Editing Many-worlds interpretation (section)

=== Decision theory ===
A [[decision theory|decision-theoretic]] derivation of the Born rule was produced by [[David Deutsch]] (1999)<ref>{{Cite journal|arxiv=quant-ph/9906015|last1=Deutsch|first1=David|title=Quantum Theory of Probability and Decisions|journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | volume=455 | issue=1988 | pages=3129–3137 | year=1999 | doi=10.1098/rspa.1999.0443 | bibcode=1999RSPSA.455.3129D |s2cid=5217034}}</ref> and refined by Wallace<ref name="wallace2003">{{cite journal | last1 = Wallace | first1 = David | year = 2003 | title = Everettian Rationality: defending Deutsch's approach to probability in the Everett interpretation | journal = Stud. Hist. Phil. Mod. Phys. | volume = 34 | issue = 3| pages = 415–438 | bibcode = 2003SHPMP..34..415W | doi = 10.1016/S1355-2198(03)00036-4 | arxiv = quant-ph/0303050 | s2cid = 1921913 }}</ref><ref>{{cite arXiv |eprint=quant-ph/0211104|last1=Wallace|first1=David|title=Quantum Probability and Decision Theory, Revisited|year=2002}}</ref><ref>{{cite arXiv |eprint=quant-ph/0312157 | last1=Wallace | first1=David | title=Quantum Probability from Subjective Likelihood: Improving on Deutsch's proof of the probability rule|year=2003}}</ref><ref>{{cite arXiv |eprint=0906.2718|last1=Wallace|first1=David|title=A formal proof of the Born rule from decision-theoretic assumptions|class=quant-ph|year=2009}}</ref> and Saunders.<ref>{{cite journal | last1 = Saunders | first1 = Simon | year = 2004 | title = Derivation of the Born rule from operational assumptions | journal = Proc. R. Soc. Lond. A | volume = 460 | issue = 2046| pages = 1771–1788 | bibcode = 2004RSPSA.460.1771S | doi = 10.1098/rspa.2003.1230 | arxiv = quant-ph/0211138| s2cid = 1459183 }}</ref><ref>{{cite book|arxiv=quant-ph/0412194|last1=Saunders|first1=Simon|title=Quo Vadis Quantum Mechanics?|pages=209–238|year=2004|doi=10.1007/3-540-26669-0_12|chapter=What is Probability?|series=The Frontiers Collection|isbn=978-3-540-22188-3|s2cid=117218061}}</ref> They consider an agent who takes part in a quantum gamble: the agent makes a measurement on a quantum system, branches as a consequence, and each of the agent's future selves receives a reward that depends on the measurement result. The agent uses decision theory to evaluate the price they would pay to take part in such a gamble, and concludes that the price is given by the utility of the rewards weighted according to the Born rule. Some reviews have been positive, although these arguments remain highly controversial; some theoretical physicists have taken them as supporting the case for parallel universes.<ref name="newsci">{{Cite news | last = Merali | first = Zeeya | title = Parallel universes make quantum sense | magazine = New Scientist | issue = 2622 |date=2007-09-21 | url = https://www.newscientist.com/article/mg19526223.700-parallel-universes-make-quantum-sense.html | access-date = 2013-11-22 }} (Summary only).</ref> For example, a ''[[New Scientist]]'' story on a 2007 conference about Everettian interpretations<ref>{{cite web| url = http://www.perimeterinstitute.ca/conferences/many-worlds-50| title = Perimeter Institute, Many worlds at 50 conference, September 21–24, 2007}}{{cite web| url = http://www.perimeterinstitute.ca/video-library/collection/many-worlds-50-2007| title = Videos}}</ref> quoted physicist Andy Albrecht as saying, "This work will go down as one of the most important developments in the history of science."<ref name="newsci"/> In contrast, the philosopher [[Huw Price]], also attending the conference, found the Deutsch–Wallace–Saunders approach fundamentally flawed.<ref>{{Cite book |last1=Price |first1=Huw |title=Many Worlds? Everett, Quantum Theory and Reality |publisher=Oxford University Press |year=2010 |editor=Saunders |editor-first=S. |chapter=Decisions, Decisions, Decisions: Can Savage Salvage Everettian Probability? |editor2=Barrett |editor-first2=J. |editor3=Kent |editor-first3=A. |editor4=Wallace |editor-first4=D. |arxiv=0802.1390}}</ref>