gK

gK is an abbreviation encountered in several fields, and there is no single, universal meaning. The term can appear in physics, mathematics, and biology, among other areas, with different interpretations depending on the context.

In physics and electrical engineering, some authors use gK to denote a quantum of conductance in mesoscopic systems. The quantum of conductance for a single spin-degenerate channel is G_Q = 2e^2/h, often written as G0; in certain texts gK is used as a shorthand for conductance in units related to e^2/h. This usage is not standardized, and many sources prefer G0 or a dimensionless conductance.

In knot theory and topology, g(K) commonly denotes the genus of a knot K, the minimal genus of a Seifert surface spanning the knot. Some older or field-specific papers may write g_K to indicate the genus associated with knot K, though this notation is not universal.

In virology, gK frequently refers to glycoprotein K, a viral envelope protein found in herpesviruses. The gK product is encoded by a gene commonly labeled gK in the viral genome and is involved in virion assembly, egress, and cell fusion. Its presence and function can vary among different virus strains, and gK is a subject of comparative and immunological research.

Overall, gK functions as a context-dependent label rather than a single standardized concept, so precise meaning must be inferred from the accompanying field and notation.