# Why the Many-Worlds Interpretation?

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## Abstract

**:**

## 1. Introduction

## 2. The MWI Is the Only Solution of the Measurement Problem without Action at a Distance

## 3. The MWI Is the Most Economical Quantum Theory Regarding the Theory’s Laws

## 4. The Paradoxes of the Quantum Theory Are Resolved in the Framework of the MWI Interpretation

## 5. Conceptual Changes in Our Approach to a Scientific Theory That Should Be Made When We Accept the World Splitting Structure of the Universe

## 6. What Is a “World” in the MWI?

A world is the totality of macroscopic objects: stars, cities, people, grains of sand, etc., in a definite classically described state.

## 7. Connection between Our Experience and the Universal Wave Function

## 8. The (Illusion of) Probability in the MWI

## 9. What Might Be the Reasons for the MWI Not Being in a Consensus?

## 10. Conclusions

- (a)
- The lack of action at a distance is a huge physical advantage which is not present in other interpretations;
- (b)
- Determinism is a huge philosophical advantage which is not considered as such due to an error in the evolution of science (apparently explained by not seeing a deterministic option for physics for too long);
- (c)
- The MWI allows us to view physics in three spatial dimensions within the particular world of the MWI we live in (however, we should not disregard nonlocality of entanglement which requires the configuration space for its description);
- (d)
- Our world defines our world wave function (the alleged preferred basis problem) and the difficult emergence program does not need a solution;
- (e)
- There is only an illusion of probability of outcomes of quantum measurements. It naturally leads to an effective Born Rule via measures of existence of worlds (and can be given an ignorance probability meaning as the probability of self-location in a particular world). Quantum worlds, contrary to classical worlds, might have measures of existence which are not just zero or one.

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**

**Measurement problem.**(

**a**) The detection of a single photon is fully understood by the creation of a particular quantum wave of parts of the single-photon detector. (

**b**) In the experiment with a single-photon source, beamsplitter, and two detectors, the quantum mechanical equations show a similar (although reduced) change in two detectors. Nevertheless, we never observe simultaneous clicks of the two detectors.

**Figure 2.**

**Action at a distance in a single-world universe.**If we do nothing at A, then at a particular moment, there will be probability $p=0.5$ of finding a photon at a spacelike separated region B. Introducing a detector just before A will lead to a superluminal change in B to $p=0$ or $p=1$. The change will not be known immediately at B, but it does not change the fact that something in B changed, e.g., the readiness of an agent in A to bet about the result of an experiment in B.

**Figure 3.**

**The world structure in the MWI and a single-world universe.**(

**a**) The whole tree of many worlds in the MWI. (

**b**) One world of the MWI until present together with the tree of future worlds splitting out of it in the future. (

**c**) One of the corresponding worlds of the theory with collapse.

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**MDPI and ACS Style**

Vaidman, L.
Why the Many-Worlds Interpretation? *Quantum Rep.* **2022**, *4*, 264-271.
https://doi.org/10.3390/quantum4030018

**AMA Style**

Vaidman L.
Why the Many-Worlds Interpretation? *Quantum Reports*. 2022; 4(3):264-271.
https://doi.org/10.3390/quantum4030018

**Chicago/Turabian Style**

Vaidman, Lev.
2022. "Why the Many-Worlds Interpretation?" *Quantum Reports* 4, no. 3: 264-271.
https://doi.org/10.3390/quantum4030018