Open Questions in Physics

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Open Questions in Physics

• Tareq Ahmed
• Research Assistant
• Physics Department, KFUPM.
• 7, Jan. 2007

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

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Outline

• Classical Mechanics
• Quantum Mechanics
• The Theory of Radiation

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Classical Mechanics

• Indeterminate behavior in the collisions of point
  particles.

After
Before
v
v
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Before
After
v
v
?
?
v
Conservation of Kinetic Energy
0.5 m v2 20.5 m v2
Conservation of linear momentum
m v 2mv cos(?)
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• Three equations
• Conservation of Energy (1)
• Conservation of Momentum (2)

• And Four parameters !!
• ( )

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The interaction between the particles have to be
included to treat collisions between point
particles. The laws of classical mechanics alone
are not sufficient.
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Quantum Mechanics( A theory of observers)
Anyone who is not shocked by quantum theory has
not understood it. -Niels Bohr

• I think I can safely say that nobody
  understands quantum mechanics. -Richard Feynman

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The WavefunctionA reality or a computational
tool?
Dirac Spinor

• Schrodinger Wavefunction

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

• Any model for the particle (or system) being in a
  superposition of different eigenstates?

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The Collapse of the wavefunction
The "spooky action at a distance."

• How does the wavefunction collapse upon
  measurement?

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The theory of quanta can be likened to a medicine
that cures the disease but kills the patient.
Hendrick Kramers
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Violation of the conservation of Energy
Conserved or not conserved? This is the question !

• The uncertainty principle allows conservation of
  energy to be violated for a very short period!

• Photons of frequencies not resonant with the
  atomic transition frequencies can still excite
  the atom for a very short periods !!

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Quantum Tunneling
How long does a particle take to tunnel through a
quantum barrier?
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Electron positron creation in vacuum
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The Nature of Quantum Jumps
Are there quantum jumps ?
"If we have to go on with these damned quantum
jumps, then I'm sorry that I ever got involved!
E.Schrodinger

• Do there exist phenomena that are truly
  spontaneous? Or do all phenomena, when
  investigated in depth, turn out to be
  deterministic?

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Quantum Mechanics and Randomness
Does Randomness Exist?

• What is the source of randomness in quantum
  mechanics?
• Can the world be deterministic but only our
  description is indeterminist?

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How does an electron absorb a photon?
Any physical picture?
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Why doesnt the electron in1s state fall on the
proton?
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The Most Beautiful Experiment in Physics
"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
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Fundamental Constants in Physics
How Many?

• What is the number of the truly fundamental
  constants

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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

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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

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The Theory of Radiation
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Why two fields to describe the force between
moving charges?

• No single expression that describes the force
  between two charges in arbitrary motion.

Gauss
What is the nature of magnetic fields?
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The Quantization of the Electromagnetic Field
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How can a constant electric field be
represented in terms of photons??
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Vacuum Fluctuations
So much fluctuations!!
Is this a beautiful universe?

• Any model better than vacuum fluctuations?

• Each theory has its own vacuum!!

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How Are Photons Produced?

• Electron Positron Annihilation

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2. Transition between different atomic states

• 3. Transition between different vibrational or
  rotational modes of molecules

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4. Charge acceleration

• e.g, Cyclotron radiation

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Any pattern to unify all these processes?
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Conclusion
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
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Acknowledgment

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

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Questions