Solutions in a Toy Universe
How physicists mathematically verified ER = EPR, the question that still lingers for the universe in which we live, and how the ramifications of ER = EPR could altar our ultimate fate.
Previously, we discussed how ER = EPR roughly translates into “wormholes equal quantum entanglement.” According to this conjecture, wormholes connect entangled particles and are, themselves, the threads that make up spacetime. The Holographic Principle has been mathematically verified in a toy universe and allows physicists to work out the math that proves ER = EPR would be real in that toy universe, if the toy universe were real. How that translates into reality isn’t quite yet known.
That toy universe is called an anti de Sitter Space (AdS).
A de Sitter space (dS), has a constant positive curvature and is expanding due to a positive cosmological constant (dark energy) that overpowers everything else. An anti de Sitter space is negatively curved and enclosed by a definite boundary. Our universe is currently neither, being a complex mingling of matter, dark matter, and dark energy within an observationally flat space, but as the universe continues to expand, it’s expected to settle into a de Sitter space. That expectation is based on the standard model, but evolving dark energy could cause the universe to stop expanding at some point and collapse.
Physicists model ER = EPR in a toy universe because of its boundary and something called AdS/CFT correspondence, which shows that a quantum theory on an anti-de-Sitter boundary is completely equivalent to a gravitational theory inside the bulk. (The Holographic Principle.) The math supporting this concept has been demonstrated, but translating that verification from a toy universe into our reality is a problem. One possibility, although one which I loathe, uses time as the boundary. The information would be captured at the beginning and end of time with the Block Universe in between being the holographic projection. A possibility that I do appreciate uses the gravitational horizon of gravitationally bound objects as local boundaries in place of a universal one.
Just as AdS/CFT applies the Holographic Principle to an AdS universe, a gravitationally bound theory would apply this to a black hole and perhaps to other objects like galaxies by using local gravitational horizons. Either way, the principle maps higher dimensional problems we cannot solve into a lower dimension we can solve.
In an ER = EPR universe, because Hawking radiation is entangled with particles at the event horizon, black holes become cosmic spindles upon which the threads of spacetime are woven. Some of these threads have stretched across billions of light years since first being emitted from their black holes, but cosmic expansion has kept them from ever escaping their localized pocket of the universe.
If the universe were static, radiation that escaped a black hole 13.8 billion years ago would be 13.8 billion light years away from where it began. Because the universe is expanding, and is taking that radiation along with it, that same radiation has actually traveled 46 billion light years. Even so, as the radiation travels, it eventually reaches a point where the universe ahead of it is traveling faster than the speed of light, removing any destination ahead forever from its reach.
As a point of reminder, nothing can travel through the universe faster than the speed of light, but the expansion of the universe itself is not held to that speed limit.
However, most of the black holes in our universe are not yet emitting more radiation than they absorb. A typical stellar-mass black hole is colder than the space around it, and the larger a black hole grows, the colder it becomes. Before a black hole starts emitting more radiation than it absorbs, it has to be warmer than the space around it.
Tiny, primordial black holes have been theorized, and they would have been incredibly hot, spinning out massively greater amounts of radiation than they took in. Currently, though, the vast majority of black holes are waiting for their moment, and when they finally produce excess threads of their own, they may be weaving a dead universe.
I mentioned earlier that in an ER = EPR universe, the evolving dark energy could result in the expansion reversing into a contraction. When I coupled this with black holes now sending out Hawking radiation and their resulting wormholes, an idea dawned on me. That idea was wrong.
My mistake was believing the entangled Hawking radiation might reverse the universe again and turn the contraction into another expansion. I assumed entangled particles and their wormholes were the sole component of empty space and thus equivalent to dark energy. Hawking radiation is regular energy and acts as such. However, the end result I anticipated is still possible.
If the universe were to contract, the role of black holes would change. As matter, dark matter, and black holes pack tightly together, their internal energies would couple with the shrinking spacetime fabric. If this is an ER = EPR universe, the dense network of entangled wormholes would act like a spring and, together with the extreme gravitational pressures, trigger a rebound effect and a new expansion.
In such an event, all matter would undergo a phase transition. There’s no surviving the universal comeback. However, because this is a rebound in an ER = EPR universe, quantum information is not crushed and destroyed in a singularity. The information would be scrambled but not deleted.
Something of the old universe survives in the new.
— Thaddeus Thomas
P.S. All corrections welcome.
The ER = EPR conjecture was proposed by physicists Juan Maldacena and Leonard Susskind. The Holographic Principle was proposed by Gerard ‘t Hooft and later given its string-theory interpretation by Leonard Susskind. The AdS/CFT correspondence (the toy universe mathematical application of the conjecture) was discovered by Juan Maldacena. Anti-de Sitter (AdS) space was named after physicist Willem de Sitter, and finally, the Block Universe theory was popularized by Hermann Minkowski.