?

In TGD, the new view of space-times as 4-D surfaces in H=M⁴×CP₂, predicts the analogy of cosmological constant as well as its weakening.

1. String tension characterizes the energy density of a magnetic monopole flux tube, a 3-D surface in H=M⁴×CP₂. String tension contains a volume part (direct analog of Λ) and Kähler magnetic part and it is a matter of taste whether one identifies the entire string tension or only the volume contribution as counterpart of Λ. In the primordial cosmology (see this), cosmic string sheets have 2-D M⁴ projection and 2-D CP₂ projection.
2. Cosmic strings are unstable against the thickening of their 2-D M⁴ projection, which means that the energy density is gradually reduced in a sequence of phase transitions as thickenings of the cosmic string so that they become monopole flux tubes and give rise to galaxies and stars. The energy of cosmic strings is transformed to ordinary particles. This process is the TGD analog of inflation. No inflaton fields are required.
3. The string tension is gradually reduced in these phase transitions and in this sense one could say that dark energy is weakened. For instance, for hadronic strings it is rather small as compared to the original value of string tension during the primordial phase dominated by cosmic strings, at the molecular level the string tension of cosmic strings is really small.
4. The primordial string dominated phase was followed by a transition to the radiation dominated cosmology and emergence of Einsteinian space-time with 4-D M⁴ projection so that general relativity and quantum field theory became good approximations explaining a lot of physics. Quantum field theory approximation cannot however explain the structures appearing in all scales and here monopole flux tubes are necessary.
5. TGD also predicts a hierarchy of effective Planck constants labelling phases of the ordinary matter behaving like dark matter in many respects. These phases would be quantum coherent in arbitrarily long scales. They would reside at the magnetic bodies consisting of monopole flux tubes and define a number theoretic complexity hierarchy highly relevant in quantum biology. The transformation of ordinary matter to this kind of dark matter would explain the observed apparent disappearance of baryons during cosmic evolution. In primordial cosmology cosmic strings as 4-D objects with 2-D M⁴ projection would dominate: during this period one cannot speak of Einsteinian space-time as space-time surfaces with 4-D M⁴ projection.

One can try to translate these analogies to a more detailed quantitative view of dark energy and dark matter.

1. The energy of cosmic string contains two contributions: volume contribution and Kähler magnetic contribution. Their sum defines the galactic dark matter (see this), whose portion is about 26 percent of cosmic energy density, and it is concentrated at cosmic strings. Ordinary matter, about 5 percent of energy density emerges in the thickening of these cosmic strings as they form local tangles. The liberated energy transforms to ordinary matter. This is the TGD counterpart of inflation and cosmic strings carry the counterpart of matter assigned with the vacuum expectations of inflation fields.
2. What about the dark energy forming 85 percent of cosmic energy density? Does dark energy correspond to the energy associated with Minkowski space-time sheets as the energy associated with the volume action with Käher magnetic part being negligible. Could the volume contribution dominate or are the contributions of the same size scale? The cosmological constant would have a spectrum being inversely proportional to the p-adic length scale characterizing these space-time sheets. The value of the cosmological constant would not depend on time but on the scale of the space-time sheet and would decrease as a function of the scale. This might explain the latest findings if they are true.
3. One can ask whether only magnetic flux tubes and sheets are present at the fundamental level and whether cosmological constant corresponds to the energy assignable to large enough monopole flux tubes. Already flux tubes of the thickness of neuron size correspond to the extremely small value of cosmological constant deduced from cosmology. Also hadronic string tension corresponds to a particular value of cosmological constant.

See for instance the article About the recent TGD based view concerning cosmology and astrophysics or the chapter with the same title.

For a summary of earlier postings see Latest progress in TGD.

For the lists of articles (most of them published in journals founded by Huping Hu) and books about TGD see this.