Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1105.3796 · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields

Multiverse interpretation of quantum mechanics

Raphael Bousso A, Leonard Susskind

Published Feb 6, 2012• 141 citations
arXivHTMLPDF

Abstract

We argue that the many worlds of quantum mechanics and the many worlds of the multiverse are the same thing, and that the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics. Decoherence---the modern version of wave-function collapse---is subjective in that it depends on the choice of a set of unmonitored degrees of freedom, the environment. In fact decoherence is absent in the complete description of any region larger than the future light cone of a measurement event. However, if one restricts to the causal diamond---the largest region that can be causally probed---then the boundary of the diamond acts as a one-way membrane and thus provides a preferred choice of environment. We argue that the global multiverse is a representation of the many worlds (all possible decoherent causal diamond histories) in a single geometry. We propose that it must be possible in principle to verify quantum-mechanical predictions exactly. This requires not only the existence of exact observables but two additional postulates: a single observer within the Universe can access infinitely many identical experiments; and the outcome of each experiment must be completely definite. In causal diamonds with a finite surface area, holographic entropy bounds imply that no exact observables exist, and both postulates fail: experiments cannot be repeated infinitely many times; and decoherence is not completely irreversible, so outcomes are not definite. We argue that our postulates can be satisfied in hats (supersymmetric multiverse regions with vanishing cosmological constant). We propose a complementarity principle that relates the approximate observables associated with finite causal diamonds to exact observables in the hat.

DOI
10.1103/physrevd.85.045007

Related papers

Multiverse

Andreas Wichert

The modern version of the wave-function collapse in quantum mechanics is based on decoherence and leads to the multiverse interpretation of quantum mechanics. The decoherence causes the universe to develop an emergent branching structure. One can interpret the branching structure either as a tree structure or as parallel different histories. Time is not continuous since there are no measurable continuous in quantum physics. Notion of continuous range of possible values of time is just an idealization. The same goes with the direction of time that is a prior assumption based on the branching structure of the multiverse. The multiverse does not exist in external space nor time since there is nothing more beside it. The observer's mind should be not in a superposition with himself. Because of this, in the Many-minds interpretations it is argued that the distinction between worlds should be made at the level of the individual observer. The human bodies are in a superposition, but the minds have definite states that are never in superposition. All possible lives, personalities that do not violate the laws of physics are facts since they represent a valid history in the multiverse. We are one of this possible personalities. Our choices are defined by our personality explained to us by our mind, our consciousness is the unchangeable part of us. It is nonphysical and it senses the world. It does not interact with the brain in the other way beside it.

Chapman & Hall/CRC eBooks•Aug 12, 2022•0 citations

On Probabilities in the Many Worlds Interpretation of Quantum Mechanics

Florian J. Boge

Quantum Mechanics notoriously faces a measurement problem, the problem that the unitary time evolution, encoded in its dynamical equations, together with the kinematical structure of the theory generally implies the non-existence \nof definite measurement outcomes. There have been multiple suggestions to solve this problem, among them the so called many worlds interpretation that originated with the work of Hugh Everett III. According to it, the quantum state and time evolution fully and accurately describe nature as it is, implying that under certain conditions multiple measurement outcomes that are seemingly mutually exclusive can be realized at the same time – but as different 'worlds' contained in a global, quantum mechanical structure, sometimes referred to as 'the multiverse'. The many worlds interpretation has, however, been confronted with serious difficulties over the course of its development, some of which were solved by the advent of decoherence theory. The present thesis critically investi- \ngates the state of play on a key remaining problem of the many worlds interpretation, the problem of the meaning and quantification of probabilities in a quantum multiverse. Recent attempts of deriving the pivotal statistical ingredient of quantum mechanics, Born’s rule, from either principles of decision theory or from quantum mechanics alone, supplemented with a few general premises about \nprobability are analyzed and their premises are scrutinized. It will be argued that, though both approaches yield promising results, they both ultimately fail \nto clearly establish the validity of Born’s rule in the context of the many worlds interpretation. It is hence suggested that further research on this problem is indicated.

