While usual gapless points that are not geometrically defective i.e. Dirac points (Left column) possess only eigenvalues within [0, 1] (Bottom Left), defective exceptional points (Right column) also ...

Exactly 200 years ago, a French engineer introduced an idea that would quantify the universe’s inexorable slide into decay. But entropy, as it’s currently understood, is less a fact about the world ...

Thermodynamic spontaneity—whether a reaction can go—can be measured by changes in either of two parameters: entropy or free energy.