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 region of China is Jiangsu located?" is in "A dense wave of smog began in the Central and Eastern part of China on 2 December 2013 across a distance of around 1,200 kilometres (750 mi), including Tianjin, Hebei, Shandong, Jiangsu, Anhui, Shanghai and Zhejiang. A lack of cold air flow, combined with slow-moving air masses carrying industrial emissions, collected airborne pollutants to form a thick layer of smog over the region. The heavy smog heavily polluted central and southern Jiangsu Province, especially in and around Nanjing, with its AQI pollution Index at "severely polluted" for five straight days and "heavily polluted" for nine. On 3 December 2013, levels of PM2.5 particulate matter average over 943 micrograms per cubic metre, falling to over 338 micrograms per cubic metre on 4 December 2013. Between 3:00 pm, 3 December and 2:00pm, 4 December local time, several expressways from Nanjing to other Jiangsu cities were closed, stranding dozens of passenger buses in Zhongyangmen bus station. From 5 to 6 December, Nanjing issued a red alert for air pollution and closed down all kindergarten through middle schools. Children's Hospital outpatient services increased by 33 percent; general incidence of bronchitis, pneumonia, upper respiratory tract infections significantly increased. The smog dissipated 12 December. Officials blamed the dense pollution on lack of wind, automobile exhaust emissions under low air pressure, and coal-powered district heating system in North China region. Prevailing winds blew low-hanging air masses of factory emissions (mostly SO2) towards China's east coast.". Can you tell me what it is?

A: Central and Eastern


Problem: I know that the answer to the question "Who died earlier, Zephirin González or Heinrich Denifle?" is in "Doctrinal development has had an important place in the restoration of the Preachers. Several institutions, besides those already mentioned, played important parts. Such is the Biblical school at Jerusalem, open to the religious of the order and to secular clerics, which publishes the Revue Biblique. The faculty of theology at the University of Fribourg, confided to the care of the Dominicans in 1890, is flourishing, and has about 250 students. The Pontificium Collegium Internationale Angelicum, the future Pontifical University of Saint Thomas Aquinas, Angelicum established at Rome in 1908 by Master Hyacinth Cormier, opened its doors to regulars and seculars for the study of the sacred sciences. In addition to the reviews above are the Revue Thomiste, founded by Père Thomas Coconnier (d. 1908), and the Analecta Ordinis Prædicatorum (1893). Among numerous writers of the order in this period are: Cardinals Thomas Zigliara (d. 1893) and Zephirin González (d. 1894), two esteemed philosophers; Alberto Guillelmotti (d. 1893), historian of the Pontifical Navy, and Heinrich Denifle, one of the most famous writers on medieval history (d. 1905).[citation needed]". Can you tell me what it is?

A: Zephirin González


Problem: I know that the answer to the question "what kind of traditions that became mainstays involved cheese?" is in "Much of the Alpine culture is unchanged since the medieval period when skills that guaranteed survival in the mountain valleys and in the highest villages became mainstays, leading to strong traditions of carpentry, woodcarving, baking and pastry-making, and cheesemaking.". Can you tell me what it is?

A:
cheesemaking