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- TL;DR Summary
- Questions after DESI 3 year data strengthens evidence in favour of an evolving dark energy parameter?
So DESI 3 year study results were revealed and when combined with other data from other sources it revealed a 3-sigma significant results that dark energy evolves with time, more specifically that it has been decreasing in the last 11 billion years or so (https://newscenter.lbl.gov/2025/03/19/new-desi-results-strengthen-hints-that-dark-energy-may-evolve/)
Another collaboration, DES, has released recently another study with lots of data also consistent with an evolving dark energy, indicating as well that it is getting weaker over time (https://www.quantamagazine.org/is-d...r-new-evidence-strengthens-the-case-20250319/)
So it seems that dark energy getting weaker is most likely a real thing and not a statistical fluctuation. I had several questions about these findings:
1. I've looked into some of the results and apparently they measured that dark energy grew stronger for some time just after the Big Bang and then it got weaker for the last 11 billion years. But it is not clear to me whether they measured a constant weakening of dark energy or whether dark energy decreasing rate has getting smaller over time, so that it seems that it would stabilize into a zero value or if it looks like it is going to vanish completely reaching 0. Does anyone know? Also, is it possible that dark energy may get negative (like in AdS)? Or even get stronger again (meaning behaving like a phantom dark energy parameter)?
2. Assuming that dark energy will vanish to zero, how are cosmological inflation and holographic models affected by this? Especially for holographic models, since our universe would not be approximating a dS spacetime, but seemingly a Minkowski one? Does this invalidate holography in theoretical physics?
3. If dark energy was to disappear, would this paper (https://arxiv.org/abs/1002.4278), which relies on applying the holographic principle and entropy to the cosmological horizon created by a cosmological constant, would be falsified?
4. A decreasing dark energy parameter gives support to Swampland models from Cumrun Vafa and others (https://arxiv.org/abs/hep-th/0509212), which had some problems with universes having a cosmological constant. However, even if the Swampland conjecture is correct, and universes with a cosmological constant are inconsistent with quantum gravity, since apparenly dark energy got stronger in the past, would it mean that universes in the "swampland" could actually exist but in a metastable form before reaching a stable state (like one without any cosmological cosntant)?
5. In this article (https://www.quantamagazine.org/wani...e-swampland-of-impossible-universes-20240819/) it is explained at the end that if dark energy decreased it could change the laws of physics, quoting it
"Perhaps dark energy will fall until it settles into a stabler, possibly negative value. With that, a new universe, with new laws, particles and forces, would replace the current one."
However, how can an evolving dark energy parameter change the laws of physics of the universe? What laws could change? Even the most fundamental ones?
I'm aware that most of the answers to these questions are temptative and it's too soon to ask them (and probably they will never be answered), but I would be rather asking what are the most likely possible answers with what we have now. If they are completely useless and meaningless questions please feel free to close the post.
Another collaboration, DES, has released recently another study with lots of data also consistent with an evolving dark energy, indicating as well that it is getting weaker over time (https://www.quantamagazine.org/is-d...r-new-evidence-strengthens-the-case-20250319/)
So it seems that dark energy getting weaker is most likely a real thing and not a statistical fluctuation. I had several questions about these findings:
1. I've looked into some of the results and apparently they measured that dark energy grew stronger for some time just after the Big Bang and then it got weaker for the last 11 billion years. But it is not clear to me whether they measured a constant weakening of dark energy or whether dark energy decreasing rate has getting smaller over time, so that it seems that it would stabilize into a zero value or if it looks like it is going to vanish completely reaching 0. Does anyone know? Also, is it possible that dark energy may get negative (like in AdS)? Or even get stronger again (meaning behaving like a phantom dark energy parameter)?
2. Assuming that dark energy will vanish to zero, how are cosmological inflation and holographic models affected by this? Especially for holographic models, since our universe would not be approximating a dS spacetime, but seemingly a Minkowski one? Does this invalidate holography in theoretical physics?
3. If dark energy was to disappear, would this paper (https://arxiv.org/abs/1002.4278), which relies on applying the holographic principle and entropy to the cosmological horizon created by a cosmological constant, would be falsified?
4. A decreasing dark energy parameter gives support to Swampland models from Cumrun Vafa and others (https://arxiv.org/abs/hep-th/0509212), which had some problems with universes having a cosmological constant. However, even if the Swampland conjecture is correct, and universes with a cosmological constant are inconsistent with quantum gravity, since apparenly dark energy got stronger in the past, would it mean that universes in the "swampland" could actually exist but in a metastable form before reaching a stable state (like one without any cosmological cosntant)?
5. In this article (https://www.quantamagazine.org/wani...e-swampland-of-impossible-universes-20240819/) it is explained at the end that if dark energy decreased it could change the laws of physics, quoting it
"Perhaps dark energy will fall until it settles into a stabler, possibly negative value. With that, a new universe, with new laws, particles and forces, would replace the current one."
However, how can an evolving dark energy parameter change the laws of physics of the universe? What laws could change? Even the most fundamental ones?
I'm aware that most of the answers to these questions are temptative and it's too soon to ask them (and probably they will never be answered), but I would be rather asking what are the most likely possible answers with what we have now. If they are completely useless and meaningless questions please feel free to close the post.
