{"id":846,"date":"2023-02-03T00:48:37","date_gmt":"2023-02-03T00:48:37","guid":{"rendered":"https:\/\/qpr.ca\/blogs\/physics\/?p=846"},"modified":"2023-02-03T00:50:41","modified_gmt":"2023-02-03T00:50:41","slug":"schrodingers-deterministic","status":"publish","type":"post","link":"https:\/\/qpr.ca\/blogs\/physics\/2023\/02\/03\/schrodingers-deterministic\/","title":{"rendered":"What is Schrodinger&#8217;s equation? Is it deterministic or not? If it is, how can we prove that? And what conditions must be satisfied for it to be non-deterministic?\u00a0"},"content":{"rendered":"<p>Schrodinger\u2019s equation was originally just the partial differential equation satisfied by the position-space wave function of a particle (or more general system) in non-relativistic quantum mechanics. The same name is sometimes also used for the equation [math]\\frac{d}{dt}\\Psi(t)=iH\\Psi(t)[\/math] satisfied by the state vector in any NRQM system regardless whether or not a position-space representation is being used (or is even available).<\/p>\n<p>It is deterministic (in the sense of determining [math]\\Psi(t)[\/math] uniquely for all [math]t[\/math] if given an initial condition [math]\\Psi(0))[\/math], so long as the Hamiltonian [math]H[\/math] is self-adjoint (symmetry is NOT enough!).<\/p>\n<p>The proof of this involves more analysis than I could fit into a Quora answer, but in the general case it follows from the fact that for any self-adjoint operator [math]H[\/math] on a Hilbert Space, the equation [math]\\frac{d}{dt}\\Psi(t)=iH\\Psi(t)[\/math] is uniquely satisfied by [math]\\Psi(t)=e^{iHt}\\Psi(0)[\/math] where the complex exponential of [math]H[\/math] is defined in terms of its spectral resolution; and for the PDE special cases it might be done by various theorems involving greens functions or Fourier analysis and convergence properties of improper integrals.<\/p>\n<p>It may be non-deterministic if [math]H[\/math] has not been specified on a large enough domain to be essentially self-adjoint (as sometimes happens if boundary conditions are omitted from the specification of a problem in which the particle is confined somehow &#8211; either by an infinite potential or by living in a single cell of a crystal lattice for example). But such cases are normally just due to inadequate specification of the problem rather than to a real physical indeterminacy.<\/p>\n<p>So I would say that in a properly defined quantum theory model the Schrodinger equation is indeed almost always deterministic.<\/p>\n[N.B. It wasn\u2019t part of the actual question, but I should perhaps add that the reason this does not make quantum mechanics deterministic is because even complete knowledge of the quantum state of a system is not sufficient to predict the outcomes of all possible experimental measurements. For any a state which happens to produce a predictable value for one observable there will be other observables for which the outcome is uncertain.]\n<p>Source: <em><a href=\"https:\/\/www.quora.com\/What-is-Schrodingers-equation-Is-it-deterministic-or-not-If-it-is-how-can-we-prove-that-it-is-deterministic-If-it-isnt-what-conditions-must-be-satisfied-for-Schrodingers-equation-to-be-non-deterministic\/answer\/Alan-Cooper-5\">(1000) Alan Cooper&#8217;s answer to What is Schrodinger&#8217;s equation? Is it deterministic or not? If it is, how can we prove that it is deterministic? If it isn&#8217;t, what conditions must be satisfied for Schrodinger&#8217;s equation to be non-deterministic? &#8211; Quora<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Schrodinger\u2019s equation was originally just the partial differential equation satisfied by the position-space wave function of a particle (or more general system) in non-relativistic quantum mechanics. The same name is sometimes also used for the equation [math]\\frac{d}{dt}\\Psi(t)=iH\\Psi(t)[\/math] satisfied by the state vector in any NRQM system regardless whether or not a position-space representation is being &hellip; <a href=\"https:\/\/qpr.ca\/blogs\/physics\/2023\/02\/03\/schrodingers-deterministic\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">What is Schrodinger&#8217;s equation? Is it deterministic or not? If it is, how can we prove that? And what conditions must be satisfied for it to be non-deterministic?\u00a0<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,4],"tags":[],"topics":[],"class_list":["post-846","post","type-post","status-publish","format-standard","hentry","category-all","category-quora-answers"],"_links":{"self":[{"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/posts\/846","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/comments?post=846"}],"version-history":[{"count":2,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/posts\/846\/revisions"}],"predecessor-version":[{"id":850,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/posts\/846\/revisions\/850"}],"wp:attachment":[{"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/media?parent=846"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/categories?post=846"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/tags?post=846"},{"taxonomy":"topics","embeddable":true,"href":"https:\/\/qpr.ca\/blogs\/physics\/wp-json\/wp\/v2\/topics?post=846"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}