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Dark energy remains among the biggest puzzles in our understanding of the cosmos. In the Standard Model of cosmology, called Lambda-CDM, it is accounted for by adding a cosmological constant term to the Einstein field equation, first introduced by Einstein himself. This constant is very small and positive, and a complete theoretical understanding of why it has such a small value is lacking. Also, dark energy has some specific characteristics, like negative pressure and not diluting with cosmic expansion, which makes at least some of us uncomfortable.

Therefore, physicists continue to search for alternative explanations for cosmic acceleration. Earlier in an article titled “On the Accelerated Expansion of the Universe” published in the journal Gravity and CosmologyI explained that if the universe exists in a pair with an anti-universe moving backwards in time, we can explain this cosmic acceleration without dark energy.

In my new work, which is the model of the harrowing world, that is. our universe, which is 3-brane, immersed in some higher dimensional mass, I could remove the elusive dark energy that I am developing now.

My new pattern and results

In this model, I start with a chosen-world scenario where our universe is itself part of some higher-dimensional mass. Think of it as a 2D sheet floating in 3D space. These lower-dimensional structures are called branes, and each brane has some constant brane tension—T—that plays a role in its dynamics. I used an alternating stress brane model and also simultaneously raised the 4D Newtonian constant G to a scalar field, keeping the 5D Newtonian constant coming from the volume to be fixed.

For convenience, some modified theories of gravity, such as Brans-Dicke theory, also promote Newton’s constant G in a scalar field. This resulted in dynamics that mimic the standard Friedman equation, but now the scalar field G effectively plays the role of matter fields in our universe, while matter effectively plays the role of dark energy. It is effective in the sense that I am now considering the combined effect also coming from the variable tension of the harrow.

Therefore, without using any cosmological constant term, I was able to explain dark energy in terms of only two known fields: a scalar field G, which is Newton’s 4D constant but now raised to a scalar field, and a matter field. We considered the radiation to be negligible, which is a good approximation to our universe. The results are published in the journal Europhysics Letters.

Having worked on the dark matter and dark energy problems, I can say that either we accept that general relativity is correct and we live in a dark universe with these elusive and peculiar particles of dark matter and dark energy, or we accept that we live in a higher dimensional multiverse.

As for modified gravity theories, I don’t like that nature would choose a law that continues to vary with distance (as is often claimed by proponents of modified gravity theories like MOND) or else that would undermine the definition of the law itself . My intuition and experience suggest that nature favors beauty, simplicity, and symmetry, and modified theories of gravity simply do not meet these criteria.

On the scientific side, it remains with observations to determine the truth, which we hope to know someday, given the scientific progress we have made so far.

This story is part of the Science X Dialog, where researchers can report findings from their published scientific papers. Visit this page for information about the ScienceX Dialog and how to participate.

Kumar is a PhD student at IIT Gandhinagar, India, under the supervision of Dr. Arpan Bhattacharyya. Kumar’s research areas include general relativity, cosmology, braneworld theory, and spacetime thermodynamics.