{"id":12396,"date":"2022-12-19T13:33:07","date_gmt":"2022-12-19T20:33:07","guid":{"rendered":"https:\/\/BigJimIndustries.com\/wordpress\/?p=12396"},"modified":"2023-01-07T13:34:27","modified_gmt":"2023-01-07T20:34:27","slug":"unitarity","status":"publish","type":"post","link":"https:\/\/bigjimindustries.com\/wordpress\/2022\/12\/19\/unitarity\/","title":{"rendered":"Unitarity"},"content":{"rendered":"\n

from WIRED<\/a><\/em><\/p>\n\n\n\n

Physicists Rewrite a Quantum Rule That Clashes With Our Universe<\/h1>\n\n\n\n

The past and future are tightly linked in conventional quantum mechanics. A tweak could let quantum possibilities increase as space expands.<\/p>\n\n\n\n

by CHARLIE WOOD<\/a><\/p>\n\n\n\n

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ILLUSTRATION: MERRILL SHERMAN\/QUANTA MAGAZINE<\/em><\/figcaption><\/figure>\n\n\n\n

A JARRING DIVIDE cleaves modern physics. On one side lies quantum theory, which portrays subatomic particles as probabilistic waves. On the other lies general relativity, Einstein\u2019s theory that space and time can bend, causing gravity. For 90 years, physicists have sought a reconciliation, a more fundamental description of reality that encompasses both quantum mechanics and gravity. But the quest has run up against thorny paradoxes.<\/p>\n\n\n\n

Hints are mounting that at least part of the problem lies with a principle at the center of quantum mechanics, an assumption about how the world works that seems so obvious it\u2019s barely worth stating, much less questioning.<\/p>\n\n\n\n

Unitarity, as the principle is called, says that something always happens. When particles interact, the probability of all possible outcomes must sum to 100 percent. Unitarity severely limits how atoms and subatomic particles might evolve from moment to moment. It also ensures that change is a two-way street: Any imaginable event at the quantum scale can be undone, at least on paper. These requirements have long guided physicists as they derive valid quantum formulas. \u201cIt\u2019s a very restrictive condition, even though it might seem a little bit trivial at first glance,\u201d said Yonatan Kahn<\/a>, an assistant professor at the University of Illinois.<\/p>\n\n\n\n

But what once seemed an essential scaffold may have become a stifling straitjacket preventing physicists from reconciling quantum mechanics and gravity. \u201cUnitarity in quantum gravity is a very open question,\u201d said Bianca Dittrich<\/a>, a theorist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.<\/p>\n\n\n\n

The main problem is that the universe is expanding. This expansion is well described by general relativity. But it means that the future of the cosmos looks totally different from its past, while unitarity demands a tidy symmetry between past and future on the quantum level. \u201cThere is a tension there, and it\u2019s something quite puzzling if you think about it,\u201d said\u00a0Steve Giddings<\/a>, a quantum gravity theorist at the University of California, Santa Barbara.<\/p>\n\n\n\n

[ click to continue reading at WIRED<\/a> ]<\/p>\n","protected":false},"excerpt":{"rendered":"

from WIRED Physicists Rewrite a Quantum Rule That Clashes With Our Universe The past and future are tightly linked in conventional quantum mechanics. A tweak could let quantum possibilities increase as space expands. by CHARLIE WOOD A JARRING DIVIDE cleaves modern physics. On one side lies quantum theory, which portrays subatomic particles as probabilistic waves. On […]<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[8],"tags":[],"class_list":["post-12396","post","type-post","status-publish","format-standard","hentry","category-weirdness"],"_links":{"self":[{"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/posts\/12396","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/comments?post=12396"}],"version-history":[{"count":0,"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/posts\/12396\/revisions"}],"wp:attachment":[{"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/media?parent=12396"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/categories?post=12396"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bigjimindustries.com\/wordpress\/wp-json\/wp\/v2\/tags?post=12396"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}