Chronology |
Current Month |
Current Thread |
Current Date |

[Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |

*From*: Bill Nettles <bnettles@uu.edu>*Date*: Thu, 3 Jan 2013 14:10:19 -0600

John Denker's question about gravity prompted my thinking about what other concepts have some type of duality. My first finding was kinetic energy.

In classical mechanics, we often use the equation E = K + U, with E being total (mechanical) energy, K being kinetic and U being potential energies. Hence, classically, K = E-U. We also, classically, determine K = (mv^2)/2 = (p^2)/2m, or with SR K=mc^2(gamma -1). All 3 are positive definite, and everyone is happy.

In QM, with the time independent SWE, <psi|(E-U)|psi> = -(hbar^2)/2m <psi|psi''>, and we allow the quantity (E-U) to be negative (barrier penetration) and when it is we say it's "classically forbidden." Is it proper to also call this occurrence of (E-U) kinetic energy, and that it is negative? I generally do, and I even mention that while classical or SR kinetic energies are positive, QM kinetic energies can have negative values. Does someone have a vocabulary for this that avoids negative K?

B Nettles

x6588

- Prev by Date:
**Re: [Phys-L] gravity + tunneling to the antipodes** - Next by Date:
**Re: [Phys-L] electronic devices on planes?** - Previous by thread:
**Re: [Phys-L] electronic devices on planes?** - Next by thread:
**Re: [Phys-L] The second law of thermodynamics** - Index(es):