The detection of gravitational waves (GW) was a remarkable breakthrough for many reasons, one of which is the possibility of testing or disproving different theories describing gravity. Some of these new theories require the existence of extra dimensions in addition to the standard 3D+1 of general relativity (GR). These additional dimensions are mainly required to provide an alternative route in the dark matter and energy hypothesis, since gravity would leak into these additional dimensions, diminishing the amplitude of the observed GW signal. This would produce an error in the inferred distance to the gravitational wave source predicted by GR. If true, it could account for the yet undetectable dark matter and energy at the cost of challenging GR theory, since the existence of dark matter and dark energy depends on the assumption that GR is valid at all scales and distances.
The GW170817 Event: Unveiling the Secrets of Spacetime
The collision of two neutron stars detected last year provided additional insight, due to the electromagnetic waves that accompanied the gravitational signal. The GW170817 event detected in LIGO on Aug. 17, 2017, produced gravitational waves, gamma-rays, X-rays, radio waves, optical and infrared light. This type of event begs the question: do large-wavelength gravitational waves and short frequency photons experience the same number of spacetime dimensions? [1].
For the first time, researchers from the University of Chicago tested modified gravity theories by comparing the differences in the time delays of the propagation of GW and EM waves through spacetime. According to GR, the GW amplitude decreases inversely with luminosity distance. Deviations from this relationship could suggest the existence of compact extra-dimensions. If gravity leaks into these other dimensions along the way, the signal measured would be weaker than expected, while the electromagnetic waves would be unaffected. Comparing the luminosity distance of GW170817 found under GR with the EM-measured distance to its host galaxy, NGC 4993, authors found strong deviations from theories with gravitational leakage. In other words, the researchers involved in this study found no evidence of extra spatial dimensions. GW170817 is fully consistent with GR.
The Holographic Principle and Dimensionality in Physics
It appears for now that the universe has the same familiar dimensions—three in space and one of time—even on scales of a hundred million light-years.
Louise Lerner, Physicist at University of ChicagoUnified Science in Perspective
The issue of spatial dimensionality, understood as the number of the spatial dimensions that we defined in physics, lends itself to much confusion. There are models in physics that require more spatial dimensions than the usual 3D -height, width and length-, for example, in string theory, there would be a total of 11 dimensions, 8 of which would be compact dimensions that would be impossible to perceive at our scale, and only the usual three dimensions would be accessible.
Likewise, in physics it is usual to work with 2D models, for example, when we talk about electromagnetic waves we usually describe them as an oscillation in 2 dimensions. And this habit is so common, that we usually forget that it is only an approximation, it is not real. There is nothing in nature that is truly 2-dimensional because no matter how narrow an object is, it will always have a thickness.
And this is the key to the generalized holographic model; to have defined a unit of volume for space, which is also spherical, with diameter of Planck length. With these units, called Planck spherical units, packing a larger volume, for example, the volume of a proton, it is possible to explain the origin of the proton’s mass.
In order to address and solve assertively the most important problems of physics, such as the origin of the nuclear strong force, the vacuum catastrophe, and so many others, it is essential to get rid of the two-dimensional notion, and describe systems in terms of their volume, and their ability to exchange information with their environment through their surface. Nassim Haramein’s generalized holographic model [2.3], based on the fundamental holographic surface-to-volume ratio φ, solved these fundamental problems from first principle calculations, with no adjusting parameters. And there is no need to resort to extra dimensions.
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Gravitational waves provide dose of reality about extra dimensions
References
[1] Kris Pardo et al Limits on the number of spacetime dimensions from GW170817, JCAP, 07 (2018) 048. DOI 10.1088/1475-7516/2018/07/048
[2] Haramein, N. (2012). Quantum Gravity and the Holographic Mass, Physical Review & Research International, ISSN: 2231-1815, Page 270-292
[3] Haramein, N. (2013). Addendum to “Quantum Gravity and the Holographic Mass” in view of the 2013 Muonic Proton Charge Radius Measurement, Hawaii Institute for Unified Physics.
