Observers and Observables in Physical Theory| Observers and Observables in Physical Theory |
Observers > s.a. Covariance;
reference frames [including accelerated].
* Types of observers: Lagrangian (non surface-forming
observers) or Eulerian (surface-forming ones, or hypersurface-orthogonal), inertial or non-inertial.
* Observer space: The 'observer space' of a Lorentzian
spacetime is the space of future-timelike unit tangent vectors.
@ Role of observers: Klajn & Smolić EJP(13)-a1302 [comments];
Knuth CP(14)-a1310 [observer-centric physics];
Clough a1801
[3+1 description vs 4D spacetime description];
Ben-Ya'acov a2007
[observers within physical systems and incompleteness of theories];
Contreras-Tejada et al a2102 [agreement between observers as a physical principle];
> s.a. Agency.
@ Accelerated observers: Mashhoon AdP(13)-a1211
[non-local connection between non-inertial and inertial observers];
Kolekar PRD(14) [in a thermal bath];
> s.a. observables in classical gravity [non-inertial].
@ In general spacetimes: Page CQG(98)gq/97 [stationary axisymmetric, maximal acceleration];
Garat JMP(05)-a1306 [Euler observers in geometrodynamics];
Dahia & Felix da Silva GRG(11)-a1004 [static];
Dupré a1403 [two symmetric tensors
observed to be equal by all observers at a specific event are necessarily equal at that event];
Chęcińska & Dragan PRA(15)-a1509
[communication between observers without a shared reference frame].
@ Physics in observer space: Gielen & Wise JMP(13)-a1210 [observer-space formulation of general relativity];
Gielen PRD(13)-a1301 [observer-space geometry].
@ In quantum theory: Konishi IJMPB(12)-a1212 [and time-reparametrization symmetry];
Ahluwalia IJMPD(17)-a1706-GRF [in quantum gravity];
Vedral a1803
[can an observer know he/she is in a superposition?];
Stoica a2008 [without observers];
Nyman a2010 [observer theories];
> s.a. origin of quantum theory;
types of interpretations.
Observables
> s.a. information; Observers.
$ Idea: When there are no
constraints, an observable for a classical theory is any measurable function
on the phase space Γ for a theory; In quantum theory, this leads
to operators on the Hilbert space of the theory; Since classical observables
are usually real, quantum operators are usually self-adjoint.
* Remark: There are observables for
which actually constructing a measuring apparatus is difficult or impossible.
* Linear theory: Linear
observables are labelled by vectors X ∈ Γ, and
given by wX(V)
= Ω(X, V), for all V ∈ Γ.
* Theory with constraints: In addition,
(for Dirac observables) the Poisson brackets with the constraints must weakly vanish.
@ General references:
Fernández PLA(03) [perturbative];
de Groote mp/06;
Hartmann FP-a1504 [and foundations of physics];
Anderson a1505 [differential equations];
Zalamea a1711 [two-fold role of observables];
Morchio & Strocchi a2102 [and manifold topology, gauge group].
@ Theories with constraints:
Lusanna ht/95-conf [presymplectic approach];
Hájíček CQG(96)gq/95 [and time evolution];
Lucenti et al JPA(98) [N relativistic particles];
Dütsch & Fredenhagen CMP(99)ht/98 [gauge theories];
Bratchikov IJGMP(07)ht/04 [space of orbits vs gauge fixing],
JGP(06) [second-class];
Hellmann a0812
[kinematic observables, physical interpretation];
Pons et al PRD(09)-a0905 [generally covariant theories and gauge];
Quadri EPJC(10)-a1007 [non-linearly realized gauge theories];
Pitts FP-a1907 [Hamiltonian Einstein-Maxwell theory];
Chataignier a1910 [and emergent WKB time].
Related Topics > see Coarse-Graining; conservation laws; lattice theories [observable currents]; structure of physical theories [unobservable quantities].
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