Imagination of spatial interface 3

Third Level: Quantum Parallel World

The parallel worlds predicted by the first and second layers of the multiple universe are so far apart that they are beyond the reach of astronomers. But the next multiple universe is around you and me. It comes directly from the famous and controversial interpretation of quantum mechanics - any random quantum process causes the universe to split into multiple, each possibility.

Quantum parallel universe. When you play the dice, it will randomly get a specific result. However, quantum mechanics pointed out that at that moment

You actually thrown out each state, and the dice stop at different points in different universes. In one universe, you throwing 1 and the other universe you throwing 2... However, we can only see a small part of the whole reality - one of the universes.

In the early 20th century, the theory of quantum mechanics successfully set off a physical revolution in explaining phenomena at the atomic level. In the field of atoms, the movement of matter no longer obeys the classic laws of Newtonian mechanics. Quantum theory explains their remarkable success while triggering an explosive and fierce debate. What exactly does it mean? Quantum theory points out that the universe is not the position and velocity of all particles that determine the state of the universe as described by classical theories, but a mathematical object called a wave function. According to Schrödinger's equation, the state evolves over time in a way that mathematicians call unity, which means that the wave function evolves in an infinite dimension space called Hilbert space. Although quantum mechanics is described as random and uncertain most of the time, the evolution of the wave function itself is completely certain and there is no randomness.

The key question is how to associate the wave function with what we observe. Many reasonable wave functions lead to a seemingly absurd and illogical state, such as the cat that is both dead and alive under the so-called quantum superposition. In order to explain this strange situation, in the 1920s, physicists made a hypothesis that when someone tried to observe, the wave function immediately "collapsed" into a certain state in classical theory. This additional hypothesis can solve the problem of observational discovery, but it makes the original elegant, harmonious and unified theory pieced together and loses unity. The nature of randomness is usually attributed to quantum mechanics itself as the result of these unpleasant assumptions.

Many years later, physicists gradually abandoned this hypothesis and began to accept a view put forward by Hugh Everett, a graduate of Princeton University, in 1957. He pointed out that the hypothesis of "wave function collapse" is completely redundant. Pure quantum theory does not actually produce any contradictions. It indicates that a real state will gradually split into many overlapping real states, and the observer's subjective experience in the split process is only to experience a slight random event that is exactly equivalent to the previous "wave function collapse hypothesis result". This overlapping traditional world is the third layer of multiple universes.

For more than 40 years, the physical world has been hesitant about whether to accept Everett's parallel world. But if we treat it from different points of view, it will be easier to understand. Physmaticians who study its mathematical equations stand at the external point of view, like a bird flying in the air looking at the ground, while observers living in the world described by the equation stand at the internal point of view, like a frog overlooking by a bird.

In the bird's view, the whole third layer of multiple universe is very simple. Only a smooth evolution and definite wave function can be used to describe it without causing any division or parallelism. The abstract quantum world described by this evolved wave function contains a large number of parallel classic worlds. They are constantly splitting and merging, like a bunch of quantum phenomena that cannot be described by classical theories. In the eyes of the frog, the observer perceives only a small part of the whole truth. They can observe the first layer of the universe they are in, but it imitates the collapse effect of wave functions while retaining unity, which is called "de-congherence" that prevents them from observing other universes parallel to it.

Whenever an observer is asked a question, makes a decision or answers a question, the quantum effects in his brain lead to compound results, such as "continue reading this article" and "giving up reading this article". In the bird's view, the act of "making a decision" led to splitting the person into two, one continuing to read the article and the other doing something else. In the frog's view, the two splits of the person did not realize each other's existence, and their perception of the split just now only experienced a slight random event. They only know what "they" have made, but they don't know that "he" has made different decisions at the same time.

Although it sounds strange, this kind of thing also happened in the first layer of the multiverse mentioned earlier. Obviously, you have just made the decision to continue reading this article, but another in another galaxy far away, you put down the magazine after reading the first paragraph. The only difference between the first universe and the third universe is where the "other you" are. In the first universe, he is located far away from you - usually "far" in the concept of dimensional space. In the third layer of the universe, your split lives in another quantum branch, separated by an infinite dimension of Hilbert space.

The existence of the third layer of multiple universes is based on a crucial assumption: the unity of wave functions evolving over time. Fortunately, the experiments so far have never deviated from the unified hypothesis. In the past few decades, we have confirmed the existence of unity in various larger systems: including carbon-60 cloth balls and optical fibers up to several kilometers. On the contrary of the theory, unity is also supported by the discovery of "de-relevant" effect. [ see"100YearsofQuantumMysteries,"byMaxTegmarkandJohnArchibaldWheeler;ScientificAmerican,February2001】 Only some theoretical physicists in quantum gravity question unity. One of the views is that black holes in evaporation may destroy unity and should be a non-uniform process. However, a recent study on string theory called "AdS/CFT consistency" suggests that the field of quantum gravity is also unified, and black holes do not erase information, but transmit them elsewhere.

If physics is unified, the standard picture of how quantum fluctuations worked in the early days of the Big Bang will have to be rewritten. They do not randomly produce an initial condition, but all the possible initial conditions that overlap together and exist at the same time. Then, the "decoherence" effect ensures that they evolve in their respective quantum branches like traditional theories. This is the key point: the distribution results of the evolution of different quantum branches (i.e. the third layer of multiple universes) in a Hubble volume are no different from the distribution results of the evolution of the same quantum branch (i.e. the first layer of multiple universe) in different Hubble volumes. This property of quantum fluctuations is called "erervelation" in statistical mechanics.

The same principle can also be applied to the second layer of multiple universes. The process of destroying symmetry does not only produce a unique result, but a superposition of all possible results. These results will then develop in their own direction. Therefore, if the physical constants and space-time dimensions are different in the quantum branches of the third layer of the multiple universe, those parallel universes in the second layer will also be different.

In other words, the third layer of multiple universes does not add anything new to the first and second layers, but they are more difficult to distinguish replicas - the same old story is repeated over and again in parallel universes of different quantum branches. The once fierce suspicion of Everett's theory disappeared after everyone found that it was the same substance as other less controversial theories.

There is no doubt that this connection is quite deep, and the research of physicists is only in its infancy. For example, examine the long-standing question: Will the number of the universe soar exponentially over time? The answer is surprisingly no. In the eyes of birds, the whole world is described by a single wave function; in the eyes of frogs, the number of the universe will not exceed the total number of all distinguishable states at a specific moment - that is, the total number of Hubble volumes containing different states. Such as the planet moving to a new position, marrying someone or something else, these are new states. Below the open temperature of 10^8, the total number of these quantum states is about 10^(10^118), that is, at most so many parallel universes. This is a huge amount, but it is very limited.

From the perspective of the frog, the evolution of the wave function is equivalent to jumping from one of these 10^(10^118) universes to another. Now you are in the universe A - at this moment you are reading this sentence in the universe. Now you jump to the universe B - you are reading another sentence in the universe. Universe B has an observer who is the same as Universe A, with only a few more seconds of additional memory. All possible states exist in every moment. Therefore, "time lapse" is probably the transition process between these states - the idea originally put forward in Greg Egan's science fiction novel [PermutationCity] in 1994, and then by Oxford University physicist David Deutsch and Freedom Physicist Julian Barbour and others have developed.