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检验能量 - 动量张量的对称性 Testing the symmetry of the energy-momentum tensor

检验能量 - 动量张量的对称性 Testing the symmetry of the energy-momentum tensor. 陈相松 华中科技大学物理学院 2012-11-01@ 科大. Outline. Message 1: Gluon momentum fraction: 50% or 20%? Symmetric and nonsymmetric energy-momentum tensors The symmetry can be tested experimentally!

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检验能量 - 动量张量的对称性 Testing the symmetry of the energy-momentum tensor

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  1. 检验能量-动量张量的对称性Testing the symmetry of the energy-momentum tensor 陈相松 华中科技大学物理学院 2012-11-01@科大

  2. Outline • Message 1: Gluon momentum fraction: 50% or 20%? • Symmetric and nonsymmetric energy-momentum tensors • The symmetry can be tested experimentally! • Prediction for the experiment: the nonsymmetric canonical expression is correct • Implication for gravity and inertia • Gauge invariance, composite particles, etc. • Summary and suggestion for experiments

  3. Gluon momentum fraction: 50% or 20%?

  4. The symmetric and nonsymmetric energy-momentum tensors

  5. Take-home message Symmetry of the energy-momentum tensor can be tested experimentally!

  6. Property of the symmetric energy-momentum tensor momentum density P =energy-flow density K Total angular momentum (Spin + Orbital)

  7. A concrete prediction of the symmetric expression A collimated beam of spin-s particles Can be tested by measuring the transverse energy flux density！

  8. The spin-1/2 electron beam Prediction of the symmetric expression Magnetic moment Quantization of the election: Another Prediction

  9. Symmetric vs. canonical expressions It is the nonsymmetric canonical energy-momentum tensor that agrees with current conservation ---Another take-home message

  10. The case for orbital angular momentum No spin polarization, no nonsymmetric effect

  11. The photon energy-momentum tensors The same energy flow density (for free photons) Momentum densities are different Measurement of momentum flow can tell the symmetry!

  12. Implication for gravity and inertia Symmetric? Equivalence Principle?

  13. Extended discussion • Effective degrees of freedom for composite particles, especially of higher spin • Gauge invariance and Lorentz transformation of the canonical expressions • Equivalence principle at the tensor level? • A possible gravitation theory using the canonical energy-momentum tensor?

  14. Summary and suggestion for experiments • Message 1: the energy-momentum tensor does not have the often assumed arbitrariness. Its symmetry can be tested experimentally! • Message 2: Concordance between conservation of energy and charge refutes the symmetric expression and favors the canonical expression • Measurement with electron: most direct test • Measurement with proton, neutron, higher-spin nuclei: to reveal the effective degrees of freedom • Measurement with photon: to address the gauge-invariance problem 敬请指正，谢谢！

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