Black Holes and Thermodynamics – Jennie Traschen

Date: Thu. March 31st, 2011, 4:15 pm-5:15 pm
Location: Rockefeller 301

In 1971 Hawking published the Area Theorem, which shows that the area of a black hole either increases or stays the same. Two years later, Bardeen, Carter, and Hawking proved a theorem which relates the changes in the mass of a black hole, to changes in its area. These two results had a striking formal resemblance to the second and first laws of classical thermodynamics respectively. However, since nothing comes out of a black hole, it seemed that a black hole can not radiate and can not have a temperature, and so can not really be a thermodynamic system. Then in 1975, Hawking calculated that black holes do indeed radiate quantum mechanical particles, in a black body spectrum, at temperature proportional to Planck’ s constant. Over the past thirty-five years, Hawking radiation has (almost) become a household word. The lure of understanding the thermodynamics of black holes has fueled both physicists’ imaginations and calculations. In this nontechnical talk, we will aim to (1) explain the classical geometrical meaning of the mass, area, and surface gravity of a black hole, which are the quantities which appear in the first and second laws, and (2) present the main geometrical steps in Hawking’ s calculation of black hole radiation. As time permits, intriguing extensions of the first law in higher dimensions will be discussed.