•Apr 4, 2016•2 citations

A discrete, finite multiverse

McKenzie, Alan

The Many Worlds Interpretation (MWI) famously avoids the issue of wave function collapse. Different MWI trees representing the same quantum events can have different topologies, depending upon the observer. However, they are all isomorphic to the group of block universes containing all of the outcomes of all of the events, and so, in that sense, the group of block universes is a more fundamental representation. Different branches of the MWI tree, representing different universes in MWI, ultimately share the same quantum state in a common ancestor branch. This branching topology is incompatible with that of the Minkowski block universe; the resolution is to replace the branches with discrete, parallel block universes, each of which extends from the trunk to the outermost twigs. The number of universes in a branch is proportional to its thickness which, in turn, depends upon the absolute square of the probability amplitude for the state in that branch. Every quantum event may be represented by a kernel of universes, which is the smallest group of universes that will reproduce the quantum probabilities of the outcomes of that event. By considering the ratios of the probabilities of the outcomes of any event, it can be shown that the number of universes in every kernel must finite, as must be the total number of universes in the multiverse. Further, every universe in the multiverse must be finite both in space and time. Another consequence is that quantum probabilities must be rational, which suggests that quantum mechanics is only an approximation to a discrete theory. A corollary is that not every conceivable universe exists in the multiverse, no doubt to the disappointment of those who enjoy alternate-history novels.

arXiv:1609.04050•Sep 10, 2016•1 citation

Schrödinger Cat's Experiment's Interpretation and Parallel Universe or Multiple Universes

Rupak Bhattacharya, Pranab Kumar Bhattacharya, Upasana Bhattacharya +7 more

Quantum mechanics provides us most fundamental descriptions of our most early universe, but there is a long-standing debate amongst theoretical physicists about what all these mathematics really mean in real world? The present three-dimensional (3D) universe, we humans experience daily since our birth, is probably just one of an enormous numbers of essentially classical worlds, and all quantum phenomena arise from a universal force of repulsions that prevented many universes (Multiverse) from having identical physical configurations like ours. Probabilities arise only because of our human ignorance as to which in our world an observer occupies a position in space time. This picture is all that is needed to explain bizarre quantum effects such as particles that can tunnel through solid barriers and wave behavior in double-slit experiments or in a warm hole. Our many-interacting-universes approach hinges on our assumption that interactions between deterministically evolving worlds cause all quantum effects. Each world is simply the position of particles in three-dimensional space time, and each would evolve according to Newton’s laws, if there were no inter world interactions. A surprising feature of human approach was that the formulation contains nothing that corresponds to the mysterious quantum wave functions, except in the formal mathematical limit in which the number of worlds becomes infinitely large. Conversely, Newtonian mechanics corresponds to the opposite limit of just one world. Thus, our approach should incorporate both classical and quantum theory. As few as two interacting worlds can result in quantum like effects, such as tunneling through a barrier. Many interacting worlds theory (MIW) explains that rather than standing apart, an infinite number of universes in the early time shared the same space and time as ours. They show that the theory can explain quantum mechanical effects while leaving open the choice of theory to explain the universe at large scales. This is a fascinating new variant of multiverse theory that, in a sense, creates not just a doppelganger of everyone but an infinite number of them all overlaying each other in the same space and time. The fine tuning of parameters required to reproduce our present day universe suggests that our universe may simply be a region within an eternally inflating super-region. Many other regions beyond our observable universe might have existed in earlier times with each such universe governed by a different set of physical parameters and laws. Collision between these regions, if they occurred, should have left signatures of anisotropy in the cosmic microwave background (CMB) but have not been seen yet. We assess different mechanisms for this residual emission and conclude that although there is a 30% probability that noise fluctuations may cause foregrounds to fall within 3σ of the excess, there is less than a 0.5% probability that foregrounds can explain all the excess. A plausible explanation is that the collision of our universe with an alternate universe, whose baryon to photon ratio is a factor of ∼ 4500 larger than ours, could produce enhanced Hydrogen Paschen-series emission at the epoch of recombination. Future spectral mapping and deeper observations at 100 and 217 GHz are needed to mitigate systematics arising from unknown galactic foregrounds and to confirm this unusual hypothesis. After careful analysis of the spectrum of the CMB, Chary et al. found a signal that was about 4500x brighter than it should have been, based on the number of protons and electrons. Scientists believe that this existed in the very early universe. Indeed, this particular signal, an emission line that arose from the formation of atoms during the era of recombination is more consistent with a universe whose ratio of matter particles to photons is about 65x greater than our own. There is a 30% chance that this mysterious signal is just noise, and not really, a signal at all; however, it is also possible that it is real, and exists as a parallel universe. Keywords : Quantum mechanics, multiverse, Newtonian mechanics Cite this Article Pranab Kumar Bhattacharya, et al . Schrodinger Cat's Experiment's Interpretation and Parallel Universe or Multiple Universes. Research and Reviews: Journal of Space Science and Technology. 2016; 5(1): 35–52p.

