Isolated wavefunctions deterministically calculate future possible states. However, observing a particle measures particle position or momentum, putting particle into a definite phase-space state, and so cancels particle wavefunction {wavefunction collapse} {collapse of wavefunction}| {reduction of wave packet} {wave-packet reduction} {collapse of the wavefunction} {state vector reduction}. Wavefunction collapse is a discontinuity in physics. Collapse is time asymmetric. After observation, particle again has a wavefunction, until the nect observation.
observation and measurement
Observers and measuring instruments are too large to have observable wavefunctions, matter-wave wavelengths, matter-wave frequencies, or energy quanta. Observing and measuring cause particle interaction with a macroscopic system and make a new macroscopic system that includes the particle. Observers and instruments put particle wavefunctions into definite phase-space states {state preparation}, ready for measuring. Macroscopic systems have definite object positions and momenta.
Measuring requires that observer or instrument has definite phase-space state, and particle has definite phase-space state. Observers and instruments measure along one direction and detect particle position, time, momentum, angular momentum, or energy. Therefore, position, time, momentum, angular momentum, or energy observation/measurement operates on particle complex-number wavefunction and transforms it into a position, time, momentum, angular momentum, or energy real positive value. The value is any one of the set of possible different-probability quantum values (operator eigenfunction) described by the observer/instrument/particle wavefunction. State selection is completely random. Measurement results in a single value, not value superpositions or multiple values. The observer/instrument/particle wavefunction collapses to zero {measurement problem}. At measurement, particle phase-space state no longer exists, because particle wavefunction no longer exists.
operators
Measuring wavefunctions mathematically uses linear differential Hermitean operators.
causes
Measurements, absorptions, collisions, electromagnetic forces, and gravitational forces collapse particle wavefunctions. Gravitational effects can be gravitational waves, mass separation changes, gravitational self-energy changes, or fixed-star gravitational-field disturbances. Perhaps, measuring equipment is large and so affects wavefunction drastically (Bohr). Perhaps, collapse is large information gain (Heisenberg).
Perhaps, wavefunction collapse is due to particle and wavefunction properties. Perhaps, previous states have lingering wavefunctions that affect later wavefunctions. Perhaps, Gaussian wavefunction distributions coincide at random. Perhaps, wavefunctions have continual operators. Perhaps, wavefunctions are unstable every billion years {Ghirardi-Rimini-Weber} (GRW), so large masses collapse immediately (Giancarlo Ghirardi, Alberto Rimini, Tullio Weber).
Perhaps, wavefunction collapse is due to quantum mechanics. Perhaps, quantum fluctuations average {quantum averaging} to make definite energy states and space and time. Perhaps, cosmic inflation caused macroscopic-size quantum uncertainty and fluctuations {quantum uncertainty}.
wavefunctions and reality
Are wavefunctions just calculating devices, or do they exist in physical reality? Why do physical laws follow mathematical laws? How does perception relate to physical laws, mathematical laws, and material world? How does wavefunction collapse relate to physical laws, mathematical laws, and material world? How does wavefunction collapse relate to wavefunction time and space changes? How can observation/measurement and wavefunctions unify into a continuous explanation, rather than a discontinuous one?
alternatives: real wavefunctions
Perhaps, classical potential and quantum-mechanical potential both exist, so wavefunction is real. Measuring real wavefunction releases energy, starts wave fluctuations, and collapses wavefunction.
alternatives: undefined and defined states
Perhaps, particles have no wavefunction, so there is no collapse. Instead of wavefunctions, particles have only defined and undefined states. Undefined states can become one defined state. For example, particle density matrices represent possible different-probability physical states. Particle moves from undefined states to one state on the matrix diagonal. However, particles can be in superposed states, which matrices cannot represent. Particles can have only one or two possible states, which matrices cannot represent.
alternatives: subquanta
Perhaps, quantum levels involve even smaller properties, or quantities that cause them. However, particles have no hidden variables and so no subquanta.
alternatives: larger whole
Perhaps, physics has another conservation law about a larger whole. Observers and instruments measure only observable parts, while other parts are not observable. Whole system, observable and not observable, is deterministic, continuous, and time symmetric. For example, objects always travel at light speed, but some are time-like, and some are space-like. However, particles have no hidden variables and so no larger whole.
alternatives: two state vectors
Perhaps, quantum states have two phase-space state vectors, one starting from last wavefunction collapse and going forward in time and the other starting from next wavefunction collapse and going backward in time (Yakir Aharonov, Lev Vaidman, Costa de Beauregard, Paul Werbos) [1989]. Before and after phase-spaces are different. At events, forward-state vector happens first, and then backward-state vector happens. Their vector product makes density matrices, allowing smooth transitions between wavefunctions and collapses. This theory gives same results as quantum mechanics with one state vector. Forward and backward effects allow consistency with general relativity. However, time cannot flow backward, by general relativity.
alternatives: positivism
Perhaps, only measured results count, and wavefunctions are non-measurable things. However, experiments involving primitive measurements demonstrate that quantum state is deterministic and unique, so wavefunctions seem to have reality.
Physical Sciences>Physics>Quantum Mechanics>Wavefunction>Collapse
5-Physics-Quantum Mechanics-Wavefunction-Collapse
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0224