Problem: I know that the answer to the question "Which field does not define a vacuum as also free of all photons?" is in "In quantum mechanics and quantum field theory, the vacuum is defined as the state (that is, the solution to the equations of the theory) with the lowest possible energy (the ground state of the Hilbert space). In quantum electrodynamics this vacuum is referred to as 'QED vacuum' to distinguish it from the vacuum of quantum chromodynamics, denoted as QCD vacuum. QED vacuum is a state with no matter particles (hence the name), and also no photons. As described above, this state is impossible to achieve experimentally. (Even if every matter particle could somehow be removed from a volume, it would be impossible to eliminate all the blackbody photons.) Nonetheless, it provides a good model for realizable vacuum, and agrees with a number of experimental observations as described next.". Can you tell me what it is?

A: quantum chromodynamics


Problem: I know that the answer to the question "What is worshipped?" is in "According to a National Geographic article, the novel is so revered in Monroeville that people quote lines from it like Scripture; yet Harper Lee herself refused to attend any performances, because "she abhors anything that trades on the book's fame". To underscore this sentiment, Lee demanded that a book of recipes named Calpurnia's Cookbook not be published and sold out of the Monroe County Heritage Museum. David Lister in The Independent states that Lee's refusal to speak to reporters made them desire to interview her all the more, and her silence "makes Bob Dylan look like a media tart". Despite her discouragement, a rising number of tourists made to Monroeville a destination, hoping to see Lee's inspiration for the book, or Lee herself. Local residents call them "Mockingbird groupies", and although Lee was not reclusive, she refused publicity and interviews with an emphatic "Hell, no!"". Can you tell me what it is?

A: novel


Problem: I know that the answer to the question "Who has hemoglobin?" is in "In nature, the red color of blood comes from hemoglobin, the iron-containing protein found in the red blood cells of all vertebrates. The red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars. The red sky at sunset and sunrise is caused by an optical effect known as Rayleigh scattering, which, when the sun is low or below the horizon, increases the red-wavelength light that reaches the eye. The color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the human population has red hair; the color is produced by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin.". Can you tell me what it is?

A: all vertebrates


Problem: I know that the answer to the question "What was the outcome of selling grain that belonged to the church?" is in "Throughout most of his career, Athanasius had many detractors. Classical scholar Timothy Barnes relates contemporary allegations against Athanasius: from defiling an altar, to selling Church grain that had been meant to feed the poor for his own personal gain, and even violence and murder to suppress dissent. Athanasius used "Arian" to describe both followers of Arius, and as a derogatory polemical term for Christians who disagreed with his formulation of the Trinity. Athanasius called many of his opponents "Arian", except for Miletus.". Can you tell me what it is?

A:
personal gain