The difference between a Klein-Gordon random field and the complex
Klein-Gordon quantum field is characterized, explicitly comparing the roles
played by negative frequency modes of test functions in creation and
annihilation operator presentations of the two theories. The random field and
the complex quantum field can both be constructed from the same creation and
annihilation operator algebra, making them equivalent in that sense.Comment: 4 pages; more explanation of background in response to EPL referee;
mathematics unchange
