Turing machine The Church—Turing—Deutsch thesis[ edit ] The classic Church—Turing thesis claims that any computer as powerful as a Turing machine can, in principle, calculate anything that a human can calculate, given enough time. Turing moreover showed that there exist universal Turing machines which can compute anything any other Turing machine can compute—that they are generalizable Turing machines. But the limits of practical computation are set by physicsnot by theoretical computer science:
Introduction Holism has often been taken as the thesis that the whole is more than the sum of its parts. Several different interpretations of this epigram prove relevant to physics, as we shall see. Here is a correspondingly vague initial statement of nonseparability: The state of the whole is not constituted by states of its parts.
It is already apparent both that holism and nonseparability are related notions and that their exact relation needs to be clarified.
In one interpretation, holism is a methodological thesis Section 2to the effect that the best way to study the behavior of a complex system is to treat it as a whole, and not merely to analyze the structure and behavior of its component parts.
Alternatively, holism may be taken as a metaphysical thesis Section 3: There are some wholes whose natures are simply not determined by the nature Oxford particle physics thesis their parts. Methodological holism stands opposed to methodological reductionism, in physics as well as in other sciences.
But it is a certain variety of metaphysical holism that is more closely related to nonseparability. What is at issue here is the extent to which the properties of the whole are determined by the properties of its parts: In turn, nonseparability can be analyzed either as state nonseparability Section 5or as spatiotemporal nonseparability Section 6.
By and large, a system in classical physics can be analyzed into parts, whose states and properties determine those of the whole they compose Section 7. But the state of a system in quantum theory resists such analysis. The quantum state of a system specifies its chances of exhibiting various properties on measurement.
In ordinary quantum mechanics, the most complete such specification is given by what is called a pure state. Even when a compound system has a pure state, some of its subsystems may not have their own pure states.
Superficially, such entanglement of states already demonstrates nonseparability. At a deeper level, it has been maintained that the puzzling statistics that arise from measurements on entangled quantum systems either demonstrate, or are explicable in terms of, holism or nonseparability rather than any problematic action at a distance Sections 89.
The Aharonov-Bohm effect Section 10 also appears to exhibit action at a distance, as the behavior of electrons is modified by a magnetic field they never experience.
But this effect may be understood instead as a result of the local action of nonseparable electromagnetism. Puzzling correlations arise between distant simultaneous measurements even in the vacuum, according to quantum field theory Section A form of quantum theory used to study them represents systems by algebras of operators with new kinds of states defined on them, thereby making room for failures of state and system separability with no analogs in ordinary quantum mechanics.Curriculum Vitae.
LISA RANDALL. Harvard University—Department of Physics.
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Particle physics ambassadors communicate about international particle physics research and innovation and inform about new developments and the benefits of particle physics . In these excellent new translations of Einstein's papers, the economy and freshness of Einstein's style come through with undiminished force To re-read these papers is to relive perhaps the most dramatic year in the history of physics.
Texas Tech University Department of Physics Homepage. Includes announcements, calendars, news, and the vision. The Question In the year BCE, the Babylonians destroyed Jerusalem and brought many of the Jews back home as captives.
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