Paradigms and Assumptions in Physics  

In General > s.a. history of physics [paradigm shifts].
* Idea: Paradigms are the higher-level ingredients of physical theories.
* Underlying assumptions: The universe is governed by few, understandable laws; Physics takes place in a smooth continuum spacetime; The assumptions change as our knowledge increases, especially recently regarding the role of determinism and predictability, locality, stability; And quantum gravity challenges our view of spacetime.
* Practical idealizations: Fields are defined by limits of vanishingly small charges, a limit which cannot be realized operationally.
@ References: Margolis 93; Holton FP(96) [role of themata]; Bornholdt et al PRL(11) [model for rise and decline of paradigms].

Copernican > s.a. Copernican Principle.
* Idea: There is nothing special about our position in the Solar System (originally), or the Universe; Has been formalized as the cosmological principle; > s.a. cosmology [including anthropic principle].

* Idea: Different levels of description give different laws; The fundamental scale in questions asked is related to physical length scales; This theme is associated with the concept of incomplete (as opposed to right or wrong) theory.
@ References: Cui ht/01 [levels of description for particles]; Kulish 02 [electrodynamics].

Reductionism (of complicated things to simple ones) > s.a. complexity; duality [and fundamentality]; emergence; theories [fundamental].
* Idea: The practice of describing complex phenomena and theories in terms of simpler, more fundamental concepts and theories; In common examples it is based on the assumption that substance is fundamental.
* Examples: Planetary motion reduced to simple orbits; Properties of matter to atoms, particles.
* History: The idea can be traced back to Leucippus' and Democritus' atomistic theory, and is related to the concept of a model; One of the most fundamental manifestations is the development of QCD and the Standard Model of particle physics, but it has been recently challenged by emergence ideas in quantum theory, complexity/chaos and computation (earlier opposition by J W von Goethe [@ in Gleick 87] or D'Arcy Thompson [biology]), and in particle physics alternative approaches were Chew's bootstrap theory and Hagedorn's ideas; 1980s, A paradigm shift is under way.
* Point of view: (& Lucy James) Fundamentality is relative, a partial order among theories and things, with an epistemic and a formal or semantic aspect.
@ References: Rohrlich FP(89), FP(90); AS 78(90)14-15 & refs there; Cohen & Stewart 94 [I]; Cornwell ed-95; Casti SA(96)oct [models]; Price qp/96-conf [independence of systems]; Harte PT(02)oct [simplicity vs complexity]; Forster 03 [in mathematical logic]; Gunter CSF(05) [history]; Morrison PhSc(06)dec [new ways of thinking, condensed matter and other areas]; Bolotin PE(13)-a1301 [and the measurement problem]; Redlich & Satz in(16)-a1501 [Hagedorn]; Rosaler a1802-PhD [more general approach, quantum mechanics and quantum field theory]; Rosaler a1810; Leifer a1810-FQXi [against fundamentalism]; Verma a1904 [hydrodynamics vs kinetic theory, hierarchical description]; Del Santo & Cardelli a1802 [fundamentality].
> Online resources: see Wikipedia page.

Symmetrical > s.a. symmetry.
* Remark: A very powerful theme, that reduces many problems of numerical naturalness to questions of structure.
* Hidden symmetry: The apparent symmetry of the world can vary with the length scale and the state of the system; Systems with hidden (or spontaneously broken) symmetries usually support wave motions.

Unification > s.a. physics [theories of everything]; unified theories.
* Idea: Understanding seemingly different phenomena in a unified way (e.g., unification of interactions), and relating different levels of description of reality (s.a. hierarchical above).
@ References: Cat HSPBS(98) [XX century]; Durham a1001-FQXi [and difficulties caused by emergence].

Causality > s.a. causality; Predictability; Teleology.
* Idea: There is a hierarchy of properties a theory may have, that goes causality → determinism → predictability.

Related Topics > s.a. covariance; field theory, quantum field theory [linearity]; Fine Tuning; information; spacetime.
@ References: Israel FP(96) [permanence of matter, continental drift and compact stars]; Svozil FP(02) [conventionalism, in special relativity and quantum mechanics].
> Other: see locality; mach's principle; realism.
> Working assumptions: see Large-Number Hypothesis; Totalitarian Principle.

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