•May 16, 2016•0 citations

Quantum Multiverses

James B. Hartle

A quantum theory of the universe consists of a theory of its quantum dynamics and a theory of its quantum state The theory predicts quantum multiverses in the form of decoherent sets of alternative histories describing the evolution of the universe's spacetime geometry and matter content. These consequences follow: (a) The universe generally exhibits different quantum multiverses at different levels and kinds of coarse graining. (b) Quantum multiverses are not a choice or an assumption but are consequences of the theory or not. (c) Quantum multiverses are generic for simple theories (d) Anthropic selection is automatic because observers are physical systems within the universe not somehow outside it. (e) Quantum multiverses can provide different mechanisms for the variation constants in effective theories (like the cosmological constant) enabling anthropic selection. (f) Different levels of coarse grained multiverses provide different routes to calculation as a consequence of decoherence. We support these conclusions by analyzing the quantum multiverses of a variety of quantum cosmological models aimed at the prediction of observable properties of our universe. In particular we show how the example of a multiverse consisting of a vast classical spacetime containing many pocket universes arises automatically as part of a quantum multiverse describing an eternally inflating false vacuum that decays by the quantum nucleation of true vacuum bubbles. In a FAQ we argue that the quantum multiverses of the universe are scientific, real, testable, falsifiable, and similar to those in other areas of science even if they are not directly observable on arbitrarily large scales.

arXiv:1801.08631•WORLD SCIENTIFIC eBooks•Dec 9, 2020•5 citations

Many Discrete Worlds

McKenzie A

We present the case for a fixed, finite number of discrete, non-interacting, spatiotemporally finite, decohered spacetimes emerging from Everett’s Universal Wave Function, which we refer to as “Many Discrete Worlds” (MDW). No universes “split” in MDW. We argue that a Many Worlds Interpretation (MWI) branching structure that emerges after decoherence is equivalent to individual, weighted universes, each of which is divided into an immense number of discrete, identical copies, the number being proportional to the individual weighting. This ensures that repeated experiments within any such universe will demonstrate consistency with the Born rule. Each of these universes should be considered as complete, containing every decohered outcome over the entire extent of its spacetime, including every event/interaction occurring beyond any cosmological particle horizon for the entire duration of the given universe. We show that a countably infinite number of interactions needs an uncountably infinite number of universes, and show why measures such as the Lebesgue measure will fail in that case, with the result that the Born rule would not be demonstrable. This leads to the conclusion that the number of universes in the multiverse must be finite and, as a surprising corollary, that the universes themselves are finite, both in space and duration.

