1 Open Questions in Physics Tareq Ahmed Research Assistant Physics Department, KFUPM. 7, Jan. 2007

2 The job of a theoretical physicist is to try to find the right answers for the good questions.

3 Typical Questions 1. Where and what is dark matter? 2. How massive are neutrinos? 3. What are the implications of neutrino mass? 4. What are the origins of mass? 5. Why is gravity so weak? 6. Why is the universe made of matter and not antimatter? 7. Where do ultrahigh-energy cosmic rays come from?

4 Outline Classical Mechanics Quantum Mechanics The Theory of Radiation

5 Classical Mechanics Indeterminate behavior in the collisions of point particles. Before After v v

6 θ θ BeforeAfter v v’ 0.5 m v 2 = 2*0.5 m v’ 2 Conservation of Kinetic Energy Conservation of linear momentum m v= 2*m*v’ * cos( θ )

7 Three equations Conservation of Energy (1) Conservation of Momentum (2) And Four parameters !! ()

8 The interaction between the particles have to be included to treat collisions between point particles. The laws of classical mechanics alone are not sufficient.

9 Quantum Mechanics ( A theory of observers) I think I can safely say that nobody understands quantum mechanics. -Richard Feynman Anyone who is not shocked by quantum theory has not understood it. -Niels Bohr

10 The Wavefunction A reality or a computational tool? Dirac Spinor Schrodinger Wavefunction:

11 A single wavefunction of the Universe! If [quantum theory] is correct, it signifies the end of physics as a science. Albert Einstein What is it?

12 The Concept of Superposition Any model for the particle (or system) being in a superposition of different eigenstates?

13 The Collapse of the wavefunction How does the wavefunction collapse upon measurement? The "spooky action at a distance."

14 The theory of quanta can be likened to a medicine that cures the disease but kills the patient. Hendrick Kramers

15 The uncertainty principle allows conservation of energy to be violated for a very short period! Violation of the conservation of Energy Conserved or not conserved? This is the question ! Photons of frequencies not resonant with the atomic transition frequencies can still excite the atom for a very short periods !! hw 0 hw

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17 Quantum Tunneling How long does a particle take to tunnel through a quantum barrier?

18 Electron positron creation in vacuum e e e+e+

19 The Nature of Quantum Jumps Do there exist phenomena that are truly spontaneous? Or do all phenomena, when investigated in depth, turn out to be deterministic? " If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved!” E.Schrodinger Are there quantum jumps ?

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21 What is the source of randomness in quantum mechanics? Can the world be deterministic but only our description is indeterminist? Quantum Mechanics and Randomness Does Randomness Exist?

22 How does an electron absorb a photon? Any physical picture?

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24 Why doesn’t the electron in1s state fall on the proton?

25 "We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.“ R.Feynman The Most Beautiful Experiment in Physics

26 Fundamental Constants in Physics What is the number of the truly fundamental constants How Many?

27 The identity of particles Do quarks have a well defined identity? "If you cannot - in the long run - tell everyone what you have been doing, your doing has been worthless." - Erwin Schrodinger, Science and Humanism

28 And the result….. "I don't like it, and I'm sorry I ever had anything to do with it." - Erwin Shrodinger, speaking about quantum mechanics

29 The Theory of Radiation

30 Why two fields to describe the force between moving charges? No single expression that describes the force between two charges in arbitrary motion. v1v1 q2q2 q1q1 r v2v2 Gauss What is the nature of magnetic fields?

31 The Quantization of the Electromagnetic Field

32 How can a constant electric field be represented in terms of photons??

33 Vacuum Fluctuations So much fluctuations!! Any model better than vacuum fluctuations? Each theory has its own vacuum!! Is this a beautiful universe?

34 How Are Photons Produced? 1.Electron Positron Annihilation

35 2. Transition between different atomic states 3. Transition between different vibrational or rotational modes of molecules

36 4. Charge acceleration e.g, Cyclotron radiation

37 Any pattern to unify all these processes?

38 Behind it all is surely an idea so simple, so beautiful, that when we grasp it - in a decade, a century, or a millennium - we will all say to each other, how could it have been otherwise? How could we have been so stupid for so long? - John Archibald Wheeler Conclusion

39 Acknowledgment I would like to thank Dr. Hucine Bahlouli, Dr. Abdulaziz Aljalal and Abdallah Baziyad for their valuable comments

Questions