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Quantum Theory The worst scientific theory of all time Dr Mark J Hadley Dept of Physics.

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Presentation on theme: "Quantum Theory The worst scientific theory of all time Dr Mark J Hadley Dept of Physics."— Presentation transcript:

1 Quantum Theory The worst scientific theory of all time Dr Mark J Hadley Dept of Physics

2 Plan Introduction to QT Why it is bad A bad theory of classical Mechanics –Classical probability Why the quantum world is different –Why QT is a bad response An alternative to QT

3 Quantum theory Predictions are intrinsically probabilistic. A state is represented by a vector, , in a complex Hilbert space.  contains the maximum possible amount of information. A rule to get probabilities from . A rule to describe the evolution of .

4 Includes Quantum mechanics Quantum Field Theory String Theory

5 How bad? 1.Quantum Theory 2.Genesis

6 Why is it so bad? Fails to explain Nature –What is an elementary particle Particle spectrum Fundamental forces –What is happening in an experiment Prevents progress

7 (x)(x) Gives probability information only. It is not the particle. It does not exist. It requires a new meaning to probability Cannot say what a particle is.. where it is… what it is doing.

8 A bad theory of classical mechanics Throwing a projectile at a target.  (r,  ) describes the probability of a certain result.  (r, ,z,t) describes the evolving wave- packet. Nothing else can be said about the projectile

9 A dice throw  (n) gives the probability of a particular result. The throw is governed by classical mechanics.  (n) = 1/6 Why?

10  (n)  evens  high  lucky

11  (n)= 1/6 Not from Newtonian mechanics Structure Phase space of initial conditions + Deterministic evolution = Space of final conditions Symmetry Nothing else

12 Structural Implications Phase-space of initial conditions  (n) Boolean Logic Deterministic evolution

13 Classical Probabilities Satisfy Boolean Logic Are a measure of our ignorance of initial conditions. Can always be represented as Volume integrals.

14 Quantum Theory Probabilities Do not satisfy Boolean Logic Are represented by projections of a vector Are an intrinsic feature of Nature A completely new meaning to probability

15 Classical and Quantum worlds are very, very similar. For a single experiment –Can use classical probabilities Boolean Logic Individual trajectories No complex wave function For incompatible experiments –Cannot construct a single phase-space of initial conditions that gives the observed results.

16 The quantum World is context dependent QT is one response –It hides the difference State => Evolution => results –At a cost A new meaning to probability No underlying explanation

17 The quantum World is context dependent Explain it with an existing theory –Sensible Explain it with a brilliant new theory –Genius Don’t explain it –Pragmatist Deny that anything needs explaining –Philosopher

18 The quantum World is context dependent Explain it with an existing theory –lazy Explain it with a brilliant new theory –insane Don’t explain it –loser Deny that anything needs explaining –bad loser

19 Using an existing theory Choice between: 1.GR 2.GR 3.GR

20 GR and QT Can GR explain context dependent effects? –Yes Will it agree with QT predictions? –Yes it has to Structure + Symmetry & Continuity = all equations of QT

21 Using GR GR allows a non-trivial causal structure –Measurement apparatus can set additional boundary conditions Any Geometric theory of spacetime can have the same structure

22 From GR to QT Can GR get the equations of QT directly? –No (Not yet) –But remember  (n)= 1/6

23 Progress The Logic of Quantum Mechanics Derived From Classical General Relativity Foundations of Physics Letters Vol 10, No.1, (1997) Topology change and context dependence International Journal of Theoretical Physics Vol. 38 (1999) 1481 Charge and the topology of spacetime Class. Quantum Grav. 16 No 11 (November 1999) Spin half in classical general relativity Class. Quantum Grav. 17 No 20 (October 2000) The orientability of spacetime Class. Quantum Grav. 19 (August 2002)

24 The Quantum World Explain it with an existing theory –GR (sensible) Explain it with a brilliant new theory –insane Don’t explain it –loser Deny that anything needs explaining –Quantum Theory (bad loser)


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