Philosophy International Journal•Jul 10, 2026•0 citations
We argue that the many worlds of quantum mechanics and the many worlds of the multiverse are the same thing, and that the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics. Decoherence---the modern version of wave-function collapse---is subjective in that it depends on the choice of a set of unmonitored degrees of freedom, the environment. In fact decoherence is absent in the complete description of any region larger than the future light cone of a measurement event. However, if one restricts to the causal diamond---the largest region that can be causally probed---then the boundary of the diamond acts as a one-way membrane and thus provides a preferred choice of environment. We argue that the global multiverse is a representation of the many worlds (all possible decoherent causal diamond histories) in a single geometry. We propose that it must be possible in principle to verify quantum-mechanical predictions exactly. This requires not only the existence of exact observables but two additional postulates: a single observer within the Universe can access infinitely many identical experiments; and the outcome of each experiment must be completely definite. In causal diamonds with a finite surface area, holographic entropy bounds imply that no exact observables exist, and both postulates fail: experiments cannot be repeated infinitely many times; and decoherence is not completely irreversible, so outcomes are not definite. We argue that our postulates can be satisfied in hats (supersymmetric multiverse regions with vanishing cosmological constant). We propose a complementarity principle that relates the approximate observables associated with finite causal diamonds to exact observables in the hat.
The modern version of the wave-function collapse in quantum mechanics is based on decoherence and leads to the multiverse interpretation of quantum mechanics. The decoherence causes the universe to develop an emergent branching structure. One can interpret the branching structure either as a tree structure or as parallel different histories. Time is not continuous since there are no measurable continuous in quantum physics. Notion of continuous range of possible values of time is just an idealization. The same goes with the direction of time that is a prior assumption based on the branching structure of the multiverse. The multiverse does not exist in external space nor time since there is nothing more beside it. The observer's mind should be not in a superposition with himself. Because of this, in the Many-minds interpretations it is argued that the distinction between worlds should be made at the level of the individual observer. The human bodies are in a superposition, but the minds have definite states that are never in superposition. All possible lives, personalities that do not violate the laws of physics are facts since they represent a valid history in the multiverse. We are one of this possible personalities. Our choices are defined by our personality explained to us by our mind, our consciousness is the unchangeable part of us. It is nonphysical and it senses the world. It does not interact with the brain in the other way beside it.
Quantum Mechanics notoriously faces a measurement problem, the problem that the unitary time evolution, encoded in its dynamical equations, together with the kinematical structure of the theory generally implies the non-existence \nof definite measurement outcomes. There have been multiple suggestions to solve this problem, among them the so called many worlds interpretation that originated with the work of Hugh Everett III. According to it, the quantum state and time evolution fully and accurately describe nature as it is, implying that under certain conditions multiple measurement outcomes that are seemingly mutually exclusive can be realized at the same time – but as different 'worlds' contained in a global, quantum mechanical structure, sometimes referred to as 'the multiverse'. The many worlds interpretation has, however, been confronted with serious difficulties over the course of its development, some of which were solved by the advent of decoherence theory. The present thesis critically investi- \ngates the state of play on a key remaining problem of the many worlds interpretation, the problem of the meaning and quantification of probabilities in a quantum multiverse. Recent attempts of deriving the pivotal statistical ingredient of quantum mechanics, Born’s rule, from either principles of decision theory or from quantum mechanics alone, supplemented with a few general premises about \nprobability are analyzed and their premises are scrutinized. It will be argued that, though both approaches yield promising results, they both ultimately fail \nto clearly establish the validity of Born’s rule in the context of the many worlds interpretation. It is hence suggested that further research on this problem is indicated.
The Many Worlds Interpretation (MWI) famously avoids the issue of wave function collapse. Different MWI trees representing the same quantum events can have different topologies, depending upon the observer. However, they are all isomorphic to the group of block universes containing all of the outcomes of all of the events, and so, in that sense, the group of block universes is a more fundamental representation. Different branches of the MWI tree, representing different universes in MWI, ultimately share the same quantum state in a common ancestor branch. This branching topology is incompatible with that of the Minkowski block universe; the resolution is to replace the branches with discrete, parallel block universes, each of which extends from the trunk to the outermost twigs. The number of universes in a branch is proportional to its thickness which, in turn, depends upon the absolute square of the probability amplitude for the state in that branch. Every quantum event may be represented by a kernel of universes, which is the smallest group of universes that will reproduce the quantum probabilities of the outcomes of that event. By considering the ratios of the probabilities of the outcomes of any event, it can be shown that the number of universes in every kernel must finite, as must be the total number of universes in the multiverse. Further, every universe in the multiverse must be finite both in space and time. Another consequence is that quantum probabilities must be rational, which suggests that quantum mechanics is only an approximation to a discrete theory. A corollary is that not every conceivable universe exists in the multiverse, no doubt to the disappointment of those who enjoy alternate-history novels.
