Dark Matter and Dark Energy Are the Same Thing

The 'Dark Dimension' theory proposes that dark matter and dark energy are unified through the existence of a single extra dimension, about a micron in size, which causes graviton excitations to manifest as dark matter.

• Dark matter and dark energy are unified through a micron-sized extra dimension in the 'Dark Dimension' theory.

• This theory predicts that dark matter consists of excitations of gravitons, explaining its weak interactions.

• Our de Sitter universe is predicted to be unstable, with an estimated decay timescale of a few trillion years.

The 'Dark Dimension' scenario suggests that dark matter and dark energy are intrinsically linked via an extra spatial dimension approximately a micron in size. This theory, derived from the Swampland principles and distance conjecture, unifies gravity with dark matter, positing that dark matter consists of weakly interacting graviton excitations. This framework also offers a potential explanation for the hierarchical scales observed in physics and suggests that our de Sitter universe is not eternally stable, with an expected decay timescale related to its current age.

The Dark Dimension Theory

• 00:00:05 A new theory, termed the 'Dark Dimension' scenario, proposes that dark matter and dark energy are related and unified. This concept emerges from applying the Swampland principle's distance conjecture, suggesting an underlying 'tower' of light particles. The theory indicates that one of the universe's microscopic dimensions is larger than the others, scaled by dark energy to approximately a micron (one thousandth of a millimeter), with our familiar three plus one dimensional spacetime residing on a hyperplane within this larger dimension.

Observability of Extra Dimension

• 00:01:54 This micron-scale extra dimension could be potentially observable by detecting changes in the gravitational force. If the force of gravity deviates from the inverse square law (1/r²) to an inverse cube law (1/r³) at distances less than a micron, it would indicate the presence of this additional dimension. Experiments currently measure gravity down to 30 microns without observing such a deviation, but further refinement could test this prediction of a relatively large extra dimension, contrasting with the often-assumed extremely compactified dimensions in string theory.

Unification of Dark Matter & Energy

• 00:03:41 The 'tower' of light particles predicted by the theory is identified not as multiple new particles but as excitations of the graviton. While a three plus one dimensional graviton is massless, a four plus one dimensional graviton is not, allowing for oscillations in the extra dimension that manifest as weakly interacting particles. This effectively unifies dark matter with gravitons and dark energy into a single framework, explaining dark matter's weak interactions as a consequence of gravity's inherent weakness.

De Sitter Instability and Universe's Fate

• 00:06:31 Quantum gravity models within the Swampland program suggest that de Sitter space with positive energy, like our universe, cannot be truly stable over long periods. These ideas indicate that the instability timescale is set by the Hubble scale, implying that our universe is expected to decay within approximately two to three trillion years, rather than being everlasting. Recent observations from the Dark Energy Survey (DESI) hinting at a changing, decreasing dark energy support the notion of a dynamical and unstable de Sitter universe.