Quantum mechanics provides us most fundamental descriptions of our most early universe, but there is a long-standing debate amongst theoretical physicists about what all these mathematics really mean in real world? The present three-dimensional (3D) universe, we humans experience daily since our birth, is probably just one of an enormous numbers of essentially classical worlds, and all quantum phenomena arise from a universal force of repulsions that prevented many universes (Multiverse) from having identical physical configurations like ours. Probabilities arise only because of our human ignorance as to which in our world an observer occupies a position in space time. This picture is all that is needed to explain bizarre quantum effects such as particles that can tunnel through solid barriers and wave behavior in double-slit experiments or in a warm hole. Our many-interacting-universes approach hinges on our assumption that interactions between deterministically evolving worlds cause all quantum effects. Each world is simply the position of particles in three-dimensional space time, and each would evolve according to Newton’s laws, if there were no inter world interactions. A surprising feature of human approach was that the formulation contains nothing that corresponds to the mysterious quantum wave functions, except in the formal mathematical limit in which the number of worlds becomes infinitely large. Conversely, Newtonian mechanics corresponds to the opposite limit of just one world. Thus, our approach should incorporate both classical and quantum theory. As few as two interacting worlds can result in quantum like effects, such as tunneling through a barrier. Many interacting worlds theory (MIW) explains that rather than standing apart, an infinite number of universes in the early time shared the same space and time as ours. They show that the theory can explain quantum mechanical effects while leaving open the choice of theory to explain the universe at large scales. This is a fascinating new variant of multiverse theory that, in a sense, creates not just a doppelganger of everyone but an infinite number of them all overlaying each other in the same space and time. The fine tuning of parameters required to reproduce our present day universe suggests that our universe may simply be a region within an eternally inflating super-region. Many other regions beyond our observable universe might have existed in earlier times with each such universe governed by a different set of physical parameters and laws. Collision between these regions, if they occurred, should have left signatures of anisotropy in the cosmic microwave background (CMB) but have not been seen yet. We assess different mechanisms for this residual emission and conclude that although there is a 30% probability that noise fluctuations may cause foregrounds to fall within 3σ of the excess, there is less than a 0.5% probability that foregrounds can explain all the excess. A plausible explanation is that the collision of our universe with an alternate universe, whose baryon to photon ratio is a factor of ∼ 4500 larger than ours, could produce enhanced Hydrogen Paschen-series emission at the epoch of recombination. Future spectral mapping and deeper observations at 100 and 217 GHz are needed to mitigate systematics arising from unknown galactic foregrounds and to confirm this unusual hypothesis. After careful analysis of the spectrum of the CMB, Chary et al. found a signal that was about 4500x brighter than it should have been, based on the number of protons and electrons. Scientists believe that this existed in the very early universe. Indeed, this particular signal, an emission line that arose from the formation of atoms during the era of recombination is more consistent with a universe whose ratio of matter particles to photons is about 65x greater than our own. There is a 30% chance that this mysterious signal is just noise, and not really, a signal at all; however, it is also possible that it is real, and exists as a parallel universe. Keywords : Quantum mechanics, multiverse, Newtonian mechanics Cite this Article Pranab Kumar Bhattacharya, et al . Schrodinger Cat's Experiment's Interpretation and Parallel Universe or Multiple Universes. Research and Reviews: Journal of Space Science and Technology. 2016; 5(1): 35–52p.
A quantum theory of the universe consists of a theory of its quantum dynamics and a theory of its quantum state The theory predicts quantum multiverses in the form of decoherent sets of alternative histories describing the evolution of the universe's spacetime geometry and matter content. These consequences follow: (a) The universe generally exhibits different quantum multiverses at different levels and kinds of coarse graining. (b) Quantum multiverses are not a choice or an assumption but are consequences of the theory or not. (c) Quantum multiverses are generic for simple theories (d) Anthropic selection is automatic because observers are physical systems within the universe not somehow outside it. (e) Quantum multiverses can provide different mechanisms for the variation constants in effective theories (like the cosmological constant) enabling anthropic selection. (f) Different levels of coarse grained multiverses provide different routes to calculation as a consequence of decoherence. We support these conclusions by analyzing the quantum multiverses of a variety of quantum cosmological models aimed at the prediction of observable properties of our universe. In particular we show how the example of a multiverse consisting of a vast classical spacetime containing many pocket universes arises automatically as part of a quantum multiverse describing an eternally inflating false vacuum that decays by the quantum nucleation of true vacuum bubbles. In a FAQ we argue that the quantum multiverses of the universe are scientific, real, testable, falsifiable, and similar to those in other areas of science even if they are not directly observable on arbitrarily large scales.
We present the case for a fixed, finite number of discrete, non-interacting, spatiotemporally finite, decohered spacetimes emerging from Everett’s Universal Wave Function, which we refer to as “Many Discrete Worlds” (MDW). No universes “split” in MDW. We argue that a Many Worlds Interpretation (MWI) branching structure that emerges after decoherence is equivalent to individual, weighted universes, each of which is divided into an immense number of discrete, identical copies, the number being proportional to the individual weighting. This ensures that repeated experiments within any such universe will demonstrate consistency with the Born rule. Each of these universes should be considered as complete, containing every decohered outcome over the entire extent of its spacetime, including every event/interaction occurring beyond any cosmological particle horizon for the entire duration of the given universe. We show that a countably infinite number of interactions needs an uncountably infinite number of universes, and show why measures such as the Lebesgue measure will fail in that case, with the result that the Born rule would not be demonstrable. This leads to the conclusion that the number of universes in the multiverse must be finite and, as a surprising corollary, that the universes themselves are finite, both in space and duration.